1. Home
  2. Automotive Technologies
  3. Battery Being Depleted ?

Battery Being Depleted ?

Hello:

Have a '84 Toyota Cressida waggon as sort of a "spare" car.

Has a brand new alternator. Has a brand new battery.

The problem is that it sits in the driveway for, at times, up to three to four weeks or so without being used. After the three-four week period, the battery is totally dead.

My guerss was, that for a car this old, very little is really drawing any current, as contrasted to the newer cars perhaps . Probably some to keep the radio presets, but hard to come up with anything else.

Certainly seems like something, though, is depleting the battery. I would certainly think that 3 to 4 weeks should not deplete a new battery; heck, it was probably sitting for a longer period on the shelf.

So, today, with the battery removed from the car, I put my voltmeter (VOM) on the battery cables (no battery in place) to measure resistance. Here's what I read for Resistance:

With the red meter lead on the wire that would have been going to the + battery terminal I read 12 ohms.

Reversing the meter leads reads 40 ohms.

Wow !

This shows that there are diodes somewhere, but it seems to me that's an incredibly low resistance. If the battery was in place, that would be a current of 12 V/12 ohms = 1.0 amps being drawn (with the ignition off). No wonder it's being depleted.

- Am I interpreting this correctly ?

- Is this a meaningful test ?

- Should one expect a brand new battery to run down in 3-4 weeks sitting in an unused car ?

Any thoughts on this, what possibly to check, and what might be the problem ?

Much thanks, Bob

Reply to
Robert11
Loading thread data ...

Hard to say...

No.

Depends on what the normal parasitic key off draw is supposed to be. 30-50 milliamperes is pretty much standard for cars of that era.

Standard procedure in a case like this is to connect an ammeter in series with one of the disconnected battery cables and measure how many amperes or milli-amperes are flowing with the key off, all doors closes and everything that is supposed to be powered down, powered down.

If you really had a one amp draw on the battery, the battery would be close to dead in one day, not one month.

Reply to
aarcuda69062

Hi Robert,

Please see Sections 15 and 10 in the FAQ on

formatting link

Kindest regards,

BiLL.......

Reply to
Bill Darden

Robert = put a multimeter between the battery and battery cable. Measure the current passing through - you know its not too high to blow the meter(those are regularly 10A dc).

Then check for what's causing the drain. I had a trunk light that was on all the time - the switch latch was bent by some shopping once. Had to get into the trunk and close it to see that it was still on! (Do this with a very trustful friend!)

Reply to
Dean

The dome light on 80s Toyotas is also notorious. And some cars have a little light under the hood... You get the idea.

Another thing to consider is that on some of them, as they get old, it becomes easy to withdraw the key in the play-the-radio position rather than the off position.

Any of the above are quite capable of draining your battery in a matter of a day or two, let alone weeks.

I have an '89 Camry that often sits for 2-3 weeks at a time, with an alarm LED and whatever other tiny current draws it is supposed to have. No worries.

Be sure to also check the voltage you're getting right across the actual battery terminals when the engine is running. Not the cable terminations -- stick your probes into the lead that sticks out of the battery. That'll tell you whether to look to battery wiring/connectors or to "vampire" current draws for your problem (though on a car that old, spending a dull Saturday afternoon chasing and cleaning the big connections, both hot and ground, in the charging circuit can't hurt).

Finally, after you've snaked all that out, look at the fluid level in your battery (adding distilled water if needed to bring it up to the proper level) and then charge it with a real charger, not just the alternator. These frequent deep discharges have probably left it in a rather depleted state. This isn't your main problem but it can cause others in the future and confuse the issue in the meanwhile.

Best of luck,

--Joe

Reply to
Ad absurdum per aspera

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.