|Re: AA NiCad battery cells are now 1100 mAh rated|
Message #3 Posted by robert rozee on 31 Mar 2011, 5:35 a.m.,
in response to message #2 by Eric Smith
you are quite right that in HP calculators a set of Ni-Mh batteries will be a pretty much ok substitute.
the only caveat (in some other applications), is that when charged using any sort of 'smart' charger circuitry that is not designed with Ni-Mh cells in mind, it is likely the charging circuitry will not recognize the 'end of charge' conditions, which are far most subtle with Ni-Mh's than with Nicads.
as a general rule, as long as you don't charge at higher than 1/10th of the rated capacity (1/20th would be preferable), and don't leave the calculator sitting on charge for way TOO long, then all will be well. in other words, a 2000mAh Ni-Mh cell will be perfectly happy being charged at 150mA or so for a not too long time interval (no more than a day perhaps).
btw, Nicads do still have some advantages over Ni-Mh cells in certain quite specific applications. A Nicad can deliver a MUCH higher instantaneous current than a Ni-Mh cell without causing itself internal injury, making Nicads a good choice in applications like battery drills. The environmental concerns of cadmium in the environment, of course, are a whole different matter!