Been wondering about this for a while. I've got rechargeable coins for the backup battery, which I can swap and charge through USB on my desktop. Just been wondering about charching main batteries on the device though - after buying some cheap (really cheap, 800mA) nimh cells, I was wondering if I could convince it that the battery pack is a rechargeable battery pack.
I had a proper rechargeable pack once, but it was broken, so I tried to reverse-engineer it. The main difference I found was that (aside from the cells being a little smaller than AAs, and there not being room for AAs) there was a second metal contact at each end, which was wired to the first - basically meaning that instead of something like
with the two contacts. Likewise, there's two contacts in each side the battery compartment in the device itself.
This being the case, would wiring both contacts on each side together - to simulate what the "proper" rechargeable pack had - enable me to charge AA cells using the device, rather than an external charger? I've done it preliminarily, and it seems to be working so far - I just don't know if it's something I'd "get away" with...
(And could I use a USB charger for a PSP*? )
*It's a PSP mains charger I'm using. It does everything I've got except the Jornada - the Compaq, my OpenPandora, my Toshiba e350 and e800. I don't even own a PSP, and never have.
I believe the extra contacts are used to measure the reverse bias...to determine the amount of remaining battery energy. The thing that would worry me is how does the charger know the battery is charged and to not overcharge the cells. I pwesonally would use an external charger made fot AA cells and swap them out when needed.
On the other hand I've heard of people charging their units for 6 hours and then unplugging it to prevent overcharging. Even knew a guy who used to charge until his unit got warm as his telltale cutoff point.
Ohh OK. So if I've not wired the contacts together correctly, then, I take it it's not going the be the end of the world...? I was wanting to avoid having to remove the batteries, is all. I might give it a go, I've just got cheap batteries (from my local Poundland) as pretty-much-disposable ones for testing. I don't know how the charger works exactly. The charging light comes on with alkaline batteries, so I will have to be careful. That's one convenience of modern hardware- you can see at a glance how much charge there is, if it's done, blah. This makes the radio geek in me want to keep a tiny voltmeter hooked in.
The batteries I've got *supposedly* have a high overcharge tolerance. We'll have to see.