"Jason" wrote in message
...

"The Medway Handyman" wrote in message
. uk...
Hi

Three questions.

Is it possible to find out how much charge remains in a drill/driver
battery? Connecting a multi meter doesn't seem to give sensible figures.
Any way of measuring the charge remaining?

Generally they need to be tested under load, so that with a given load,
for a given amount of time, the voltage and/or current will drop by a
certain amount, and from that it ought to be possible to calculate the
charge left. Clever battery chargers do the complete opposite, but I'm not
sure if there are any clever battery monitors that will simply tell you if
the battery is any good.

Also, I have a rechargeable torch with apparently a sealed lead/acid
battery. Can I simply charge this whenever, or will the battery develop
a memory? Should I wait till it goes flat?

If it is lead-acid, then *don't let it go flat*. Keep it fully charged at
all times, and you will get a good many years life out of it. The memory
for lead-acid tends to be the fact that they won't forgive you if you let
them go flat - they have a memory better than an elephant (something to do
with permanent and irreversible chemical changes that only happen to a
flat battery).

Lastly, I have an SIP 18v circular saw about 9 months old with 2 x 1.9
a/hr batteries, but they don't seem to last any length of time at all -
never have done. Anything I can do with them?

At 18v, 1.9x2 AH, which we will call 4AH to be generous, would deliver
18x4 = 72W for a full hour. That is being very generous. I'm just
guessing here, but assuming the saw sucks up 200W of power (reasonable?)
then we are talking about a maximum time of 72/200 = 1/3 of an hour, or 20
minutes. Add in the 'real world' factors of differing loads, loss of
voltage over the discharge cycle, duff batteries or inaccurate labelling,
better values for my guesses, heat losses, and you probably would not get
much change out of ten minutes.

I'm assuming these are two 18V batteries in parallel, or used one after the
other. If they are two 9V batteries used in series, then halve that
theoretical 20 minutes down to 10 minutes straight away.

-- JJ