Battery Drain, PLEASE HELP... - Page 2 - PeachParts Mercedes-Benz Forum

chytaan · #16 11-14-2006, 10:02 AM

Well, i picked up my car from the mercedes dealer and he basically said the same thing as my mechanic. He said he got about .1 draw, but he couldnt find a specific drain. He also added that its normal for some w140 to do this. (which i doubt, since i have owned several 140's and this is a first).

The advisor also added, that the battery will go to a low level if the vehicle is not started within a week. So he recommended regular start up.

Not the answer i was looking for, as my mechanic and I did the same test, and was hoping the dealer would find something we overlooked.

My mechanic suggested, that i leave my car for a day not started, and then try to start it, then for couple more days not started and start it again, just to see how long before we have difficulty starting it again.

Anyhow, thanks for everyone's help, much appreciated.

gmercoleza · #17 11-14-2006, 11:03 AM

Just as a suggestion, you might try installing a battery tender in the meantime, to avoid needing a jump every time this happens.

mpolli · #18 11-14-2006, 01:24 PM

.1 Amp will not kill a good battery. It should be able to handle that for a month easy.

Mike

Gilly · #19 11-14-2006, 05:50 PM

1000 milliamps=1 amp. .1 amp is 100 milliamps, this is too high. 50 milliamps is borderline, although 140's may get close to this, but 100 ma is way too much. PM me on who worked on the car at Z's, or who the advisor is.
Gilly

Moneypit SEL · #20 11-14-2006, 11:21 PM

Quote:

Originally Posted by Gilly

MoneyPit: You connect an ammeter between the neg post of the battery and the neg cable and watch the current draw. Accomplishes the same thing as leaving the battery connected, doesn't require and special wire-rigging. If you have a multiple scale ammeter you are accomplishing the same thing. The components should function just fine through the ammeter, up to a few amps.
Gilly

Ahhh. I recalled a detail after I posted that. Caddys had an issue where excessive current draw would not occur until after the components were powered up. Disconnecting the battery reset everything and hid the problem. The jury-rigged test leads were to permit cycling the ignition key to power up everything without blowing the fuses in the multimeter.

OTTOBUN · #21 11-23-2006, 03:23 PM

Quote:

Originally Posted by Gilly

1000 milliamps=1 amp. .1 amp is 100 milliamps, this is too high. 50 milliamps is borderline, although 140's may get close to this, but 100 ma is way too much. PM me on who worked on the car at Z's, or who the advisor is.
Gilly

I have a 75ma draw on my 124...kills a good charged battery in a week or so.

I did the fuse-pulling trick but the meter never fell from 75. Where should I look next?

kiwi_bloke · #22 11-23-2006, 04:28 PM

I have seen - in one car a fault with the boot (trunk) light switch. It was somehow causeing the boot light to stay on. Im not sure how. Also check the glove box light switch. Although I doubt it would be these. Have you checked to see if the alternator is charging correctly?

I have had on a 300E an alternator that was showing it was charging by voltage - but when it heated up the brushes were arcing and causing it not to charge - a result of dust from the brushes.

Gilly · #23 11-23-2006, 06:13 PM

If none of the fuses reduce the amperage draw, then you need to go after the unfused items in the car. Any add-on accesories that have been added to the car? Sometimes a careless installer taps into a "bad" circuit to be tapping in to. I'd also pull the connector off the alternator to make sure that's not it. Other wise grab a wiring diagram and look for hot circuits that aren't fused.
Gilly

sixto · #24 11-24-2006, 02:54 AM

chytaan, if your S600 is anything like my 300SD, ahead of and above the battery is a distribution center. The positive cable splits into a couple of small cables and a big cable. One small cable goes to the fuse box above the battery. The other small cable and the big cable go the passenger footwell where there is another distribution center. From the front distribution center a small cable goes to the alternator, another to the starter, then there's a series of smaller wires I haven't investigated. I assume something goes to the ECU cluster and the front fuse box.

What's the point of this? Pulling fuses in a W140 might not localize a ground fault because the systems are interconnected. How the fuses even function as fuses is a mystery to me. Maybe your mechanic can isolate the circuit by disconnecting cables at these distribution centers.

In my case I'm chasing a draw that discharges my battery overnight. I localized it to the small cable that goes to the rear fusebox. I get the draw if any of a particular set of 5 or 6 fuses is in place. I haven't figured out what that set of fuses have in common (stereo, convenience module, and something else).

Sixto
93 300SD

PatOne · #25 11-24-2006, 09:46 PM

Quote:

Originally Posted by mpolli

.1 Amp will not kill a good battery. It should be able to handle that for a month easy.

Mike

I'm not sure that's right Mike. Taking 70+ amps out of a battery that can deliver only 80-90 total is probably expecting too much. I am fairly certain that this kind of cycling will make a good battery go bad fast.
A quick and inexpensive fix, CHY, if the vehicle is stored outside, is to replace the missing amps via a cigarette lighter plug-in solar charger/maintainer.
But here's the thing, something started using power that should not. Why?
If it were my car and finances permitted me to avoid the quick fix, I'd be compelled to follow the same course you are. These guys are terrific.
My two cents - maybe the ignition switch?
Pat

mpolli · #26 11-24-2006, 10:59 PM

Well that was a "top of my head" calculation. Maybe not too good on second thought. But my reasoning was if the Ahr rating of the battery is 80 and that is based on a 10 Hr discharge rate (8A) and if you are only discharging it at .1A then the capacity is effectively increased, by 50% maybe, so there you go, around 48 days. But I dont have the discharge graphs to back me up. Also that is based on a "fully" charged battery which I doubt a battery in a car is ever fully charged. Under ideal conditions it might make it but in pracitice probably not. The main issue here is that 100 mA is more than everyone thinks that car should draw. However I am suspicious of such a round number. Did they actually measure 60mA or 145? Big difference. As far as the solar charger, I have one on my Toyoya. Harbor Freight had them for 9.99 !!

Anyway, if it is really drawing .1A then .1A x 12V is 1.2W. So whatever is drawing the load should get somewhat warm. So you could leave the car overnight and then use touch or an IR thermometer to see what is warm.

Mike

Gilly · #27 11-25-2006, 05:20 AM

You have to realize that especially on a 140, especially a S600, there is quite a high resting draw, but should be on the order of 40ma, not 100ma (.1a), so actually it's a question of where the excess 60ma is going in a case of a 100ma resting draw. May not be easy to find, as in something "warm", and not enough to be a bulb, even a small trunk or glovebox light will be a couple amps (couple thousand ma). The thing that's bothersome is about 100ma will be what you'd see before all the modules go in to "sleep" mode, maybe just a module is still active, not sleeping?
Gilly