Battery protectioin circuit required when using nPM1100?

[Rashid Talib]

Hi

We plan to use the nPM1100 for charging a LiPo battery and provide power to an nRF52810 processor and subsystem. The battery is very small and has no PCM.

Questions:

1. Is a PCM required when using the nPM1100 or will this IC make sure the battery will be protected from under discharge and over currents?
2. If wee need to add our own PCM, what do we need to consider in order to make it work with the nPM1100? As discussed here  RE: nPM1100 doesnt start charging empty battery the nPM1100 is not able to detect and charge a deeple discharged battery with a PCM module.

Thanks & best regards

Rashid

[ketiljo]

Is a PCM required when using the nPM1100 or will this IC make sure the battery will be protected from under discharge and over currents?

Yes, battery protection is a requirement.

If wee need to add our own PCM, what do we need to consider in order to make it work with the nPM1100? As discussed here  RE: nPM1100 doesnt start charging empty battery the nPM1100 is not able to detect and charge a deeple discharged battery with a PCM module.

The PCM will cut the connection to to the battery when the battery voltage is below a certain limit, usually ~3 V. The nPM1100 will release the protection by applying a voltage to the battery for some time, then check if the battery is accessable and start charging. But if the battery voltage is below Vbat,charge,min of 2.1 V, the battery is damaged and can't be charged https://docs.nordicsemi.com/bundle/ps_npm1100/page/chapters/charger.html#ariaid-title11. Both overcharging and undervoltage is damaging to LiPo batteries. 

[Rashid Talib]

Hi Ketiljo

Thanks for your reply. So you're saying, that the nPM1100 is still applying voltage to the battery even if it has been disconnected by the PCM (0 V detected at the PCM terminal). If the battery is discharged but still working, this will slowly bring up the battery voltage and finally release the protection.

I ask, because I have already experienced other battery charger ICs, that will give up once they see a battery voltage of 0V. The only solution with these ICs was to add a diode and series resistor to bypass the charger IC until the battery voltage is high enought.

[ketiljo]

Yes, it will release the protection and continue charging if the battery voltage is above 2.1 V. The overdischarge protection in the battery is releates by applying a voltage from the outside. The nPM1100 does this. 

[Rashid Talib]

Thanks, that was very helpful!

Best regards
Rashid