Apparently Late Night Math is Not My Strong Suit

Lots done today. Let's take a look at some of it.


This is the new location for the shunt. It's at the front right corner of the back battery rack. I had to cut and re-crimp a couple cables to get them the right length, but it worked out well.


Just to the left of that is the emergency breaker, or battery disconnect. I had thought that I'd mount it dead center on the back rack, but the cable for the positive feed to the contactor didn't reach the extra 2 inches. The symmetry in the engine bay will be off, which is kind of too bad.


Here's a shot of the new throttle assembly set up, installed and tested. It's difficult to make out what's what here, so I'll take another once the batteries are in. But you can see the cable anchor in the right side of the picture, and the pedal assembly just to the left of center.


And last we have a shot of the whole assembly mounted in place with the back row of batteries resting in their place as well. There's a bit more tie down work to do, then I can install the front row.

In addition to all that, I also got a few other things done. I re-installed the tray under the motor that holds the fan for the motor as well as the box that contains the new vacuum pump. I ran all the necessary power lines to the items and the vacuum line from the pump to the reservoir. I also installed the new cross brace that stiffens the chassis.

I don't think I mentioned it before, but the fellow that owned the car before me clearly ran it up on a curb or something. There was a bit of damage under the car, mostly cosmetic. However, the original cross brace took most of the abuse, and was a bit twisted. It still fit in place, but was very difficult to bolt in and was under stress once in place. The new one slipped on so easy, it was a pleasure bolting it on the car.

Which brings me to the odd title of this post. You may remember that I had 31 batteries up front in the original configuration. During the rework, I drew up multiple designs trying to get the cleanest install of all the batteries in as tidy a package as I could. Well one night, very late I came up with this design. It is the cleanest by far and I'm very pleased with it. There's just one nagging problem. There are 12 batteries in the front row, and then two rows of 9 in the back rack. In most worlds, that adds up to 30. Apparently for me, in the middle of the night, that sometimes equals 31.

For the life of me, I don't know why I never added them up again, but I didn't. (This is the part where you all laugh at me.) After standing and shaking my head in disbelief, I started laughing at myself. But eventually I started thinking about it objectively. This really was the cleanest design I'd come up with, and it's going to look great. I don't think I want to change it, or would have if I realized it at the time. There is room for one more battery in the trunk box. It will make the end of the box a bit cramped, and I'll have to redo some of the lines in there, but I think it's going to be worth it in the long run.

The worst thing is that it will delay my relaunch by a day or so.

New Battery Rack is Done

I didn't post much last week because I didn't work much last week. At least not on the car. 60 hours at work kind of steals all your time. And much of your will to live. But that's all behind us now and I'm back to working on the car!

The battery rack that will be mounted over the motor is done!


In this shot the part nearest the front of the picture will mount closest to the fire wall. I've placed a couple batteries in it so you can get a sense of scale. You might have noticed a slight rise in the cross beam the batteries rest on. There was no way to mount them straight across because the motor was in the way. Those cross members have a five centimeter rise from the edge to the center of the rack.

I also worked out the throttle assembly which is mount on the left side of the rack. Here's a shot of the left side.

I need to build some sort of enclosure for the throttle pedal to keep the dust and water off of it. On the opposite side, I need to mount the shunt for the Link-10 meter. That should be pretty easy, it should bolt straight to the new frame with out any problems.

I've built the rack big enough that I'll still have room to use some of the clamps that came with the batteries so compress them together, helping to prevent them from swelling (as one astute reader pointed out). I may need to address that issue for the batteries in the trunk box at some point as well.

Perhaps the best news is that I've realized I will be able to use the existing front battery tray the way it is, with only some minor modifications. When looking at my measurements of the space from before, I neglected to take into account that they included the white plastic boxes the batteries were originally mounted in. Well, I won't be using those boxes which means I gain 1/4 of an inch. Along with moving the front rack back by about an inch, I'll have about 1.25" between the top of the battery strap and the hood. In fact, I will be able to put the sound deadening cushion that was affixed to the bottom side of the hood back on, with room to spare.

But the best thing about that is that I don't have to re-figure and rebuild the brace that holds the power steering pump, which is suspended below that rack. I was at a loss for how I was going to handle that, but now I don't have to at all. It just means I'll be back on the road that much sooner.

Some Tests

Though I haven't heard back from the distributor of the batteries yet about the discharge capacity, I feel safe in saying that my original belief was true. These batteries are capable of putting out the current I'm asking them to dump. A kind reader of the blog pointed me to a great page at EV Works that detailed some tests they performed on the Sky Energy and Thunder Sky batteries. The tests reveal many things, but key among them is the discharge potential. So at this point, I feel safe saying the batteries are not the issue.

I took some measurements on the HEPI pedal yesterday. There are 6 wires coming from the pedal. One is a 5 volt power (Red), one is ground (Black), and the others are signal wires. The voltage on the signal wires changes as the pedal is depressed. Here's what I found.

In the up, or "not depressed" position
Red - 4.94 V
Green - 1.58 V
White - 4.94 V
Orange - .792 V

Fully depressed position
Red - 4.94 V
Green - 4.83 V
White - 4.94 V
Orange - 4.33 V

It would seem that the White wire is also just providing power. Truthfully, I don't know if the differences in these readings has any significance, but I find it interesting that neither the Green nor Orange wire come up to the full 4.94 Volts when depressed. But even more interesting is the fact that the Green and Orange wire don't match. My understanding is that the pedal has two sensors in it for redundancy. I would think that would mean the voltage they put out should match, but that's just an assumption. I'll be sending this data off to the distributor I bought the pedal from to ask for help and assistance.

The Zilla controller has the ability to put out a stream of data for diagnostic acquisition or DAQ. All the data is displayed in Hex format, at the rate of 10 lines per second. I connected my MacBook to the Zilla, set everything up and then captured some data during a full, pedal to the floor, acceleration. Once I had the data, I imported it into a spread sheet and converted all the Hex to decimal. What I found backed up what I was experiencing. Under full acceleration the current across the motor's armature peaked at 150 amps.

So, what did we learn from all this? I think all I really learned was that the Zilla is indeed sending a fraction of the current to the motor that it's capable of. And it re-enforces my previous beliefs that it's either the pedal, or the Zilla. Now that I have some data, it's time to get the manufacturers and distributors involved.

By the way, thanks to all that have been offering help and advice! It's truly appreciated.

Throttle Assembly II

Today I visited my accountant Bob. One year ago I told Bob about this project and he's been following it ever since. As I walked into the office, he was unwinding an extension cord saying "We've been expecting you." It was hilarious. Sadly though, I couldn't help but feel little disappointed that I wasn't driving the Z3. Bob was kind enough to help me get the ONE and ONLY tax credit that I can for this entire endeavor; $75 for the installation of the charging station in the garage. Buy an electric car and the government throws money at you. Build one and they have nothing for you. Of course that's not why I'm doing it, so on to the build

Once I got home I started working and got a few things done. Remember that I had to redo the charging port in the car to handle the higher current? Well the one part I hadn't done yet was upgrade the connection from the plug under the gas cap to the charger itself. I took off the connectors that were there and installed proper 50 amp Anderson connectors. Easy work, but important.

Next I installed the first of the smaller battery boxes up front. Not difficult, just time consuming working in the tight space. Once that was in, I was able to do the final work on the throttle assembly.

In the picture, the firewall is off to the right. The throttle pedal is sitting in the newly installed smaller battery box, and the bracket you see to the right is mounted to the larger box I was working on last week. The pulling distance on the pedal is perfect. When I push the pedal in the cabin all the way to the floor, it pulls this pedal it's full throw. I built this Rube Goldberg device because it just seemed better than cutting up the factory pedal assembly and trying to rebuild it and fit in the new pedal. I just couldn't envision that going well.

The rest of the day I worked on cutting, bending and fitting some of the aluminum straps I'll be using to anchor the batteries. I'll work on getting the last box in tomorrow and finishing up the straps. I'm waiting on some ring connectors to come before I can start running all the interconnects between all the batteries.

Throttle Assembly

Today I sorted out the throttle assembly, and it turned out pretty good. Here's a quick shot:


The first thing I built was swage assembly where the throttle cable terminates. It holds a plastic spacer that holds the cable in place in the assembly. The swage assembly is held in place on a screw that I've put through the pedal arm. As you can see, I've sawed the pedal it's self off.

The cable was originally passed through and was mounted to a metal plate. You can see on the right side, I've built something that approximates that piece. The cable goes though that piece of steel, and is held in place by a bushing. You can turn that piece behind the bushing to move it closer or further from the connection point at the end, essentially for fine adjustments to the throttle cable position. (Eventually the C clamp will give way to a permanent mount on the box.)

The cable has 46 mm of travel from when the pedal in the car is up to fully floored. I've measured and mounted it the assembly carefully so that it also has exactly 46 mm of travel. Of course with the fine adjustments I can make to the cable in, and a movable hard stop located under the pedal in the car, I should be able to get it exactly right.

I tested the pedal and it's a bit stiffer than I would have liked, but such is life.

Over the weekend I wrote down a list of everything left to do at this point. There are 43 items on the list, 14 of which are dependent on the batteries being here in the garage. Well I found out yesterday that the soonest they will arrive is the end of November. That means I have roughly 3 weeks to do the remaining 29 items. Today I knocked 3 off, so I'm down to 26. I'm sure that others tasks will be added to the list as things pop up, but overall, I'd say I'm making good progress.

Fitting Details

Over the past few days I've come to realize that it's time to solve some of the problems that have been nagging me for months. There was only one way to solve them, and that was through careful planning, measuring and fitting. Boring, maybe; necessary, absolutely.

There are three components to the high voltage lines that I need to find a home for. There's the rather large push button kill switch. If things go horribly wrong, or I need to work on the car and I want the battery pack disengaged, that switch will allow me to take care of that. There's the 500 amp shunt for the instrumentation. It allows the Link 10 meter to monitor the pack without "seeing" the full amperage, which would fry the meter. Last, there's the fuse. And that thing is big. It's about 5 inches long and the diameter of a half dollar coin.

I had originally thought that I'd put each of those in the trunk near the back battery box, but after thinking about it, I realized that would be kind of stupid. All 48 of the batteries will be wired in series, starting at one end (the trunk) and moving to the front. In order to put the disconnect and the shunt in the trunk, I'd have to run a line from the negative terminal up front all the way back to the trunk for those components, and then run it back up to the front again to the controller. A better answer was to find a place up front.

I put all the battery trays and boxes in place, just looking for extra space somewhere around them. While doing that, I remembered that the way the new batteries will be laid out in the two small trays means there will be some space left over on the ends. It had never occurred to me that I might use that space in a tray for something other than a battery, but when I got to looking, I realized it would work just fine for the disconnect switch. Some quick fabrication, and I had it mounted. I still need to locate the shunt, but it's small. The fuse can still go in back because it only needs to be inline on the positive side.

Can't miss that sucker!

On top of that, I found a location for the throttle pedal. The pedal is meant to be a direct replacement for the pedal that came with the car. But Trust me, if you saw the new pedal and the car's pedal assembly, you'd say the same thing I did, "Oh, there's no way..." Well, not without taking the whole assembly out of the car, cutting it up, welding new bits to it at odd angles and refitting it. Well, I realized that extra space in the second box may work out for me, and it did.


Obviously it's not mounted up yet, just propped into place. But you can see that it fits nicely in the space, and you can see the car's existing throttle cable just peeking over the corner of the tray is in perfect alignment to mount to the pedal. Basically what I'll do is lop off the pedal part, and mount a swivel harness to the remaining stump. When I press on the car's accelerator pedal, it will pull that cable and activate the new throttle assembly. How great is that!? Well, it excited me.