| If you do decide to go that route, keep in mind that | there's an enormous difference in the self discharge rate | between nicads and nimh's.
By enormous he means about 3x. NiMH cells seem to self-discharge at about 3x the rate of NiCd cells. Of course it'll depend on the cells themselves.
| Perhaps if you have one of those teenagers that talks on | the phone 16 out of every 24 hours it would be to your | advantage, but otherwise not so sure...
I'm guessing it would be. These phones tend to die in a week or so without charging with the stock batteries.
| And - if you do use nimh's, make sure that you do *good* | quality work. The internal impedance is so low that | they're quite a fire/burn hazard.
NiCd cells have even lower internal resistances.
| I still have a scar on my leg from stupidly putting a couple of 1400 | ma aa's in my pant pocket. (I use 'em in digital cameras)
Really? I've put lots of AA NiCd and NiMH cells in my pocket loose and while I should know better, I still do it from time to time. I've occasionally had them short out against my keys or something similar, but in every case I just noticed that my pocket was getting hot. Sometimes very hot, but never anywhere near hot enough to burn me. Maybe my keys just didn't make a good enough connection.
Now, if you were to bang the cell hard enough to short internally, then you've got a hot steamer going on.
| Finally, remember the charge times. If it takes you overnight | to re-charge your 600's; it will take you 4x's as long to | charge up 2500's.
Longer, actually -- don't forget about the self discharge rate.
| I suggest considering that though nicad's and nimh's are virtually | the same price now - no manufacturer to the best of my knowledge has | built them into any.
Huh? I'm not sure I understand what you're saying here.
Lots of devices have NiCd cells, and lots have NiMH cells. Including cordless phones.
Personally, since NiMH and NiCd cells have very similar charge and discharge curves, I suspect that simply replacing the 600 mAh NiCd pack with a 2500 mAh NiMH pack in a cordless phone will work perfectly
95% of the time. Yes, charges will take much longer (if starting from a dead battery) and the self discharge rate will be higher (but I suspect that the added capacity will more than make up for that assuming that the phone is actually on when not in the charger.) I suspect that even the battery charge indicator will still work, though it might become somewhat inaccurate (i.e. it may not be as linear as it was before, if it was ever linear (it's difficult (at best) to accurately determine the state of charge of a NiMH/NiCd cell based only on the voltage now. You can make a guess, and you can tell that the battery is almost dead, but before that, it's pretty much a crapshoot, especially if the battery was not fully charged before.)
The only complications I see are if the phone quick charges -- if it claims to be able to fully charge the battery in a few hours, then there's a good chance that either 1) it won't fully charge the battery, or 2) won't detect when it's full, and will keep charging. But in my experience, most cordless phones are slow charged, which will be OK.