Minimalist 2 cell Li-ion Battery charger

[LazaKamikaza]

I have a 1 cell charger from a mobile power bank that charges a 3,7V Li-ion battery. I have another battery that's the the same as the one in the power bank and I would like to extend the capacity. So I came up with this circuit and would like to ask you if i need to change or add anything or if it will even work. Thanks for your answers!

 

[Harald Kapp]

Welcome to electronicspoint.

Batteries are always different, even if they are nominally the same. You will need a charge balancer (Google) to protect the batteries from destruction.

 

[duke37]

With 3.7V out and a 3.6V zener, you will be left with 0.1V to charge battery 2. This will not work.

Are you going to connect the batteries in parallel for use? What will be the effect if they are not exactly equal. You would be better to use and charge the batteries separately.