Dear TI team,
we are developing a PCB for charging an 18650 Li-ion battery using the part BQ25302. We connected a status LED to the STAT pin to monitor the charging status.
On our first prototype, we noticed a strange behavior. The charging seems to work fine. When connecting an almost fully discharged battery, the LED turns on and the charging process works. After some time, the LED starts to blink which seems to occur because of the increasingly high temperature of the PCB. When cooling it, the LED turns on constantly again.
The strange behavior starts when the battery voltage increases further. At a battery voltage of approximately 4V, the LED turns off, but the charging continues. When the battery voltage reaches 4.2V, the charging still does not stop, but increases the charging voltage further until the built-in overcharging protection of the Li-Ion battery stops the charging at approximately 4.3V. At that point, the charging voltage suddenly jumps to 4.6V which may be related to the built-in overcharging protection getting active.
I attach our schematics. Do you have an idea what may be the problem?
All the best,
Hermetica.
