On Sat, 23 Oct 2004 16:10:57 +0100, Andrew McKay
wrote:

On Sat, 23 Oct 2004 10:48:18 +0100, "Dave Plowman (News)"
wrote:

Like for like, the faster you charge the batteries, the less time they
will last. And more so with poor cells - which is one of the main problems
with cheap power tools.

Do you have any reliable information to support that claim?

I'm not saying you are wrong, and indeed it's entirely possible that
you are right. But it would carry a lot more conviction if there were
supporting evidence that the jury could convict on.

Andrew

Have a look at these....

http://www.national.com/appinfo/power/files/f19.pdf

http://www.national.com/appinfo/power/files/f7.pdf



Regarding batteries - it is possible to get batteries that are
designed to tolerate fast charging without damage or degradation.
Unsurprisingly, these cost more.

Fast charging implies (or should imply) implementing good quality
chargers to look at battery voltage and or temperature.

NiCd and NiMH batteries can both be charged using the Delta V method
which involves monitoring the battery voltage very accurately to
detect the small voltage drop that occurs just after peak charge and
to stop the charging. With NiMH, the drop is about 2mV per cell, so
implementing chargers is not easy.

The other approach is to use detection of cell temperature as well and
to stop when the temperature starts to rise, which it will
significantly at the end of charge.

Another interesting approach is that by Rayovac who have cells with
charge control circuits built into the cells.

http://www.rayovac.com/products/rech...nutes/qa.shtml




..andy

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