I thought I had done everything right !
I left the battery sit at 36 V for winter.
When I go to check on the battery since sun came back
I was at only 2,35 volt…
Each cells are wether at 0 v or 0,35 v
There’s nothing I can do right ? Like all those brand new 30Q cells must go to trash ?
Lithium based batteries do not get damaged solely from being over discharged.
What will kill a lithium cell is pulling reasonable amounts of power at low voltages. When this happens the electrolyte will “offgas” and build up pressure within the cell. This is what causes prismatic cells to puff. Internal resistance will increase as voltage drops, and any drawn power will cause electrolyte decomposition.
Luckily for you, these cells were not under load at such a low voltage. They simply discharged VERY slowly. This probably did not damage them.
Do NOT try to power anything with them, as this could cause instant permanent damage.
You can likely recover these cells. You’ll need a non-standard charger like a bench power supply that can do CCCV.
Set the voltage to your max pack voltage, and limit the current to 0.25 - 0.5A. The lower you set this, the higher the likelyhood of recovery and the slower the pack will charge. You can do the math regarding how long it would take to charge (5Ah pack at 0.5A would take 10 hours, etc)
You also have the option of charging each P group individually by using the same current settings but setting your voltage to 4.2V. I would highly recommend this over charging the whole pack at once as your series groups are likely out of wack.
Did you say some are at 0V and some are at 2.35?
If they are actually at 0V then those P groups are toast. And you won’t be able to replace them with new cells as the new cells wouldn’t match well with the other recovered ones.
I’m hoping the 0V was just a measurement error. Could you give a detailed list of all the P group voltages?
If the cells are seriously that out of wack, then your BMS is probably what caused it and is toasted.
To clarify : the whole pack is at 2,40 v
Each P group is between 0,34 and 0,45 V
The only charger I have are regular ones, and a 4S lipo charger…
What should I buy to restore this battery ? All the cells are brand new it would be a shame not to try to revive them.
The battery was sitting with just an antispark plugged into it… maybe that’s the culprit
What I would do is to try to charge each individual group separately with some power supply with limiting resistor in between. Take any 5V power supply (like USB power supply) and add a resistor in between say 50ohms will max pass 100milliAmps, Add a mutimeter to check the voltage that it will never exceed 4.2V in a cell. When you have reach say 3.7Volts, you can start charging the next group untill all groups are 3.7Volts. Then you can start charging the pack normally. Some chargers refuse to charge empty cells.
I have tried with my lipo charger… No luck it says low voltage and won’t charge
@TowerCrisis BMS is charge only
Whole pack voltage : 3,30v at charge port and 4,14 v at output
P1 - : 00,28 v
P2: 00,28v
P3: 0,28v
P4: 00,44v
P5: 00,45v
P6:00,46v
P7:00,47v
P8:00,48v
P9:00,48v
P10 +: 00,48v
Yeah I have to be fast before the voltage drops again ?
I am currently charging P1 at 0,2 amps to avoid any stress on the cells.
P1 went from 0,28 to 1,79 v in a few minutes of charging
Yeah I was so joyful at the idea of riding this board again ! I guess I have to stick with my other builds for now.
I already see myself spend the week looking at this charger, hoping I won’t have to build a new battery