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383SBC 08-23-2011 07:01 PM

Max. current draw with engine off keys in my pocket?
Hi guys, Car is 1991 civic 1.5 Liter, a real eye-turner, I know. Anyways I was having a problem where my battery would die to the point where I couldn't crank the engine over within 48 hours of sitting. I got out the DMM and began pulling fuses on the dash fuse block while observing the current draw. I can't recall what my exact current draw was since this was about 3 months ago now but IIRC it was around 0.3A (300mA). I got to the last fuse (ofcourse) and when I pulled this fuse the current draw dropped to next to nothing, so I knew I had isolated the cause of the excessive current draw. This fuse was named "cigarette lighter relay". Well...... I don't smoke so I didn't care if I left this fuse out if it meant my battery wouldn't die on me in 2 days. With the fuse pulled however my factory radio does not work either. Somehow the radio is wired through that fuse. I am planning on taking another look at this problem soon since I have been driving around now for 3 months with no music!! :mad: My question is, what is the maximum or acceptable current draw you would expect to see with the ignition off?

Keith :welcome:

EOD Guy 08-24-2011 03:49 AM

I recently help a friend who had a simular problem with the batt lasting 24 hrs after a chg...... It turned out to the the factory amps killing the batt, we replaced the amps and the problem went away. Might try unplugging the radio harness and put that fuse back in, see if you still get the draw, if you have amps....... try the same, that way you would know what was draining it.

75gmck25 08-24-2011 04:33 AM

I recently checked the current draw on my truck, which has a Pioneer radio/CD and no other accessories, and the current draw was about 15ma with the ignition off. My analog multimeter is very old, but I think its still fairly accurate.


MouseFink 08-24-2011 05:12 AM

parasitic current draw
I have read where 50 ma parasitic current draw is on the high end. Some examples of accessories with their current draw: Voltage regulator 1 - 2 ma, digital clock 3 - 5 ma, quartz clock 7 ma, ECM 7 - 8 ma, radio & clock 7 ma. and there are other relays and sensors that add more parasitic draw.

After a power door lock relay shorted out, the old Autolite battery was completely discharged on my '91 S10 Blazer within 24 hours. I installed a new ACDelco battery and started using a Deltron 800 ma Battery Tender and the problem was solved. I attach the battery tender every time I park the car in the garage.

Attaching the battery tender every time I park the car in the garage is probably unnecessary if I would drive the vehicle every day or two. The Blazer may sit for two weeks before being driven again so I hook up the battery tender. I have Deltran's optional battery lead attached to the positive and negative battery terminals so it is no trouble to plug in the tender.

Be aware that the ECM in the failure mode can have a high parasitic battery drain that cannot be detected in the conventional manner. When the battery is disconnected the ECM solid state circuit will not show a battery drain until the continuity is restored. Cycling the ignition switch from off to run position may cause the electrical drain to reoccur but do not do that with the amp meter installed in series with the cable and negative battery post.

KMatch 08-24-2011 07:48 AM

.03 is good for most, .05 is acceptable, though high, for an older car that doesn't sit for long periods of time. I believe you found your draw - the radio memory.

willowbilly3 08-25-2011 03:39 AM

That draw should not run down a healthy battery. Also keep in mind that almost every fuse has numerous circuits so just pulling a fuse normally kills seveal things.
Also consider the method used to test the draw. If you have a low impedance meter in series with one of the battery cables you will get a false reading because you have circuits trying to power up and it takes way more power to power them up than it does to keep them alive but your meter doesn't pass enough currant to power them up..

Runnin'OnEmpty 08-25-2011 09:32 PM

With the fuse back in, pull the cig lighter out and see if it's warm.
If so, you've found the drain. The cig lighter and radio are normally
on the same fuse (that's still powered with the key off), to keep
the radio memory alive. You can also unplug the cig lighter to see
if the drain's in the radio.

Auto mfgs try to keep the key-off drain around 7-15 ma, to allow
a battery to start the vehicle after 30 days. This is good for long-term
parking in airports and such...

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