I have a project that I want to power from 2 18650 cells in series (7.4V)

The problem is I cant find any prebuilt protection circuits for 2 cells in series that also have micro USB input and LEDs to signify a charging/charged state.

I don't want to build my own circuit as space is limited and prebuilt circuits offer the smallest size possible in most cases.

So I've come up with a solution by using 2 TP4056 modules to charge each cell independently and then switching to a 2s PCM to handle the cells in series once charged. Ideally with 2 switched positions, ON(Load) and OFF/Charging.

What I'm unsure of is how many of the connections I have to switch to do this safely. Obviously their would need to be switch for connecting the cells in series, but what else would need to be switched?

Or am I going about this the wrong way?

The attached image is my guess, but could it be done with less switches? I want the switch action to happen all at once so for 3 would need to use a 3PDT switch, all of which are huge and I need something quite small. Suggestions?

 

You wonf find any usb series chargers because they would need a 10v supply, so if you want to charge them at once, you will need a mains charger, or two usb circuits each separately,

usb2 wont give more than 500ma, usb3 900ma.

 

You wonf find any usb series chargers because they would need a 10v supply, so if you want to charge them at once, you will need a mains charger, or two usb circuits each separately,

usb2 wont give more than 500ma, usb3 900ma.

Huh? Phone chargers can supply 2A through a USB connection...

Anyway, that's beside the point, I'm really looking for help with switch integration.

 

Would this be of help?

 

Would this be of help?

That's a 4s PCM, I only need a 2s and its already in the circuit I attached in the original post. The problem with those is unlike the TP4056, they don't have LED's or a micro USB port.

 

so you will have to switch the batteries out of circuit to charge, and switch back in to use.or use a 9v supply and bpm