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?

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?

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?


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

"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.

-- JJ

"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

The Medway Handyman wrote:

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?

Not with much certainty. The only realistic way is to charge it with a
decent delta peak sensing charger. You then get an indication of how
flat it was by the charge time.

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?

Sealed Lead Acid batteries don't have a memory effect and quite like
being "float charged". The thing they like least is deep discharge.

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?

Re-cell them with better quality (and higher capacity) cells. It is
surprising the improvement you can get from some tools just by replacing
the supplied batteries.

General tips for NiCd / NiMh batts:

Discharge them until they shown signs of fading - don't carry on using
the battery after that point.

Use a decent charger / Don't overcharge

Don't charge a hot battery - if you have been working it hard, then let
it cool for half an hour before charging. (helps to have three batts for
this reason)

Periodically recharge them if left in storage for any length of time.





--
Cheers,

John.

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The Medway Handyman wrote:

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?

How about getting it replaced under (presumably) the 12-month warranty
for (ahem) non-professional use?

David

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