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From: - René -
Subject: Re: Questions on building a battery charger
Date: Tue, 26 Nov 2002 10:41:25 +0100
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On 25 Nov 2002 10:07:51 -0800, firstname.lastname@example.org (Robert
>I am building my own battery charger with a MAX712. (Probably seen
>this post many times) I am wondering what the charge efficiency of a
>NiMH battery is if I use the slowest charge time-out available on a
>MAX712 IC (the slowest time-out is 264 minutes). I would like to
>match my amp-hours of the batteries with this safety timeout with a
>comfortable margin for determining my sense resistor, or in other
>words, the charging current. The batteries are typical AA 1600mAH
>Is it better on the crystals of NiMH batteries to use the slowest
>charge rate or a faster charge rate, such as one hour? Speed is not
>as much of an issue to me as I want the charger to be "intelligent."
>The original charger was a trickle-charger that slowly cooked the
>batteries, so I want something a little better.
You will get many wise & correct answers to this question, so let me
present you with a tangent:
Use a simple "resistor in series" type C/10 charger, and buy some
extra battery sets. As modern frequently used batteries have a life
cycle that does usually not exceed ~ 3 years anyway, why investing in
hi-tec charger technology if the return is marginal.
Sets of 4 AA NiMH are < $10 nowadays. I have 3 such sets for my
digicam which I abuse all over the place (ovecharging in el cheapo
wall charger), and all of them reached the 2 year mark with flying
colors. And always a fully charged set when I want it as I keep
topping off packs regardless of discharge state. Poor techinical
practice perhaps - but the cells don't seem to mind.
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