I pulled into the garage last night and noted the amp/hours I'd used and the mileage on the odometer so that I could record them like I do every time I charge the car. The mileage read 144,214 which is significant because that marks exactly 10,000 miles since the Z3 was reborn as an EV. I figured that this would be a good time to go over some of the numbers I've been collecting that last 2 years, 4 months and see what I could glean, and then share them with you.
530 Number of Charge Cycles
18.9 Mean average miles driven between each charge
34.9% Mean average depth of discharge
36.0% Median average depth of discharge (half the data points are above, half below 36.0)
WARNING: Wild numbers and speculation will now commence.
CALB says that these batteries are good for 2000 cycles at an 80% Depth of Discharge (DOD), and 3000 at 70%. But how long will they last if I'm averaging roughly 35% DOD? Of course no one knows. However, if you use the 50% increase we see going from 80% DOD to 70% DOD as a baseline, and extrapolate that out, we might be able to conclude that we could get 4500 cycles at 60% DOD. If we keep going and then apply it to my average DOD of ~35%, we come up with something close to 12,500 cycles. At 18.9 miles per cycle, that works out to 236,250 miles.
Of course that's all theoretical, but it's likely not too far off from reality. But let's be conservative and say I only get half that number of cycles out of the batteries, that's still 118,000 miles. However, we need to keep in mind that the original 2000 and 3000 cycles that CALB states is a bit misleading. It's not as if the batteries stop working when they get to 2000 cycles. What they really mean is that after 2000 cycles to 80% DOD, the battery will only hold 80% of it's original capacity, so they will still push the car as far as I need to drive on a daily basis.
</Wild numbers and speculation>
As you can see this whole "cycle life" or "life expectancy" question for the batteries is highly fluid with the real numbers determined by a number of factors all at once which are, for practical purposes, impossible to determine or track. One thing that is certain is that these batteries will out perform a lead acid pack by at least an order of magnitude. Seeing as they only cost 4 times as much as a lead acid pack, I call that a good bargain. And that's not even taking into account the numerous other benefits they offer, like the 60 mile range vs. a lead acid packs 20 miles (at best).
$1,402 Amount saved not buying gas
3639 Total number of kWhs used to charge the car
That $1,402 figure is derived by taking into account the price of gas when I charged the car and subtracting the cost of the electricity used to charge the car. I always charge the car at off peak hours, and I add an extra 10% to the amount of electricity consumed to take into account the inefficiencies of the charger as it converts the 240 Volts AC to 160 Volts DC.
So how has the car performed? How well has it used that energy?
376 Mean average Watt-hours consumed per mile
388 Mean avg Watt-hours/mile with the old solid brushes
319 Mean avg Watt-hours/mile with the new split brushes
You can see there's been a marked difference in efficiency since replacing the brushes. The old average of 388 Watt-hours per mile was experienced over 442 charge cycles and 8,184 miles. The average has dropped to 319, and that has been over 88 charge cycles and 1,816 miles. I don't know how one could dispute the claim that these Helwig Carbon split Red Top brushes are better.
That increase in efficiency has moved the car from a 50 mile range using the 388 Watt-hours per mile figure to 61 miles using 319 Watt-hours per mile. Of course most of you know how much range can fluctuate with an EV depending on how and where you drive. I've been on 40 mile trips with the car where I saw the energy consumption average drop to 266 Watt-hours per mile, which works out to 73 mile range. Is that useful data? I don't know, but it's interesting.
Expanding on that, I found 4 data points that fit together nicely. These are individual trips with the miles driven, the total kWhs used and the Watt-hours used per mile.
50 miles 17.23 kWhs 345 Watt-hours/mile
51 miles 17.89 kWhs 351 Watt-hours/mile
51 miles 16.49 kWhs 323 Watt-hours/mile
51 miles 14.57 kWhs 286 Watt-hours/mile
Guess which trip occurred after the new brushes were installed in the motor. By the way, those were all trips to the same destination and back.
The real question at this point is how are the batteries fairing? For those not familiar with the car and reluctant to go back and read the multitude of tedious posts, I bottom balanced the pack back in February of 2011. The only way to find out how the batteries are doing now is to draw the pack back down to the bottom and make note of the amp/hours taken out and the state of charge on each battery. Hmm... sounds like another post. Stay tuned.
Monday, July 9, 2012
Tuesday, June 5, 2012
On Power Steering and a "Normal" Feeling Drive
Anyone who's been reading this blog for a while, knows that I have a Toyota MR2 electric hydraulic pump running the power steering system. Take the ICE engine out of a car, and chances are your power steering pump goes with it.
There are a few ways of dealing with this problem. One is to simply fore-go power steering. But unless you replace the steering rack with one that's geared for non power steering, that makes turning at low speeds rather like arm wrestling with Lou Ferrigno. The second is to build some apparatus for holding the old power steering pump onto the front of the electric motor, putting a pulley on the tail shaft of the motor and powering it off that. Of course, if the motor isn't spinning, you have no power steering. For me and I'm guessing many others, there simply wasn't enough room to incorporate something like that. You'd be surprised how many times you run out of room and 1/16th of an inch more was all you needed to make something fit.
The third, and perhaps most popular remedy is to use an electric power steering pump. There are a few OEM cars out their using such devices and the second generation Toyota MR2 was one of them. They cost somewhere around $300 to $400, they don't take up much room and its relatively inexpensive to have the custom hoses made to add them to the system.
On a normal car, they run all the time and you really wouldn't care because the alternator will just produce the energy it needs to work. But in an EV, you want to try and reduce parasitic loads. That pump can draw up to 85 amps in a hard lock! So the idea of having it run all the time was troublesome to me. To resolve that, I devised a system by where the pump stayed off when driving in a straight line, but would come on as soon as you turned the wheel a few degrees. I also added an off-delay relay so that it would remain on for 10 seconds after I was going straight. In this way, it wouldn't cycle on an off while I was going through a parking lot or some other place requiring a lot of turns.
But it wasn't a perfect solution, and I grew to dislike it for two reasons. One was that it proved to be dangerous. As is bound to happen when driving, it became necessary for me to quickly dodge something in the street. The amount of effort it takes to begin turning is massive. So when the pump kicks in, you just can't react quick enough to release the pressure. I ended up nearly steering right into the car next to me. It left me with a case of the sweats as I pondered the fact that I'd nearly caused an accident and destroyed all my hard work.
The second reason was that when I would have other people drive the car (something I do as frequently as possible) they had a difficult time getting used to that sluggish, stiff steering wheel when heading into a corner. I thought, "how can I convince people that EV's are fun to drive and just like any other car, only better, when they had to wrestle the steering wheel going into any turn? This was not the message I want to convey.
I thought I would simply put a latching switch into the system that would allow me to bypass the proximity switch on the steering column which would then turn the system on and leave it on until I pressed the switch again. Seemed like the perfect plan and I even had a great place to locate the switch in the cabin. So, before I took the car apart to work on the last motor problem, I ran a few tests to find out just how much power the pump drew when I was traveling in a straight line. It turns out that it draws less than 2 amps from the high voltage pack. That translates into something like 18 to 22 amps on the 12 volt system. Not trivial, but not too bad. The system is sized to accommodate it.
The point is, I could let the car sit idle running that pump and it would take over 60 hours for it to deplete the battery pack. That means in a standard commute to work, which takes 20 minutes, the power steering pump uses an extra... let me think... about, Oh I don't care!! It's seriously not enough for me to worry about AT ALL! Since the car has been on the road, I've left that switch engaged the whole time. My previous post detailed how I've experienced a boost in efficiency seemingly from the new brushes, so the change to the system of having this pump run all the time might have had an adverse impact on that, but it's not enough that I care.
The car drives like a normal car now, in almost all respects. I don't have to explain to people that drive it why the steering feels weird at first, and they don't have to experience the sharp jerk when the pump kicks on and they aren't expecting it. This is definitely the way to go.
By the way, I have turned it off a couple times. Sitting, waiting for my daughter to finish her choir practice, I left the car on so I could listen to the radio and enjoy the air conditioning, but I turned the pump off. Honestly, I'm not sure it was worth the effort of lifting my hand to press the switch.
There are a few ways of dealing with this problem. One is to simply fore-go power steering. But unless you replace the steering rack with one that's geared for non power steering, that makes turning at low speeds rather like arm wrestling with Lou Ferrigno. The second is to build some apparatus for holding the old power steering pump onto the front of the electric motor, putting a pulley on the tail shaft of the motor and powering it off that. Of course, if the motor isn't spinning, you have no power steering. For me and I'm guessing many others, there simply wasn't enough room to incorporate something like that. You'd be surprised how many times you run out of room and 1/16th of an inch more was all you needed to make something fit.
The third, and perhaps most popular remedy is to use an electric power steering pump. There are a few OEM cars out their using such devices and the second generation Toyota MR2 was one of them. They cost somewhere around $300 to $400, they don't take up much room and its relatively inexpensive to have the custom hoses made to add them to the system.
On a normal car, they run all the time and you really wouldn't care because the alternator will just produce the energy it needs to work. But in an EV, you want to try and reduce parasitic loads. That pump can draw up to 85 amps in a hard lock! So the idea of having it run all the time was troublesome to me. To resolve that, I devised a system by where the pump stayed off when driving in a straight line, but would come on as soon as you turned the wheel a few degrees. I also added an off-delay relay so that it would remain on for 10 seconds after I was going straight. In this way, it wouldn't cycle on an off while I was going through a parking lot or some other place requiring a lot of turns.
But it wasn't a perfect solution, and I grew to dislike it for two reasons. One was that it proved to be dangerous. As is bound to happen when driving, it became necessary for me to quickly dodge something in the street. The amount of effort it takes to begin turning is massive. So when the pump kicks in, you just can't react quick enough to release the pressure. I ended up nearly steering right into the car next to me. It left me with a case of the sweats as I pondered the fact that I'd nearly caused an accident and destroyed all my hard work.
The second reason was that when I would have other people drive the car (something I do as frequently as possible) they had a difficult time getting used to that sluggish, stiff steering wheel when heading into a corner. I thought, "how can I convince people that EV's are fun to drive and just like any other car, only better, when they had to wrestle the steering wheel going into any turn? This was not the message I want to convey.
I thought I would simply put a latching switch into the system that would allow me to bypass the proximity switch on the steering column which would then turn the system on and leave it on until I pressed the switch again. Seemed like the perfect plan and I even had a great place to locate the switch in the cabin. So, before I took the car apart to work on the last motor problem, I ran a few tests to find out just how much power the pump drew when I was traveling in a straight line. It turns out that it draws less than 2 amps from the high voltage pack. That translates into something like 18 to 22 amps on the 12 volt system. Not trivial, but not too bad. The system is sized to accommodate it.
The point is, I could let the car sit idle running that pump and it would take over 60 hours for it to deplete the battery pack. That means in a standard commute to work, which takes 20 minutes, the power steering pump uses an extra... let me think... about, Oh I don't care!! It's seriously not enough for me to worry about AT ALL! Since the car has been on the road, I've left that switch engaged the whole time. My previous post detailed how I've experienced a boost in efficiency seemingly from the new brushes, so the change to the system of having this pump run all the time might have had an adverse impact on that, but it's not enough that I care.
The car drives like a normal car now, in almost all respects. I don't have to explain to people that drive it why the steering feels weird at first, and they don't have to experience the sharp jerk when the pump kicks on and they aren't expecting it. This is definitely the way to go.
By the way, I have turned it off a couple times. Sitting, waiting for my daughter to finish her choir practice, I left the car on so I could listen to the radio and enjoy the air conditioning, but I turned the pump off. Honestly, I'm not sure it was worth the effort of lifting my hand to press the switch.
Monday, May 14, 2012
Efficiency I Can't Quite Explain
With the exception of the few months the Z3 has been off the road for repairs or upgrades, I've been driving the car for just over 26 months. During that time, I've kept detailed records of every charge/discharge cycle of the batteries. Every time I plug in, I note the mileage on the odometer, and the number of amp hours I've drawn out of the pack. I then take that data and plug it into a spreadsheet that calculates a number of things for me, including how much money I've saved because I wasn't burning gas, how much the electricity I'm using is costing me, and most interestingly, how many Watt-hours per mile the car is using.
I've reported in the past the the car averages about 320 Watt-hours per mile on surface streets. That's the number I've used to calculate the range of the car: 19,400 Wh / 320 Wh = 60.625. This is why I've always stated the car has a 60 mile range. And I've proved that out once, driving 62 miles on a charge once, in preparation for doing a bottom balance on the batteries.
Of course, once I go on the freeway traveling between 65 and 70 mph, that 320 Watt-hours per mile begins to look like a distant dream. The aerodynamic drag on the car causes energy consumption to quickly rise to around 420 Watt-hours per mile at 65 miles an hour. That meant that my round trip to work, a 23 mile journey, which includes 7 miles of surface streets and 16 miles of freeway, averaged between 370 and 380 Watt-hours per mile. I've made this trip a few hundred times, I know the numbers.
It's no secret that I've had a few problems with the motor in the car. The balancing putty has come off for a some inexplicable reason, twice. Just recently it developed a short to the case that no amount of air blown through its guts could resolve. George Hamstra at Netgain has been a champion through all of this and ultimately had a new motor sent to me. In addition, we swapped out the brushes from the standard H-49 brushes used for high current applications like drag racing, to H-60 brushes which are better suited for street use. A cool feature on Helwig H-60 brushes is the split, Red Top design, which helps to ensure better contact on the commutator.
At any rate, I got the new brushes seated in the motor properly, put the car back together and launched it back onto the streets about 3 weeks ago. The car is my daily driver, so once I began driving it to work and other places, and recording the energy consumption, I was a bit surprised to notice it was more efficient. At first I thought it was maybe just an anomaly, but it's clear something has caused the car to make much better use of the energy in the batteries. My round trips to work are now averaging about 280 Watt-hours per mile. Compare that to the older 370! That's more than a 25% improvement in efficiency! I made one trip where the average dropped to 266.
Today I took a bit of a longer trip out to Scottsdale. A total of 38 miles, with 30 of those miles on the freeway, traveling around 70 mph. The average consumption for the entire trip was 274 Watt-hours per mile. In the past, I would have estimated this trip to be a 400+ Watt-hour per mile trip. But that's not all! During the entire trip, I had the AC system on (which draws about 9 amps) and of course, I've configured the power steering pump to run all the time now adding another 2 amp continuous draw. BTW, the change to the power steering is interesting, but that's another post. So there are more parasitic loads, yet, efficiency is up.
The one thing I haven't done yet is to see what average I would get if I traveled at 40 or 45 mph. There's no reason to think the gain in efficiency that I'm seeing wouldn't appear there as well, but I simply don't have those numbers yet.
It seems like an obvious conclusion to draw that the increase in efficiency can be attributed to the new motor, or brushes, or a combination of them both. But I really can't say that with certainty. Perhaps I'd made some error when installing the drive line in the past which caused some binding or friction that I simply wasn't aware of. I kind of doubt that, but who knows? There's no question I've gotten better at disassembling the drive line of the car, but there really isn't much room for error here. I have no reason to doubt the numbers the meter is giving me; after all, it's the same meeter with the same set up I was using before the motor swap.
What ever the cause, the car does seem to be more efficient. At an average draw of 280 Watt-hours per mile, it's gone from a 60 mile range to nearly a 70 mile range. I'll take it.
Since the car was put on the road, up until the motor/brush replacement, it has averaged 376 Watt hours per mile. That is the real world average. Sure there were many trips that were better, but there were also many that were worse. I can't get out of my neighborhood without consuming something like 480 Watt-hours per mile. It's all about stopping and starting. With no regenerative braking, stop signs and stop lights really affect your range. The more of them per mile, the worse your range. Well, there's 6 stop signs on one of the routes it takes to get from my house to the main streets, so you can imagine what that does to energy consumption.
The average after the motor/brush swap has dropped to 321 Watt-hours per mile. Compare that to the old 376, and you note a 14.7% improvement. That is huge! Interestingly, and I've mentioned this above, virtually all of the trips I've made in the car since putting it back on the road have been on the freeway at 65 - 70 mph. Meaning, that as more trips on surface streets are recorded I expect that 321 number to drop even further.
The bottom line is that I've been misrepresenting what the car's range really is by skewing the data toward the happier, more optimistic lower numbers. Not intentionally or maliciously mind you. The old average was 51.6, the average now seems to be 60.4. A painful thing to admit, but there you have it. Just as I could have easily squeezed 60 miles out of the car before, sticking to surface streets and avoiding stops, I expect I could squeeze 70 miles out of it now, doing the same.
I've brought all this to Jack Rickard's attention at EVTV, and just like me, he was skeptical and ultimately amazed. He's been doing some tests swapping out the original H49 brushes for the split, Red Top H60's and he's finding the same results. I have a feeling this is going to be a hot topic in the EV community for a while.
I've reported in the past the the car averages about 320 Watt-hours per mile on surface streets. That's the number I've used to calculate the range of the car: 19,400 Wh / 320 Wh = 60.625. This is why I've always stated the car has a 60 mile range. And I've proved that out once, driving 62 miles on a charge once, in preparation for doing a bottom balance on the batteries.
Of course, once I go on the freeway traveling between 65 and 70 mph, that 320 Watt-hours per mile begins to look like a distant dream. The aerodynamic drag on the car causes energy consumption to quickly rise to around 420 Watt-hours per mile at 65 miles an hour. That meant that my round trip to work, a 23 mile journey, which includes 7 miles of surface streets and 16 miles of freeway, averaged between 370 and 380 Watt-hours per mile. I've made this trip a few hundred times, I know the numbers.
It's no secret that I've had a few problems with the motor in the car. The balancing putty has come off for a some inexplicable reason, twice. Just recently it developed a short to the case that no amount of air blown through its guts could resolve. George Hamstra at Netgain has been a champion through all of this and ultimately had a new motor sent to me. In addition, we swapped out the brushes from the standard H-49 brushes used for high current applications like drag racing, to H-60 brushes which are better suited for street use. A cool feature on Helwig H-60 brushes is the split, Red Top design, which helps to ensure better contact on the commutator.
At any rate, I got the new brushes seated in the motor properly, put the car back together and launched it back onto the streets about 3 weeks ago. The car is my daily driver, so once I began driving it to work and other places, and recording the energy consumption, I was a bit surprised to notice it was more efficient. At first I thought it was maybe just an anomaly, but it's clear something has caused the car to make much better use of the energy in the batteries. My round trips to work are now averaging about 280 Watt-hours per mile. Compare that to the older 370! That's more than a 25% improvement in efficiency! I made one trip where the average dropped to 266.
Today I took a bit of a longer trip out to Scottsdale. A total of 38 miles, with 30 of those miles on the freeway, traveling around 70 mph. The average consumption for the entire trip was 274 Watt-hours per mile. In the past, I would have estimated this trip to be a 400+ Watt-hour per mile trip. But that's not all! During the entire trip, I had the AC system on (which draws about 9 amps) and of course, I've configured the power steering pump to run all the time now adding another 2 amp continuous draw. BTW, the change to the power steering is interesting, but that's another post. So there are more parasitic loads, yet, efficiency is up.
The one thing I haven't done yet is to see what average I would get if I traveled at 40 or 45 mph. There's no reason to think the gain in efficiency that I'm seeing wouldn't appear there as well, but I simply don't have those numbers yet.
It seems like an obvious conclusion to draw that the increase in efficiency can be attributed to the new motor, or brushes, or a combination of them both. But I really can't say that with certainty. Perhaps I'd made some error when installing the drive line in the past which caused some binding or friction that I simply wasn't aware of. I kind of doubt that, but who knows? There's no question I've gotten better at disassembling the drive line of the car, but there really isn't much room for error here. I have no reason to doubt the numbers the meter is giving me; after all, it's the same meeter with the same set up I was using before the motor swap.
What ever the cause, the car does seem to be more efficient. At an average draw of 280 Watt-hours per mile, it's gone from a 60 mile range to nearly a 70 mile range. I'll take it.
Update 5/20/2012:
I've continued to see the gains in efficiency I detailed above, but I've realized I've let myself fall victim to insidious creature that is over optimism. I've always maintained that the Z3 had a 60 mile range. That was based on the fact that it consumed about 320 - 330 Watt-hours per mile when driving at ~45 mph in normal traffic. What I really hadn't done is take an average over multiple trips to get a more balanced number, a real world number you can take to the bank. Well since I've seen this improvement in efficiency, I've gone back to my spreadsheet to see if I could mine some more useful, accurate data from the numbers. Here's how it works out...Since the car was put on the road, up until the motor/brush replacement, it has averaged 376 Watt hours per mile. That is the real world average. Sure there were many trips that were better, but there were also many that were worse. I can't get out of my neighborhood without consuming something like 480 Watt-hours per mile. It's all about stopping and starting. With no regenerative braking, stop signs and stop lights really affect your range. The more of them per mile, the worse your range. Well, there's 6 stop signs on one of the routes it takes to get from my house to the main streets, so you can imagine what that does to energy consumption.
The average after the motor/brush swap has dropped to 321 Watt-hours per mile. Compare that to the old 376, and you note a 14.7% improvement. That is huge! Interestingly, and I've mentioned this above, virtually all of the trips I've made in the car since putting it back on the road have been on the freeway at 65 - 70 mph. Meaning, that as more trips on surface streets are recorded I expect that 321 number to drop even further.
The bottom line is that I've been misrepresenting what the car's range really is by skewing the data toward the happier, more optimistic lower numbers. Not intentionally or maliciously mind you. The old average was 51.6, the average now seems to be 60.4. A painful thing to admit, but there you have it. Just as I could have easily squeezed 60 miles out of the car before, sticking to surface streets and avoiding stops, I expect I could squeeze 70 miles out of it now, doing the same.
I've brought all this to Jack Rickard's attention at EVTV, and just like me, he was skeptical and ultimately amazed. He's been doing some tests swapping out the original H49 brushes for the split, Red Top H60's and he's finding the same results. I have a feeling this is going to be a hot topic in the EV community for a while.
Monday, April 23, 2012
What An Ordeal
The few of you who read this blog have probably wondered what's been going on with the Z3. When I last left you, I'd received the new motor, had put the new split top, harder brushes in and was seating them by running the motor off of a 12V battery. Well, quite a lot has happened, and frankly, it wasn't all good. So sit back and enjoy the saga.
Once I installed the new brushes and turned the motor on, it made a hell of a racket for the first few hours. I remember seeing a video John Allen had made when he was breaking in new brushes for his Warp 9, and I was struck by how loud it was, so I wasn't too surprised when mine made similar noises. I ran the motor for 100 hours and at the end, it sounded as smooth as silk. Job done!
I mounted the motor up to the transmission and tightened up all the bolts and called it a day, planning to reinstall the motor/transmission back into the car the next day. During the night, I realized I'd done something kind of stupid. The manual for the car states that you should put a little grease on the input shaft before you mate it up to the motor. It already had a film of grease on it, but I thought more is better. When thinking about it that evening, I realized that I had cleaned off a little grease I'd found on the flywheel. It was in a pattern that looked like it had been thrown off the shaft. It was at that point I realized more is not better, and I'd set myself up for a greasy, slip prone clutch. So I took the tranny off the motor, cleaned the shaft of excess grease and mounted it back up. It only took 45 minutes or so, so it wasn't that bad. I'm telling this story so that if anyone out there reading this can learn a lesson from my stupidity, then I've served some purpose on this planet.
Moving on. The motor/transmission assembly went in to the car later that day without a hitch, and thanks to my dad who came out to help me. I mounted up the drive line and started the process of re-assembling the car. It went quite smooth really. I was making one of the last battery connections when I leaned my elbow on the chassis, and it felt like I got stabbed or cut. I remember thinking that I didn't remember the bolt I leaned on being particularly sharp. I touched it again and realized that I didn't get stabbed, I got shocked. That's right my friends, the leak, which I was trying to get rid of, the one for which I'd been sent a replacement motor, was not gone.
Talk about a kick in the teeth. I started testing and dis-assembling everything and came to the conclusion that, once again, the source of the leak was in the motor. How could this be?!!! I was absolutely gutted and just walked away from the car for what ended up being the whole weekend while I thought about what to do.
I decided what I had to do was figure out, definitively if it was the motor or something else. I decided the best way to do that was to assemble all of the components completely, but leave the motor out of the assembly process. In place of the motor, I simply ran a cable from the Motor + terminal on the controller to the Motor - terminal. This was simply to replicate the existence of "something" in the system at that position in the circuit. Once it was all back together (minus a few batteries) I found that there was no leak. I added the motor back in, the leak appeared.
I thought perhaps breaking the brushes in had created enough dust to cause the problem, so I decided to blow it out with compressed air. While some dust did come out, I could still measure the HV pack voltage on the chassis. Ghaaaa!!
It was time to contact George again. I can't express to you how much I did not want to darken his inbox with bad news again. George asked if I would send him and Tom Brunka of Helwig Carbon Brushes a picture of one of the brushes that I broke in. He wanted a close up of the face and shot of the profile. Puzzled, and unsure of how that would help, I obliged and sent off the photos. Tom got back and said that the brushes looked like they were broken in perfectly, so that was good. But then he apparently noticed something else, and that was the model number printed on the brush indicated it was for a 9" motor.
The pieces started falling into place for George at that point. The commutator on a 9" motor has a smaller circumference than that of an 11" motor. That means that the brushes for a 9" motor would be made with a smaller arc to the face. Aside for that, they are identical in function, composition and structure. But what that meant was that rather than the brush's surface resting with more or less complete contact on the commutator, it was riding on the very edges. That explained why they were so loud when I first put them in. Truthfully, at that time, I even wondered if I might have been sent brushes for a 9" motor, but it was just a passing thought.
So, through an innocent mistake, George had sent me the wrong brushes. He mentioned that it really was no problem to use them now that they were seated so well, and I would have had to wait another 2 weeks to get 11" brushes anyway. I was fine with keeping these. Anyway, because the brushes weren't contoured correctly for the 11" motor, that meant that a bit more material had to wear off of them than would have normally happened. Couple that with the fact that when running off a 12V battery, the motor doesn't spin fast enough to create enough airflow to vent the dust that does come off the brushes, and you have a recipe for developing and internal path to ground.
I went back and measured the resistance of the path from the motor terminal to the chassis and found that it was .880 mega Ohms. Don't ask me why I didn't measure that after I blew the motor out the first time, but I didn't think to. I saw that I could measure voltage on the chassis and felt that was enough of a problem that I didn't think to measure resistance. But what I found was that after I had blown it out, it had made a difference. .880 mega Ohms can only pass 0.13 milliamps at 160 volts. I could touch the terminal of the battery and the chassis and felt nothing.
George added that once I got the motor back on the road and spun it up to 3000 RPM, it would blow the rest of that dust out. he also mentioned that Warfield Electric consider a leak to chassis acceptable as long as it won't light up a light bulb. Well, .13 milliamps isn't enough to light a light bulb, and it's also not enough to cause my charger to complain.
Today I got everything back together, tested the systems, and flipped the charger on with fingers crossed. It came right on and dutifully charged the batteries back up to full. All systems go! I took the car down from the jack stands drove it out of the garage and put 20 miles on it this afternoon. It seemed like everyday since the car has been out of commission, I came across either a Nissan Leaf, or a Chevy Volt, while out driving and I would just grumble in envy. Today I saw Leaf while I was driving the Z3, and I simply felt joy.
Once I installed the new brushes and turned the motor on, it made a hell of a racket for the first few hours. I remember seeing a video John Allen had made when he was breaking in new brushes for his Warp 9, and I was struck by how loud it was, so I wasn't too surprised when mine made similar noises. I ran the motor for 100 hours and at the end, it sounded as smooth as silk. Job done!
I mounted the motor up to the transmission and tightened up all the bolts and called it a day, planning to reinstall the motor/transmission back into the car the next day. During the night, I realized I'd done something kind of stupid. The manual for the car states that you should put a little grease on the input shaft before you mate it up to the motor. It already had a film of grease on it, but I thought more is better. When thinking about it that evening, I realized that I had cleaned off a little grease I'd found on the flywheel. It was in a pattern that looked like it had been thrown off the shaft. It was at that point I realized more is not better, and I'd set myself up for a greasy, slip prone clutch. So I took the tranny off the motor, cleaned the shaft of excess grease and mounted it back up. It only took 45 minutes or so, so it wasn't that bad. I'm telling this story so that if anyone out there reading this can learn a lesson from my stupidity, then I've served some purpose on this planet.
Moving on. The motor/transmission assembly went in to the car later that day without a hitch, and thanks to my dad who came out to help me. I mounted up the drive line and started the process of re-assembling the car. It went quite smooth really. I was making one of the last battery connections when I leaned my elbow on the chassis, and it felt like I got stabbed or cut. I remember thinking that I didn't remember the bolt I leaned on being particularly sharp. I touched it again and realized that I didn't get stabbed, I got shocked. That's right my friends, the leak, which I was trying to get rid of, the one for which I'd been sent a replacement motor, was not gone.
Talk about a kick in the teeth. I started testing and dis-assembling everything and came to the conclusion that, once again, the source of the leak was in the motor. How could this be?!!! I was absolutely gutted and just walked away from the car for what ended up being the whole weekend while I thought about what to do.
I decided what I had to do was figure out, definitively if it was the motor or something else. I decided the best way to do that was to assemble all of the components completely, but leave the motor out of the assembly process. In place of the motor, I simply ran a cable from the Motor + terminal on the controller to the Motor - terminal. This was simply to replicate the existence of "something" in the system at that position in the circuit. Once it was all back together (minus a few batteries) I found that there was no leak. I added the motor back in, the leak appeared.
I thought perhaps breaking the brushes in had created enough dust to cause the problem, so I decided to blow it out with compressed air. While some dust did come out, I could still measure the HV pack voltage on the chassis. Ghaaaa!!
It was time to contact George again. I can't express to you how much I did not want to darken his inbox with bad news again. George asked if I would send him and Tom Brunka of Helwig Carbon Brushes a picture of one of the brushes that I broke in. He wanted a close up of the face and shot of the profile. Puzzled, and unsure of how that would help, I obliged and sent off the photos. Tom got back and said that the brushes looked like they were broken in perfectly, so that was good. But then he apparently noticed something else, and that was the model number printed on the brush indicated it was for a 9" motor.
The pieces started falling into place for George at that point. The commutator on a 9" motor has a smaller circumference than that of an 11" motor. That means that the brushes for a 9" motor would be made with a smaller arc to the face. Aside for that, they are identical in function, composition and structure. But what that meant was that rather than the brush's surface resting with more or less complete contact on the commutator, it was riding on the very edges. That explained why they were so loud when I first put them in. Truthfully, at that time, I even wondered if I might have been sent brushes for a 9" motor, but it was just a passing thought.
So, through an innocent mistake, George had sent me the wrong brushes. He mentioned that it really was no problem to use them now that they were seated so well, and I would have had to wait another 2 weeks to get 11" brushes anyway. I was fine with keeping these. Anyway, because the brushes weren't contoured correctly for the 11" motor, that meant that a bit more material had to wear off of them than would have normally happened. Couple that with the fact that when running off a 12V battery, the motor doesn't spin fast enough to create enough airflow to vent the dust that does come off the brushes, and you have a recipe for developing and internal path to ground.
I went back and measured the resistance of the path from the motor terminal to the chassis and found that it was .880 mega Ohms. Don't ask me why I didn't measure that after I blew the motor out the first time, but I didn't think to. I saw that I could measure voltage on the chassis and felt that was enough of a problem that I didn't think to measure resistance. But what I found was that after I had blown it out, it had made a difference. .880 mega Ohms can only pass 0.13 milliamps at 160 volts. I could touch the terminal of the battery and the chassis and felt nothing.
George added that once I got the motor back on the road and spun it up to 3000 RPM, it would blow the rest of that dust out. he also mentioned that Warfield Electric consider a leak to chassis acceptable as long as it won't light up a light bulb. Well, .13 milliamps isn't enough to light a light bulb, and it's also not enough to cause my charger to complain.
Today I got everything back together, tested the systems, and flipped the charger on with fingers crossed. It came right on and dutifully charged the batteries back up to full. All systems go! I took the car down from the jack stands drove it out of the garage and put 20 miles on it this afternoon. It seemed like everyday since the car has been out of commission, I came across either a Nissan Leaf, or a Chevy Volt, while out driving and I would just grumble in envy. Today I saw Leaf while I was driving the Z3, and I simply felt joy.
Thursday, March 22, 2012
Seating New Brushes
You're probably familiar with the problem I've been facing recently regarding the leak to chassis ground through the motor. It's proven to be a very strange problem. I made a quick video to demonstrate what I'm seeing, take a look.
A leak at 635 Ohms and 160 volts equates to 252 milliamps. The 436 Ohms I read the following day would produce a current leak of 367 milliamps. I've seen the reading as high as 1180 Ohms, and as low as 350 Ohms. This sort of leak is most often caused by the accumulation of dust in the motor. I've blown enough air through the motor that if that were indeed the problem, it should have fixed it. But as you all know it hasn't, so George Hamstra has decided he's seen me suffer enough at the hands of this motor, so he's sent me a new one.
Since that picture was taken, I've pulled the clutch assembly, flywheel, adaptor plate and taper-lock hub assembly off the old motor with the help of my friend Dave from Tucson. However, I haven't put it on the new motor yet. In email exchanges with George, I mentioned that I would be sending back the $320 brushes he sent me (at his expense) to try to resolve the problem with the original motor. But he replied saying instead that I should put them in the new motor. He believed that the brushes in the new motor were likely brushes better suited for racing. I peered in the motor and found they were the Helwig Redtop brushes, but when I compared them to the ones George had sent me I could see a marked difference. They were a bit shorter, but much darker in color.
So at George's recommendation, I swapped them out. But that means I need to seat, or bed in the new brushes before I put the motor in the car. Essentially, you strap the motor down, and connect it to a 12v battery and let it spin for 100+ hours. It sounds easy enough, but actually getting it done required some effort.
First I needed a 12 battery. I don't have one laying around, so I went to the local Costco and bought the cheapest 12v deep cycle battery they had for about $80. I was under the impression that the motor would draw about 3 to 5 amps, once it had spun up and was running smoothly. So I thought my little 0-12 amp battery charger could keep up. Well, that was off by a factor of 10. It actually draws about 45 amps at start up and settles in to a constant draw of about 35 amps. Fortunately a friend at work was kind enough to lend me his heavy duty charger that can put out up to 200 amps for starting a car, or as much as 40 amps for charging the battery. Perfect! Here's how the assembly looks.
At the top right, we have Fred's big charger. Below and to the right, is the 12V battery. I have both the cables to the motor hooked up to it, as well as the cables from the charger. Notice on the negative line running to the motor is a big switch; a nice way of turning the motor on and off. My meter is sitting on top of the battery with the probes connected to the terminals. In the morning, I turn the motor on. When I see the battery hit about 11.00 volts, I turn the charger on. It operates by timer, so I set it for 2 hours. It immediately pushes the voltage up to about 12.8 and puts out about 43 amps. The motor is drawing about 35, so it's a net of about 8 amps going to the battery. Over that two hours time, the voltage on the battery rises to about 13.5. By the time the battery hits 13.7, the charger is putting about about 36 amps, or one amp more than the motor draws. So I turn the charger off and let it rest. (I don't want to burn it up.) When the battery gets back down to 11V, the charger goes back on. I'm on day 4 of the break in, and it's been running about 50 hours. Since the charger is on a timer, I can't run the system at night.
When the brushes have had enough time to seat, I'll re-assemble the adaptor plate and clutch, then work to getting it back in the car.
A leak at 635 Ohms and 160 volts equates to 252 milliamps. The 436 Ohms I read the following day would produce a current leak of 367 milliamps. I've seen the reading as high as 1180 Ohms, and as low as 350 Ohms. This sort of leak is most often caused by the accumulation of dust in the motor. I've blown enough air through the motor that if that were indeed the problem, it should have fixed it. But as you all know it hasn't, so George Hamstra has decided he's seen me suffer enough at the hands of this motor, so he's sent me a new one.
Since that picture was taken, I've pulled the clutch assembly, flywheel, adaptor plate and taper-lock hub assembly off the old motor with the help of my friend Dave from Tucson. However, I haven't put it on the new motor yet. In email exchanges with George, I mentioned that I would be sending back the $320 brushes he sent me (at his expense) to try to resolve the problem with the original motor. But he replied saying instead that I should put them in the new motor. He believed that the brushes in the new motor were likely brushes better suited for racing. I peered in the motor and found they were the Helwig Redtop brushes, but when I compared them to the ones George had sent me I could see a marked difference. They were a bit shorter, but much darker in color.
So at George's recommendation, I swapped them out. But that means I need to seat, or bed in the new brushes before I put the motor in the car. Essentially, you strap the motor down, and connect it to a 12v battery and let it spin for 100+ hours. It sounds easy enough, but actually getting it done required some effort.
First I needed a 12 battery. I don't have one laying around, so I went to the local Costco and bought the cheapest 12v deep cycle battery they had for about $80. I was under the impression that the motor would draw about 3 to 5 amps, once it had spun up and was running smoothly. So I thought my little 0-12 amp battery charger could keep up. Well, that was off by a factor of 10. It actually draws about 45 amps at start up and settles in to a constant draw of about 35 amps. Fortunately a friend at work was kind enough to lend me his heavy duty charger that can put out up to 200 amps for starting a car, or as much as 40 amps for charging the battery. Perfect! Here's how the assembly looks.
At the top right, we have Fred's big charger. Below and to the right, is the 12V battery. I have both the cables to the motor hooked up to it, as well as the cables from the charger. Notice on the negative line running to the motor is a big switch; a nice way of turning the motor on and off. My meter is sitting on top of the battery with the probes connected to the terminals. In the morning, I turn the motor on. When I see the battery hit about 11.00 volts, I turn the charger on. It operates by timer, so I set it for 2 hours. It immediately pushes the voltage up to about 12.8 and puts out about 43 amps. The motor is drawing about 35, so it's a net of about 8 amps going to the battery. Over that two hours time, the voltage on the battery rises to about 13.5. By the time the battery hits 13.7, the charger is putting about about 36 amps, or one amp more than the motor draws. So I turn the charger off and let it rest. (I don't want to burn it up.) When the battery gets back down to 11V, the charger goes back on. I'm on day 4 of the break in, and it's been running about 50 hours. Since the charger is on a timer, I can't run the system at night.
When the brushes have had enough time to seat, I'll re-assemble the adaptor plate and clutch, then work to getting it back in the car.
A Great Video
On an unrelated note, a PBS station back East, WSIU, has published a story about last Septembers EVCCON and EVTV. The story is quite well done. It explains what the movement is about, why people are doing it for themselves and why Jack and Brian are producing the weekly EVTV show. It's about 1/2 hour long, and it's well worth watching. While the Z3 is not featured in the video, you can see it in the background on a few shots. Take a look:Monday, March 12, 2012
A Missed Anniversary and Motor Drama
Some of you may be distantly aware that March 2nd marked the Z3's second year on the road. Unfortunately, as you know, it's not actually on the road at this time. It has once again, fallen victim to a motor problem. Of the 12 month span starting last March until now, the car has been on the road for only 6 1/2 of those months. Not all that time was to repair motor problems. Last July, August and beginning of September was spent adding the MasterFlux AC system and getting the car ready for EVCCON. Never the less, it has has not been as trouble free as I would have liked. But I remain optimistic that those types of problems may soon be behind me and I'll be in for some extended trouble free motoring.
So let's move on with what's been happening the past couple weeks. To catch everyone up to date that hasn't read the last couple posts, the car developed a leak to ground. That means that I could measure the high voltage on the frame of the car. That poses a few problems, one being the threat of being shocked, another being the threat of arcing and potential fire under the right circumstances, and last, the charger wouldn't stay on. The charger is grounded to the chassis of the car, so when it sensed the high voltage on the chassis, it simply shuts itself off for protection.
I'd methodically tracked the problem down to the motor, finding that there was a leak from the terminals where the high voltage is sent into the motor, to the case itself. This is not supposed to happen, but it can if there's been a build up of dust inside the motor caused by the wear of the brushes. Most recommend blowing out the motor out with compressed air, which I did, repeatedly. In the mean time, I contacted George Hamstra from Netgain to find out if there was a preferred method for cleaning the motor more thoroughly. Compressed air is pretty much it. He reasoned that I must have brushes in the car that are better suited for racing and tend to dust quite a bit. So he took it upon himself to send me, at his expense!, a set of $320 replacement brushes. Not just any brushes, mind you, but Helwig split top brushes, pretty much the best money can buy.
The top two brushes are tied together on one connecting wire. That is one of the older sets. Presumably, they were the same size as the new Helwig brush at the bottom, but look how much they've worn after only 9,000 miles. Notice too how the old brush closest to the new one is shorter than the top brush. Curiously, this was the case with each pair. The brush that was in the bracket closest to the front of the motor was warn by as much as 1/8th of an inch more than the back brush. I don't know if that means anything, but it certainly happened.
I've mentioned that George is tired of seeing me suffer through problems with the motor. He also offered at that time to simply replace the motor, but I asked him to hold off to see if more cleaning and the new brushes made a difference. The new brushes arrived on the 1st of March, but I didn't get a chance to work on the car until the 4th. I was able to pull 3 sets of the old brushes out with no difficulty. But on the 4th set, I was able to get one brush out OK, but the space was so tight and constrained, I simply could not get the last brush out. After laboring over it for a few hours, and coming to terms with it for another the next 24 hours, I finally came to the decision that I was going to have to pull the motor and transmission out of the car. Believe me, that was something I did NOT want to do.
My dad was kind enough to come over and help me out. It took us about 4 hours, but we got everything unhooked, the motor free and then we were able to drop it out of the car. I've lent my lift to a friend, so I didn't have that, but it's OK, because this time I was determined to drop the motor out instead of lift it out. with the cunning use of the floor jack, several 2x4s, levers and muscle power, we were able to do it. That gave me access to the last brush, and I carefully pulled it out. It was at that point that I looked at the brush I just pulled and saw something truly astounding. Take a look:
Yes, what you see there are 3 holes drilled into the top of the brush, and a chunk of the brush missing! Where it went, I have no idea. I looked around everywhere, but could not find the piece or pieces of carbon laying about. As it was the last brush I pulled, it should have come out with the brush, but it didn't. It got me wondering if perhaps it had come off and become wedged somewhere inside the motor, causing the short. It seems unlikely, but I have no way of knowing without disassembling the motor.
With the brushes out, I took the opportunity to blow more air through the motor. A lot more air. The air gun I had been using works fine, but the nozzle is fixed and short. I bought an air gun with an 8" flexible nozzle that I was able to carefully insert into the motor and spray in harder to reach areas.
I sprayed compressed air until I saw, or could smell no more dust. Believe it or not, that dust has a funny smell (even though I was wearing a mask). I put the new brushes back in carefully, and took another reading with the Ohm meter. To my astonishment, the leak was actually a bit worse. I hooked up a 12v battery to the motor with a switch in line so that I could run the motor for a bit and try blowing more air while the motor was moving. Had to be careful not to stick the nozzle anywhere in the motor or near the brush assembly. 4 or 5 more tanks of air and no dust coming out. At this point, the motor is as dust free as I can get it without taking it apart.
After all that, the leak persists. At it's worse I measured the resistance between the S1 terminal and the case at 508 Ohms. That's enough to pass 320 milliamps. Again, not a lot, but certainly enough to feel, and enough to render the charger useless.
I contacted George with the story, telling him the results of my efforts, and sending him the picture of the brush. At this point I'm faced with either taking the motor apart and trying to clean it further, or getting a new one. George was absolutely dumbfounded when he saw that picture. He said that it looked like someone had tried to make a Brush Wear Indicator, but he couldn't figure out why they drilled three holes, or worse yet, why they left that brush in the motor. He was pissed, and justifiably so. He's paid to have this motor repaired twice and the second time he told them to pay particular attention to it so that it was done to the highest standard possible. Clearly, that didn't happen.
Fed up with the whole thing, George is sending me a new motor. I must say, that I have very mixed feelings about this. On one hand, I'm thrilled to be getting a motor that will hopefully have none of the flaws that have plagued this motor from it's first day. On the other hand, it just eats me up that this whole fiasco has cost George so much. Shipping to Illinois and back, twice, two rebuilds of the motor, and finally a whole new motor plus the shipping for that from Illinois. Dreadful! I had hoped to be one George's success stories.
While all of this is going on, I am planning a couple minor enhancements. I bought a voltage meter/display from Lightobject that can be programmed to cut a relay at a specific voltage. I'm thinking that I'd like to add that to the car as a safety backup in case the charger doesn't cut off in time. If this device sees the voltage rise to the level I've defined, it would trigger a relay that would simply cut power to the charger, protecting the batteries. Stay tuned.
So let's move on with what's been happening the past couple weeks. To catch everyone up to date that hasn't read the last couple posts, the car developed a leak to ground. That means that I could measure the high voltage on the frame of the car. That poses a few problems, one being the threat of being shocked, another being the threat of arcing and potential fire under the right circumstances, and last, the charger wouldn't stay on. The charger is grounded to the chassis of the car, so when it sensed the high voltage on the chassis, it simply shuts itself off for protection.
I'd methodically tracked the problem down to the motor, finding that there was a leak from the terminals where the high voltage is sent into the motor, to the case itself. This is not supposed to happen, but it can if there's been a build up of dust inside the motor caused by the wear of the brushes. Most recommend blowing out the motor out with compressed air, which I did, repeatedly. In the mean time, I contacted George Hamstra from Netgain to find out if there was a preferred method for cleaning the motor more thoroughly. Compressed air is pretty much it. He reasoned that I must have brushes in the car that are better suited for racing and tend to dust quite a bit. So he took it upon himself to send me, at his expense!, a set of $320 replacement brushes. Not just any brushes, mind you, but Helwig split top brushes, pretty much the best money can buy.
The top two brushes are tied together on one connecting wire. That is one of the older sets. Presumably, they were the same size as the new Helwig brush at the bottom, but look how much they've worn after only 9,000 miles. Notice too how the old brush closest to the new one is shorter than the top brush. Curiously, this was the case with each pair. The brush that was in the bracket closest to the front of the motor was warn by as much as 1/8th of an inch more than the back brush. I don't know if that means anything, but it certainly happened.
I've mentioned that George is tired of seeing me suffer through problems with the motor. He also offered at that time to simply replace the motor, but I asked him to hold off to see if more cleaning and the new brushes made a difference. The new brushes arrived on the 1st of March, but I didn't get a chance to work on the car until the 4th. I was able to pull 3 sets of the old brushes out with no difficulty. But on the 4th set, I was able to get one brush out OK, but the space was so tight and constrained, I simply could not get the last brush out. After laboring over it for a few hours, and coming to terms with it for another the next 24 hours, I finally came to the decision that I was going to have to pull the motor and transmission out of the car. Believe me, that was something I did NOT want to do.
My dad was kind enough to come over and help me out. It took us about 4 hours, but we got everything unhooked, the motor free and then we were able to drop it out of the car. I've lent my lift to a friend, so I didn't have that, but it's OK, because this time I was determined to drop the motor out instead of lift it out. with the cunning use of the floor jack, several 2x4s, levers and muscle power, we were able to do it. That gave me access to the last brush, and I carefully pulled it out. It was at that point that I looked at the brush I just pulled and saw something truly astounding. Take a look:
Yes, what you see there are 3 holes drilled into the top of the brush, and a chunk of the brush missing! Where it went, I have no idea. I looked around everywhere, but could not find the piece or pieces of carbon laying about. As it was the last brush I pulled, it should have come out with the brush, but it didn't. It got me wondering if perhaps it had come off and become wedged somewhere inside the motor, causing the short. It seems unlikely, but I have no way of knowing without disassembling the motor.
With the brushes out, I took the opportunity to blow more air through the motor. A lot more air. The air gun I had been using works fine, but the nozzle is fixed and short. I bought an air gun with an 8" flexible nozzle that I was able to carefully insert into the motor and spray in harder to reach areas.
I sprayed compressed air until I saw, or could smell no more dust. Believe it or not, that dust has a funny smell (even though I was wearing a mask). I put the new brushes back in carefully, and took another reading with the Ohm meter. To my astonishment, the leak was actually a bit worse. I hooked up a 12v battery to the motor with a switch in line so that I could run the motor for a bit and try blowing more air while the motor was moving. Had to be careful not to stick the nozzle anywhere in the motor or near the brush assembly. 4 or 5 more tanks of air and no dust coming out. At this point, the motor is as dust free as I can get it without taking it apart.
After all that, the leak persists. At it's worse I measured the resistance between the S1 terminal and the case at 508 Ohms. That's enough to pass 320 milliamps. Again, not a lot, but certainly enough to feel, and enough to render the charger useless.
I contacted George with the story, telling him the results of my efforts, and sending him the picture of the brush. At this point I'm faced with either taking the motor apart and trying to clean it further, or getting a new one. George was absolutely dumbfounded when he saw that picture. He said that it looked like someone had tried to make a Brush Wear Indicator, but he couldn't figure out why they drilled three holes, or worse yet, why they left that brush in the motor. He was pissed, and justifiably so. He's paid to have this motor repaired twice and the second time he told them to pay particular attention to it so that it was done to the highest standard possible. Clearly, that didn't happen.
Fed up with the whole thing, George is sending me a new motor. I must say, that I have very mixed feelings about this. On one hand, I'm thrilled to be getting a motor that will hopefully have none of the flaws that have plagued this motor from it's first day. On the other hand, it just eats me up that this whole fiasco has cost George so much. Shipping to Illinois and back, twice, two rebuilds of the motor, and finally a whole new motor plus the shipping for that from Illinois. Dreadful! I had hoped to be one George's success stories.
While all of this is going on, I am planning a couple minor enhancements. I bought a voltage meter/display from Lightobject that can be programmed to cut a relay at a specific voltage. I'm thinking that I'd like to add that to the car as a safety backup in case the charger doesn't cut off in time. If this device sees the voltage rise to the level I've defined, it would trigger a relay that would simply cut power to the charger, protecting the batteries. Stay tuned.
Friday, February 24, 2012
Brushes and Carbon Dust
While at EVCCON 2011 I had the good fortune to catch a talk given by Tom Brunka from the Helwig Brush Company. Tom went into great detail about how brushes for DC motors work, the different properties they can posses depending on the way they are manufactured, and the care of brushes and motors. On the face of it, it seems this talk would be astoundingly boring, and in fact I think Jack Rickard scheduled it for the last talk of the conference precisely because he figured it would be lightly attended and would be in no danger of running long and interfering with the events planned for later that day. As it turned out, it was a truly fascinating talk and it went much longer than expected due to the fact that attendees started asking questions as soon as Tom finished and simply wouldn't let up. Eventually Jack had to put a halt to the exchange so that we could all go outside and race our cars. What a great time that was.
One of the things that Tom mentioned is that brushes will wear and break in at one rate, but once they are bedded in, they will wear at a completely different rate. The wear of the break-in rate is much higher than standard wear rate. But the interesting thing is, if you disturb the brushes, i.e. remove and replace them, lift them out of their holder, nudge them, breath on them, or even look at them askance, they will begin to wear at the break-in rate again. This level of wear has a couple of effects. First and perhaps most obvious, your brushes wear out faster. As a direct result of that faster wear rate you encounter the second issue, which is an accumulation of the dust that wore off the brushes on the inside of the motor. If you have the motor ventilated with forced air, some of that dust will be carried out of the motor's vents. But not all of it.
Such is what has happened with my motor. Faithful readers will remember that I have had the motor out of the car a couple of times due to a strange phenomenon where the balancing putty fell off the armature. On both occasions George Hamstra at Netgain motors, shipped the motor back to Warfield electric and had them repair it. In order to do so, they had to dis-assemble it. Now I didn't look at the brushes when the motor came home from the first repair so I don't know if new brushes were installed, but I did look at them the second time and they were the same brushes that were in the motor when it left. How do I know? Well new brushes are not contoured to fit perfectly against the armature when they are new. As I said earlier, they must be worn, or bedded in and this can take up to 5000 miles to do. But since the brushes had necessarily been removed during the motor's repair, that meant they were going to go through another instance of excessive wear and re-bedding; meaning more dust.
What does this have to do with my current situation? Well, all that carbon dust is conductive. After all, it's through that very carbon that the current is pushed to the armature of the motor. I have a fan on the motor, pushing 110 CFM of air through it and likely carrying out a good percentage of the carbon dust along with the heat it's meant to blow out. But clearly not all the dust is going out. Somewhere within the motor, some dust has piled up and allowed a small path for current to flow from the high voltage fields to the case. That's not good but apparently not unheard of. Normally, you simply blow the motor out with compressed air and the problem leaves the motor in a plume of black dust.
So, I charged up my compressor, took the shroud for the fan off the front of the motor and started blowing. There was plenty of dust. More than I expected. I thought this was great, it meant I likely fixed the problem. Unfortunately not. The problem is that in order to get all the necessary components in the car for it to function, Or simply because I'm very bad at designing things, all the components are crammed in there so tight it's difficult for me to get a nozzle in there to blow out every nook and cranny. But my blow gun's nozzle is right at the end of the trigger limiting where I can really point it.
I've exchanged some emails with George and he suspects that the brushes in the motor right now are a high performance brush called H49 which do great for racing, but tend to dust a lot. He thinks that the H60 brushes, which are a harder, street grade brush would be better suited for my build with the added benefit that they will produce less dust. He's decided to send me a set of these at no expense. Well, no expense to me. They normally run over $300 a set and George is picking up the bill. To say that George is fed up with my motor is an understatement. He's stated that he will not RMA the motor again. Meaning, if it ever has another problem, he intends to replace it. Believe me when I say that it's very comforting knowing that he will stand behind the motor so resolutely. For now, I just don't see a reason to do that, and here's why.
The new brushes will arrive early next week. I've ordered a blow gun for my compressor with a 12" flexible hose which will allow me to better squirt air in all the nooks and crannies inside the motor. I'll remove the old brushes, and push 8 or 10 tanks of air through the motor, then replace the brushes. If all goes well, I should see the short go away. Depending on the temperature, and consequently the time of day, the resistance of that short fluctuates between 1.18K Ohms, and .85K Ohms. That means a potential leak of current in the range of 135 to 188 milliamps. If I can't resolve the short and I have to take the motor out of the car then I'll have to decide whether I want to try to disassemble it to clean it, or simply give George the go-ahead to send out a replacement. I really don't want to do that though.
One of the things that Tom mentioned is that brushes will wear and break in at one rate, but once they are bedded in, they will wear at a completely different rate. The wear of the break-in rate is much higher than standard wear rate. But the interesting thing is, if you disturb the brushes, i.e. remove and replace them, lift them out of their holder, nudge them, breath on them, or even look at them askance, they will begin to wear at the break-in rate again. This level of wear has a couple of effects. First and perhaps most obvious, your brushes wear out faster. As a direct result of that faster wear rate you encounter the second issue, which is an accumulation of the dust that wore off the brushes on the inside of the motor. If you have the motor ventilated with forced air, some of that dust will be carried out of the motor's vents. But not all of it.
Such is what has happened with my motor. Faithful readers will remember that I have had the motor out of the car a couple of times due to a strange phenomenon where the balancing putty fell off the armature. On both occasions George Hamstra at Netgain motors, shipped the motor back to Warfield electric and had them repair it. In order to do so, they had to dis-assemble it. Now I didn't look at the brushes when the motor came home from the first repair so I don't know if new brushes were installed, but I did look at them the second time and they were the same brushes that were in the motor when it left. How do I know? Well new brushes are not contoured to fit perfectly against the armature when they are new. As I said earlier, they must be worn, or bedded in and this can take up to 5000 miles to do. But since the brushes had necessarily been removed during the motor's repair, that meant they were going to go through another instance of excessive wear and re-bedding; meaning more dust.
What does this have to do with my current situation? Well, all that carbon dust is conductive. After all, it's through that very carbon that the current is pushed to the armature of the motor. I have a fan on the motor, pushing 110 CFM of air through it and likely carrying out a good percentage of the carbon dust along with the heat it's meant to blow out. But clearly not all the dust is going out. Somewhere within the motor, some dust has piled up and allowed a small path for current to flow from the high voltage fields to the case. That's not good but apparently not unheard of. Normally, you simply blow the motor out with compressed air and the problem leaves the motor in a plume of black dust.
So, I charged up my compressor, took the shroud for the fan off the front of the motor and started blowing. There was plenty of dust. More than I expected. I thought this was great, it meant I likely fixed the problem. Unfortunately not. The problem is that in order to get all the necessary components in the car for it to function, Or simply because I'm very bad at designing things, all the components are crammed in there so tight it's difficult for me to get a nozzle in there to blow out every nook and cranny. But my blow gun's nozzle is right at the end of the trigger limiting where I can really point it.
I've exchanged some emails with George and he suspects that the brushes in the motor right now are a high performance brush called H49 which do great for racing, but tend to dust a lot. He thinks that the H60 brushes, which are a harder, street grade brush would be better suited for my build with the added benefit that they will produce less dust. He's decided to send me a set of these at no expense. Well, no expense to me. They normally run over $300 a set and George is picking up the bill. To say that George is fed up with my motor is an understatement. He's stated that he will not RMA the motor again. Meaning, if it ever has another problem, he intends to replace it. Believe me when I say that it's very comforting knowing that he will stand behind the motor so resolutely. For now, I just don't see a reason to do that, and here's why.
The new brushes will arrive early next week. I've ordered a blow gun for my compressor with a 12" flexible hose which will allow me to better squirt air in all the nooks and crannies inside the motor. I'll remove the old brushes, and push 8 or 10 tanks of air through the motor, then replace the brushes. If all goes well, I should see the short go away. Depending on the temperature, and consequently the time of day, the resistance of that short fluctuates between 1.18K Ohms, and .85K Ohms. That means a potential leak of current in the range of 135 to 188 milliamps. If I can't resolve the short and I have to take the motor out of the car then I'll have to decide whether I want to try to disassemble it to clean it, or simply give George the go-ahead to send out a replacement. I really don't want to do that though.
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