I'm using a circuit to charge a 2S lipo battery, and bypass the battery while it's charging, and still supply energy the circuit.
It works. But for the new charger module I'll use now, when the battery is fully charged to 8.4V, the charger starts drawing energy from the battery.
So If I leave my circuit disconnected from the charger supply, even if the circuit's load is turned off, the charger's circuit will draw a tiny bit of current from the battery non-stop.
So I wanted to isolate physically the battery from the charger when the charger is not charging.
I came with this first circuit in falstad, but I have some doubts:
Simulation of this circuit in falstad: Circuit 1
If I simply put a diode D1 to prevent energy from the Battery going back to the charger, will the charger work normally? Will the diode's voltage drop not allow the battery to be fully charged to 8.4V? The battery will not get to the full voltage output of the charger?
I did then this other version with two mosfets and removed the diode D1, and in simulation it works. But, still do the smaller voltage drop of the P mosfet will also not allow the battery to be fully charged? Or it's so small it doesn't matter? Also, will it charge the battery normally, as if the battery was directly connected to the charger?
Simulation of this circuit in falstad: Circuit 2
Is this second circuit a good approach?
Edit: You can see the live simulation of both circuits and change it on the fly if needed by clicking in the Circuit 1 and Circuit 2 links.