Does battery Drainage 100 mA sound right?

[MoonRivertttt]

Hi there,

My 07 G35 Coupe 6MT has a 100 mA current drainage from the battery. I drove it for about 30 to 45 min at average about 40 mph the other day. The next day it cranked but very slowly, and after I left it sitting for about a month then it became too weak to crank. I guess it's the current drainage killed it.

BTW had the alternator tested at Advance Auto, it's fine. 14.17 V at idle and 1500 RPM.

Has anyone ever measured the drainage? Does 100 mA sound reasonable? The way I did it was disconnecting the negative pole, connecting a multimeter between the pole and the negative cable. Measured 100 mA without the key in ignition at all.

[arrow23]

I have not measured drainage, but I did have an incident where my battery was dead after the car sat for a few days.
It is a 2008 G37S Coupe. This happened about 2 years ago.
I took it in to the dealer and they had a Service Bulletin that had them reprogram the ECU.
They told me that the ECU performs a periodic test of some systems (i.e. check for fuel vapor / leak). These tests drain the battery, and if not driven very often can lead to a dead battery.
The reprogramming of the ECU changes the intervals of this test (to alot less frequently).
They replaced my battery and reprogrammed the ECU at no cost.
No problems since.

[telcoman]

Hi there,

My 07 G35 Coupe 6MT has a 100 mA current drainage from the battery. I drove it for about 30 to 45 min at average about 40 mph the other day. The next day it cranked but very slowly, and after I left it sitting for about a month then it became too weak to crank. I guess it's the current drainage killed it.

BTW had the alternator tested at Advance Auto, it's fine. 14.17 V at idle and 1500 RPM.

Has anyone ever measured the drainage? Does 100 mA sound reasonable? The way I did it was disconnecting the negative pole, connecting a multimeter between the pole and the negative cable. Measured 100 mA without the key in ignition at all.

If you are still under warranty I would follow arrow23's advice and have the dealer check it out.
If you still have the original battery you can test the cells with a battery hydrometer



If all cells are not accepting a full charge of 12.60 specific gravity its time to replace the battery.

Telcoman

[MoonRivertttt]

This is the 2nd OEM battery. The first one died only 3 months after I got the car brand new . Then the dealer replaced it with this one. It had been good for 66 months, out of 84 warranted. Unfortunately the car is out of warranty, the dealer wouldn't prorate it because I didn't pay the battery. Had the battery tested at Advance Auto, it's low.

Pulled out the BCM fuse, the leakage dropped by 36 mA. There is still 64 mA somewhere. The dealer charges $120 to diagnose. I can pull out every fuse one at a time to track down the culprit, but I need someone looking at the multimeter while I'm doing it, and , there are lots of fuses by the clutch pedal. Either way I got to get it fixed before putting in a new battery or sooner or later it'll drain out.

The leakage wasn't changing as I measuring it, didn't fluctuate, that makes me think it's not ECU or something being on and off such as in the case of Arrow 23. It got to be something constantly consuming the battery.

[MoonRivertttt]

Googled around and found an ITB addressing ECU. The ECU needs reprogramming. No model listed but from 1998 through 2013. Here are some limited infor.

http://www.automd.com/tsb/bulletin_b344265/

I haven't experienced any abnormal behavioral but I have to take the car to the dealer for it, hopefully it will fix the drainage. I'll report back.

[MoonRivertttt]

Took the car to dealership and was told it's normal because the security system needs current to arm and stays armed. I wonder if any you guys gets around 100 mA. I would like to compare. If someone who has a G35 or G37 can
check it for me that will be appreciated greatly.

The way to check it is following:

Engine off, insert a DMM between battery negative post and negative lead or body ground, and read the current ( DC, not AC) without the key ignition, radio, all lights, fan off and all doors closed ( so the door and doom lights are also off)

TIA

[SteveTheTech]

Hi, I think I can help. I've been doing these for a while.

You've almost got it. There is one thing you are missing. Patience. The reason you have such a pull on the battery from the bcm is that it is still awake. You set up the test perfectly but there are a few things you need to address to get a real parasitic draw number.

First, if you have iKey you will need to arm the system and relocate all fobs at least 10 feet from any part of the car. If not locking the

Secondly remove the fuse box cover in front of the battery. (pictured below)

After you set your DMM up and arm the car you will have to observe the current at about 1A for 10-15 minutes. After that you should see control units start powering down. At about 28 minutes the bcm should power down and your current draw should be in the range of .038mA. A little higher if there is anything aftermarket in the electrical system. There really is not a spec but after the bcm goes to sleep the tolerable range is probably about .02+- but less is better.

Record your readings every ten minutes.

Remove #37 fuse and record the findings. Reinsert the fuse and record the change.


Let us know what you find.

[MoonRivertttt]

Steve, Thank you for the expert detailed instruction. It's very helpful.

Yo said "At about 28 minutes the bcm should power down and your current draw should be in the range of .038mA." Did you mean .038 A instead? 'cause .038 mA is basically zero.

OK, to begin with, I measured 108 mA with no fuse removed, either hood switch up or down. More then 30 min later it dropped down to 20.3.

#37 which is labeled as radio (Bose) unplugged it was 19.2, with both #37 and FGHI removed, it's 19.3. All the readings were taken after at least 30min wait except the initial 108. BTW I don't have any aftermarket stuff installed, it's not ikey either.

Does it sound right to you?

[SteveTheTech]

I did get that wrong how a bout that, if errors don't set off my spell check it usually makes it through....saying it out loud and writing if out are two very different things. I hope that doesn't confuse anyone...I'll go back and edit it. But yes around 30 milliamps is about as low as it will go.

If you are getting a reading of 28 milliamps I do not think that parasitic draw is really factor in your car. You may have a low static charge or reserve capability in the battery but you may have something as simple as a tiny amount of resistance in the negative cable that will add load to all of your circuits. This is not something that will typically be detected with a resistance check, you may have some luck with a voltage drop across the cable but if you feel that it is abnormally warm after driving for a while or has any signs of chaffing toss it.

I have had OE replacement batteries die but it is uncommon that two would fail in that period of time.

[MoonRivertttt]

These readings were taken off a new OE battery. You are exact right, Steve, the last one was an OE as well. It died in the 66th month. I guess 66 months is about the life span of a battery. I live in FL, in such a hot weather, 66 months sounds reasonable to me. What do you think? The very first OE battery only lasted 3 months.

Those readings ease my worry. Thank you so much for providing me with your expertise. In fact the parasitic drain bothered me so much that I had to install a battery kill switch. Now I don't think I need it anyone. I don't have to reset the clock and radio every time no more.

I am glad that you came along. Thanks again for your help.