I'm trying to teach myself electronics hence my beginner skills in design. I want to design a circuit to power another with two 18650 li-ion batteries in series. Charging them in series seemed like a lot of work with load balancing - and li-ion charging ICs are cheap and abundant, so I reasoned that I could charge each battery individually with a separate IC for each li-ion battery, from USB power.
The idea is when USB is connected, the batteries need to charge. Each battery is disconnected from the other and charged via the charging IC. When USB is disconnected, the batteries are connected back in series and power the circuit. Below is a basic circuit that seems to work, but I'm wondering if there's some kind of thought process or analysis I'm missing. In the circuit I changed USB from 0V to 5V and observed the output changing from 7.2V to close to 0V. Any help is appreciated. :)