How to charge 4 1.5V li-ion batteries with pass-through charging

The TP4056 module works only with 3.7V Li-Ion batteries, and cannot be used with any other type.

My approach for a robot with small motors would be to use 1 or 2 (in parallel)18650 cells, which you could charge with the TP4056, and a DC-DC step up converter for the motors.

Pololu used a similar approach for their very successful 3Pi robot.