SL/R230: Low Battery Symptoms?
Thread Starter
Junior Member
Joined: Jun 2018
Posts: 18
Likes: 1
2009 SL550R
Low Battery Symptoms?
2009 SL550, I've owned it a couple of months, love the car! Previous owner said something about keeping it on a trickle charger if I wasn't driving, he had just had a battery replaced at the dealership maybe 4 months ago. (This statement coming from a guy that didn't put 3000 miles on the car in 2 years, I figured that was his issue.) I had been driving the car at least every other day since I got it, then we went out of town for a week, then it rained for a week, so it sat for maybe 2 weeks.
I went out yesterday, car was already unlocked so I got in, push to start would not work, had to use the keyfob in the ignition, car started, warning light on dash, top would not operate said something like "refer to the owners manual for top operation". I drive it away and the warning light goes out by the end of the block. Drive to dinner, use the fob to lock the car. Come out from dinner, fob won't unlock the car, had to use the emergency key. Drive home, suddenly everything works, top goes down, key fob locks and unlocks.
Figured it was fixed, then tonight same scenario. Then after driving the car a bit everything seems fine, top and fob works fine.
I'm guessing this is the dreaded "battery drain issue"? Any fix/resolution other than "keep it on a charger"?
I went out yesterday, car was already unlocked so I got in, push to start would not work, had to use the keyfob in the ignition, car started, warning light on dash, top would not operate said something like "refer to the owners manual for top operation". I drive it away and the warning light goes out by the end of the block. Drive to dinner, use the fob to lock the car. Come out from dinner, fob won't unlock the car, had to use the emergency key. Drive home, suddenly everything works, top goes down, key fob locks and unlocks.
Figured it was fixed, then tonight same scenario. Then after driving the car a bit everything seems fine, top and fob works fine.
I'm guessing this is the dreaded "battery drain issue"? Any fix/resolution other than "keep it on a charger"?
Member
Joined: Mar 2018
Posts: 129
Likes: 10
2011 Mauritius Blue SL550
I haven't heard of this dreaded battery drain issue, but when I was at a Mercedes mechanic the other day to run Star Diagnostics, he mentioned that the battery was quite low. (The one in the trunk.) I suppose I need to look into that, especially since my 2011 SL550 is parked in the garage right now, aside from a couple shorter 15-minute joy rides a week.
Excuse my side question, but what is this "emergency key"?
Excuse my side question, but what is this "emergency key"?
Thread Starter
Junior Member
Joined: Jun 2018
Posts: 18
Likes: 1
2009 SL550R
And yes, after doing a bit more reading on the forum it appears that battery does indeed drain. I'll get a charger on it from now on if it's going to sit.
MBworld Guru
Joined: Dec 2009
Posts: 10,782
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NO LONGER ACTIVE
If you drive the car several times a week, the consumer (rear) battery should be maintained. If you don't drive it that often, then a C-Tek trickle charger might be a good idea. If you do drive it often and still have battery issues, you may have something discharging it, such as the PSE pump. Often, an air leak, such as in the trunk latch, can cause the PSE pump to run and drain the battery. If the battery is more than 4 years old, it's probably time to repalce it.
Thread Starter
Junior Member
Joined: Jun 2018
Posts: 18
Likes: 1
2009 SL550R
If you drive the car several times a week, the consumer (rear) battery should be maintained. If you don't drive it that often, then a C-Tek trickle charger might be a good idea. If you do drive it often and still have battery issues, you may have something discharging it, such as the PSE pump. Often, an air leak, such as in the trunk latch, can cause the PSE pump to run and drain the battery. If the battery is more than 4 years old, it's probably time to repalce it.
Junior Member
Joined: May 2011
Posts: 23
Likes: 3
'92 500E, '07 SL550
Would also suggest renewing the batteries in the fob if you haven't done that already. Mine worked for doors and starting in the steering column, but keyless go didn't work until I changed batteries.
