[remy_martian]

While I am thinking of it, DO NOT use a cheap multimeter to measure cell voltages.

I used a Harbor Fright freebie meter (was handy in the toolbox, too lazy to grab the HP out of the house) and got dozens of millivolts of variation among the Model X modules I had harvested.

A couple of days later I walked out of the house with the HP and decided for some reason to remeasure...they were all almost perfectly matched. I have no explanation why the HF meter would vary so much, but it did.

 

[Duncan]

So, buy a Sharpie, number the cells, measure each, put them away.

I don't understand why the risk and complexity of charging is needed at this point when all he plans to do is hoard a Volt battery 😉

Its exactly what I did when I got my second battery (its not mine its for a maniac who wants to build a drag bike)

I checked the voltages - decided that they were too close to the 3.5 volts that I use as a minimum and charged them up to 3.9 volts

I feel much happier about that battery being stored with a middle ish charge

I did have a power supply with a large enough voltage that I could simply charge each module individually

 

[Zieg]

Admittedly, most of my experience comes from RC car/plane batteries, but with those it's always recommended that you store them at a certain voltage. Otherwise they can degrade faster.

I pulled up the 2018 Volt owners manual and it says to run the battery down to 2-3 bars SOC on the dash if the vehicle is going to be stored for between 4 weeks and a year. It looks like there are 10 bars, so I'm tempted to assume that means 20-30% soc, but so far I can't correlate that to a specific voltage.

 

[piotrsko]

Hey Duncan: why do you consider 3.9 to be middle charge? I must be missing something. My middle for storage is 3.6, about a volt over my calculated low warning under heavy operation.

 

[brian_]

Check out the miata zeroev built with a direct-drive hyper 9 on YouTube. It has a torquebox (1.6:1 i think) to a 4.1 rear end ...

It has a reduction gearbox, so it's not direct-drive, although it is fixed-ratio (or single-speed).

Zero EV built their own reduction gearbox for this car, and were testing it in preparation for putting it into production... but it has never appeared as a product on their website. Zero EV's own YouTube videos provide much more detail than The Late Brake Show.

 

[brian_]

I checked the voltages - decided that they were too close to the 3.5 volts that I use as a minimum and charged them up to 3.9 volts

I feel much happier about that battery being stored with a middle ish charge

While at mid-point charge would be to the nominal cell voltage (3.75V in this case), recommended storage state of charge is usually significantly more than 50%, and 3.9 V/cell seems generally reasonable.

 

[Duncan]

Hey Duncan: why do you consider 3.9 to be middle charge? I must be missing something. My middle for storage is 3.6, about a volt over my calculated low warning under heavy operation.

Hi Piotrsko
I don't have a "low under load" number - I always back off before looking at the voltage
Just had a look at my videos of the 1/8th mile drags - the peak "sag" was about 20% which would give me a voltage under full load of 3.1 volts

With the cells just sitting I am treating 3.5 volts as empty and 4.1 volts as full -
Yabert provided the actual curve I'm using
Somewhere in the middle of this thread

2012 Chevy Volt Battery:

Paid $2000 + $150 shipping from a junkyard. It is a work of art. I'll be sad to tear it apart for the cells, but that's life. I'm getting 373 vdc for the battery, and 3.88 vdc per cell. IF there are 288 cells. Already things aren't making sense. I count 72 modules about 1" thick...

www.diyelectriccar.com

 

[piotrsko]

Thanks. Hmm I can get to 2.5 like I said, but that is winter voltage sag under 15C temps. Since they pop back up to what I guesstimate original values, and lacking any firm expertise, that's my storage target. It's below the 4.2 I use for max charge. Am I killing cells? Can't tell, but may have lost some capacity and I don't do my old go to work and back max range test.

 

[Zieg]

Okay, been a bit busy with other life stuff but I have the battery all torn apart and charged up to 3.65v. Each cell took 10 Ah just to go from 3.5v to 3.65v. Wow.

I was hoping to use as many parts out of the battery module as possible, but sadly I don't think I will get much.

The current sensor is a Lem DHAB S/51. Looks like it is rated for up to 350A according to the datasheet. Unfortunately it is not listed as compatible with the Thuderstruck MCU that I'm hoping to use.

The BMS/BECM is also probably not usable to me, because it doesn't seem like anyone has managed to interface with it, or use it in a configuration with fewer cells. If anyone knows differently, please let me know!

The HV contactors are an interesting one. Panasonic AEVS760122. Not a lot of hits when I googled the number, but I did find a datasheet for the AEVS series. If this is the correct datasheet, it's rated at 60A continuous, 180A for 1 minute. A bit disappointing, I was hoping they would have been rated a little higher. It has spade connectors that are approximately 5/8" wide. I can't tell if it has an economizer but at 12v it was drawing about 0.4A, which is pretty close to the datasheet. If I do reuse these, I may have to drill holes through the spades so I can bolt an eyelet, and that sounds pretty janky. What do you guys think?

As for the pre-charge contactor, it is labelled AEC11012 M11. I honestly haven't really looked into these. I found a datasheet for an AECN11012 that says they are good for 5A. The same sheet says the coil current is 0.117A but I haven't verified that yet. There are actually two of these relays included, I believe the other is for charging. I do plan to re-use these.

The resistor has 50W printed on it and measured 69.0 Ohms on my Fluke. I'll re-use this too.

I've also ordered my Openinverter kit and it should be arriving any day now.

 

[Duncan]

I tried to use the large contactors from the battery - but my "abuse" made them stick shut !! - so I bought a pair of big contactors

I'm still using one of the large contactors for my pre-charge circuit

Pre-charge resister --- I use an old kettle element

 

[remy_martian]

You know you're ready to put it in drive when there's a good strong tea brewed by your precharge resistor 😂

 

[piotrsko]

Gen 1 packs had 400 amp hydrogen quenched panasonic main relays good for 600 volts. Good for gen1 volts and odd switching where you never get over 200 amps. They will operate once at 400 amps but thats all you get.

 

[Zieg]

Well, the pile is growing. What we're looking at here is a gigantic EVSE, Thunderstruck MCU, 4x Dilithium BMS satellites, Dilithium touchscreen display, current sensor, LEV200 contactor. Not shown: The Openinverter board already installed in the inverter, second contactor on my bench for testing, 30ft of 2/0, Gen 1 Volt DC-DC converter, and the charger which is coming in a separate box.

I'm working on designing an enclosure to cover the exposed DC input connections on the inverter. Already made a protective cover for storage.

I'm also working on a RC economizer for the contactors. I put 12v to one for about an hour and it drew 1.2A initially, tapering to 1A as it heated up. But I wasn't entirely comfortable with how hot it got:

So I think this circuit should do the trick. I'm going to try to get fancy and print a custom PCB to hold the resistor/capacitor and a smaller relay to switch the current to the coil. I think this should work decently enough. Should draw about 5w after 200ms.

I'm also still working on the Leaf transmission modification, will post an update in that thread shortly.

 

[Zieg]

PCB design is a bit of a learning curve, but I am making progress. Here's what I'm looking at for an economizer circuit for my two main contactors:

Software is called KiCad if anyone is interested, and there are some GREAT tutorials here:

 

[remy_martian]

Oshpark.com is good for fabbing a small qty of boards. I use them all the time.

Fast, excellent quality, US made.

 

[remy_martian]

Turn your relays 180 degrees for a nicer layout

 

[Zieg]

Okay, ordered the boards from Oshpark. Their pricing model is you pay by the square inch, but you get three copies. Figured I'd cut the cost in half by redoing the board for a single economizer circuit since I'm getting three anyway. Feeling pretty good about that!

 

[remy_martian]

My hand calcs on your circuit are 15.4W with the cap dead short (t0) and 8W when the cap is fully charged (open DC) assuming a 13V battery/DC-DC.

I'm wondering where the 5W came from, unless it was estimating coil power vs coil plus resistor power?

 

[Zieg]

Ah, good catch. I was playing around with the circuit and decided I wasn't comfortable going as low as 5w, so I dropped R1 down to 10 ohm. I'll be testing it once the components show up, and I was careful to select components that could be easily changed if I see something I don't like.

 

[Zieg]

Okay, time for another update. I've been trying to push multiple fronts simultaneously so I can hop from one task to another when I get stuck or tired of working on any one thing.

The economizer board I designed seems to work great. Apparently I picked the wrong footprint for the resistor, but thankfully it wasn't off by much and I was able to make it work by bending the leads a bit. The contactors stay nice and cool now!

I've been revisiting the placement of the motor and in light of the projected cost of building a custom reducer box, plus having another driveshaft made, I thought I should try harder to see if I could fit the motor in the back with an IRS setup. It's taken quite a few iterations but I think it is possible. I had to go back to the textbooks I bought on suspension design and make sure the geometry would work out (both on its own right and relative to the front suspension geometry). I think I have it in a pretty good place now. The motor is offset to the passenger side a bit, which is fine because it will help offset my own weight. I still need to add some tubes for bracing and to support the coilover, but so far so good. Losing the solid axle will save me 135 lbs plus whatever the driveshaft weighs (probably 50 lbs?), while adding back the weight of the CV axles, uprights, wheel bearings and wishbones. Lower wishbones est weight is about 3 lbs, uprights would be 2.5 if made from 6061. Not sure about the other components, but certainly the difference in unsprung weight would be huge. It would also free up space in the tunnel to run the power and coolant lines, as well as maybe some electronics (dc/dc converter?).

For cooling, I found an electric water pump out of a Prius, which seems to be a common choice. I don't think I want to try splitting the flow between the motor/inverter and batteries, so I'm looking at connecting them in series on one big loop. The BMS will be reading battery temp directly and I think I can get motor/inverter temp through CANBUS, but I think it would also be wise to install a flow switch or something, so if the pump fails or there's a blockage I will know about it right away. I also need to figure out a way to control the electric rad fan. A simple fan switch in the coolant would be awesome, but I can't seem to find one with a suitably low 'on' temperature. Being made for ICE engines they are all 160*F or more. Even the digital adjustable controllers don't seem to adjust low enough, and the ones that do use a radiator probe that you shove into the fins, and I don't think I'm a fan of that. Any suggestions would be appreciated.

I got my hands on a used GE Wattstation EVSE, my goodness this thing is huge! I thought it was interesting that the control board has an ethernet port and multiple serial ports.. Apparently they were made to be expandable so you could connect card readers and bill people for usage if you mount it in a public space. It's only rated for around 7kW but that's still way more than I need.

I also got my MCU talking to my laptop and the Dilithium touchscreen. It can't really do much until it's connected to a few more things, but it was still encouraging to see. I also started on an overall wiring diagram and it's getting very complicated. Lots of details to work out there.

And finally, while playing with the Leaf reducer housings I 'did a stupid' and tried to reinstall the jackshaft without first removing the grounding brush. Result: broken grounding brush. Looks like a replacement from Nissan is >$125 which seems like utter insanity to me. After searching around on my own I wasn't able to find any similar brushes. Thankfully, I eventually found a local brush supplier (carbonbrushes.ca). I had a great conversation with the owner Dan, and he found me something that should be a direct fit. I had no idea brush selection could be so complicated, but there are apparently many different materials and characteristics, so I'm glad I was able to talk through the application with him and make sure the replacement brush would live up to its task.

I think that's all for now. I have decided not to race the car for the rest of the season, so as soon as I can clear space in my garage, I will be pulling the car in and removing the ICE components. Currently my side of the garage is full of the vinyl plank flooring I am using to replace the carpet on the top floor of the house, and all that has to be done before the baby comes in October. I'm about halfway done at the moment (two rooms and the stairs done, two rooms and a hallway left). Busy busy!