How to repair a lithium battery? (Chapter One)

How to repair a lithium battery? (Chapter One)

Lithium battery failures typically include: BMS (Battery Management System) or cell wire disconnection, BMS failures, a cells aging faster than others, cause voltage differences.

A damaged cell or a series of cells can cause a voltage drop in that series compared to other series, We should check the appearance of the battery pack for

any damage, leakage, scorching, overheating, and then check the voltage at the charging and discharging terminals.

0V Battery pack voltage:

First, measure if there is any voltage between B- and the Total positive terminal of the battery pack. If there is voltage, check for possible problem like disconnected.

 If the circuit is normal, check the BMS for any damage to the temperature sensor, which might made the battery stop charge and discharge.

This way, we can find the faulty point on the BMS and replace it or make charging test on the battery pack.

If there is still 0V between the total positive and total negative terminals of the battery pack without going through the BMS,

it is likely due to self-discharge during long time storage. So you can charge the total positive and negative terminals of the battery pack without going through the BMS (or individual cell charging to activate the cells) .

The charging voltage must be right, and the single-cell charging voltage should be the highest working voltage of the cell.

The charging voltage for the pack will be:

(LiFePO4) charging voltage = 3.65V × S (number of series cells)

(Li-ion) charging voltage = 4.2V × S (number of series cells)

When you start the charging, use a small current less than 0.2C, and after the voltage goes up, We  can gradually increase the current, but it is better less than 0.2C.

After the voltage more than min working voltage of the cells, We can reconnect the charging through BMS. Once the cells are activated, measure the voltage of each series.

If there is a significant voltage difference, it indicates that some cells are damaged and cannot be activated