Many people ask about manual discharge of the P3 battery ... and I always quote the Telesin Battery Discharger .... this of course does not mean the auto discharge routine DJI has created in the battery board should be ignored - far from it.
But here is a picture that shows what you can do with the Telesin and a DJI battery.

The picture is of one of my DJI P3 batterys with Telesin discharger, (switch set at 15.2V cut-off), plugged into it ... battery switched on ... and then USB lead to my Soloshot 3 Robot Camera. The DJI battery then is not just discharging and wasting that energy - but energy is recycled to charge up my SS3 system.
The Telesin will auto cut-off at 15.2V .... leaving the DJI battery at storage level.
Nigel
But here is a picture that shows what you can do with the Telesin and a DJI battery.

The picture is of one of my DJI P3 batterys with Telesin discharger, (switch set at 15.2V cut-off), plugged into it ... battery switched on ... and then USB lead to my Soloshot 3 Robot Camera. The DJI battery then is not just discharging and wasting that energy - but energy is recycled to charge up my SS3 system.
The Telesin will auto cut-off at 15.2V .... leaving the DJI battery at storage level.
Nigel