Answer to: rechargable toothbrush battery dying fast can it be replaced?My Braun Sonic powerbrushes use an AA size battery with spot-welded connections. I can't spot weld a battery, but you can get around that by cutting the wire to the old battery and using a replacement with tabs that allow a soldered connection. I don't recall why, but think my battery was embedded in such a way that you have to destroy part of the works to get lt out, so I had to buy a new brush. If you can get the battery out, replacement batteries, NiCad and NiMH, are readily available on the internet with tabs that allow a solder connection. Each one will cost around $6 with shipping. Then you need to do the soldering. There's a glue-like substance that works as a low load solder, but inside a toothbrush there's a lot of vibration and moisture and I'd think regular solder would be better.