Electronics > Projects, Designs, and Technical Stuff

Robotic floor mop Li-ion conversion

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drummerdimitri:
When I bought this product, it didn't work out of the box and after disassembling it, the internal NiMH battries were leaking acid so they needed to be replaced.

I'd like to replace those cells by a single 18650 battery but the problem is for some reason the provided charger is rated at 6 V and 0.25 A and when I tried inserting the 18650 into the circuit and charging it, it would keep climbing above 4.2 V. I had to stop at 4.35 V since it would potentially explode and/or catch fire.

I tried inserting diodes to drop the voltage down but it seems to limit the current to ridiculously low levels so it would probably take a week to charge the device that way.

What else can I try to do to stop charging at 4-4.2V without limiting the current much?

Siwastaja:
NiMH has a very special charging algorithm.

Remove the NiMH charging ICs and add a proper li-ion charger IC in place. Not your smallest project, though.

NiHaoMike:
Get one of those lithium charger boards that accept USB input and remove the existing charging jack to prevent it from being used. If you're using a bare 18650 instead of one with built in protection, you can get boards that also have the protection circuit built in.

tunk:
Is this any help:
https://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.html
https://lygte-info.dk/review/Review%20Charger%20TP5000%204.2-3.6V%20module%20UK.html

drummerdimitri:

--- Quote from: NiHaoMike on September 05, 2020, 02:36:28 pm ---Get one of those lithium charger boards that accept USB input and remove the existing charging jack to prevent it from being used. If you're using a bare 18650 instead of one with built in protection, you can get boards that also have the protection circuit built in.

--- End quote ---

That's actually a great idea since those boards protect from overcharging.

Why didn't I think of that?  :-DD

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