Thursday, February 25, 2010

Odds & Ends Part XII

Well, there isn't a lot to do these days. I'm still waiting for the replacement tachometer, so it's given me the opportunity to fiddle around the car and clean things up or tie up some loose ends.

Over the past couple days I've run more wiring loom to contain all the exposed wires. I re-wired the fog lights so that they will come on whenever the car is on. I'm waiting on the LED lights to replace the halogen bulbs that were in the fog lights, but that will take only moments to finish up. I put connectors on all of the wires that are sticking out of the dash in preparation for the new tachometer. And I vacuumed the inside of the car. Like I said, there's not a lot to do.

I'm hoping that once the tach comes, it won't be too hard to fit into the space in the instrument cluster. Once I get that in, then I can re-install the instrument cluster, re-install the airbag and steering wheel, and then roll it out of the garage. Keep an eye out, I'll be posting a video tour of the car, and it's maiden voyage.

Wednesday, February 24, 2010

Instrument Cluster

When I had first started up the car last week, I had plugged in the instrument console to see what I would get. As I mentioned before, the speedometer worked, which was a big relief. Obviously, the fuel gauge and the temperature gauge did not. Curiously, the fuel gauge was pegged at Empty and temperature sensor showed the car was over heating.

In addition to that, were numerous warning lights that simply wouldn't, and won't go out. There was the Traction Control warning, Low Fuel lamp, over heating warning, ABS light, and of course the Check Engine light. Most of those lights (with the exception of the Check Engine light) I simply removed from the back of the console. They'll never go out, so there's no point in having them there. Of course the other thing that didn't work was the tachometer.

Since I need to replace the tachometer, I want to try to get the new one to look as stock as possible. I realize that the Fates are not behind me on this, but I'm going to try anyway. I want to fit the new one where the old one is. I opened up the cluster to remove the existing tachometer. Here's a shot of the cluster; notice no needle for the tach:

I've ordered a replacement that should fit in the space, and match somewhat closely. The dial is 3 and 3/8" round, it has white numbers and markings that glow red at night; the stock glows orange, but orange wasn't an option. The needle will be white and remain white when illuminated. I'm going to have to carefully cut out the old dial so the new one will fit. So I took the assembly apart so I could get to it.

You can see the old tachometer at the bottom of this shot. It fit into that space just above it in the assembly. If you look at the dial area on the assembly, you'll see a raised piece of plastic that traces the perimeter of the dial at the top with a sort of staggered look to it. That is there simply to distribute light around the dial. I'll likely have to cut the dial out, leaving that light distributor, as well as leaving enough plastic on either side so as not to compromise the structural integrity of the whole assembly. It doesn't need to be too stout, but it does need to hold together while I put it all back together. You can also see in the picture that I've put some shrink tubing on the pins for temperature sensor to the left. I did the same for the gas gauge. This way, they'll just be dead in the console.

I mentioned that I didn't remove the light bulb for the Check Engine light. That's because I intend to use that for the Zilla controller. If the Zilla recognizes a fault situation, it will illuminate that warning light. I've soldered a wire to the circuit board on the back to route the signal to it.

The yellow wire will be connected to a lead that is already in place and runs to the Zilla. The red wire will provide power to the new tachometer for the back lighting. That wire is soldered to the board on a place that only has power when the dash lights are on. So far, so good. Now I just need to wait for the new gauge to show up.

Yesterday, I did one other thing. I thought I'd re-assemble the passenger side dashboard, glove box and all. But last week as I started to fit everything I realized that I'd placed the fuse for the Link 10 meter in a place that can only be accessed if I disassemble the dash. Well that won't do, so I moved it to the electrics bay for easier access.

This means I'll have to re-program the Link 10, which will be OK. Apparently I did something wrong with the first go at programing it. When I came out to look at the care Tuesday, the "Gas gauge" showed that there was only 34 % of the battery's capacity remaining. I know that's not true. While there is a draw on the batteries when the car is off, it's on the order of milliamps. In fact the meter showed that I'd only used 1/2 a kWh since I'd charged the car. That seemed about right with all the testing I've done. But if the meter thinks the batteries have only 34% capacity remaining after I've used 1/2 kWh, then it's set wrong. So, I'll have to sort that out.

Friday, February 19, 2010

Testing the RPM Sensors

Today, I downloaded and set up a program that John Lussmyer wrote called ZillaConfig. It's essentially a desktop application that connects to the Zilla controller and provides you with a desktop window for configuration. It's really pretty slick. If you interested, you can get it here.

But perhaps the neatest thing it does is allow you real time graph of the Zilla's output while the car is running. You can watch motor current, throttle position and lots of other things, including RPM. So, with the ZillaConfig program loaded up and running on my laptop, I set off for testing.

Loyal readers (both of you) will remember that I installed both sensors on the car a few weeks ago; however, I could only wire one up to the Zilla at a time. So first up was the older style sensor that sits on the end of the tail shaft.

I decided the best way to test would be to put the car in first gear and spin the wheels up to 10 MPH, then 15, 20 and 25, taking RPM readings at each point. Simple enough. I ran the test on the old sensor, and then swapped the leads to the Zilla and re-ran the test with the newer sensor. Here are the results:

Old Sensor
10 MPH = 1600 RPM
15 MPH = 2500 RPM
20 MPH = 3400 RPM
25 MPH = 4300 RPM

Huh, I just noticed that there's a 900 RPM difference between each entry. Anyway, here are the results of the second, or newer style sensor:

New Sensor
10 MPH = 2500 RPM
15 MPH = 3700 RPM
20 MPH = 5000 RPM
25 MPH = -

The Zilla wouldn't let me over 5000 RPM, so I couldn't get to 25 MPH. Clearly, the two sensors are not sending the same signal to the controller. Bad news for me. I need to use an RPM sensor to protect the motor from over spinning it, so doing without really isn't an option. But if the only one I can use is the older one, that means the end of the tail shaft is occupied by the sensor. That in turn means that there is no room for the pulley that I need to use to drive the A/C system. In short, old RPM sensor equals a very hot summer in the Z3.

There are a couple rays of hope on the horizon. First, the supplier that I got the sensor from is working with the manufacturer to find out what can be done, if anything, to make it work. Second, I could have a piece machined that would screw into the tail shaft and extend it by an inch or so. While not optimal, that would work.

Before I run off and have that piece made, I need to go to an A/C shop and have them look at the car and determine if it's even feasible to run the lines needed in the very cramped spot the compressor sits in. Of course I can't do that until the car is out of the garage. That tachometer can't come soon enough!

Thursday, February 18, 2010

Testing the Heater

I realized today that I've never tested the heater. I tested all the various wires, relays and switches that are installed to provide power to it, but since it runs off the full pack voltage and I haven't had that until only recently, I couldn't test it. Well now I can.

I turned the car on, turned the fan switch to "4", which makes the heater switch live, and then flipped the switch. I was watching the Link 10 to see if I'd see an increase in the current being drawn and sure enough, it jumped a bit. Truthfully, the amp numbers on the meter don't make sense to me just yet, but I know a bigger number means more draw. Anyway, I put my hands over the vents that were pumping out cold air, and waited for the heat to arrive thinking "oh this is gonna be good."

I could smell some vague burning type odor, which made me a bit nervous. Kind of what you'd expect to smell the first time you turn on a heater, with any residual oils being burnt off. I waited for 20 seconds or so, no heat yet. Meanwhile the smell was increasing. Hmm, not good. Another 30 seconds or so and still cold, but now the smell seems to be subsiding. So that's good.

Another 1/2 minute goes by and I'm beginning to think that I'd made a mistake wiring this heater so that it only worked when the fan is on high. Clearly that much air moving through it is rendering it useless. By now the alarming smells have all but gone, so my initial fears of burning the car, and my house to the ground have subsided. I look down under the dash to where it's installed. No fires, no smoke, but I can feel heat near the pocket. It's at that point that I look at the center console and realize that the temperature control is all the way to cold. Take a look at yesterday's post and the picture of the center console. See it there? Set to cold? Yeah, me too.

Feeling a bit foolish, I casually reach up and nudge the dial to the hot side. Wouldn't you know it, tons of lovely warm air come streaming out of the vents. Apparently, if you allow air to flow over the heater, it's much more effective.

With the heater tested, and having successfully not burned up the car, I felt it was OK to go ahead and re-assemble the dashboard on the driver's side. I carefully put all the metal supports and plastic pieces back together being sure not to pinch any of the new wires under there.

I'm considering turning the fog lights into daytime running lights. Right now they only come on if the switch is on and the headlight switch is on in the "running lights" position or just on. The thing is, we don't have much need for fog lamps here in Arizona. In the 38 years I've been here, I've seen fog - oh let's see... twice. And it wasn't thick enough that one needed fog lamps. It was more of an atmospheric anomaly. People came out of their houses to point in wonder at the air which was something other than the usual clear and sunny. Old folks reminisced about the fog they'd seen one time back in the 30's, and children ran around trying to catch it. Then, in 20 minutes, it was gone. So I think that running lights may be a better use for the fog lights.

I figured I'd get a couple of super bright LED lights, and switch the wiring a bit so that they are just on when ever the car is. Those LED lights aren't bright enough that you'd want to rely on them to drive at night, but you can see them during the day quite nice. If I can make the car just a little safer, I think it would be worth it. Total cost should be less than $30.

Wednesday, February 17, 2010

The Home Stretch

I took care of a few more odds and ends today. Installed the new radio.

There's the new radio. Just above the gear shift is the Link 10 I've mentioned in other posts. It's reading 160 Volts at the moment. I can cycle it through the current Amps being drawn off the pack, the total number of kWh's drawn since the last charge, and the percentage of charge left. The little green lights across the top are the "fuel gauge". The switch just to the left of the Link 10 is the new switch for the heater.

I also ran all the wires that go from the back of the car to the front, or vice-versa, in a wire loom. Those wires all go under the car in the transmission/drive shaft tunnel. I then anchored it, as well as the battery cables that run up front, to the chassis. That was long tedious work that I'm glad I only had to do once.

To protect all that wire, and to help make the car a bit more slippery through the air, I covered up the tunnel as best I could with some left over sheets of aluminum.

That first seam there looks crooked, but it's not really. The front piece was slightly longer on one side. To get each plate to stand off from the chassis evenly, I used a 1 inch nylon dowel, cut into the proper lengths as stand offs. There were several screws and bolts sticking down from the chassis that had been used to hold either heat shielding for the exhaust or the fuel system. I simply cut a proper length of dowel, drilled a hole in it on one end and then screwed it onto the existing bolt or screw. Once they were all event I screwed the aluminum to them for a nice flush surface. I don't know if it will make any difference in the drag coefficient of the car, but it protects the motor and the wires.

I also finished cutting the carpet and the plastic trim pieces that had been in the trunk and refit them as best I could.

I need to get some Velcro to hold down the back corners of the flooring, but it turned out pretty good. The floor of the trunk is about 1/2" higher than it was and it's a bit wobbly. I'll see if I can't shim it later on sometime. Eventually I'm going to have to figure out some way to keep groceries from falling into the equipment in the back. For now, I'll probably just get a plastic crate or two.

Well, that's just about it. The only thing left is to install the new tachometer when it arrives, and then re-assemble the dashboard. I desperately want to drive it around, but it will be easier to do all that while it's still up on the jack stands. So, for now, it stays put.

Tuesday, February 16, 2010

Charger Set Up and More

Well, after the initial test, and after the excitement passed of seeing the wheels spin, it was time to get back to work so I can actually get the car out of the garage.

Here's a quick rundown.

  • Ran power from the main battery pack to the DC to DC converters
  • Hooked the DC to DC converters up to the auxiliary battery
  • Tested the output of the converters while car is off and while it's running
  • Installed all the inline fuses for the Zilla controller and Link 10 meter
  • Connected the reverse lights to the reverse switch in the transmission
  • Went through the menus and set up the Link 10 meter
  • Went through the Zilla's configuration menu and set that up
  • Cut and refit all the carpet and plastic parts for the trunk
  • Checked the air pressure on all the tires, set them all to 40 PSI
  • Charged the batteries completely and set up the charger
Setting up the charger was a pretty straight forward task, but it took a long time. Five hours to be exact. The reason it took so long is because the batteries come with only something like a 40% charge. Apparently that's how you're suppose to leave them if you're not going to use them for a while. Anyway, when charging these batteries, you need to be careful that you don't go over the manufacturer's recommended 3.6 Volts per battery. In reality, even that's a bit high. The manufacturer even states that you'll extend the life of the batteries if you leave them slightly under charged.

To keep them safe, and extend their lives, I've opted for a target charge of 3.5 Volts per battery; times 48 batteries equals 168 Volts. I didn't come up with this value on my own, I learned a great deal from Jack Rickard and his web site: EVTV.ME . Jack has done a hell of a job exploring the limits of these batteries, posting the results and explaining what he's learned from doing so.

So with the target of 168 Volts, I plugged in the car and started pushing some current to the batteries. The charger can read the pack voltage, and it has a potentiometer that allows you to set the voltage you're pushing. Once the pack reaches the voltage you want, you turn the potentiometer down until a light comes on. That indicates the target voltage has been reached and the charger goes into a timer mode and backs down the current until it switches off.

The whole endeavor took 5 hours, with me checking voltage every 5 minutes to be sure I didn't miss the target. It was a long day, but I got the charger set, and I only had to do it once.

I ordered a replacement for the stock tachometer. I fiddled with it for an hour and couldn't make it move at all. It's too bad, I really wanted the stock look. But I found a place on line that makes custom ones, with what ever color numbers printed that you want, what ever background light, a number of fonts to choose from etc. And it was very reasonable at $120. The bad news is 7 days before it ships.

More tomorrow!


First test, and everything worked perfectly! Well, almost everything, more on that in a sec.

I hooked up the last component to the battery pack, the DC to DC converters, and checked everything again. All checked out. I threw the main breaker and the Zilla came to life. I turned the key and all of the components came on. I slowly pushed the pedal. I could hear the motor spin, but no wheel movement. Doh! It's in neutral. Put it in gear and they started spinning away.

The speedometer works! No modifications needed. That's good news. The only bad thing is that the vacuum pump for the brakes didn't come on. I fiddled with the wires and it came on for a second. Checked everything with a meter, and it's all wires are good. It' looks like the pressure switch may be bad.

Going out to work on more stuff, so more later.


Monday, February 15, 2010

Odds & Ends Part XI

Let's start with a list of things I did today...

  • Installed high voltage (HV) fuse
  • Ran +HV line from trunk to fuse
  • Ran +HV line from fuse to breaker
  • Ran -HV line from trunk to forward batteries
  • Ran -HV line from shunt to controller
  • Ran +HV line from breaker to contactor
  • Re-routed signal wires away from HV cables
  • Attached all signal wires for the Link10 monitor
  • Attached throttle control wires to the Zilla controller
  • Attached the RPM sensor wires to the Zilla
  • Connected the hairball (Zilla's brain) to the Zilla controller
  • Attached wires for heater to the battery
  • Attached charger to the battery

Here's a shot of the breaker and the shunt to the right and above it. As I was running all the wires to those two, I realized that there was no safe way to get all those wires in place while the batteries on the right side of the picture were in place. So, I had to disassemble the pack in that box to get that work done.

Here's a shot of the fuse I installed today. That fuse can easily handle the 1000 amps I could draw from the battery pack. But it would blow quickly in the event of a dead short.

Here's the zilla controller at the bottom of the frame, and the hairball at the top. I think I've got all the components wired to it at this point. In fact, I think I'm ready to test the system and see if I can spin the wheels. But before I do, I think I'll go over the wiring of each item, just to make sure I haven't made any bone-headed mistakes.

Friday, February 12, 2010

Installing Batteries Part IV

The batteries are all in the car!

It took about 3 hours to finish up the front box there, and I'm done. Which is a good thing because I'm tired of all the scraped knuckles and pinched fingers. Those batteries are not pleasant to work with.

The pack of batteries in the trunk are still isolated from the ones up front, so I need to run the lines between them. After that I need to start running all the remaining high voltage lines that I haven't built yet.

Thursday, February 11, 2010

Batteries, Nothing but Batteries

Another day spent fitting batteries into the car. The first part of the day, I finished up the battery box closest to the firewall.

It's surprising just how long this takes to do. In spite of being exceedingly careful, I had one mishap today that really scared me. I was installing an interconnect on one of the front batteries there. I had the bolt in, but not cinched down, so the strap was still free to move. The strap slipped out of my hand and casually swung down to land on the one below that. There were lots of sparks, my heart raced, and I think there may have been a few expletives shouted. Fortunately the two straps of copper didn't weld themselves together and short the batteries. Man that would have been bad. Instead, it bounced and landed harmlessly on an edge of plasitc. So, new method; I'm securing the first interconnect to the battery before it goes onto the stack.

With the new method, the next boxes' install went without incident.

The only change I had to make was to move the shunt from it's original position. If you look on the forward box all the way to the left side, you'll see an object made of brass on a black base. That's the sunt and it was originally going to be a little to the right and horizontal. But the batteries in the forward box would interfere with it, so I had to move it. The shunt allows the car's new Link10 meter to measure the high amps without letting out the blue smoke. You attach the high voltage lines to the big bolts, and most of the current goes between those two brass blocks over the thin plates between them. On the other side are a couple of small screws you attach the meter's wires to, one on each block. The shunt allows only a few milliamps to go down the wires attached to the screws. Since the amperage is scaled down so much, a small sensitive piece of electronics can measure 500 amps without catching fire.

Getting close. I have to install the last 8 batteries, run a bunch of high voltage lines, install the fuse and start re-assembling the inside of the car. I think my goal of getting it off the jack stands and on the road by the end of the month is totally feasible.

Wednesday, February 10, 2010

Installing Batteries Part III

Today I got the final box in place, anchored down and ready to hold the batteries. I spent a great deal of time making all the pieces that will hold the batteries down and in place.

Shortly after noon, the mail came and delivered the rings that I've been needing for all the testing lines. I mounted the bus bars, two in the front and two in the back. Then I started wiring each set of 4 batteries to the bus bars so that I can test the voltage on each group easily. I got the ones in the back of the car done because all those batteries are in place and wired together already.

The bottom bus has all the leads going to the positive side, and the ones on top to the negative. After I wired them together, I took a reading off of each group and they all came up the same, 13.18 volts. This way I can move down the line, testing one group after another and look for any anomalies. I still need to label the wires at the bus bars and the battery groups for easy identification.

So at this point, half the batteries are in place and secured down. Tomorrow, I'll try to get the other half in place. I still have to build all the 2/0 cables I'm going to need to jump from one box to the other, and those are time consuming, plus I need more heat shrink tubing.

Tuesday, February 9, 2010

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.

Thursday, February 4, 2010

RPM Sensor Mount

Yesterday I finished fabricating the mount for the two RPM sensors. Regular readers will remember that the older style sensor is guaranteed to work with the Zilla controller, but it interferes with my ability to use the tail shaft of the motor to run the A/C compressor. The newer one will allow me to use the tail shaft, but has never been tried with the Zilla. I'm going to find out if it will work.

This is a side shot of the motor's tail shaft with the RPM sensors attached. On the right hand side, closest to the motor you can see the sensor with the wires protruding toward the camera. that ring just in front of it is the exciter ring mounted on the shaft of the motor. You can see that the rest of the shaft would be free if the second, older style sensor were not mounted over the end of the shaft, which you can see on the left. It has a little black cup (which you can see) mounted over a magnet (which you can't see) that is screwed onto the end of the tail shaft. The whole point of having both mounted at the same time is so that once I get the motor spinning, I can simply swap which leads are attached to the controller and monitor the output from each.

The controller expects four pulses per revolution, which each sensor can do. I don't expect there will be a problem with either, but I'm really hoping the newer style one works, or it's no A/C for me!

I must have an RPM sensor on the motor. The motor's red line is 5500 RPM. It will tolerate higher speeds for short times, but not for sustained periods. The danger is that the all the copper in the motor will unwind off of the armature, thus destroying the motor. The controller has a feature that will allow me to set a red line that the controller simply won't pass. Of course I have to be careful and not drop the car in the wrong gear and over spin the motor. You can also set the controller so that it limits the RPM to a much lower number when the car is in reverse. That should be handy. But one of the coolest features is called Valet mode. All I have to do is press a button (yet to be installed) and it tells the controller to put it in Valet mode. I can set that up so that the controller limits current and RPM of the motor. Essentially keeping someone who isn't used to the car (a valet, mechanic, or teenager) from taking off like a nut.

After I finished that I got to work on the large battery box up front. I managed to get the brackets made and half the batteries installed and fastened down.

That was exceedingly difficult, the spaces are very tight. Notice that gap between the top of the battery on the right hand side and the bracket? I'll be shimming that somehow. You'll also notice that the terminals on the batteries are facing each other, which probably alarms the more astute readers. If they were to touch... It's kind of like crossing the streams. you don't want to allow that to happen. Well the brackets won't allow them to move closer than they are toward each other. But to be certain, I'll be placing some non conductive material between them just to be sure.

Today I had planned on finishing the battery installation on this box, but it looks like that's going to have to wait. I'm under doctor's orders not to lift anything heavy for two weeks. *Sigh* The other day I pinched a nerve in my neck and lost all feeling in my left arm. I can assure you that was a bit scary. But all is well. The Dr. has put me on anti-inflammatory medication and want's me to take it easy for two weeks. I'm sure lifting one battery at a time isn't a problem, but wrestling with stacks of 4 is probably not wise. I think progress will slow for a while. I'm going to see how much other stuff I can get done in the mean time.

Monday, February 1, 2010

Installing Batteries Part II

In the last post I mentioned that I'd finished the mounting brackets for the A/C compressor and here is the picture I promised of the whole assembly.

You can see there are two aluminum angle pieces that are mounted to the face of the motor. The bottom one supports the compressor directly while the top one is bolted to the black bracket attached directly to the compressor. There is a slot in the top aluminum piece that allows me to adjust belt tension by pivoting the assembly back and forth. Now I need to get a belt.

The last thing will be taking the car down to an A/C shop to have some custom hoses made. Truthfully, I'm kind of worried about that. The space is so cramped that it will be hard to work in unless I dis-assemble parts of the car. That means driving it there, taking it apart at their garage, and then re-assembling it when they are done. Hmmm.... we'll see how that goes.

The big news today is that I finished the work on the back battery box. All the batteries are securely mounted in the box. There is plenty of room to allow air to move through them to cool them. And I have all the interconnects wired up.

I ended up putting 17 batteries in the back. Such a strange number, but there is that one space up front where I had intended to put a stack of 4, but can only fit 3. So, the extra one goes in the back. Notice up in the top left hand corner, there is an unconnected + terminal. That is the start of the battery pack. Below and slightly to the left, you will see an unconnected - terminal. I will be running a line from that terminal to the next positive terminal at the front of the car, continuing the series.

Truthfully, I'm not too happy with all of this. It's way too complicated. While it's strong and there's no way any of those batteries are shifting around, I approached the whole endeavor of securing the batteries as an after thought; I hadn't planned it from the onset. I don't know that it would have made much difference if I had, but I'd like to think that I could have come up with a much more elegant solution. But, at least it's done.

One thing I don't have in place yet are some "testing" lines that I'll be putting on each group of 4 batteries. I'll attach a small wire at the start, or + terminal of the first battery, and then another on the negative terminal of the fourth. I'll be doing that from start to finish, which will give me a total of 12 groups of 4, so 12 pairs of wires (a negative and a positive for each). I'll attach each to a terminal, paired up next to each other. This will allow me a handy way of checking the voltage of each group of 4. If the voltage on one battery in the group starts to get too high, or sag behind the others, I can more easily locate it and deal with it.

The real danger with these LiFePo4 batteries lies in the extremes. The closer you get to fully charged, the more likely one or more batteries is to run away, accepting too much of a charge and in the process, frying itself. The closer you get to draining the batteries, the more likely one takes a dive in voltage before the others and dies an early death. They are extremely finicky at the extremes. However, kept in the middle of the range they are stable. I'll be setting a charging scheme that will charge them to approximately 95% full, avoiding the top end where one can run away. And as I've said before, I won't be taking them below an 80% depth of discharge, meaning that they will always have at least 20% capacity left, avoiding the death spiral. It means that I'm leaving some untapped potential in the batteries, but it also means I should extend their life by not pushing them to their limits.

At some point in December, someone in my family decided to make a commentary on my progress. Well, they were probably just trying to be cute, but I took it as a comment on the progress I've made. Or rather on the slow pace of the progress I've made.

I had hoped the project would be done sooner, but with the delays I've faced waiting for components, it's pushed things back a bit. Still, when it's done, there should be few things I have to re-address. In either case, I took vengeance upon them all just to be sure I got the guilty party.