98 V70 Battery Discharging

My V70 seems to have an electrical leak: when I put an ohm-meter on
the battery cables (with battery removed and car turned off) it shows
full conductivity. This can't be good for battery life! I have
pulled out every fuse in the two fuse blocks under the hood one at a
time, and none of them cut off the circuit.

I have an in-line fuse for my trailer lights and pulling that did
nothing.

Any idea where my juice is going? What circuits do not go through the
fuses?

Also, on related note: how long does it take to charge a 12 Volt
battery to full power on a 10A battery charger? I don't want to leave
it on too long or not long enough.

 

In an earlier contribution to this discussion,

What do you mean by "full conductivity"? Zero ohms? If so, with the battery
connected, a very high (theoretically infinite) current would flow - which
is very unlikely!

What are the original symptoms which you are trying to investigate? Is the
battery going flat with everything (apparently) turned off? If so, how long
is it taking to go flat?

When re-charging a battery off the car, most chargers will drop to a trickle
when the battery is nearly fully charged, so over-charging shouldn't be a
problem. If the battery is completely flat, it will take quite a few hours -
probably over-night - to charge fully.
--
Cheers,
Roger
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You're not doing it right, you can't just measure the impedance across
the leads, any capacitors in electronic devices will appear as a short
circuit until they charge. You need to disconnect one battery lead, then
set the meter to measure DC Amps and put one probe on the empty battery
terminal and the other on the lead that normally occupies it.

 

In an earlier contribution to this discussion,

But don't try to start the engine with the ammeter in series with the
battery lead - unless it's a very hefty one which can handle several hundred
amps - in which case it won't be much use for measuring a small leakage
current.

I'm not sure how much/little current you're looking for - it depends on how
quickly the battery is discharging. For example, (assuming battery capacity
is linear - which it isn't, so this is only approximate) if (say) 100mA is
flowing (equivalent to a 1.2 watt lamp being on) a 100 amp-hour battery
would take 1000 hours (over 40 days) to discharge - so you wouldn't notice
it because it would get charged up by running the engine in the meantime. So
you must be looking for a lot more than this - maybe one amp or more
(discharging in about 4 days). If it still happens with all the fuses out,
it suggests that it must be something like leaking diodes or smoothing
capacitor in the alternator. To check this, you'd have to disconnect the red
cable from the alternator - but don't let the bare end of the cable touch
anything earthy - so disconnect it with the battery disconnected, and
insulate it before re-connecting the battery!
--
Cheers,
Roger
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My V70 (UK) has also fuses in the trunk and at the end of the dash.

Dave

 

Can you be more specific as to where in the trunk and end of dash? Is
yours a 1998?

 

Yes, my battery was going flat after sitting for 2 or 3 days. I tried
a (newer) battery and same problem. While driving, my ScanGauge shows
between 13.5 and13.7 V, so it seems the alternator is charging ok,
unless those readings are low. Lights and accessories seem to work
fine while driving.

I did not try to get an exact measurement on the meter: the needle
went right to the peg stop. I suppose I should zero it first and get
something more specific.

Thanks for your interest.

 

OK, I can try that. What should the reading be with this process, 0
DC amps?

 

Thanks!

I did consider that the amp might be the source of the leak but did
not know how to test. If I can find the end of the red cable I will
do as you suggest. Is it accessible from the engine compartment or
must I crawl in the dirty snow under the car? (Located in Toronto.)

 

Yes.

You should see no more than a few tens of milliamps.

 

Mine is a 2004. Looking from the rear of the car,there is a panel in
the lefthand side just inside the tailgate. The dash box is under a
cover at the right hand end of the dash.

Dave

 

In an earlier contribution to this discussion,

'Fraid you can't deduce much from that - other than if it 'happens' to be in
the same place. A 2004 V70 (built on the S80 platform) is a completely
different animal from the 1998 model (derived from the 850).
--
Cheers,
Roger
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In an earlier contribution to this discussion,

Not sure what you mean by 'amp' but I assume that you're referring to the
alternator.

This is located at the front of the engine (on the left when standing in
front of the car looking into the engine compartment) under the power
steering reservoir. You should be able to get at from under the bonnet/hood
(depending on whether Canadians use British or American terminology!)
although things like power steering reservoir and auxilliary drive belt
might get in the way a bit. [I don't think it would be any easier from
*under* the car]. As far as I can see from my Haynes manual, the red cable
should simply unplug - if you can get your hand in - it doesn't appear to
need any tools. [But I could be wrong!]
--
Cheers,
Roger
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Thanks Roger. I will try to find that cable and pull it to see if that
makes a difference.

We call it the "hood" not "bonnet" by the way!

 

In an earlier contribution to this discussion,

Shame on you! <g>

[I was hoping that your British heritage would carry more weight than the
proximity of your American Neighbo(u)rs].
--
Cheers,
Roger
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We do spell it neighbour (and colour etc.) But we wear our boots on
our feet and Wellingtons are for flying.

 

OK, I zeroed my meter and redid the tests:

Resistance seems to be around 10 ohms, if I am reading it correctly,
with battery removed.

I also did the test with the battery in and there seems to be 3 amps
coming through.

I also did both tests with the red/white wire removed from the
alternator and no difference.

Thoughts?

 

Ignore the resistance, as I said before, that's a worthless measurement
in this case.

3 Amps seems high to me, what I would do now is pull fuses one at a time
and see when the current drops substantially. You might check the glove
box light too, that getting stuck on is a common cause of a dead battery.

 

In an earlier contribution to this discussion,

If you mean the thin red and white wire - that's only the sensor for the
instrument lamp - you need to disconnect the *thick* red wire!
--
Cheers,
Roger
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In an earlier contribution to this discussion,

Agreed. But I've never seen a 36watt lamp in a glovebox!
--
Cheers,
Roger
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