Now I hope that this is done, for now. I chose the LTC4055 from Linear, which, besides having a Li-ion charger from USB power, it can also seamlessly switchover the source power from battery and the USB line, thus allowing the robot to be used also while recharging. The LTC4055 datasheet says that the output current is only 900µA, but, according to some feedback I got from asking to the professors and to stackexchange, I’m almost sure that this figure must be wrong (probably they meant 900mA). A design note from linear proposes a circuit that can balance the load from the USB power and the battery, which means that we can not only use the robot while it is recharging, but also to draw some power from the battery if the USB power is not enough to power the robot.
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