I need a solution to charge two 3.7 V lithium-ion cells that are in series. However I have a very limited access to modules and I need to have current limitation as my source won't stand beyond 0.5 A.

I have this module available (TP4056 based), but it's for a single cell. Is there any way to make two of these modules do the job?

enter image description here

Datasheet: TP4056

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    \$\begingroup\$ We will probably need more than a picture of a PCB to tell. Please link the datasheet to the BMS. \$\endgroup\$
    – Lundin
    Commented Feb 9 at 7:22
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    \$\begingroup\$ Almost certainly not. There don't appear to be any transformer-type isolation components on there. Unless you power each from a separate 5 V wall-wart. \$\endgroup\$
    – Neil_UK
    Commented Feb 9 at 8:05
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    \$\begingroup\$ You can IF the input to each charger board is isolated (floating). Each battery will then be dealt with separately. || A usually less desirable way is to transfer the charger between batteries as needed - eg using a DPDT relay. \$\endgroup\$
    – Russell McMahon
    Commented Feb 27 at 0:50

1 Answer 1



If you try, KABOOM!

That's because they are not isolated. Upon connection, they make a short circuit across one Li-ion cell.

Is there any way to make two of these modules do the job?

Yes, but it's more expensive than buying the correct charger. It involves adding an isolated DC-DC converter between the USB port and one of the charger modules.

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    \$\begingroup\$ Or simply using two isolated chargers. \$\endgroup\$
    – Justme
    Commented Feb 9 at 15:18

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