Re: battery hydrometer


"Duncan Wood" <nntpnews@xxxxxxxxxxxx> wrote in message
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On Tue, 03 Feb 2009 18:11:18 -0000, Miike G
<postmaster@xxxxxxxxxxxxxxxxxxx> wrote:


"Mrcheerful" <nbkm57@xxxxxxxxxxx> wrote in message
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"Miike G" <postmaster@xxxxxxxxxxxxxxxxxxx> wrote in message
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"Duncan Wood" <nntpnews@xxxxxxxxxxxx> wrote in message
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On Mon, 02 Feb 2009 17:31:44 -0000, Miike G
<postmaster@xxxxxxxxxxxxxxxxxxx> wrote:


"Stephen" <invalid@xxxxxxxxxxx> wrote in message
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On Mon, 02 Feb 2009 12:18:35 GMT, "Mrcheerful" <nbkm57@xxxxxxxxxxx>
wrote:

A accurate DVM is actually more use in general terms, and a loading
type
tester is even better.

Please don't get me started on that again ;)

I posted about battery testers a couple of weeks ago and I was told
that testing under load with a DVM was the way to go. Apparently the
people round here didn't like the load testers because the load of
the
tester doesn't necessarily equal the load of your starter motor. I
had
read quite a few old posts recommending load testers and was about
to
buy one until everyone here talked me out of it!

I don't think a load tester 'has' to equal the load of a particular
starter
motor, to give give a good idea of a batterys cranking capability.
They do put a heavy load on a battery, and as long as the volts don't
drop
during the test, the chances are that even a higher load wont make a
significant difference.
Mike.

Yep, it does, battery resistance is very non linear. If the volts
don;t
drop during the test then your tester's knackered :-)

Of course there is an initial drop when the tester is switched on after
it reads the no-load volts, but the voltage shouldn't drop during the
10
secs or so when the test load is actually applied.

If it does drop with a fully charged battery, IME the battery is no
longer reliable.
It might still start the car in the summer, but come winter and cold
mornings and the chances are that it will not.

I've had my load tester for well over 10 years. I know how to read it
and
I also know it's not knackered.
Mike..

If the battery volts do not decrease to some extent when the starter
operates or the load is applied

I think you are misreading my post.
My load tester has a spring loaded switch to apply the load.
When first connected it simply reads the no-load battery voltage. When
the
switch is depressed to apply the load, the voltage reading drops.
If the voltage continues to drop, assuming the battery is fully charged,
the
battery is on it's way out, and should be replaced. A constant voltage
reading during the time, (10 secs or so) the load is applied would
indicate
the battery is OK.
Mike.



At that load.

Which was why I wrote 'would indicate'.

Which was the point the rest of us where making,

My point was was that IME, any drop after the load is applied with my
tester, would indicate a failing battery. Obviously a higher load wont alter
that situation.

if you don't know enough to work the answer out from the dvm during
starting

Which in effect is simply doing a load test.

then a battery tester doesn't give you a pass/fail result, if you do know
enough then they're a usefull source of information, but again you still
have to interpret the difference between a Ford Ka's battery & a diesel
Landrovers.

Within reason, whatever a cars batteries capacity is or it's cold cranking
amps, if it fails a test with my load tester, when it's charged and not low
on electrolyte, it's on it's way out. That doesn't mean if it passes, there
is nothing wrong with it. Which it would appear, is what you think I'm
saying.
Mike..


.

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