Need help identifying a bms (LiFePO4, 48V, 20-30A)

[legend@gazeta.pl]

It was purchased 2-3 ago on eBay. The seller was from Isreal (if that matters). I can't find it's exact specs, documentation etc.

Anyone recognize it?

Thanks

 

[dnmun]

if you have no documentation for the balancing voltage then it could be for lifepo4 or lipo. no way to know without documents.

 

[legend@gazeta.pl]

It was included with dead LiFePO4 battery.
I was trying to compare it visually with other units using Google Graphics (it usually works for me), but no luck this time :/

 

[dnmun]

so where is the picture of the battery and what were the cell voltages?

 

[legend@gazeta.pl]

It was DIY battery with 16x HK Flighmax cells. Two cells were dead. The other are out of balance with 40-80% of nominal capacity.

 

[999zip999]

So the batteries are lico and not lifepo4 ? A pic of the batteries and maybe we can tell you. Or your seller could have mismatched things ? Do we know the seller or is a secret agent from behind the weeping wall.

 

[dnmun]

no, the battery is a lifepo4 pack and was dead to him because it is outa balance from sitting for a long time. too bad because he coulda likely forced it back into balance and restored capacity by cycling it.

 

[999zip999]

I would do as dnmum said and list the voltage here like
1. 2.85 v
2. 1.98v
3. 3.65v


12. X.xx volt
What are hk flight max cells ? Zippy flight max lico ? Pic ?

 

[dnmun]

he has already decided not to fix it. people do not understand how you can restore capacity by forcing the cells into several full cycles anyway. so it is normal that he thought it was 'dead'.

 

[legend@gazeta.pl]

It's the battery: http://www.hobbyking.com/hobbyking/store/__14070__ZIPPY_Flightmax_4200mAh_4S1P_30C_LiFePo4_Pack.html

I was considering restoring the battery by cycling it but I don't have proper tools for it.
I was using stock charger or imax b8+ charger but the progress was so small I gave up.

 

[dnmun]

It's the battery: http://www.hobbyking.com/hobbyking/store/__14070__ZIPPY_Flightmax_4200mAh_4S1P_30C_LiFePo4_Pack.html

I was considering restoring the battery by cycling it but I don't have proper tools for it.
I was using stock charger or imax b8+ charger but the progress was so small I gave up.

it is a fight to force them to work when the BMS shuts off the charging. not to diss you, but wish more would ask for guidance when this is the situation they face.

we coulda helped you some. have had to do similar before. but totally dead cell is hard to recover. you can hack the battery down in series or cut and splice the remaining into the same series and shrink the width.

the imax is limited in power too and it is a hassle because it can only span 6S.

 

[legend@gazeta.pl]

My IMAX can work with 8s.
I started by replacing bad cell for new ones but the IMAX balancing does not work (or work, but insufficiently).
One or two cells quickly reach max voltage and the other remains ~0.2v lower (I was leaving it overnight but in vain).
Discharging is pretty the same but opposite. One cell reach the min voltage at around 0.3-0.5 its original capacity and it's done.
Also I can't solder properly the tabs that were not primed in the factory (usually, when I split two cells one tab remains primed from the balancing wire but the other is not).
I was trying an acid and alumweld flux but no luck. If I manage to prime it a little, the solder come away when I heat it again :/

 

[dnmun]

when lithium cells are dropped below a voltage where there is no longer available lithium ions then they can be damaged as current is pushed through them. if they discharge down to low voltages on their own then the copper electrode dissolves and coats the other electrode so the lithium ions have no place to go.

if you can recharge them right away when they slowly discharge without a large current passing through them then sometimes they will come back and they usually have higher internal resistance so they do not charge up like the others and do not discharge like the others.

if they discharge down to low voltage and stay there for a long time then you can cycle them to full charge and back to full discharge several times and they recover some if not all of their capacity.

since your pack had a BMS they were not discharged below the LVC under load so i hoped they would not be damaged.

you may be able to find enuff good cans in the pack so you can cut them down in width and use the ones you remove from each channel to build 2 new channels to replace the dead ones. cut the tabs between cans and solder to the tabs since the tabs will be spot welded to the cans. nickel can be wetted with flux so you can solder to it.