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Raw beginner salvages some cells

Jockmacrea

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Jan 6, 2022
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I managed to get hold of failed a 24v 40AH golf buggy LifePo4 battery pack from my pal hoping to to salvage some cells.

I Stripped it completely cleaned up all the cells and here's what I got,

40 cells @ 3.2v or slightly above
20 cells from 2.4v to 2.6v
Remainder all at 1.6v or below, lowest cell voltage was 1.4v

BMS PCM-L10S80-664 was fitted.

The first 40 cells I hope I can use to make a 12v 40ah battery (New Bms will be needed I expect)
If this is feasible can someone please let me have a cell layout using all 40 cells.

Are the remaining cells Junk. ? Can they be saved. ?

I'd like to use the finished battery with my Solar panel (340W) and inverter to output 240vac

This is probably been posted a thousand times so please forgive me.

Many thanks
 

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I recovered several dozen 40Ah CALB cells that had discharged to about 0.6V very slowly over time due to their balancing boards pulling microamps.

Would try individually feeding all cells that are < 3.0V with something on the order of 50mA until they're over 3.0V, then charge with whatever you have up to their rating.
 
Have you tried to charge any of them? Some of them might be OK (or OK enough to do something with). You might need to make a jig to clamp them in, but put them in parallel as needed and charge them all at 3.6 to 3.65 volts. Perhaps charge them in the groups you already made with your first measurements. See "Top Balancing."

After you determine which ones will fully charge, load test each one with a 1 to 2 Amp load. Old car headlamps work great for this, and you can put them in series/parallel combinations until you get the current load you want. Watch the voltage and time as they discharge, and stop at a minimum voltage of no less than 2.0 volts. The current used times the time it takes to deplete the cell is your amp hour measurement for that cell. You can then match them up by rating to make a battery.

Every four cells in series will make a 12V battery, so you can parallel them in groups of four to get more capacity.
 
Have you tried to charge any of them? Some of them might be OK (or OK enough to do something with). You might need to make a jig to clamp them in, but put them in parallel as needed and charge them all at 3.6 to 3.65 volts. Perhaps charge them in the groups you already made with your first measurements. See "Top Balancing."

After you determine which ones will fully charge,

I would discourage the parallel charging as it's counterproductive to the stated goal. High cell count packs of an unknown condition need individual attention if the goal is to build a well functioning battery in the end.
 
I would discourage the parallel charging as it's counterproductive to the stated goal. High cell count packs of an unknown condition need individual attention if the goal is to build a well functioning battery in the end.
While that is true, I thought that cycling through 80 cells might take a while, thus the suggestion to parallel those with similar resting voltages.
 
Thanks all, well as a starter I bought a few bits n bobs, new regulated Psu, some nichol strips along with a spot welder. Now I will study the Top Balancing article and give it a go. I may join 4 of my 26650 together and charge em in one go. I also bought a couple of 8 way cell monitors, they should prove useful. Is there anything else I should get to star me off ?
Thanks
Goeoge...
 
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