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JRC JHP500 handheld transceiver
On Mon, 30 Jan 2006, Greg Copeland wrote:
Be careful when switching to alternate battery technologies. NiCads are designed to be charged at rates up to 3C while most NiMH are typically designed to be charged no faster than 1 to 1.2C. Can you back this up with some documentation? I'm not an expert, just a relatively well informed user, but this runs counter to everything I've read. The rule of thumb for most common battery chemistries is C/10 (1/10 the amp-hour rating) for 12 hours. As far as I'm aware there's no way to safely (that is, without damaging the cells) speed that up significantly without microprocessor controlled chargers and special waveforms. Even with those things I doubt it's possible to charge NiCd's or NiMH's anywhere near as fast as you suggest (20 min. to 1 hour) without severely shortening their lifespan. Take care of your batteries, and you might actually get the 1000 charges the manufacturers advertise; abuse them, and you might get only a dozen or so charges. In short, get an extra set or two of batteries, charge them slowly, don't ever overcharge them, and they'll live a lot longer. Long of the short, if you change battery technologies, make sure you change chargers too! Otherwise, you may be in for a surprise including very short battery life, batteries which never hold a full charge, and maybe even fires. To the contrary, all information I've ever come across indicates the charge cycles are identical for NiCd and NiMH. In other words, they're completely interchangeable, assuming of course that one accounts for the different capacity when charging. NiCd's are lower capacity (usually _much_ lower), so generally, NiMH's can be safely charged in chargers designed for NiCd, but the reverse isn't necessarily true. For some years I've been using NiMH's in cordless phones designed for NiCd's, with absolutely no problems. Battery life between charges is much longer with NiMH's, and lifespan is also much greater because of NiCd's memory effect. -Dan |
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