Unknown (long gone) LiFePo4 cells 4lb 14oz

Inwo

Inwo

10 kW
Joined
Dec 13, 2016
Messages
666
Location
SE MN. USA
Picked up a few hundred prismatic cells. Us made international battery.
~ 4 years old. Seem to be 60-80ah.
I think I'm killing them, or at least mutilating the corpse, if the are already dead. :shock:
The first batch yielded 80%. Brough them up slow. About 1 amp. Too fast?
Then using 6 single cell 10a chargers, topped them off. Discharged at 10a rate to a 2.4v dip. (about 3v actual)

The last 20pcs I left on 1a balance charger for days. Removing as they went high. They don't seem to like this at all.
Have not discharged yet, but ir is thru the roof. My hope is that I'm not getting a good reading at 1 amp rate. Discharge test will tell.

Is even 10a too low? Should I hit them hard after up to 3 volts?

View attachment 2MVC-009F.JPG
 
Do you know what the voltage was before charging? If they were below 2v, they are probably toast.

Another test is to charge and watch the self-discharge rate for a few days. Good cells will stay above 3.6v
 
Looks bad. None stay above 3.3v.
If that works, it will be quicker than discharge test.
 
What about ir?
What would the cutoff be for 70ah cells?
Say 1mΩ, 2 mΩ, 4mΩ.
I'm looking for cells>50% useful.
Most likely market would need low-c rate.
 
....
 
e-beach said:
Charge them to 3.65v each and then do a discharge test with a watt meter inline. It might take time but testing a single cell at a time will give you best results. Some may be good and some may be bad. The only way to know is individual cell testing.
Click to expand...
 
That's what I'm doing.
Started with about 80% yield. >70ah.
My last 10 pack only 2 are >70ah.
I charged these slow all the way through. Now I'm thinking it best to charge at 10a after I get them above 2.5v.
May be able to crank my chargers up a little bit. All my big chargers are 12v+.
I can discharge 8 at a time 10a rate.
I think I'll buy an, 8 discrete cell, auto cycler.
 
2/3s came back over 70ah.
This next batch of 60 I'm charging with a 500v 60ma cc 1/2 wave supply. 500v so I can use it up to 160s full pack.
Hoping to get all over 2v before charging.

View attachment 1
 
First full battery built for Don’s BadBoy 48v.
4pcs 2p4s.

Test charging from bottom balanced 2.7v with no bms/balancer.
Random connected cells tested from 71 to 74ah.
10a to start, then switch to 20a.
Notice the banding! Don came over with an $850 tool and 3/8 galv steel.
One on left is first test with plain steel.

MVC-016F.JPG
 
The bands look great. Too bad the tool is so expensive. I've seen kits that resemble super-long stainless steel hose clamps you can cut to length.
 
This set is working great so far. All came up nicely balanced from bottom 2.7v.
These were only matched by capacity.
Hope to get them installed for real world testing.
No bms to start, as is recommended by ev builders using life.
Top balancing is futile, but still may need cell monitor and hv. cuttout.
 
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