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I am buying some Li-ion pouch batteries (3.6 V) and charging circuits for a project. The batteries come with overheating, over-voltage, and over- and undercharging protection circuitry.

In the reviews, someone mentions that you can use any source to charge it due to the protection. I googled it but it seems people make a difference between protection and charging circuitry, and I cannot find an example of someone using it without charger. I see why, but wonder if a protective circuit would work as a make-shift charging circuit, at least it won't explode, right?

In short, can I just hook the battery on the Vin on my D1 mini, supply the board from the battery, and charge the battery when hooking the board onto USB?

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  • \$\begingroup\$ On a related note: charge them (through a charger) and discharge them one at a time. Do not connect protected Li-ion batteries in parallel. Bad things can happen if you do. \$\endgroup\$ Jan 19, 2023 at 0:13

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No, don't. A BMS is not a charger.

  • A BMS can't limit the charging current, let alone provide a constant current for the CC charging stage; it can only stop charging altogether when the current is too high;

  • A BMS doesn't terminate the charging properly; some just keep the battery floating at its maximum voltage indefinitely;

  • The maximum voltage on many BMSes is set at just over the maximum recommended voltage for charging, and this will overcharge the battery;

  • Etc.

Even if you get away with it (as in "no immediate fireworks"), it will seriously limit the cycle life of the battery, and possibly not charge it at all if you don't limit the charging current.

Also, your ESP is 3.3 V, and you can't charge a Li-po with that, and simply connecting a 5 V voltage source from the USB to a Li-po battery is not a good idea, BMS or not.

There are plenty of cheap ICs and modules (with USB on their input side) around for charging Li-po batteries; you should use one of those. The BMS is there as a last-ditch protection when things go wrong.

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