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Discussion Starter · #1 ·
my Honda Civic with 45 180ah Calbs (grey cells) in storage. My friend was charging it once a month but cells still managed to go almost to zero. DC-DC converter and orion bms was the load. The cells I checked were below .5 volt the whole pack reads 30 volts, should be 144v I’m thinking they are toast. I was researching this and ran across a forum post about bringing LiFePo4 to zero to increase capacity. It was about A123 cells .
Most posts/research seem to indicate they are gone. The one cell I started to charge very slow has come up to voltage and is staying there when idle, but haven’t tested capacity yet.
 

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Cells should be 100% isolated in storage, most especially from their BMS.

Don't get your hopes up but

A super slow baby trickle a few 0.X V higher than they are at 0.1C rate or lower

once past 3.2Vpc get them all the way to 3.45Vpc

do what you have to do to balance, without going over 3.5Vpc

never letting current rate going too high, watching cell temperatures

If they look OK, cycle 3-6 times like that, between say 3.1Vpc as zero and 3.5Vpc as Full

Then try cap testing.
 

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Discussion Starter · #4 ·
Thank you
I am using an RC charger to control voltage and amperage of charge. So set charger no higher than 3.5 at say 10 amps
(.1C would be 18 Amps). Once I got to 2.5 volts, I have been charging first to 3.4 for 2+ hours now at 3.5v amperage is already tailing down below 10 amps with no detectable heating of cell at all.
 

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Yeah, they're gone. I came into possession of a pack where half of the cells were below a couple of volts. Every single one of those would not hold a charge. The lower voltage cells self-discharged faster than others, but all were ultimately not usable.
The implication of self-discharging is that the separator is damaged and charge is leaking across that barrier. The risk (beyond your pack constantly going out of balance) is that in actual high current usage that membrane damage will get worse and allow enough current to flow to cause local heating, more damage, more heating, etc. You won't necessarily get runaway cells spreading through the pack like other lithium chemistries, but bad lifepo cells will overtemp and vent.
 

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Thank you
I am using an RC charger to control voltage and amperage of charge. So set charger no higher than 3.5 at say 10 amps
(.1C would be 18 Amps). Once I got to 2.5 volts, I have been charging first to 3.4 for 2+ hours now at 3.5v amperage is already tailing down below 10 amps with no detectable heating of cell at all.
Sorry I was not more clear.

Charge TO 3.45Vpc and STOP is 100%, CV only

No CV Absorb stage is needed, no point just hurts longevity (if cells were good)

Holding at 3.5Vpc is only for "if needed" for the hardware you are using for balancing.

With a good pack, needed maybe a few times in daily usage cycling.
 

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Discussion Starter · #7 ·
After charging to 3.45 I started a charge discharge cycle test.
In cycling between 3.1 and 3.5 I get 170ah on 1st charge and 200 milliamps on discharge and then a similarly low charge (a few hundred milliamps with the Icharger at 20 amps. the Icharger quickly goes through 5 cycles that way.
It looks like high IR?
for a capacity test what bottom voltage should I keep to? I cycled 2 cells this way when charged to 3.5 they both settle at 3.34 volts after 12 hours. both cells stayed stone cold throughout the process.
Both cells took in 160 ah to 170 ahs.
 

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Charge Ah is irrelevant.

Cap test is discharging after charging using their spec sheet maxV, holding to 0.01C endAmps

at a very low C-rate say 0.05C,

going down to the spec sheet minV

in order to truly compare to nameplate

Personally I think 170Ah is a "good enough" but it's great to get exact benchmarks and track declining SoH% every 300 cycles or whatever.


when charged to 3.5 they both settle at 3.34 volts after 12 hours. both cells stayed stone cold throughout the process.
That is your "healthy 100% Full" definition for normal cycling.
 

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Discussion Starter · #9 ·
What do you think on Internal Resistance? and the Icharger short cycle time? Is a 20 amp draw pulling voltage down below 3.1 thus stopping the discharge cycle sound like a battery with decent capacity but high IR or am I missing something? I will capacity test next and then an IR test Thank you for your help.
 

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the Icharger short cycle time?
I did not understand any of that, cannot see mAh being relevant on a 170Ah scale

What do you think on Internal Resistance?
I think it is very difficult to measure properly, even comparative benchmarks from one session to the next. All the variables must be held constant, lab level equipment etc. Rick Distler aka rampman's ESR meter (V2) Lipo ESR Meter Mark II, designed by Wayne Giles

available from HobbyKing, also from RampMan direct

and RC Battery (Liperior Lipos)

Is a 20 amp draw pulling voltage down below 3.1 thus stopping the discharge cycle sound like a battery with decent capacity
20A is only 0.12C so ESIR should not be an issue.

At that rate constant current draw from Full should last 7+ hours if they are actually 170Ah

There really isn't much Ah capacity left between 3.1V and whatever spec min V is.
 
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