schufti wrote:your setup as shown in the first post does have only one gnd connection between the "power supply" and the "watering circuit". gnd is only run via the battery management module, so due to gnd being disconected by battery monitor it does not matter that your battery measurement directly contacts Vb+. There is no other way for any current to flow.
To be honest, it does not matter if you contact the Vb+ at the battery or the out+ terminal of the bm module, they are solidly interconnected - look at the traces.
Many many thanks man, I appreciate the help.
I added another step up module to push the pump to 9v, the step up is connected by gnd to the battery and to the relay for the positive that received power from the battery.
The second step up module is directly connected to the water pump
Really, this is the last question.
Why the tp4056 cut the power at 2.5V?
Isn't better to cut it around 3.3v?