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How many of you have been running a battery tender/trickle charger on your trunk battery (or both batteries) for 4-5+ years without damaging your Load Separator Module/Battery Control Module?
I did not drive my 2004 SL55 AMG regularly for the first few years of ownership and sometimes got the consumer battery (rear trunk battery) light which goes out after a few minutes of driving. I started using two battery tenders on the car about 4 years ago and this solved my issues.
However, recently my starter battery (front, underhood battery) failed (probably due to age) and I jumpstarted the car twice (without disconnection the rear battery per the owners manual...I did not see that section-see below). I could not get the battery light to go out and my independent M-B shop found an electrically overstressed (burn smell, soot, etc...THIS CAN BE CATASTROPHIC) Load Separator Module. My independent said to not put a trickle charger on the car...just drive it more often.
Sure enough, life/weather got in the way and I did not drive the car for a month...and the consumer battery light came on (on start). Again, it goes out after 30 seconds BUT I know that depleting a battery like that reduces its life.
Do you think this is the secret: https://mbworld.org/forums/sl55-amg-...or-module.html https://mbworld.org/forums/sl-class-...ol-module.html I have learned a few things about changing the rear battery (at least on my 2004 SL55 with keyless go). Do not have the key fob anywhere near the car when you change the battery as it may (will) reinitialize and cause the key fob to be in-op.
I installed a consumer battery disconnect on the battery negative post to protect the BCM when I use the trickle charger on the battery. This one fits well. I added a plexiglass spacer to keep the “Off” condition. I got it from the local parts store.
Top Post Battery Disconnect Switch, Ampper Battery Master Switch Isolator for Power Disconnect Cut Off
I installed a consumer battery disconnect on the battery negative post to protect the BCM when I use the trickle charger on the battery. This one fits well. I added a plexiglass spacer to keep the “Off” condition. I got it from the local parts store.
Thanks...two questions:
1) Doesn't separating the battery from the circuit (while trickle charging) lose your radio preselects, clock, etc...?
2) I do not understand: "I added a plexiglass spacer to keep the “Off” condition."
1) only the clock needs to be reset.
2) the shim is not required. I just made a spacer in the gap of the disconnect when it was unscrewed in the off position.
1) only the clock needs to be reset.
2) the shim is not required. I just made a spacer in the gap of the disconnect when it was unscrewed in the off position.
Just sold my '11 Porsche TurboS cab for an '03 SL55!
I've been using this one from Amazon for a year...........$29, seems fine. And I like the display that shows the current draw, voltage etc. I've hard wired it to the rear battery, and it fits pretty neatly to the rear of the battery. I dangle the 120 VAC cord out through the trunk when its in use.
I've been using this one from Amazon for a year...........$29, seems fine. And I like the display that shows the current draw, voltage etc. I've hard wired it to the rear battery, and it fits pretty neatly to the rear of the battery. I dangle the 120 VAC cord out through the trunk when its in use.
I had no issues for 5 years (doing essentially what you do)...so I think my problem started when I had to jump start the car to move it. Anyway, I am now paranoid.
Tom
My 65 stays on a Ctek charger and has for the last 6 years with no issue and I very rarely drive the car.
Rumor has it that only a couple of years of SL55 have this electrical configuration. I am almost convinced that jump starting it with the consumer battery in the loop exacerbated the issue.
Jump starting any of these generation Mercedes will cause extreme issues with electrical components. I won’t even do the 40amp battery charge start. Too much voltage.
I have to fess up to not starting my car for about 2 months for a bunch of reasons (I know- shame on me). When I went to start it yesterday, the key remote would not work. I had to use the metal key to open the driver's door and the keyless start did not function. But... key in the ignition and she fired up confidently on the first attempt. Shut off the engine almost immediately and restarted with pushbutton without problems. Electrical consumers came back on after about 10 minutes and all good as new. The starter battery is more than 3 years old, but still held enough juice for over 2 months to start the car.
The starter battery is more than 3 years old, but still held enough juice for over 2 months to start the car.
It is my interpretation/understanding that the starter battery has NO load on it when not trying to start...so it should last a darn long time. The consumer battery is supposed to take all the sleeping load.
I have battery tenders on all of my cars and have never had a problem.
Me too...some nicer than my AMG, AND I am leaning towards the jump starts (twice in a row when starter battery failed); BUT electronic architecture of the 2004 SL55 seems to have a weak point (control module).
01-23-2022, 03:49 PM
