Cotty <[EMAIL PROTECTED]> writes: > As Frits and maybe others (I'm on digest) have mentioned, NiCad's > respond well to this sort of treatment. It keeps them at best > performance vs use, and prevents the dreaded 'memory' effect.
I think you mean "the nonexistent memory effect". :-) There is an enormous amount of misinformation floating about concerning NiCd (and NiMH) cells, but the low-down is this: The "memory effect" has been demonstrated, but it's not easy to achieve. You need to discharge the pack to the exact same level many times in a row to do it. After a large number of such charge cycles, you then try to discharge beyond that level -- and you will see a marked voltage drop as you pass it. Modern cells probably aren't susceptible to it anyway: it's been decades since this was discovered, and that was in a solar powered satellite, which is why the repeated, exactly equivalent discharges came about. A related issue is voltage depression due to lengthy overcharging. This shows up when a pack has been on a slow charger for a very long time (like, say, in a portable device that's always hooked up to the mains, so the battery pack is being continuously charged). After sufficient such abuse, the pack will be found to supply power at a lower than normal voltage when you try to use it. Both of these conditions (memory effect and voltage depression) are repaired in the same way: one full discharge/recharge cycle. In normal use, both NiCd and NiMH should be treated the same way: charge them and use them as you see fit, but try not to leave them connected to a charger "forever", and try to remember to run them down in a controlled fashion now and then (say, every three or four months), to reassure yourself that they're still working well. When you do this, and discover that the pack lasts a significantly shorter time than it used to, it's time to replace it before it fails on you at a time of its own choosing. Both types of cell have limitations on the useful life you can expect, in calendar time number of discharge/recharge cycles. (Note that if you discharge and recharge needlessly, you're using up battery life!) For more information about rechargeable batteries, check out "Red" Scholefield's excellent web site at <http://www.rcbatteryclinic.com/>. -tih -- Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway www.eunet.no T: +47-22092958 M: +47-93013940 F: +47-22092901
