passthrough

Okay so, currently wanting to set up a test for some rechargeable batteries, and developing a lower power mode for a system. The goal is to connect fully charged batteries to my devices to see how much current they actually drain. I have an estimate how long they should last, but its not exact...

I'm trying to design a passthrough charging system for my rpi4b which requires 5v 3a max. I assume it means the regulator needs to handle 6a output if it handles the lipo charger too. I drew out a schematic with power transistors for control, but I'm not sure I set it up correctly. Will this...