I've an old cellphone I was hoping to resurrect for my mum with a free Virgin sim, but the battery looks to be shot (it's not been used for about a year). Only giving 2.5V instead of 3.6V. The proper new ones, shown here, are expensive, but it will take 3 AAA dry cells so I was wondering about fitting 3 AAA NiMH. Thing that worries me, the battery pack has 2 connections on the sides to + & - that match where dry cell ends would touch (and show the 2.5V) but has another 4 as well on the flat, that contact other bits, but don't show any significant voltage. Anybody know what these do? Overcharge protection?
I have dissected at least 20 misc rechargeable battery packs, and i have found that most times, these extra connectors are any of the following, most usual first: -Heat sensor diode for heat regulated charging. -Reference connection to get voltage over one cell to enable a charger to charge packs with different voltage using the same regulator settings. -nothing -internal chargeing chip (only very new packs) If you replace the cells with rechargeable NiMh-cells, you might find that the cells in the phone now does not have the little nipple on the plus pole, and that might make your retail AAA cells hard to fit. Otherways my best tip is to see if you can open the broken pack and replace the cells in it and keep the original battery connector. But first leave the phone on charge for about a day to see if the problem fixes itself, unless you have allready done so.
The cells in the pack are a bit shorter than standard AAA so I hoped to be able to stick rechargeables in where dry cells fit. For the size reason I can't rebuild the pack with standard AAA NiMH. But it does need to recharge in the phone as usual. Found a few tips here on restoring batteries, will give them a try before spending money.
AFAIK they are used to monitor the current charge state of the battery so as to prevent overcharging and for the pretty bargraph on screen, however I don't know how they are connected to the cells. If the batteries are expensive on their own it may be worth scouring ebay for a replacement handset with battery.
The "quick tickle with 12V" tip seems to have worked a treat. Battery subsequently fully charged up (Sunday) and is still holding well (Wednesday).
