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Discussion Starter #1 (Edited by Moderator)
Do any of you know of a procedure to test the voltage on a used chevy volt battery pack?
I am trying to purchase a new battery pack but the battery pack was removed from the car almost 2 years ago.
I am worried that the battery status is bad and would like to test before purchasing.
 

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Wow, 2 years is a long time for a battery to sit. Depending on how high the charge was on the pack when it was disconnected I would be concerned that at least some of the cells have dropped their charge too much. Normally the electronics in the Volt help balance cell voltage, but being disconnected, that feature probably isn't functioning. Unless the price is CHEAP compared to others and your willing to take the gamble, I'd suggest looking at something that was more recently removed.
 

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My crashed spark EV I picked up at the auction sat inside for ~1 year from the time of the crash to the time of me re enabling High Voltage system and charging the battery. In ~1 year of car not being charged, it lost <10% of charge. Basically, a year later the battery still had 7 bars, and I could see that the owner that crashed the car drove the Spark EV for 12 miles since last charge.
Spark EV and chevy volt batteries are very similar, both made by LG.
One thing you can do is had the salvage yard measure DC voltage of the pack. You can look up exact numbers, but Volt battery has certain voltage at 100% charge and certain lower Voltage at 0% usable charge. Lithium cells should not be discharged below certain Voltage - it ruins them. So if the battery pack is above certain Voltage, you good to go, otherwise - stay away.
Post voltage here and you will get thumbs up or down.
There is no magic in measuring DC battery pack Voltage - if salvage yard does not want to do it - STAY AWAY. Every Voltmeter I have used goes up to at least 400VDC.

Also, you can let them know they ruined the pack by letting them sit for so long, but that you will not willingly take it for $500 less than what they are asking, and that you are doing them a great favor ;). It does not hurt...
 

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Discussion Starter #4
hahaha good idea.

As far as they can tell me the car had 14 miles left on battery.

I called GM and it seems like the battery pack needs 12vdc applied to 2 pins on the extra harnesses that go into the battery in order for the battery to activate a relay that will let them output voltage to the battery terminal ports. :(
 

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If the battery is out - then measure DC Voltage at HV connector pins.

If the battery is still in te car, then applying 12VDC will allow you to see miles left and % battery charge (at least Spark EV and Gen II Volt does). If you can connect GDS2 tool like VXDIAG VCX NANO, then you can check Voltage of the pack and of each cell.

15miles/35miles*100 = ~= 43%. That's actually really good storage charge. I guesstimate the battery should have 20% left - which is workable, assuming the yard did not lie about the miles left, and the original owner was not a hyper-miler.

Without huge discount stay away unless you get answers.
 

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If the battery is out - then measure DC Voltage at HV connector pins.

If the battery is still in te car, then applying 12VDC will allow you to see miles left and % battery charge (at least Spark EV and Gen II Volt does). If you can connect GDS2 tool like VXDIAG VCX NANO, then you can check Voltage of the pack and of each cell.

15miles/35miles*100 = ~= 43%. That's actually really good storage charge. I guesstimate the battery should have 20% left - which is workable, assuming the yard did not lie about the miles left, and the original owner was not a hyper-miler.

Without huge discount stay away unless you get answers.
You have to actuate the contactors in order to check the voltage at the HV connector.. Someone knowledgeable could take the main disconnect out, then take the cover off the battery and carefully access the terminals directly, after reinstalling the disconnect.
 

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Discussion Starter #7
The battery is outside of the vehicle. It seems like the HV connector pins are not actually energized until you have the main battery disconnect plugged in and apply 12v to two other pins in the harness in order to activate two relays that will actually energize the HV connectors. I was also estimating the battery to be at 20% since gm doesn't actually allow the battery to go bellow 20%, so 0 miles should be 20% battery charge?
 

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Then apply 12V for contractor to close and get the voltage, or take the cover off and get the voltage.
There is a pdf service manual floating on the web for Gen I Volt.
Without knowing pack Voltage you taking a risk of buying a brick.
If battery is less than 340V - I would stay away.
 

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I charged two complete chevy packs this way, it works perfectly well if you have a good power supply (digital is better) basically adding to what dcb mentioned, set it to 50v, confirm the open circuit voltage is 50v with a trusted meter. Dial the current down to an amp or half an amp, if possible, if not you may want to find a better power supply. Now short the leads together, voltage should drop to near zero and the current should be what you selected. If your power supply can do this without going into a hickup mode/short circuit mode, blow a fuse or other undesirable things, it will make a fine battery charger.

I used a few Agilent E3631A's using the 1A 50v output, rather slow but worked like a charm, I charged each 12 cell pack to 50v and terminated at 500ma (give or take since it was manual). I wouldn't use this method any closer to the 4.2v per cell or you risk overcharging. In my case I checked each cell voltage periodically to ensure the packs were balanced, and 95% of the groups were perfect through the whole charge process, there were a couple that I tweaked slightly by using the 6v 5A section (set to 4.2v @5A) of the power supply to bring up a low cell slightly or a resistor to bring down a high cell slightly. On the whole the Volt packs are very well balanced.
 

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Discussion Starter #10
I ended up taking the chance on two Chevy Volt batteries that were taken out of totaled cars almost 2 years ago and a third battery that was just 3 months out of the vehicle. I disassembled all 3 batteries for solar energy storage and it seems like voltage loss during storage is not that high on these batteries. A picture from the junkyard showed 30% charge on the old modules when the cars were dismantled and the old batteries showed 42v and 45v when I took them apart.
 
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