I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl

Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl




Karl,

Pull *ALL* the fuses - then replace one at a time for the test.
Then remove that one and try another.

cavelamb wrote:
Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked
down. So, today I put the ohm meter between the + post and ground. Got
180 ohm. Pulled one fuse at a time hoping to find a faulty circuit. No
joy, same reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl




Karl,

Pull *ALL* the fuses - then replace one at a time for the test.
Then remove that one and try another.

Then disconnect the alternator. Could be
a shorted diode.

Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?


Everything isn't on a fuse...

Both the alternator and the starter are on a fusible link that is tied
into the wiring... If pulling all the fuses doesn't find it, pull the
large wires off the starter and alternator...

Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Use the ammeter function between the + post of your battery and the
wires that normally connect to it.

You will see the amount of current that is draining the battery.
As others have posted, remove the connections to fusable links
as well as to the starter to determine where the current is
going.

--Winston

--

Don't *faff*, dear.

"Karl Townsend" wrote:

I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl



That would take 43 days to drain a decent battery using my conservative numbers.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked
down. So, today I put the ohm meter between the + post and ground. Got 180
ohm. Pulled one fuse at a time hoping to find a faulty circuit. No joy,
same reading the whole time.

Any suggestions on how to find what's draining my battery?

Use the ammeter function between the + post of your battery and the
wires that normally connect to it.

You will see the amount of current that is draining the battery.
As others have posted, remove the connections to fusable links
as well as to the starter to determine where the current is
going.

--Winston

Agreed. Use an amp meter, not an ohm meter to isolate the issue.
Start on the largest setting first, then work your way down if you can.
I had to do this on a camper recently.

Wayne D.

"Karl Townsend" writes:


Any suggestions on how to find what's draining my battery?


How much is it drawing? Put an ammeter in the GROUND lead; set it to 10
amps, and go downscale from there. If it's an amp or more, put a 1034 or
similar taillamp in series. Then you can disconnect things and observe
success.

Others have suggested the alternator, which I second. Pull both the
output wire and the field connections.

Also, do you have one or 2 fuseboxes on your truck?





--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Karl Townsend wrote: (clip) So, today I put the ohm meter between the + post
and ground. Got 180 ohm. (clip)
^^^^^^^^^^^^^^^^^^^^^
Are you reading from the positive battery post to chassis ground with the
ohm meter? That's not a meaningful reading, since you are putting the 12
volts in series with whatever your ohm meter has internally. Actually, if
this is the connection you are using, you are making some kind of across the
battery itself, and not looking at the circuits that could be draining the
battery.

Do what others have suggested: The handiest way to measure is to disconnect
the ground cable and insert a current range of your VOM. You should see
any current being supplied by the battery. Then disconnect the positive
battery cable and the current should drop to zero. That will tell you that
you are on the right track. Then pull fuses or disconnect wires until it
drops to zero again. That will be the *aha* moment.

On Apr 22, 2:29*pm, "Karl Townsend"
wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl

On my 91 Ranger the leak was a stuck relay under the air cleaner box
that kept the engine control computer ON all the time.

Applying voltage to a digital meter on the Ohms scale gives a bad
reading, with an analog meter the smoke makes the scale hard to read.
I put a low value power resistor in the Ground lead and a voltmeter
across it to check the current. It doesn't matter too much that the
current reading isn't accurate and if I accidently turn on a power
load the meter will survive.

The light bulb in series with the ammeter is a good idea too. If they
still sell them, a replacement tail light socket has two separate
wires you can attach alligator clips to. That was the only test
equipment I carried on my motorcycle, for checking bulbs and fuses and
setting ignition timing.

Jim Wilkins

I narrowed the problem down to my alternator. Drain of .2 amp.


So, I tried to remove the alternator a got into A REAL MESS. the bottom bolt
is rusted on. Put a 3/8 x 9/16 socket on it and couldn't budge it. Put a
1/2x9/16 socket on it with my S-K Wayne ratchet and couldn't budge it.
Bounced on it, the wrench came loose along with a bunch of knuckle blood.
Put a cheater on a 9/16 impact 6 point socket - the socket spit in two
parts - never seen that before. Took the radiator out and put my impact
wrench on it, still no joy. I said something like mother f%^& cock %^*&( and
called it a day.

Karl

On Apr 23, 10:16 am, "Karl Townsend"
wrote:
I narrowed the problem down to my alternator. Drain of .2 amp.


Bounced on it, the wrench came loose along with a bunch of knuckle blood.
Put a cheater on a 9/16 impact 6 point socket - the socket spit in two
parts - never seen that before. Took the radiator out and put my impact
wrench on it, still no joy. I said something like mother f%^& cock %^*&( and
called it a day.

Karl

Karl, as the liberals would say, with feeling - "I feel your pain" -
and what makes you feel even worse is having set yourself up to do it -
there is ALWAYS a strategically placed bracket whose only function is
to inflict injury.....

Well, so much for humour - is this the same truck you were having
trouble with a while ago (last winter?) - it was giving you a hard
time in the battery charging area, then it sort of spontaneously fixed
itself for a while. As others have said, its probably the diodes in
the alternator (or, possibly, the voltage regulator)- while your in
there, particularly if its got a lot of miles on it, replace the
brushes on the slip rings, and the front and rear bearings.If your not
comfortable with doing the electrics, your local auto-electrician (if
there still is one) should be able to test/diagnose it for you.

I have pulled a few apart in recent months, want to make a wind
generator out of one - interesting devices, particularly in how the
get the rotor onto the driveshaft......the 9 inch angle grinder DOES
have many uses....

"Karl Townsend" wrote in message
anews.com...
I narrowed the problem down to my alternator. Drain of .2 amp.


So, I tried to remove the alternator a got into A REAL MESS. the bottom
bolt is rusted on. Put a 3/8 x 9/16 socket on it and couldn't budge it.
Put a 1/2x9/16 socket on it with my S-K Wayne ratchet and couldn't budge
it. Bounced on it, the wrench came loose along with a bunch of knuckle
blood. Put a cheater on a 9/16 impact 6 point socket - the socket spit in
two parts - never seen that before. Took the radiator out and put my
impact wrench on it, still no joy. I said something like mother f%^& cock
%^*&( and called it a day.

Karl



Did you soak it in Liquid Wrench for the night?

Well, so much for humour - is this the same truck you were having
trouble with a while ago (last winter?) - it was giving you a hard
time in the battery charging area, then it sort of spontaneously fixed
itself for a while. As others have said, its probably the diodes in
the alternator (or, possibly, the voltage regulator)- while your in

You got a good memory. Also, the volt drain must not be a constant, it
drained a new battery in a couple days. I'd check and couldn't get any ohm
reading ( or current - same thing)

Maybe I'm too rich, I just trade in alternators. Too much trouble to rebuild
wrong and have to do it again.


To the other post - deep creep once per hour till bedtime. if that don't
work, I'll give the alternator the rose bud - but I got to remove a whole
pile of rubber hoses before I do that.

If that don't work - I may be screwed glued and tattooed. Don't see how else
to remove it. Probably pull the engine.

Karl

"Tim" writes:



Did you soak it in Liquid Wrench for the night?

Kroil
hammer tap...
Kroil
hammer tap...
Kroil


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Wed, 22 Apr 2009 16:45:06 -0700 (PDT), Jim Wilkins
wrote:

On Apr 22, 2:29*pm, "Karl Townsend"
wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl

On my 91 Ranger the leak was a stuck relay under the air cleaner box
that kept the engine control computer ON all the time.

On senior son's 68 Firebird, it was the horn relay.
Gerry :-)}
London, Canada

"Karl Townsend" writes:


You got a good memory. Also, the volt drain must not be a constant, it
drained a new battery in a couple days. I'd check and couldn't get any ohm
reading ( or current - same thing)

No.... not the same.. Use an ammeter, or the lamp trick. The ohmmeter
can lie to you, and send you down dead ends.

Your concern is current leaks, look for that...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:

"Tim" writes:

Did you soak it in Liquid Wrench for the night?

Kroil
hammer tap...
Kroil
hammer tap...
Kroil

Kroil is so good that sometimes just showing the offending bolt the
Kroil can is enough to scare it into submission...

"Karl Townsend" wrote in message
anews.com...
Well, so much for humour - is this the same truck you were having
trouble with a while ago (last winter?) - it was giving you a hard
time in the battery charging area, then it sort of spontaneously fixed
itself for a while. As others have said, its probably the diodes in
the alternator (or, possibly, the voltage regulator)- while your in

You got a good memory. Also, the volt drain must not be a constant, it
drained a new battery in a couple days. I'd check and couldn't get any ohm
reading ( or current - same thing)

Maybe I'm too rich, I just trade in alternators. Too much trouble to
rebuild wrong and have to do it again.


To the other post - deep creep once per hour till bedtime. if that don't
work, I'll give the alternator the rose bud - but I got to remove a whole
pile of rubber hoses before I do that.

If that don't work - I may be screwed glued and tattooed. Don't see how
else to remove it. Probably pull the engine.

Karl



It probably isn't, but check that there is not a nut on the bolt hiding
behind the bracket. It is fairly likely that the bolt is siezed in the frame
of the alternator and will require drastic measures. If accessible,
application of a heavy hammer as if to drive the bolt in lengthwise often
helps. Just remember to sacrifice the correct parts first. ;)

Don Young

Theory that is.

In these days dropping below a certain level kills the CPU card.

I've seen small batteries that can 'fill' a flat one in seconds -
floating it long enough for the engine to have a brain - then it generates.

I couldn't leave my 80's New Yorker when it first came out - The battery
would not last 2 days. I could not fly out of town and leave it.

The clock and internal computer and the 12V CMOS processor - the regulator
for the processor blocked all until above a level.

Martin

Wes wrote:
"Karl Townsend" wrote:

I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl



That would take 43 days to drain a decent battery using my conservative numbers.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On Wed, 22 Apr 2009 19:16:43 -0500, the infamous "Karl Townsend"
scrawled the following:

I narrowed the problem down to my alternator. Drain of .2 amp.

That'll drain a battery in no time.


So, I tried to remove the alternator a got into A REAL MESS. the bottom bolt
is rusted on. Put a 3/8 x 9/16 socket on it and couldn't budge it. Put a
1/2x9/16 socket on it with my S-K Wayne ratchet and couldn't budge it.
Bounced on it, the wrench came loose along with a bunch of knuckle blood.
Put a cheater on a 9/16 impact 6 point socket - the socket spit in two
parts - never seen that before. Took the radiator out and put my impact
wrench on it, still no joy. I said something like mother f%^& cock %^*&( and
called it a day.

Soak it overnight with Kroil and try -tightening- it first, then
loosening it tomorrow. Sometimes it loosens easier the wrong way.

--
I am beginning to learn that it is the sweet, simple things of life
which are the real ones after all. --Laura Ingalls Wilder (1867-1957)

On Wed, 22 Apr 2009 19:16:43 -0500, the infamous "Karl Townsend"
scrawled the following:

I narrowed the problem down to my alternator. Drain of .2 amp.


So, I tried to remove the alternator a got into A REAL MESS. the bottom bolt
is rusted on. Put a 3/8 x 9/16 socket on it and couldn't budge it. Put a
1/2x9/16 socket on it with my S-K Wayne ratchet and couldn't budge it.
Bounced on it, the wrench came loose along with a bunch of knuckle blood.
Put a cheater on a 9/16 impact 6 point socket - the socket spit in two
parts - never seen that before. Took the radiator out and put my impact
wrench on it, still no joy. I said something like mother f%^& cock %^*&( and
called it a day.

I forgot to ask if the alternator turns easily on the bolt.

A hammer on the end of the bolt can help loosen it, too, so try a few
taps there now that you have the radiator out, Karl.

--
I am beginning to learn that it is the sweet, simple things of life
which are the real ones after all. --Laura Ingalls Wilder (1867-1957)

"Don Young" writes:


It probably isn't, but check that there is not a nut on the bolt hiding
behind the bracket. It is fairly likely that the bolt is siezed in the frame
of the alternator and will require drastic measures. If accessible,
application of a heavy hammer as if to drive the bolt in lengthwise often
helps. Just remember to sacrifice the correct parts first. ;)

On a friend's Hyundai with a Mitsu engine, I had the tube that the
alternator pivot bolt went through splint lengthwise and come off. I took
the car sans alternator to a welding shop. He ixnayed that, as the other
side of that alum. front/side cover was the oil pump.

I cleaned both halves, wrapped a pencil in teflon tape and used JB Weld,
then rubber bands to hold it in place to set. Four days later, we put the
alternator back it, and it held. I heard later it lasted the three years
until they sold the car.

(Remember, it's a goat for a SCSI chain, but the correct sacrifice for
a rusted bolt and bracket is a Norway rat...)

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Stuart Wheaton" wrote in message
...
Karl Townsend wrote:
I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked
down. So, today I put the ohm meter between the + post and ground. Got
180 ohm. Pulled one fuse at a time hoping to find a faulty circuit. No
joy, same reading the whole time.

Any suggestions on how to find what's draining my battery?


Everything isn't on a fuse...

Both the alternator and the starter are on a fusible link that is tied
into the wiring... If pulling all the fuses doesn't find it, pull the
large wires off the starter and alternator...

It's not likely to be the starter! A failed diode in the alternator is more
common than most may think.


Steve R.

"Karl Townsend" wrote in message
anews.com...
Well, so much for humour - is this the same truck you were having
trouble with a while ago (last winter?) - it was giving you a hard
time in the battery charging area, then it sort of spontaneously fixed
itself for a while. As others have said, its probably the diodes in
the alternator (or, possibly, the voltage regulator)- while your in

You got a good memory. Also, the volt drain must not be a constant, it
drained a new battery in a couple days. I'd check and couldn't get any ohm
reading ( or current - same thing)

Maybe I'm too rich, I just trade in alternators. Too much trouble to
rebuild wrong and have to do it again.


To the other post - deep creep once per hour till bedtime. if that don't
work, I'll give the alternator the rose bud - but I got to remove a whole
pile of rubber hoses before I do that.

If that don't work - I may be screwed glued and tattooed. Don't see how
else to remove it. Probably pull the engine.

Karl




If you know much about electrical circuits, and electronics, it's pretty
hard to do a bad rebuild. I did my own for a couple of decades. Then I did
it for a living for a while. There was not one bad rebuild in the lot!


Steve R.

Maybe I'm too rich, I just trade in alternators. Too much trouble to rebuild
wrong and have to do it again.

Over the years, I've had questionable results from rebuilt altenators
from auto parts stores. Someone on a forum I happenned across in a
search for something else mentioned that a junkyard unit was usually a
better unit, since it at least hadn't failed once already like the
"rebuilt" ones. Since I've switched, I've not had a bad replacement,
so they may be on to something...

--Glenn Lyford

Follow up. JOY! Got it out with the torch. melted AL on the alternator I had
it so hot.

Now I really really hope this is the cause of the current drain.

Karl

David Lesher wrote:
"Karl Townsend" writes:


Any suggestions on how to find what's draining my battery?


How much is it drawing? Put an ammeter in the GROUND lead; set it to 10
amps, and go downscale from there.

Hey David,

I grok that it doesn't matter where the ammeter is in this 'series'
branch of the network but I wonder what advantage there is in placing
the meter in series with the ground side of the battery in relation
to placing it in series with the hot side of the battery?

Is it a safety thing, to prevent bad stuff from happening should one
of the wires slip and find ground?

--Winston -- About to learn today's lesson.

--

Don't *faff*, dear.

Winston writes:

How much is it drawing? Put an ammeter in the GROUND lead; set it to 10
amps, and go downscale from there.

I grok that it doesn't matter where the ammeter is in this 'series'
branch of the network but I wonder what advantage there is in placing
the meter in series with the ground side of the battery in relation
to placing it in series with the hot side of the battery?

Is it a safety thing, to prevent bad stuff from happening should one
of the wires slip and find ground?

You got it. The first bad thing is when you loosen the Hot terminal with
a socket set, and the handle hits grounded metal.

The second is when you burn your hand on the now-hot wrench.

The third bad thing involves getting the acid and lead chucks washed out
of your eyes.

Disconnecting the ground side first is just smart. It makes no difference
in measuring.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:
Winston writes:

How much is it drawing? Put an ammeter in the GROUND lead; set it to 10
amps, and go downscale from there.

I grok that it doesn't matter where the ammeter is in this 'series'
branch of the network but I wonder what advantage there is in placing
the meter in series with the ground side of the battery in relation
to placing it in series with the hot side of the battery?

Is it a safety thing, to prevent bad stuff from happening should one
of the wires slip and find ground?

You got it. The first bad thing is when you loosen the Hot terminal with
a socket set, and the handle hits grounded metal.

The second is when you burn your hand on the now-hot wrench.

The third bad thing involves getting the acid and lead chucks washed out
of your eyes.

Disconnecting the ground side first is just smart. It makes no difference
in measuring.

I'll disconnect the ground side first and use it for current sensing,
from here on in.

Thanks!

--Winston

"David Lesher" (clip) Disconnecting the ground side first is just smart. It
makes no difference
in measuring. (clip)
^^^^^^^^^^^^^^^^^^^^^^^
Same safety precaution should be followed any time you are disconecting or
reconnecting the battery, whether for measurement, replacement, cleaning or
stealing ;-)

Leo Lichtman wrote:
"David Lesher" (clip) Disconnecting the ground side first is just smart. It
makes no difference
in measuring. (clip)
^^^^^^^^^^^^^^^^^^^^^^^
Same safety precaution should be followed any time you are disconecting or
reconnecting the battery, whether for measurement, replacement, cleaning or
stealing ;-)

I shall leave a note on the air cleaner for Señor Herrera.
(Wouldn't want him to hurt himself. That would make me feel badly.)

--Winston

--

Don't *faff*, dear.

"Karl Townsend" wrote:

I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl



As others pointed out, the ohm meter reading isn't very reliable. My bad.

Harbor Freight has a centec multimeter that will read 10A DC. Slow response, yada but
what do you expect for 4 bucks. If there is a HF near you, get one and check current
with battery in circuit then get back to us.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Wes writes:


As others pointed out, the ohm meter reading isn't very reliable. My bad.


There are several reasons to avoid the ohmmeter approach. First is you
are asking to screw up and toast the meter. Even if it is a Harbor Fright
$3 special, it's still a bummer.

But the bigger is this. The ohmmeter applies a test voltage to the circuit.
It's going to be far less than the 13-15v a running car has. One of several
failure modes for semiconductors is to leak, and the leak is proportional
to the voltage drop... and not just linearly. Raising the voltage from
say 5 to 10v might get you 10 or 100x the leakage, not just double.

Result? You do NOT see the leakage with an ohmmeter. You will see it in
ammeter mode.



--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote: (clip) the leak is proportional
to the voltage drop... and not just linearly.(clip)
^^^^^^^^^^^^^^^^^^^^^
Basically what you say is right, but I have to correct you on this small
nit: Proportional *IS* linear.

On Apr 23, 8:50*pm, "Leo Lichtman" wrote:
"David Lesher" wrote: *(clip) the leak is proportional
to the voltage drop... and not just linearly.(clip)

^^^^^^^^^^^^^^^^^^^^^
Basically what you say is right, but I have to correct you on this small
nit: *Proportional *IS* linear.

An Ohmic resistance is linear but semiconductor behavior is often
exponential or logarithmic. A good example is the drop across a diode:
http://www.allaboutcircuits.com/vol_3/chpt_3/1.html
Scroll down to the part about kT/q.
The effect is that the voltage drop rises with the logarithm of the
current.

This one shows how the forward drop changes inversely with
temperatu
http://www.cryocon.com/S900/S900ds.pdf

In the 1980's 4-1/2 digit DVMs were very expensive and I built my own,
using a constant-current source for the resistance function instead of
the usual MickeyMouse shortcut that obscures the actual voltage and
current passing through the resistor. Mine forced 1uA, 10uA...10mA and
showed the true voltage. It would clearly demonstrate the logarithmic
VI curve of a diode, from ~400mV to ~700mV. Unfortunately my ex used
it to check her car and fried that circuit with 12V.

Jim Wilkins

On Apr 24, 8:30 pm, Jim Wilkins wrote:
On Apr 23, 8:50 pm, "Leo Lichtman" wrote:

"David Lesher" wrote: (clip) the leak is proportional
to the voltage drop... and not just linearly.(clip)

^^^^^^^^^^^^^^^^^^^^^
Basically what you say is right, but I have to correct you on this small
nit: Proportional *IS* linear.

An Ohmic resistance is linear but semiconductor behavior is often
exponential or logarithmic. A good example is the drop across a diode:http://www.allaboutcircuits.com/vol_3/chpt_3/1.html
Scroll down to the part about kT/q.
The effect is that the voltage drop rises with the logarithm of the
current.

This one shows how the forward drop changes inversely with
temperatuhttp://www.cryocon.com/S900/S900ds.pdf

In the 1980's 4-1/2 digit DVMs were very expensive and I built my own,
using a constant-current source for the resistance function instead of
the usual MickeyMouse shortcut that obscures the actual voltage and
current passing through the resistor. Mine forced 1uA, 10uA...10mA and
showed the true voltage. It would clearly demonstrate the logarithmic
VI curve of a diode, from ~400mV to ~700mV. Unfortunately my ex used
it to check her car and fried that circuit with 12V.

Jim Wilkins

So, could you do the usual electronics fault finding thing of using
the diode check function on the output lead of the alternator? - (then
reverse, repeat, see difference or none) even cheap DMM have them now
- (BTW - was yours a SABTRONICS kit?)? - or is it getting too
complicated and as Karl has identified the Knuckle Crunching
Alternator as being the culprit....

And I would humbly disagree re ohmmeters vs ammeter's - its all to
easy to fry an ammeter, the 10a range on most DMM's is rated for a few
seconds only, then the copper wire shunt disengages itself....besides,
10a is leakage current in a vehicle...and DMM's are now cheap, throw
away items, but a decent ammeter is still expensive....

Andrew VK3BFA.

Wes wrote:
"Karl Townsend" wrote:

I need the truck to haul home my latest toy...

I've had to leave the battery disconnected cause the juice gets sucked down.
So, today I put the ohm meter between the + post and ground. Got 180 ohm.
Pulled one fuse at a time hoping to find a faulty circuit. No joy, same
reading the whole time.

Any suggestions on how to find what's draining my battery?

Karl



That would take 43 days to drain a decent battery using my conservative numbers.

I just wanted to back up a minute and point
out what was happening. 43 days with a decent
battery is believable. The problem is that
a shorted diode in the alternator is causing
the leakage and is also preventing the battery
from being fully charged.

I've seen this on one of my vehicles. A drain
disproportionate to the discharge rate because
of inadequate charging.

wrote:

(...)

So, could you do the usual electronics fault finding thing of using
the diode check function on the output lead of the alternator? - (then
reverse, repeat, see difference or none) even cheap DMM have them now

You could do that if you could access the inside of the alternator.
I guess that you could sort alternators with shorted diodes from the
outside, by comparing the forward drop of the 3 phase rectifiers.
The shorted units would have ~0.7 V less forward drop than the good
units. A unit with two shorted series diodes would have ~1.4 V less
forward drop, at least theoretically.

And I would humbly disagree re ohmmeters vs ammeter's - its all to
easy to fry an ammeter, the 10a range on most DMM's is rated for a few
seconds only, then the copper wire shunt disengages itself....besides,
10a is leakage current in a vehicle.

What vehicle normally experiences as much as 10A of battery drain,
with the key out of the ignition and the lights off? Are there any?

Note that Karl revealed the high value of leakage current to be well
within the range of his DMM:

Karl: I narrowed the problem down to my alternator. Drain of .2 amp.

And I would humbly disagree re ohmmeters vs ammeter's - its all to
easy to fry an ammeter, the 10a range on most DMM's is rated for a few
seconds only, then the copper wire shunt disengages itself...

The 10A current shunt built into the DMMs I use are 100% duty cycle
and will tolerate 20A for 30 seconds without damage.

No fear that any of my DMMs will be damaged if used properly.

The DMM ammeter in series with the negative battery terminal is a safe
and effective method for troubleshooting leakage current.

--Winston


--

Don't *faff*, dear.

Jim Wilkins writes:

On Apr 23, 8:50=A0pm, "Leo Lichtman" wrote:
"David Lesher" wrote: =A0(clip) the leak is proportional
to the voltage drop... and not just linearly.(clip)

^^^^^^^^^^^^^^^^^^^^^
Basically what you say is right, but I have to correct you on this small
nit: =A0Proportional *IS* linear.

An Ohmic resistance is linear but semiconductor behavior is often
exponential or logarithmic. A good example is the drop across a diode:
http://www.allaboutcircuits.com/vol_3/chpt_3/1.html
Scroll down to the part about kT/q.
The effect is that the voltage drop rises with the logarithm of the
current.

This one shows how the forward drop changes inversely with
temperatu
http://www.cryocon.com/S900/S900ds.pdf


Yep, quite true.... I've also had ordinary diodes
"go zener" instead of behaving.

But Leo seems to think proportional == linearly proportional.
I disagree but decided it wasn't worth arguing about.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433