I'd like to add multiple Li-po batteries to my octocopter without worrying about different voltages across different batteries while also allowing regenerative braking.
I have seen designs where people use 'ideal diodes' to isolate batteries so they don't charge each other when there's a voltage difference. However, this also means that ESC can't push energy back to batteries when decelerating via regenerative braking.
I think this problem can be solved with a skimped BMS design.
Drone ESCs' power are controlled by high power MOSFETs (Q1,Q2)
Q1, Q2 are controlled by an MCU that's powered by 'LOW POWER+'.
LOW POWER+ is always available.
Diodes (D1, D2) are added to the LOW POWER route to prevent the batteries from charging each other. Power loss over diodes should be minimal since current in the LOW POWER section of the circuit is expected to be small.
Q1 and Q2 are only simultaneously closed when BT1 and BT2's voltages are close to each other (+- 0.05V for example).
The battery with the highest voltage are prioritized to be connected to the circuit.
All batteries are expected to have the same chemistry and amperage ratings and etc. This ensures the current draw from the batteries are shared equally when multiple batteries are powering the ESCs.
I need some second opinion on this. I'm sure similar designs have been done elsewhere. DJI's matrice 200 drone supports multiple battery but I don't know how they implemented.