30mA draw on battery: should I care?

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Old 01-01-05, 09:55 PM
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30mA draw on battery: should I care?

Drove the car to dinner. Came back out and the battery was completely dead. No clicks whatsover or any little lights when I turned the ignition key.

A jumper got the car going, and I drove home with headlights on. As soon as I arrived home and turned off the engine, I tried the ignition again, and same symptom: completely dead (no little lights, no relay clicks, nothing).

I disconnected the radio and recharged the battery. When I inserted a little test light bulb in series between the positive post and positive cable, the bulb did not glow (unless I opened the doors or turned on headlights, etc) so that makes me think that there is NOT a short that would drain the battery. (Am I right so far?)

I put my multimeter in place of the little lamp to see if there was ANY trickle whatsoever. It showed 30 mA of continuous flow out of the positive post. Should I care about that? Is that enough to drain a battery empty? (What else besides a car radio needs a little juice? The computer(s)? etc)

Or are you thinking this is an alternator/regulator problem?

If you think it's the alternator, what are your comments about the following observation? I had a battery charger connected to the battery terminals. When I turned on car lights, the needle moved from 0 to 3 amps. When I then started the engine, the needle slammed back to 0. That made me think that the alternator/regulator was working just fine...but is that where my error is? Can the alternator/regulator send back some "but not enough?"

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Old 01-02-05, 01:56 AM
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If your able to drive home with your lights on.

You need to replace the battery. I don't think its holding a charge.
My car battery's go bad, one year before the warrantee expires.

Check the battery voltage with the car running if the alternator is working the voltage will be 13.5 to 15 volts. across the battery terminals.

A 30ma drain is nothing, maybe your clock.
My car has a 200ma drain.
Old 01-02-05, 02:28 AM
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Originally Posted by GWIZ
My car has a 200ma drain.
That's way too much. That would kill a battery in a day or two. I would bet you still had timers running when you tested it. 50ma is about max acceptable.
Old 01-02-05, 04:06 AM
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Amp Draw

Desi501 is right with a 200ma drain the battery should go dead. Like he said it probably hasn't had time to go to sleep. We give it at least 1 hour on the drain test for all modules to go to sleep. 50ma or less.
Old 01-02-05, 08:55 PM
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Originally Posted by hogfan
Desi501 is right with a 200ma drain the battery should go dead.
Hello, Desi501 and hogfan

I give you the sleep mode.
That's one thing I did check into.
I don't think my 82 Subaru 4 cylinder has any sleep mode. so I cant say.

The factory book on my car does not say what the normal drain is.
I know it checked 200ma, about 7 years back after I changed my battery.

A 200ma drain is not going to kill my battery in 2 days.

Lets do the math.

Amps are calculated at the rate per hour.

I have a 60 amp per hour battery.
about 600 amps CC amps.
200ma is per hour drain.

60 amps divided by 200ma = 300 hours
300 hour's divided by 24 hour's = 12.5 days.
A 200ma per hour drain, will take 12-1/2 days to kill my battery.

My starter pulls from 100 to 150 amps for about 5 seconds to start my 4 cylinder car.
with a 200ma drain on my battery for 6 days will reduce the battery capacity to 50 percent.

that should equal to: at 6 days
30 amps per hour left in the battery.
300 CC amps.
My car will start after 6 days.
My starter only needs 100 to 150 amps to start.( yes I think 100-150 amps is low but that's what it pulls)
I give my car 8 days before it may not start.

I measured some older car clocks at 100ma drain.
Old 01-03-05, 04:18 AM
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You need to have the battery and charging system tested because either the battery can't hold a charge or it is not being charged by the alternator.May be faulty parts,connections or a broken wire but you need to look as we can't see the car.Btw a 200ma drain is way to high under 50ma is ok as stated.This point will not be argued however because it has no bearing on repairing your problem.A drain is not causing your car not to start if it was draining that fast the smoke would be visable from the current burning a wire.
Old 01-03-05, 04:41 AM
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The original question of a 30 ma draw as being a problem was answered as normal.

Normal draw is in the 25-40 ma with some high end computer/module luxury cars I up to 80 ma (thatís why they will have a 900-1000 cca battery)

You calculation sounds correct about the 6-8 day start. If the vehicle were used for short trips the battery would be dead after a month or two. Even on longer use the battery would fail prematurely from the stress of large draw. Therefore this draw would be unacceptable.

I agree about something wrong in the method of arriving at a 200 ma draw on that vehicle. Timer, key in ignition (not on, just in), also old analog clocks had a wind mechanism that could draw 100 ma or more but only for sec or two to wind every so often.

The original poster has been given the information he requested and then some. So letís get on to new business.
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