In message , The Medway
Handyman writes
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?
The voltage of NiCd or NiMh cells is almost constant from full charge to
flat, so it can't be used to judge capacity accurately. The only way to
test capacity is to use a device that charges the battery then
discharges it at a fixed current and monitors how long it lasts until
the voltage falls.
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?
Lead acid should be kept topped up as much as possible. If you let it
run flat the plates sulphate and it loses it's ability to take charge.
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?
Standard battery packs are often only rated between 1.2Ah or 2Ah.
That's not an awful lot for a very heavy load. Maybe you're
underestimating just how much cutting you do get with them. Also note
that the more you force the saw the higher the battery demand will be as
the motor struggles against the force. Go easy on the cutting and let
the blade keep a relatively high speed.
I'll also remind everyone that as soon as your tool battery starts to go
"weak" recharge it immediately. As tempting as it is to finish drilling
the hole, it is damaging the battery because the first cell to go flat
gets run in reverse by the other cells in series and may lose capacity
leading to it going flat even sooner next time.....
Contrary to popular belief you don't need to discharge NiCd battery
packs completely before you charge them. You can top them up at any
time and just give them a full discharge every so often to keep them
fit.
And those dumb "7 hour" chargers where you are advised not to leave the
battery on charge? Dump them and get yourself a proper cordless power
tool!
--
Clive Mitchell
http://www.bigclive.com