These (idle) cars suck power like a vampire sucks blood. Parasitic draw is the reason. If you got nothing, I would suggest that a new battery is in order.

You can put it on a slow charge but in all likelyhood she wont hold the charge. IMO.

AND do not jump start with another car. You'll probably fry the electronics. MT might get it going but if it's dead as you say, probably won't and be left with a car in the middle of the road.

What most do (including me) is after you get the new (AGM?) battery, when you know she'll be idle like that, put it on a trickle charger like a Battery Tender or Ctek .

I do that if I know she'll be sitting for more than a day. Cheap insurance. Something else I found: if i leave it unlocked (no charger), the draw is more than if I lock it.

She charges faster if locked as this shuts everything (well, most everything) down.

 

I just put a multimeter on the battery and it read 2.5V. I've never seen a lead acid battery that low. Even if the battery was good before the trip, taking it that low likely ruined it, right?
What kind of parasitic draw kills a battery that fast? Maybe if the headlights had been left on for two weeks.
Don't most wealthy Benz owners expect to be able to go on extended vacations and still have their Benz function when they return? I'd consider that to be a prerequisite of a quality car.

 

I just put a multimeter on the battery and it read 2.5V. I've never seen a lead acid battery that low. Even if the battery was good before the trip, taking it that low likely ruined it, right?

I've got one that went right down to almost nothing and now it will not charge any higher than 11.6v on either of my chargers, both chargers are saying Full Charge attained or words to that affect so my battery is obviously now FUBAR, yours maybe. Varta 5yr warranty is void if I let it go below 10.5v .. dunno how that works tbh :frown:

 

Also, that's very interesting that the idle draw is higher if the car is left unlocked (which I think it was). Seems strange to me.

 

Lots of posts about parasitic draw

https://www.slkworld.com/search.php?searchid=15188424

 

I had this with my R170 - turned out to be the alarm - it contains a rechargeable battery which eventually fails and then draws from the main battery. Totally fixed with mine by disconnecting the alarm



Sent from my iPhone using Tapatalk

 

I have had this with my car, it did it 3 times in about 2 months and hasn't done it again in 8 months. I don't know what was going on, but it was frustrating. Mine would die in a weekend. I even changed the battery and it still did it one more time. I don't know what it was, but I am glad it is gone!

 

Hi,

What I would do is fit a new Battery first, and once the car has had a good run then check it for parasitic (quiescent) drain ..................

Now I've never checked my R170 which has about 16 modules on it, my W220 has double that at least .................

On a fully loaded W220 anything up to circa 50mA is acceptable, and a decent Battery will get to the point of no start by around 4th week of standing unused.

So, regarding the R170, I don't know the exact figure off the top of my head, but I'd be suspicious of an abnormal quiescent current drain if I saw any more than a 25 to 30mA draw once the car is asleep :wink:

Perhaps someone like @efair may know the correct figure for the R170's

HTH, Cheers Dave

 

IIRC WIS says 25ma which is what mine dropped to once I disconnected the alarm siren with its leaking internal battery.

Sent from my SM-T210 using Tapatalk

 

I only use AGMs any more.

That said drains can come from many places but modern computer cars should be "less than 50 ma". 20-30ma is preferable.

NOTE: always disconnect the negative battery terminal first and reconnect last. Don't ask just do it.

 

Thanks all.

I got a new AGM battery. Previous battery at 2.5V sounds ruined to me.

I will check amperage across neg. with the car shut down (w/ and w/o alarm). Is there some shutdown period that I should be aware of, to let all systems go to sleep? Should I be wary of any alarm system idiosyncrasies when messing with the battery? (I've been locked out of my own car before by the alarm/autolock/disabler, and I don't want to go through that again.)

Due to the previous alarm system failure debacle, I have considered disabling the alarm system altogether. It creates more stress than it alleviates for me. How difficult is that procedure?

Thanks,
Ben

 

Hi,

If you are worried about getting locked out, leave the door open, but click the latch to closed (2 clicks) with a Screwdriver, you need to do the same with the Bonnet (Hood) latch(es) too, then the Car thinks all is closed and should go to sleep within 15 to 25 seconds. also look to make sure there isn't a pin switch, if there is wedge / tape that to it's closed position :wink:

Regarding worrying about the Alarm and disabling it, just fit a new MB Siren, they are chump change from MB and not worth messing with !! Then you will not have any more grief with it for another 16 years :wink:

Likely cause more grief by messing around leaving stuff un plugged, jury rigging things etc

HTH, Cheers Dave