# Chevy Volt Battery exploding



## Elanimal28 (Nov 18, 2013)

I have 4x 48v modules for a while now but haven't put any miles on them, just a couple of test drives on my block. About 3 month ago I checked the voltage on the pack and it was 96v. I haven't check on then until today and this is what I found 0 volts and looking like this:


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## dcb (Dec 5, 2009)

that is most unfortunate :/

more details please?

1. what is the temperature range in storage?

2. are any cells still holding a charge, how many volts?

A quick search suggests they expand when discharging, and need to be clamped (and not unnecessarily discharged). The lack of clamping on top could be a factor (steel band?), and whatever those wires are connected to might be draining the pack as well?

Sorry though, hope we can learn what we need to from it.


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## Elanimal28 (Nov 18, 2013)

dcb said:


> that is most unfortunate :/
> 
> more details please?
> 
> ...


The storage is on my detached unheated garage. The weather has fluctuated from 30-80 degrees since they have been in the garage. 
The 96v charger will not charge as they are all at 0v.
I tried to use a smart battery charger/ battery tender on a few of the cells and they quickly charged up to the 16v the charger can supply. I did that for only 5 minutes but I'm so upset that I stopped messing around with it.

The device that discharge the battery is my charger that has a built-in dc-dc converter 
The other 3 modules where strapped and didn't bulge out as much.


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## EVisa (Jun 30, 2014)

This looks pretty scary indeed. Any chance something conducting fell on top of the exposed cell terminals, shorting them?


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## Elanimal28 (Nov 18, 2013)

EVisa said:


> This looks pretty scary indeed. Any chance something conducting fell on top of the exposed cell terminals, shorting them?


The terminals have an oem plastic cover. I took it off to take these pictures and to try and change the cells individually. I knew of cells swelling because of over charging but not because of slow discharged to over time.


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## Elanimal28 (Nov 18, 2013)

I guess my question is what to do next?
Throw them away? Disassemble the pack and see which cell takes charge?
Once a cell bulges up, is trash even if it holds a charge?


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## EVisa (Jun 30, 2014)

Elanimal28 said:


> The terminals have an oem plastic cover. I took it off to take these pictures and to try and change the cells individually. I knew of cells swelling because of over charging but not because of slow discharged to over time.



Good that you left the cover on. From the pictures I was afraid your left the terminals exposed. 
I still find it odd to see this kind of damage from slow discharging only. It would be nice to get to the bottom of this.

Be careful when separating the individual cells. I'm no expert in batteries, but I would guess you could measure the individual cells, and balance the onces that are good.


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## dcb (Dec 5, 2009)

I don't know about salvaging cells like that, would probably involve a fair bit of testing per cell, plus disassembly/reassembly at the cell level, and even then. Again really sorry, expensive "lesson" here.

Was there no contactor? Or was the wiring off?

Edit: I did find this, was the "circuit breaker" accidentally left closed here? 

EDIT: you confirmed it was the charger (built in DC converter), again sorry.


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## EVisa (Jun 30, 2014)

Looks like it blew some holes through the plastic on top. 

I'm also wondering whether the rods at the bottom of the pack are supposed to be bolted to the chassis. I suppose they do not touch the cells. It does look like they touch the aluminum liquid cooling plates inside the pack. Which shouldn't be far away from the cells. I'm just guessing here.


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## rwaudio (May 22, 2008)

That's typical of a pouch cell, they're dead. I've had a number of A123 20Ah pouches do this, it's just a by product of overdischarge and is not reversible. Some cells may still work at very reduced capacity and high internal resistance but nothing you'd want to use to drive a car. Basically you need to be able to disconnect ALL loads from a pack when storing it.

It's good to know for all of us with Volt packs, sorry you had to suffer the loss for that piece of information.


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## Elanimal28 (Nov 18, 2013)

Well this has been an expensive lesson. The only thing connected to the pack was the charger but it has a built-in dc-dc converter and I was told not disconnected because it drew very little power. I put the car in the garage on 10/24/14 so in less than 2 months they drained completely.


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## rwaudio (May 22, 2008)

Elanimal28 said:


> Well this has been an expensive lesson. The only thing connected to the pack was the charger but it has a built-in dc-dc converter and I was told not disconnected because it drew very little power. I put the car in the garage on 10/24/14 so in less than 2 months they drained completely.


The problem is the context for "don't disconnect it" is typically for every day use, where that small drain won't have any real impact on range etc. When storing an EV for anything more than a week or two I believe all loads should be disconnected. That reminds me I should go check my car because I have a Brusa NLG513 that's always connected and I'm not sure if it has any slow draw.


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## Moltenmetal (Mar 20, 2014)

Wow...that's very sad indeed! What a drag- must be heartbreaking!

That's a good motivation to pull the emergency disconnect on my pack when storing it over the winter.


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## Elanimal28 (Nov 18, 2013)

Moltenmetal said:


> Wow...that's very sad indeed! What a drag- must be heartbreaking!
> 
> That's a good motivation to pull the emergency disconnect on my pack when storing it over the winter.


Thanks. I'll start saving a again for a new pack. It's a shame I messed up at this point because I was so close to finishing the project.


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## PStechPaul (May 1, 2012)

The problem with a DC-DC converter or other switching supply is that it will attempt to hold the output constant even as the supply voltage drops, which means it will draw more and more current as the battery pack is depleted. There should be an undervoltage detection circuit that operates a relay to disconnect the pack before irreparable damage is done.


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## dcb (Dec 5, 2009)

another way is to sense when ac is plugged in, then close a relay to charge the battery, that is way less complicated than additional cutoff voltage sensing (literally, just need a relay). Still the charger would have to notice that the battery needs a top-off charge if you left it plugged in for a long time, which the delta-q implies it does:
http://www.delta-q.com/home/serve_p...iQ_Charger_Specification_Sheet_720-0012_R2_EN 
"* Auto-recharge for low voltage / storage ensures equipment is ready for use"

That would allow you to leave it plugged in ready to go (with a bit of cycling in storage) or unplugged for cold storage.

Edit: I don't know exactly why a charger would drain the pack when not plugged in without extra circuitry, that seems like a miss, or certainly something to be aware of.

A suitable relay looks like a $15 part, http://www.digikey.com/product-detail/en/T92P7A22-120/PB489-ND/365924
the coil goes in parallel with the charger plug, the contacts isolate the charger from the pack when unpowered.


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## Elanimal28 (Nov 18, 2013)

So here's an update. I couldn't get the charger to charge the battery pack because of 0v. I used a couple of motorcycle 12v battery charger/tender to charge the cells enough to a point where the 96v charger would start charging. I left the pack plugged in overnight and In the morning the charger said they where fully charged. The meter said the charger used 7.8 kw and the battery voltage was 104 volts. My pack should have drawn 8.64 kw (96v × 90 amp = 8640) but I'm guessing the difference is because the 12 chargers did some of the charging. 

I drove the Trike once up and down my block and did a couple of burnouts  and the voltage stayed steady at 104v.

I'm buying an icharger 1010B so I can read the individual resistance of each cell and get a better idea of how the cells are doing.


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