DIY replacement cordless phone battery

For a few years now I have been using a Uniden cordless telephone system at home. Nothing special, a base unit with three handsets. However three years have passed and the batteries on the three handsets no longer hold any charge. The local excuses for electronics stores wanted almost $33 for a new battery pack (which consisted of three nickel-metal-hydride AAA cells of 800mAh capacity and a JST connecter). Hmm… three phones need three batteries…almost $99 for three batteries. Ouch.

Upon examination the battery packs were quite simple to reproduce, and there was plenty of length from the plug connectors to reuse them.
So let’s have a look. Here’s the original pack:

Here I have used three AAA NiMH 1.2V 900mAh (greater capacity cells!) with solder tabs. Thankfully there were not wider than the original cells.

So I tape them together and do a test-fit…

… solder the tabs together, keeping mind of positive and negative terminals. Two cells need to be aligned in the same direction, so some 28AWG wire connects between the + and -, covered with some electrical tape. Some narrow heatshrink would have been better, but that’s expensive as I don’t have any at home…

And here we have the finished pack in the phone. I placed the phone handset in the charge unit and kept an eye on it for three hours, it charged perfectly and the standby time is back to around seven days.

Money saved as well as the environment. Currently you can buy a whole new set including three handsets, one base unit and two charging stations for $99, but that would generate demand for much more materials, transport and so on. By replacing the packs with the cheaper cells the lesser of two environmental evils has been chosen.

Please note that I’m not involved in nor responsible for the Goldilocks project, however I’m happy to promote it as a worthwhile endeavour. In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.