Re: converting probles to clamp-on



*selah* wrote:
> "ehsjr" <ehsjr@xxxxxxxxxxxxxxxx> wrote in message
> news:aqfDe.10216$R83.6916@xxxxxxxxxxx
> > *selah* wrote:
> > > "*selah*" <pzion.naax@xxxxxxxxx> wrote in message
> > > news:dbi8k40r44@xxxxxxxxxxxxxxxxxxxx
> > >
> > >
> > > Oops - sorry. I just realized - the manual calls for .05A
> sensitivity -
> > > not mA - so I can't use this meter. Got it confused because the test
> can
> > > also be done with a shunt and a meter that has .05 mV sensitivity.
> > >
> > > Thanks for the responses anyway.
> > >
> >
> > You more than likely can use the meter.
> > .05 A = 50 mA and it is likely that your meter has a
> > range that will accomodate that. On your next post,
> > tell us the model number of the Micronta meter,
>
> The model # is 22-191
>
> and
> > what the current measuring ranges are.
>
> The current drain is supposed to be less than .05A.
>
> Also, as other
> > posters have indicated, the information you provide
> > is incomplete, making it next to impossible to give
> > you a good answer. For example, you say "the manual
> > calls for .05A sensitivity". What manual?
>
> Ford shop manual.
>
> What is
> > the manual telling you to do?
>
> Battery Drain Test with a Clamp-On DC Ammeter
>
> Test Procedure
>
> 1. Turn the ignition to OFF and make sure there are no electrical loads.
> After determining that the underhood lamp is shutting off properly,
> disconnect the bulb.
>
> 2. Clamp the meter clip securely around the positive or ground battery
> cable (all cables if two or more leads to the post).
>
> NOTE:
> Do not start vehicle with clip on cable.
>
> Test Conclusion
>
> The current reading (current drain) should be less than .05 amps.
>
> Why are you doing it -
> > what problem are you trying to solve or what information
> > are you trying to gather? etc.
> >
>
> Our battery went dead recently although we just bought it new. We
> recharged it. The charger showed that it was at very low charge at the
> beginning (the charger ammeter was showing 10A going to the battery),
> after about 6 hours it was fully charged and the charger ammeter showed
> 4A going to the battery. I tested the battery with a hydrometer and the
> hydrometer practically didn't float, (it read at the top of the tube in
> the dead battery region.) We took the battery in to a repair shop and
> they tested it with their "snap-on" tester. I assume it was a load test.
> It said the battery was good. These are the results:
>
> Battery size 660 CCA
> Available Amp 798 CCA
> % Rated Capactiy 120%
> Battery Temp 70 F
> Initial Volts 12.90 V
> Final Volts 12.33 V
> Impedance 4.00 m ohms
>
> They also tested the alternator (good) and starter (good).
>
> > Ed

Hi, Selah. As is frequently the case, the shop manual for the car is
assuming you have tens of thousands of dollars in factory-approved,
factory-supplied equipment. Given that armamentorium, their bean
counters have determined the least expensive, least labor-intensive
method of making the measurement.

I've had your problem before -- an infuriating slow leak of unknown
origin that drains the battery over a day or two. Here's the simple
low tech way to approach the problem:

SAFETY ALERT
Before starting this, put a cover over the positive battery terminal
and clamp to prevent accidentally shorting it out. And use goggles
while doing this.
SAFETY ALERT

Now, with the key in the OFF position and all accessories turned off,
place your DMM on DC current. Then use alligator clips to connect the
leads of the DMM to the negative terminal of the battery and the
negative battery clamp. Carefully loosen the nut for the negative
clamp, and then carefully remove the clamp from the terminal. At that
point, the circuit and leakage current should be from the POS terminal,
through the car, then through the DMM ammeter to the NEG terminal. You
can then measure the current (which should be less than 0.05A, or 50mA,
according to your manual).

You may have to just use the test probe instead of an alligator clip,
if you don't have a dual terminal battery. In that case, just hold the
probe right on the negative terminal as you carefully twist off the
negative terminal clamp.

For newer cars, it can be a big pain to reset and reprogram stuff if
the battery is removed from the car electrical system. However, the
added series resistance of the DMM on DC current shouldn't cause enough
voltage drop to make the computers reset, as long as it's less than a
couple of amps. Avoid even momentarily opening the circuit here, or
you might have a lot more problems.

When this happened to me, I did the above and found about 1/4A of
"leakage" current when everything was supposed to be off. Of course,
it took over an hour to finally track down that a small normally closed
switch for a little convenience bulb in one of the convenience
compartments was jammed in the ON position, even with the convenience
compartment door closed. How inconvenient.

You also always have the option of buying a Hall Effect meter clamp,
which should set you back quite a few bucks. This clamp uses a hall
effect sensor to sense the magnetic field produced by the current
flowing through the wire, and outputs a DC and/or AC voltage
proportional to that current. Several manufacturers make them, they're
all probably too expensive for what you want.

I hope this is of help. If you're not familiar with car electrical
work, you should let someone qualified handle this. And again, don't
forget to cover the positive terminal of the battery to avoid shorting
it out if you do handle it yourself. Worst case, you could enjoy a
sulphuric acid face wash if you're not careful.

Good luck
Chris

.

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