Hi Paul:
OH!! I did not understand the question then, my fault. This is a very valid
and low cost way to measure leakage. From here you just disconnect loads
until the leakage drops to zero or near-zero and viola! you have found the
short.
So from your experience, you would suggest that one should clean the
battery(s) themselves before using this technique, eh Paul??
Also for those of you who winter-over your cars (I know we all drive them
right??) that there are very real discharge currents happening with dirty
batteries. Maybe those plastic battery liners aren't such a bad idea, huh?
Another way to do the leakage test, is with a 3 1/2 digit DVM. Connect
across battery and pull fuses and/or disconnect suspect loads until the
battery voltage pops up at least 1 digit (10 mV or more). Even milliamp
loads will bring the battery voltage down a couple tenths of volt. Note
that
we are not worried about microamps (millionths of an amp). The battery SELF
discharge rate alone (with no load connected) is on the order of 1/2 % per
day with flooded lead acid batteries. And it is higher when hotter. It is a
very good idea then to use a trickle charger on batts that are not being
used, if even for a month. Longer than this and you risk the sulfate that
is
collecting on the lead plates to harden so that it will be difficult to
dissolve under charge.
Thanks for the clarification Paul.
Tim Economu
Mona '69 MGBGT
> ----- Original Message -----
> From: "Paul Hunt" <paul.hunt1@virgin.net>
> To: "Tim Economu" <economu@whidbey.com>; <Speedo79@aol.com>
> Cc: "MG List" <mgs@autox.team.net>
> Sent: Tuesday, May 02, 2000 12:15 PM
> Subject: Re: Alternator Woes
>
>
> > I think Steve means he has disconnected the ground strap and connected a
> > voltmeter in its place as a very sensitive ammeter, but one which will
not
> > be destroyed if a significant load is placed on the system. You do this
> to
> > check for very small drain currents, smaller than can be detected by
using
> a
> > test-lamp in place of the ground strap. In damp conditions, though, the
> > voltmeter will even reveal leakage across the top of the battery,
> > particularly on batteries with exposed cell links. Led me a merry dance
> > this winter.
> >
> > PaulH.
> >
> > ----- Original Message -----
> > From: Tim Economu <economu@whidbey.com>
> > To: <Speedo79@aol.com>
> > Cc: MG List <mgs@autox.team.net>
> > Sent: Tuesday, May 02, 2000 6:45 PM
> > Subject: Alternator Woes
> >
> >
> > > Steve:
> > > If there is voltage between bat neg and ground then there is an OPEN
not
> a
> > > short. This is a wiring problem. Clean the ground connections on the
> > > chassis, at the battery and at the motor. Check for frayed ground
> straps.
> > >
> > > Tim Economu
> > >
> > >
> > >
> >
>
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