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By sblantipodi
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?
User avatar
By sblantipodi
schufti wrote:Hi,
that you'd have to ask the designers of the DW01 chip. Mostlikely because they only protect the absolutely worst case: overdischarge @ 2.4V overcharge @ 4.3V
TP4056 limits @ 4.2V and trickle charges under 2.9V

what does it means " trickle charges under 2.9V"???
should I worry about the "low discharge voltage"?

using genuine Sony VCT6
User avatar
By schufti
#86304 worry - only if you need to max out the cycles on the cell.
LiIon don't like being cycled to the upper/lower extremes, it is said to reduce their capacity.
Best seems to be between 10% to 90% according to "the net".
On the other hand, that increases the frequence of cycles.
But I have never seen a comparison about the total "lifecapacity" = cycles*loadcapacity

tricle charge is important on deep discharged cells, below a certain voltage it can be dangerous to start the usual 1C charge - so they need to be tricle charged up to a safe voltage where they accept full charging current without danger.