Electronic – How to use two TP4056 with two li-ion batteries, but single load

battery-chargingchargercircuit-protectionlithium ion

I have two TP4056 modules (with protection circuit), which I am using to charge two batteries respectively, off a single power line. The modules are the ones that have charge output (B+/B-), and another regular output.

I'd like to be able to use both batteries (increased capacity) to power a single load, even while charging. The batteries are rechargeable 3.7V 16340 Li-ions, same make and capacity.

I'm not sure how to do this in a safe manner. I don't know if it would be safe to conjoin the outputs with this module, and I would like to avoid using diodes because of the voltage drop.

The question is:
How can I make this work, in order to be able to use the device even while charging, and how can I connect the two batteries safely to the device in the first place?

My use case is described in the image.
charging circuit

EDIT: Look to the comments for an answer regarding more than two cells. As the original question was for two cells, I had to choose one of two valid answers.

Best Answer

Don't.

Just use one TP4056 and connect both cells in parallel after balancing them first. Don't connect batteries with more than 0.2V difference in parallel as this can risk fire and explosions (excessive charging current from one to another).

This will work because Lithium cells have a wide voltage range. So when connected in parallel they will self-balance.

the TP4065 module includes over-discharge protection circuitry power should be taken from the out terminals of the TP4056 module, not directly from the battery.

Parallel connection