Wednesday, November 13, 2013

RE: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

 

It’s probably just as important to find out how they went bad as well.

 

Steve in Solomons MD

Testing is easy:

 

Check individual resting voltage.

If near 0V  they are probably toast, but you can try to gently charge them (a couple amps), and see if the voltage rises during charge. If not, they're goners.  

If they are 2V or more you can charge them to about 3.5V per cell. This is almost a full charge. Resting voltage should be around 3.35V

 

Once charged, either:

1. Time the discharge into a constant load (lights, heater), measure the current, stop the clock when cell measures at 2.5V under load (or maybe 2.8V or  bit more if you want to be conservative), so you can calculate the Ah capacity of the cell.

or

2. Apply a load, and monitor the Ahs consumed with an Ah counter (LinkPRO, JLD404, etc.). Keep an eye on the voltage., stop test at 2.5V or so.

 

I'll bet that if the sellers of the car say the cells are bad, they are bad.

-Tom



---In electricboats@yahoogroups.com, <mark.internet@...> wrote:

I am thinking of purchasing a vehicle with these batteries.

They say their pack is dead.

 

Any suggestions on how to test the pack or cells and what to worry about if they are used batteries.

 

Or should I just consider the pack bad and recycle them?

 

Thanks


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