This past weekend I was out doing some errands and I could not "start" my truck because my 12V battery went dead. This is kind of a funny situation to be in because the vehicle has a large traction battery with plenty of charge to power the vehicle, and yet I can't use it because the 12V lead acid battery is dead.

Elcon PFC 3k charger

I bought the Elcon PFC 3000 charger for my truck.  This is a 3kW charger that can handle 120 or 240VAC input.  I thought this would be handy and I would be able to normally charge using 240 at my house, but opportunity charge at 120 when there is a normal 5-15 plug available.

After many weeks of working on wiring, we are finally at the point where we can attempt to charge the batteries. So, Sunday night we plugged it in (after preliminary electrical checks) and the battery pack was charging!

EV Display showing initial charging current and voltage

If you have read some of my older posts then you know that I originally ordered my batteries and other stuff from EV Components.  There is ongoing legal action and it is moving at a snail's pace.  Therefore I decided that I wasn't going to wait any longer and so I placed a new battery order and now I have received those:

Crates of batteries

I ordered batteries, a battery management system, and a charger from EV Components back in February.  EV Components has now gone out of business without delivering prepaid order to a number of customers.  At this point I don't know what equipment or money, if any, I will recover.

I can't …

Edited on 6-13-2010:

I originally posted the links below to various threads on diy electric.  The posts themselves tell the story and needed no further comment from me.  However, it appears that these posts have now been taken down, likely for litigation reasons.

So I will summarize.  These are the facts as far as I know.

Overdischarging Oops

I've had a chance to experiment some more with the small Lithium Iron Phosphate (LiFePO4) cells that I purchased from batteryspace.com.  I originally purchased 4 of these 1300 mAh cells.  I've since learned what happens when you over-discharge a cell.  I was discharging the 4-cell pack using a stepper motor as I described in this earlier post.  I was periodically recording the cell voltages, with the goal of spotting the knee when the cell becomes fully discharged.  This was going okay but at some point I ended up in a hallway conversation (this was at work), and when I got back to check, one of the cells had a negative voltage (about -0.6 volts).  Interestingly the motor was still running and the other cells were still delivering current.  I disconnected the cells and let them sit for a while.  The reversed cell eventually became positive again, about 0.2 volts.  I attempted to charge it, and when I did the cell voltage pretty quickly came back into a normal range.  But when I stopped charging, the voltage eventually dropped back to about 0.6 volts.  Clearly this cell is no longer good.

We want to better understand how these LiFePO4 batteries work, so I ordered 4 small hobby cells.  These are the same chemistry and cell voltage as the big battery cells that will make up the truck battery pack, so I think it is reasonable to study these to learn how the big battery will work.

I ordered 4 1300 mAh cells.  These are not expensive at all.  I also ordered a 4-cell charger which was a little pricey but I want to get straight to studying the battery characteristics,