On 23 Oct 2004 20:23:44 GMT, wrote:

wrote:
Andy Hall wrote:

Considering the low end, the batteries are so poor and have such
limited capacity, that the only way to achieve any degree of
acceptability is to fast charge them. it also adds an additional
marketing ploy that they can claim a fast charger. Is the charger
designed with all of the electronics necessary to correctly charge the
batteries and preserve their lifetime? Of course not.

How do you know that?

I suspect that with the advent of cheap, single chip, fast charger ICs
it's just as cheap, if not cheaper to provide a proper, 'intelligent'
fast charger as it is to supply a 'unintelligent' one.

I'm almost tempted to take apart the charger from my cheapo, generic,
cordless lopper to see if it does have an intelligent charger. It
certainly acts like it has one.

I've just done exactly that with my 18v NiCd battery and charger from
B&Q. It's one of their Performance Power range and is common to a
whole lot of their cordless garden tools (I have the mini chainsaw
lopper).

It turns out that, to my mind at least, they've done it the most
expensive way possible, so much for shaving off the last few cents.

It has a fairly solid looking transformer rectifier power supply,
full wave rectification by the way, no corner cutting there. There are
then various indicator LEDs, a microswitch (with an external button to
press it) and a latching relay. There are *three* connections to the
battery, one of which is a temperature sensing one, when the
temperature rise indicating full charge is detected the relay is
latched off.

As I said, this surprised me, because it makes the charger relatively
complex. A crude rectifier and series resistor would be cheaper and
so would a delta/V detecting IC. As it is they have to have a
latching relay in the charger, three connections to the battery and a
temperature sensor in every battery. Certainly not corner cutting to
my mind.

This would all be a point if you were considering western component
costs and labour rates. The electromechanical components are very
cheap indeed and the labour rates to assemble them a tiny fraction of
western levels.

The charger you describe could be put together by virtually unskilled
labour whereas as soon as ICs and PCBs are used, the game changes.






..andy

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