# Charging Chevy Volt batteries for beginers



## dcb (Dec 5, 2009)

you should probably test with a dummy load (wire in a bucket of water for a short while). Most power supplies are voltage regulated, with a current limit cutout, so it will probably try to keep it at 50v and then cut out (or blow a fuse) as it increases current to attempt to maintain 50v.


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## piotrsko (Dec 9, 2007)

You need an automatic shut off device at 48 volts or you need to be there watching all the time. If the powersupply is tightly regulated then you're somewhat safer. Current will drop as charge rises but not significantly until almost charged.

10 amps should show a voltage rise of about .1 volt in about 2-5 minutes. This is not reliable enough to use as a timer. 

10 amps is about .1C so cooling shouldn't be necessary.

I would end charge at 46 volts and then bump it up after that to 48 in 2 jumps to see how well the regulation on the power supply is.

No the cells dont drift down that much. Perhaps to 3.955. After overnight mine are at 4.015 ending from 4.02


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## ken will (Dec 19, 2009)

Oh I sorry.. What I called a 50 volt power supply is actually adjustable from 0 to 50 volts. The power supply volt meter only goes to a tenth of a volt, but the hand held meter goes to a hundredth of a volt.

Until I get a good battery charger I will hover over the charging cells like a mother hen!

Should I start the power supply at the starting battery voltage and slowly turn it up to keep a constant 10 amps till the batteries get to a voltage I feel comfortable with?...( 42v the first time.. 46v when I get more confident)


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## rwaudio (May 22, 2008)

ken will said:


> Switching from Lead Acid to Lithium can be a scary big step!
> 
> I have a 12 cell ( 45 AH) Chevy Volt module that has been sitting at 3.50 volts per cell (42 volts total).
> I plan to manually moniter the charging useing a 50 volt power supply that puts out a maximum of 10 amps.
> ...


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.

The one thing to remember, Li-ion is nothing like LiFePO4, if you charge till the current starts to drop at 48v the cells WON'T slowly drop to 3.7v They will drop a bit because of the surface charge, but it will stay at 3.9 or 3.95v.

When you charge a li-ion cell to 4.2v CCCV with a suitable curve, it stays at or just shy of 4.2v. There is a much more linear voltage decline as the cell is discharged, you can get a better (not good, but better) indication of SOC from a li-ion cells open circuit voltage than a LiFePO4 cells open circuit voltage.

My 944 has an 83 cell pack of CALB's my resting voltage is 275, it stays that way from basically full to less than 40% SOC, the only difference is slightly more sag under load closer to 40% SOC than full. This makes for a very poor SOC indicator on voltage alone.

The 914 I built has a 90 cell pack of Volt cells (2 packs in parallel 333v 90Ah), Even though there is less sag, the voltage is always dropping as the pack is discharged, it's much easier to get a rough SOC from voltage, full it's 375v, and it steadily drops in a reasonably linear fashion till it hits the cliff. For example right now the car is sitting at 52% SOC and 341v


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## ken will (Dec 19, 2009)

Thanks everyone..!


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