Greetings!
I want to make a circuit to charge THREE 3.7V li-ion batteries connected in series (total voltage = 11.1V). The circuit must include overcharging protection. And i want to be able to charge the battery as well as use the circuit powered by the battery (while its not being charged).

 

Is there a question there?

 

Use a lm317 set to 12V, or lm7812,

 

Greetings!
I want to make a circuit to charge THREE 3.7V li-ion batteries connected in series (total voltage = 11.1V). The circuit must include overcharging protection. And i want to be able to charge the battery as well as use the circuit powered by the battery (while its not being charged).

In past designs it was not allowed to have a load attached to a LiPo battery under charge because the charger is looking at current draw during the pre-charging and charging phases and voltage during the terminal phase. Having a load attached and drawing current made these measurements difficult and interfered with the charging process.