On 23 Oct 2004 17:43:21 GMT, wrote:

Andy Hall wrote:

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.

It's trivially easy with a ready made chip that does all the hard work
for you. They can be bought 'off the shelf' now. One off price is
only a dollar or two and I'm pretty sure they'd be a lot cheaper in
quantity. The most well known manufacturer is Dallas/Maxim.

Yes I know.

However, consider the impact of a dollar or two on the costs and
margins for a Chinese factory making a power tool that will end up in
B&Q for a few tens of pounds. The ex-works price is probably around
£10-15 tops so anything that does not need to be there is likely to be
left out. Every cent counts.

The game is not quality, it is of meeting a minimal price and a
minimal spec. and having an acceptably low return rate within the
intended warranty period.

If usage is low enough, then with cheap batteries and a crappy charger
circuit, these parameters can be met simply because the battery will
not be subjected to that many recharges during the warranty period.
After that the retailer doesn't care. They would rather have the
marketing ploy of fast charge because that sells product.

The retailers are taking a reasonable gamble that a large proportion
of the customers will not be discerning, will have low usage rates,
sling the tool when it breaks and probably have lost the receipt
anyway.



..andy

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