Wednesday, October 03, 2012

Replacing the non-replaceable battery

At the WT20 matches in Sri Lanka, the England Women's cricket team are now the only unbeaten team left in the tournament. They will be playing their semi final match against New Zealand on Thursday. On the way they have already beaten the teams from Pakistan, India and Australia. Sarah Taylor and Danni Wyatt put on some great batting performances. Apparently some team members think that they can still improve their overall performance. Let's hope so.

The chargeable battery in my Braun electric toothbrush seemed to be holding a charge for a lesser and lesser time. I decided to replace it even though it is claimed to be non-replaceable. This may be because there is a bit of soldering involved. I purchased a battery from ebay and used the chosen method of rotating the unit on the charging base to get at the innards.

Removing the battery was a bit fiddly and my eyesight isn't what it used to be.

Eventually the battery was out and I set about fitting and soldering in the new one. Somewhere in this process I must have shorted something out with the soldering iron tip and there was a tell-tale puff of smoke.
A functional test showed that unit did not work anymore.

Could I find a circuit diagram on the Internet ? No.

Having gone to the bother of getting a new battery, I was blowed if I was going to scrap the toothbrush. I must admit that the timer feature that was built into the electronics was rather annoying in practice. I could see that when fitting the charging base, that the battery was charging as shown by the flashing LED. So I had only damaged the control circuit and not the charging circuit. I drilled a hole in the case and wired up an external switch. The switch gives simple manual control of the toothbrush motor. I reassembled everything and it still charges porperly when on the charging base. The external switch is not that much of a nuisance, although it does not look great as can be seen below. At least I should get another few years out of the toothbrush.

External motor switch

Not that beautiful
Hoping the England girls will bring home another trophy.

All the best.

Posted by Picasa

No comments: