SOLVED: Rechargable battery - replace Li ion with NiMH? - Braun Razor

Rechargable battery - replace Li ion with NiMH?

I have a Braun shaver that needs a new battery. Thankfully this one doesn't have a soldered battery, it has a removable AA. The one that came out is generic (red covering, manufacturer wasn't anything I'd ever heard of). It does say it's Li ion, though. Meanwhile, the only rechargeable AAs I have are NiMH.

As far as I can tell the only difference is the NiMH has a much higher capacity (2300 mAh compared to like 750 for the old one). Is there any reason to think a NiMH wouldn't work?

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Posted: Mar 30, 2026

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Hi @deilayborer

It won't work.

Charging Li-Ion batteries is different to charging NiMH batteries as they have different output voltages i.e. Li-Ion = 3.7V/cell, NiMH = 1.2V/cell.

Li-Ion batteries require a higher charging voltage than NiMH batteries i.e. Li-Ion need 4.2V, NiMH need 1.6V.

The battery charging circuit in the shaver would be designed to deliver the 4.2V necessary to charge the Li-Ion battery, which would damage the NiMH battery (overcharging) and possibly the shaver as well.

Search online for the battery model number that is printed on the Li-Ion battery to hopefully find suppliers.

Scroll down to the A Firm No, and Here’s Why section in this article to read and see what would happen if you tried to do this.

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Rechargable battery - replace Li ion with NiMH?

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