Now in its second year, the REFUEL all-electric expo and race at Laguna Seca Raceway was held last Sunday, the 11th of July. Held by Speed Ventures, it’s an opportunity for owners of electric cars or motorcycles to drive on track in a track-day setting, as well as compete in a time trial style race against the other electrics. I missed the event last year but made a point to attend this time, and to my great satisfaction was able to bring the electric MX5.

It was a bit of a stretch to get the car down to Monterey, arranging trailer and towing facilities around my friends’ schedules, but in the end things worked out well- the car made it down and back safely with no incident. There was even enough space to bring the electric bike and electric recliner- both of which fulfilled their purposes very well and were great fun to have along.

We arrived at about 8:30 AM after about three hours on the road and found the racetrack hidden in thick fog. By the time the first session came around the fog had burned off though, leaving beautiful sunny, breezy weather for the rest of the day. I made it out for two sessions on the track, for exactly two laps each before the batteries were too soft to continue. Coming over the big hill to the corkscrew corner on the second lap was accomplished at near a crawl.

I had a good chance to get more of a feel for how the new Rudman regs perform, mainly how much additional convection cooling they need in operation- I had to keep chasing the overheating reg around the pack with an electric fan. It’s definitely good to be putting some cycles on this pack, it’s clearly starting to work itself out and become more balanced. The battery I thought was weak and having self discharge problems seems to be behaving better. I am wondering if perhaps my old balancer system was causing a higher quiescent discharge on it than on the others.

My car was the only one driving on track with lead batteries, and one of only two brushed DC powered cars- it’s not a surprise that it was the slowest car out there. Despite that it was incredibly fun and gratifying to take around the track- and what a beautiful track. Sure I could have done better racing in practically anything gas-powered, but that’s not the point. Finally after three years working on the car I can drive it and charge it at a racetrack 120 miles from home- that’s really something. The car is unique- smooth, quiet and really pleasant to drive, even reasonably fast when fresh off the charger. Two laps, about four and a half miles of hard driving is pretty much the limit before the voltage sag completely destroys the driveability of the car. According to the Cycle Analyst that’s about 12-16 AH in- I’m not sure if this is a reasonable useful capacity out of the 55AH Optimas or if they have suffered in the last year they’ve been sitting full but rarely cycled.

The bike performed excellently as usual as a speedy runaround, and was passed around a bit for test rides. The electric recliner was the real star of the show. Sitting out of view in the truck while remote-crusing it around the paddock was stupid fun. We maneuvered it over near the Palatov Motorsports trailer and distracted them from their cars for a bit with some antics that Dennis ended up mentioning on his site (See dp1e section, 7/9/10 post). Then at the end of the day I traded a ride in the chair for a ride in a Tesla Roadster- something I had never managed to get before. Suffice it to say the Tesla knocked my socks off.

All in all, a fantastically successful day.

See part Two for my thoughts about the other cars that showed up to the event.

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Despite the troubles I was having before, the DC/DC converter has mended itself and appears to be working entirely as it should. It looks like the problem was caused by enabling the converter with the ignition signal before the precharge was done. The idea being that the precharge circuit is usually used in situations where the converter is disconnected from the pack when the ignition is off, so that it soft-starts itself and starts running on its own when it is energized. The enable input apparently overrides the soft-start procedure. When used with the enable input the converter is supposed to be connected to the pack all the time. The converter is usually not meant to be run using both like I am. So, if I switch on the pack and then switch on the ignition too soon it will close the main relay inside under the cap charging load, which probably caused the relay contacts to lightly weld shut. I spoke to Belktronics about the problem, they recommended testing the precharge circuit by attaching the converter to the pack through a 110v lightbulb- the first time I did it I got a big flash as the caps charged. At some point after then the fused contacts seem to have un-fused and the precharge circuit works OK again. I just have to make sure to always leave it adequate time to precharge before enabling it.

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After having the last couple weeks of my life stolen by first illness, then jury duty, I’m finally back in control and ready to get the stuff that needs to get done done to make the projects that need to happen happen- like the car and the kart. I didn’t shave until I was booted from the jury selection- It’s probably just superstition but hey, it can’t hurt to cultivate a “you don’t want me on your jury” look. What a relief to get out- the trial presentation for those selected will likely stretch into August. A real messy attempted murder case.

So, what’s up now? I’m making plans to get the electric MX-5 down to Monterey on Sunday for the Refuel expo/trackday/event at Laguna Seca. I’ve installed a set of MK3 Rudman Regulators to replace my home-built balancer setup as I discussed before. I’ve given the car a couple of test cycles to try to figure out what is really working and what’s not- the new regs look promising but need to be dialed in. There appears to be one really weak battery that is limiting the performance of the whole pack. And the brand new Belktronix DC/DC has something going on that I need to figure out. It’s blown a couple of HV fuses now (where do I recognize this scenario from?) If I can’t get it working it won’t ruin the weekend however, the aux. 12v battery seems to be up to the task of running the car. I got about 15 miles of driving today with heavy vacuum pump and headlight use before the aux battery ran hit the Zilla’s cutout point, and it wasn’t fully charged when I started.

It’s the little things that stack up and become seriously frustrating. The cycle analyst reports wildly varying and totally wrong current readings while charging the car, while seeming about correct under discharge. Even my Fluke 337 current clamp meter is acting sketchy and not entirely trustworthy, particularly for voltage or resistance measurements. There’s definitely something wrong with it.

So, like usual with the practice of trying to get stuff to work there is the sweet and the sour- some things go right the first time, more often things need more attention. Patience and perseverance.

I’m really looking forward to the event on Sunday, I know some people I want to see will be there and I expect plenty of people I will enjoy seeing but haven’t thought of will show up as well. Hopefully the Miata performs OK. Looks like my friends and I will also have the electric recliner in tow. After reworking the battery box today it is even more solid, and stealthy than before. Good stuff. Sadly we didn’t get a chance to set up the remote-controlled auto-recline feature. Another day.

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In the seemingly never-ending parade of not-quite dialed in and failed components preventing the EV Miata from being able to be a car instead of a project the latest issue arose with the DC/DC converter. After spending a couple days working on the stupid battery balancing system, thinking it had a better chance of being finished than ever before, I went to go take the car for a drive. You can instantly tell if the DC/DC is online or not with the sound of the vacuum pump, if the DC/DC is running the pump runs much faster than if it’s not. It wasn’t. I scoped the connections out and realized that the DC SSR that was supposed to switch power to the DC/DC had failed closed and that the fuse was blown. I tried a spare fuse, which instantly blew. Then I tried a spare 25A fuse up from 12, which also blew instantly. Yuss- $20 of fuses blown in 5 minutes.

I was using a IOTA DLS55 as a DC/DC converter- so I tried plugging it into AC power- no circuit breaker popping, and 13.8v output. What the fuck. Not really wanting to try to troubleshoot the cause of the problem, and leery of the general suitability of the IOTA to vehicular DC/DC duty anyways I decided to replace it.

After shopping around I decided that the isolated 675W DC/DC from Belktronics was the best replacement, features and cost wise. I really wanted a 12v enable input so that I could skip worrying about switching the HV input, given the patterns of long periods of disuse this car gets I like to be able to disconnect all loads from the battery. Several chinese DC/DCs have come on the market lately with similar pricing to the Belktronics, some with enable inputs as well. The “product support” line at Cloud electric was unable to confirm if the enable input was on the 12v side, as a HV side enable input would be much less useful.

After confirming it would do what I want over Email, I ordered the Belktronics converter with remote enable and soft start options. I consider the fact that you can actually get in touch with the guy who designed and builds the Belktronics converter a selling point over the Chinese one, I have a feeling if it broke you would be pretty much without recourse, particularly considering the generally under-capitalized support-averse nature of EV part dealers.

A month later the DC/DC was built and shipped. I installed it and it appears to work exactly as I would expect and hope. It’s a bit smaller than the IOTA but similar weight. It’s in a sealed box, should fare better under the hood than the IOTA. I’m not a huge fan of the recessed faston terminals but I think they well do the job just fine.

I used an 80A MEGA fuse to protect the 12v side and an A60Q 10A 600VDC Ferraz-Shawmut fuse on the HV side.

I bypassed the old SSR and used the 12v signal used to switch it to feed the Enable input on the converter.

I had to grind down the plastic shroud on the 10GA crimp fastons to make them fit in the recessed connectors

I mounted the converter to a 1/4″ aluminum plate which I mounted to the bottom of my battery rack in a similar fashion to the IOTA mounting.

I took the car for a drive after this (first time in almost 6 months). I only got 22AH out of the batteries before the car was reduced to a crawl. I’ve never pulled the batteries down so low before. I expect the combination of the batteries being kind of tired after all the disuse and the pukert effect as well as one underperforming battery are mainly to blame. I think I made it about 10 miles. It was really nice and fast at first, but a 1/2 mile jaunt on the freeway at about the 15 AH mark (at 55mph) really killed the pack. I was getting about 4kw of power at the end. It was real slow.

I charged it back up and verified that indeed my battery balancing system is not ready for prime time, now it’s exhibiting the frustrating behavior of crashing out occasionally. I’m really tired of dealing with it and feeling like I can’t trust it and must babysit the batteries all the time. I’m seriously considering tossing it out and replacing it with something off the shelf, probably something I should have done a long time ago with the interests of actually getting the car running in mind. It’s a push-pull between finishing the project I’ve started, that I’ve invested a bunch of money and time in or accepting that its failure doesn’t define my abilities and tossing it out to enable me to move on to other better-conceived projects and actually have a car here instead of a never-ending project.

While I figure out that part at least it drives with its new DC/DC. A lot of things on the car work really well. It’s just the nagging last few issues that are causing all this grief.

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Click through for the HD version–

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Before:

The only thing I found a bit unclear in the above linked direcions was how to reattach the ball joint to the lower A arm after it has been removed. When you pull out the two 17mm head bolts as specified, you can swing the whole upright out of the way then lever the lower arm down to pull the shock out.

Lower A arm with ball joint bracket removed:

It’s easy enough to set the bracket back into the A arm, then thread the bolt through the hole in the bracket. The bolt that comes in from the top (just under the shock mount bolt) is a bit tricky as the way it’s sprung the bracket tends to swivel itself down away from the hole in the top of the A arm. I realize this all will seem a bit vague if you’re not looking at it in front of you.

So, I used a scissor jack and an awl to push the bracket back up toward the hole through a small hole in the bottom of the A arm.

The blue screwdriver is holding the bottom of the shock absorber out of the way. The side-bolt on the lower arm has been inserted, the awl on the jack is pushing the bracket (which is hinging on that first bolt) so that the top bolt can be threaded into the bracket.

It worked well enough.

The big white zip tie is holding the ABS wire bracket to the shock absorber, since the shock did not come with the mounting tab on it. I am confident this will be good enough. This mounting tab is the only difference between “for cars with ABS” and “for cars without ABS” shock absorbers.

It was a bit scary beating on the spring perches of the brand new shocks- it’s not tricky or difficult, just a bit hair-raising the first time. So I made this video showing how I did it, just so you can see it’s not that big a deal

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The Ground Control people sent me all the same spring rates (I asked them to decide what would be best for my application) I think it’s 350 all around. Or maybe 375. The rear spring perches are sung off the ground, the fronts are preloaded maybe 1/2 inch. Probably could have had higher rate in the front, but I think it’s OK.

After installing the shocks I got an allignment- I hadn’t gotten it alligned since installing the steering rack either, so it was quite off. The difference in rolling resistance after getting the allignment was very noticible and impressive. It coasts beautifully now.

Moving on- I got an opportunity to take the car out for this year’s Solano Stroll parade right here in town- A friend of mine hooked me up with some folks from the Chamber of Commerce, I offered to give the Albany Citizen and Youth of the year a ride in the car down in the parade. So I washed and waxed the car up and took it out- It worked out great.

And even with an extra 300 LBS on the back of the car (it’s not a 4 seater, you know) the rear suspension wasn’t behaving too badly. Good! Good!

Later that day my friends and family threw me an amazing surprise birthday party. It was great.

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I did a little more reading tonight and made up my mind on a suspension solution for the Miata- I’m going with Ground Control coilovers and KYB AGX shock absorbers. Simple enough, plenty of people have done it before. Tons of adjustability. Reading these pages about the AGXs and coilovers help reassure that this is a good and easy way to go, as well as the mention on this page of a 3200 lb miata using this setup. I’m just ready to stop worrying about it and get something reasonably priced, proven and simple on the car. I think the main thing keeping me from driving it now besides charging being still a bit of a pain is the ridiculously bad ride and allignment. I don’t want to get it alligned until I put suspension on it, and the ride won’t improve until I put suspension on it. It’s just not fun to drive like it is now. It doesn’t coast well and bumps and ruts are really unpleasant. And the steering wheel points about 70˚ off straight when the wheels are straight. It’s the little things.

The KYB AGXs are not supposed to be used for cars with ABS, as mine does have- the stock shocks have a little bracket welded on that supports the ABS wire. I figure I can make a replacement bracket and attach it with hose clamps or some such BS. Not a deal breaker.

I did manage to pick up some nice stock daisy rims with good Potenza tires reasonably cheap on craigslist- the car looks much better without the chrome abominations that were on it. Which I learned also don’t seal on the sidewall too well. I spontaneously got a flat tire- the guy at the tire shop said “these chrome plated alloy rims are trash”.

Looks like I may be able to get a spot in the Solano Stroll parade with the car- I should be able to get this suspension on by then… as well as giving it a good wash and wax (2 years overdue!)

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Sunset in Southern Oregon (firefox kind of sucks the life out of this picture, unfortunately. Imagine it much more saturated...)

I’ve got three big areas that need work on the car:

1. Overloaded suspension
2. Plug-n-Play chargability
3. Amp-hour/range remaining instrumentation

Starting with #1

I’ve been researching and pondering suspension options. I was thinking about sticking some off the shelf eibach springs and nice shocks on it, but there are no aftermarket off the shelf springs that I have found for the Miata that have a higher spring rate but aren’t lowering springs. I don’t particularly want the car much lower than stock. I just think that option wouldn’t achieve what I’m trying to achieve. I thought about threaded coilovers, but was advised against the cheaper ones, the good ones are very expensive. So then, thinking about maybe combining custom heavy duty springs with OEM style shocks, I contacted Valley Spring Works and was quoted $328/pr for custom springs- nearly $700 just for springs all the way around. I also have been checking out air-shocks, and have found a couple packages- which are ~1500 and up. Similar cost to high end threaded coilovers. I’m not sure about the performance characteristics of the air springs, it seems like their primary purpose is for easily adjustable ride height. Seeing the price of air springs make the custom steel springs seem cheap… which they are not really.

And it just today occurred to me to check the GVWR of the miata- 2770, if you recall, dry it weighs about 2700 now. So it’s definitely over. Damn. Oh well.

#2

I have been planning modifications to the BMS master to allow the landline cord to be attached, the system to start charging then stop when it’s finished- I’ve picked up a few parts for that purpose. I will house the master board in an aluminum box with an AC solid state relay to provide/cut power to the charger. By default the charger will be unpowered, so in the case of a system failure or problem it will just be disconnected. I think I will set it up so that the master board can detect if itself or any of the slaves has crashed on account of software failure or EMI, and reset. There will also be a built in 12v supply to power the BMS off the landline-power, and circuitry for switching the power from landline to car’s power to entirely off. I have decided what sort of connector the charge inlet will use, and will be used in the in-car wiring and on the out-of-car cords and adapters- Neutrik PowerCon 32 amp:

Neutrik PowerCon 32

Power-in will use the chassis mount connector, Power-out will use the cable-mount. Unlike the PowerCon 20, there is no alternate style for power-in and power-out. So, on the long 10/3 cord I have to use with the car I will need to have both a cable mount and chassis mount connector on the ends of the cord- I think I will try making a round sleeve/strain relief on the lathe to mount the chassis mount connector on the cord instead of using a box- on the less prominent connectors inside the car trunk I will just use boxes. These connectors are expensive (best prices I found: here and here) and aren’t supposed to be used to break under load- but they are of very high quality and I feel better about using them than mis-using some NEMA twist lock that is actually supposed to be used with some particular H/N/G 120/240 circuit instead of this more flexible voltage input. These connectors also have a really high quality look and feel that I like. Note- if you screw the strain relief ring on a Neutrik connector down, then unscrew it again with great force, don’t expect the ratcheting action to be nearly as good subsequently- try to avoid taking these connectors apart after you’ve assembled them once!

#3

I ordered a 1000 amp shunt and an Albright SW-200 contactor to replace the Kilovac one on Otmar’s recommendation- in line with what I observed at UC Davis (four welded-shut kilovac contactors kicking around in the hybrid car lab), apparently the Kilovac contactors have an alarmingly high likelyhood of welding shut in break-under-load situations as compared to the Albright ones. Bonus with the Albright- you can inspect and clean the contacts if you’re worried about them. So, I’m going to rework the high-power wiring center in the front of the car to incorporate these new parts. I think I’m going to make interconnects out of copper busbar material instead of welding cable as well… Anyways, I’m working on figuring out how to amplify and detect the +/-50mv signal from that shunt in such a way that it can be used for peukert-corrected coulomb-counting. Which of course opens the door to some useful instrumentation. More on that as I get it working.

Oh, and the vacuum pump is getting to really annoy me. Every time I switch the car on it makes a huge noise, for a way long time. I think I might just get fed up with it- I’ve seen the YT STABLE product in person, I was pretty impressed- it’s powerful enough to replenish the vacuum fast and it’s not a diaphragm pump so you get much less vibration and noise. EV Source is carrying it now. It’s a little expensive but jeez that diaphragm pump is getting on my nerves. I turn the key and invariably whoever is around says- what’s that NOISE- man!?

Much more in the works. Stay tuned.

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On my Pacific Northwest roadtrip, as described before, I stopped in Portland for the Wayland Invitational at PIR- set during open weekend drag nights, but with John Wayland's organization a whole EV get together on top.

Some of the photos have clicky links to relevant pages. Mouseover to see if you get the little clicky linky hand.

Bunches more photos lie BELOW- click “Continue Reading”!

Neon's electric buggy was there

As were four Roadsters

Otmar's Quick-change Zilla swapper in his orange 914- test bed for hundreds of Zillas

Crazyhorse Pinto

Bill Dube's Killacycle

Killacycle's trick pneumatic brush-timing actuator

SSIC had their T-Bucket and Daytona Coupe (as seen in the first photo)

Electric Motorsport was there with bikes

The Killacycle toasted a motor Friday night

Saturday morning Jim Husted took a look at the SSIC Daytona's 11" WarP

Jim Husted's sweet mini-cruiser

On to the fun part- racing!

The Crazyhorse Pinto's crazy torque caused the tires to deform and fold over- sort of "flap". I understand this often happens on high-torque drag cars, but with the quiet electric drivetrain that "flapping" was the loudest sound you could hear as it went down the strip.

Tesla Roadster drag racing is not all that interesting- very consistant, quick for a street car, very quiet. The sound of a couple roadsters flying by at 100+ mph at the finish line is pretty neat though.

The SSIC Daytona was blazingly fast off the line, but wasn't geared well for top end speed.

This converted Samurai NEV was very slow. I think it hit 38 or so MPH, 1/4 mile in 50+ sec. They only raced it once though so it was OK

Speaking of NEVs, someone brought a ZENN out also. It quickly reached and then sat right at its limiter, 43 MPH or so

Obligatory sequence of Killacycle shots

The Killacycle is so mind-bogglingly fast, it is absolutely worth it to see it in person

The T-Bucket was detuned and running 15/16sec that weekend, still looked like a load of fun. I got a little spin around the parking lot in it- running similar power level to my Miata. Was very fun. It's on my list of goals to have a car without a windshield someday.

The White Zombie takes another victim.

The SSIC Daytona leaves a fat Audi in the dust

Then- a surprise. Dave Cloud has a reputation for showing up last minute with something crazy and cool- True to form he showed up Saturday at 9pm with this sort of Jr dragster- Let's see- tube frame, 24+ costco lead batteries, came to the track with the tires uninflated, reverse by way of flex plate and starter motor attached to one of the motor shafts, dual motor main drive with Curtis controller for creeping around and set of pneumatically actuated contactors for series/parallel switching of the motors and battery banks (72/144v)- This thing was seriously impressive in a homebuilt, most-from-the-least sort of way.

Rumors were flying that this run could easily result in some kind of disaster- but it didn't, the car turned in a respectable 95mph trap speed

It is likely that given good tires and batteries this dragster could turn in very good times- those contactors are going to be able to deliver more power than any controller if the rest of the system can handle it. I really enjoyed seeing this creation, it was definitely one of the high points of the weekend for me.

A good time had by all- Maybe I’ll have to tow the Miata up next time…

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I visited ohio and drove my great-uncle Cal’s tractor on the old family farm:

The semester ended, I got good grades.

As I have hinted, I drove the car- three times now. I still haven’t edited the video from the first drive, maybe I’ll do that tonight. The second time was to the DMV to get the car “verified” and registered, and the third time was just last Sunday, down to the autocross event at Golden Gate Fields. I have been working hard on the BMS/automatic charge balancing system, I think it’s almost working. In fact, that ‘s what I’m working on right now. I’m doing the first run of the charging system with a very basic charge profile set up, just getting a feel for how (if) it works. I’m babysitting it here in the car right now, I figured I might as well use this time to write about what has transpired… as you can imagine I’ve been putting it off.

So, what first-

I am feeling more and more confident about the powertrain of the car, now having driven it three times, I have not detected any issues with the clutch, adapter plate/hub, motor mount, batttery mounts, battery cables or other electrics. The DC/DC converter (IOTA DLS 55) works just fine and quite unobtrusively once I upped the HV fuse for it (it instantly blows 6a fuses, works fine with a 17a fuse) I have a class J fuseblock and fuses installed presently, that’s what EVSource.com was selling at the time I was buying- now they’re selling smaller circular fuses and blocks, I may need to change to this new type of fuse- it’s surprisingly hard to source DC rated class J fuses for reasonable prices. Of course that’s another good $100 bucks on the table, so I’ll hold off for now.

I drove the car to the DMV with my Dad following me with a tow rope, just in case. The drive there and back was mechanically straightforward, and pretty fun. The inspection went fine, they verified the VIN and the electric-ness of it then took the old title, gave us a new registration sticker and sent us on our way. Unfortunately, as is described on the Wikipedia page on EV conversions, I came away with a Q motive power code as opposed to the rightful E power code- apparently that’s the default behavior of the computer system. Q designates hybrid power- as of now hybrids are not subject to smog checks, so this problem is not an imminent issue for me, but it is kind of dumb. I have heard that this is generally a pain and that one way to tackle it is to complain to the governor’s office. I have higher priorities on my list now but this is something I may take on later.

On the way back from the DMV Dad and I stopped by our mechanic’s shop to show off the car, they’ve heard about it plenty of times over the last two years and have been interested in seeing it. I wasn’t expecting all the mechanics from Steve’s Auto Care and the neighboring Albany Tire to come out onto the street and check out my car, but it sure was neat.

Then last Sunday I took the car down to the autocross at Golden Gate Fields parking lot- (1.5 miles away) I had heard they would have scales there, I have been quite curious how much weight the car gained and how my gut-feel engineering worked out for the weight balance-

2705 lbs, very evenly distributed- could be worse. I was hoping it wouldn’t weigh quite so much, but all in all it’s pretty good and I’m quite pleased about the weight balance. I definitely need to install stiffer suspension components- either OEM style shocks and custom heavy springs or fancy ground control coil-overs, depending on what sort of advice I get and what the budget is.

I gave one or two people rides through the parking lot although I didn’t attract that much attention as I was not officially part of the event- that’ll come another time. I think the car has potential to be a pretty competent autocrosser. When I arrived back home I tried the speedy launch technique with the clutch a couple times- it really is a rush to wind up the revs and then feather the clutch out. 0-40mph is stupid fast. Just for the heck of it I tried letting the clutch out a bit faster and did a tidy little burnout-

I boosted the contrast a bit to enhance visibility, the super crummy tires on the car now don’t really leave much behind. The tracks are about 15ft long and pretty even, I think it confirms the car has an LSD. It was super loud and pretty fun. I’ll have to refrain from being so obnoxious on my street in the future…

As for the BMS system, I haven’t got a lot of photos, but it is coming along well. Like I said, I am as I type watching the character VFD (vacuum fluorescent display) I programmed to display battery related data from the BMS bus as the PFC 20 charger is cranking about 13 amps into the battery pack. The battery voltages are within about .6v of each other, the top one is about 14.2 right now. At 14.7 the shunt resistor is supposed to start kicking in and the master node is supposed to start slowing the charger down via the REGBUS port. Since we haven’t hit 14.7 yet I’m not sure if all that is going to work… but I’m hopeful. Some things are already looking good, despite the charger generating an insane amount of EMI- it destroyed the radio reception here in the garage- the BMS data bus does not seem to be having any issues- now the PakTrakr is also not having issues, and it consistantly has problems whenever the Zilla is powering the motor. I feel hopeful for the bus though, it uses the differential-signaled CAN transcievers and operates completely over twisted pair wire. I was able to get the system to crash by cycling power to my old school flourescent desk lamp, but I already knew that it generates some pretty nasty EMI pops- it’ll make loud pops in headphones attached to the computer. Hopefully the system will be able to take it OK, it would be neat to have the individual battery volt readouts while driving.

The first battery has hit 14.7 and the shunt resistor duty cycle is about 1/5 right now, drifting up and down, but successfully clamping the battery voltage to 14.7. The real test will be when the duty cycle hits 245/255 and the master node tries to slow the charger down… so far so good at least.

Good news- good good news- most of the batteries have hit 14.7 now and all the shunt resistors seem to be working perfectly. Even better, some of them have reached high enough duty cycle to make the master crank the charger down some, which seems to be working just fine. In fact, everything seems to be working exactly as it’s supposed to. I wish I had my camera out here… and I don’t want to leave this unattended.

Well I can use the iSight camera:

As you can see in that photo there are two batteries that seem to be lagging significantly. I’m not sure about them but I’m going to give it some more time.

Ah, well. So here’s the weird part- I noticed two batteries venting very slightly- number 10, which seemed to charge and act just like all the other batteries was hissing slightly from the (-) side vent. Number 6 which was the laggiest battery, its voltage would rise then fall then rise but I don’t think the shunt ever turned on for it was hissing more noticably from the seam where the top meets the casing. Pressing down on the seam would stop the hiss. I know for a fact that the datasheet figures were not exceeded, in addition to my BMS system which is reasonably consistantly accurate to .1v I checked all the batteries and these ones in particular several times with my fluke meter and found the voltages to be well within the expected range, 14.6-14.8v usually exactly 14.7v. I did not even attempt the Optima specified finish cycle (2 amps, constant current) where the battery voltage would certainly excede 14.8v. Hmmmmm. I’ll need to check these voltages tomorrow to get a good SOC approximation and call up the experts. During the previous two times I charged this pack, using the Husky brand 2/10/20 amp digital charger I never noticed these hissing noises, however the Husky charger fan is very noisy- although the hissing noises persist after removal of charge current and I never noticed it before.

I still count this test as a success, my BMS system performed exactly as I expected and intended. I have heard about how touchy these optima batteries can be, I hope I can figure out what exactly is going on here.

… so that’s the massvie update. I will attempt to keep more consistantly up to date in the future. It’s been a stressful and busy last few weeks though, believe me.

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