ph1958

The convenience battery (in the trunk) of my 2005 SL500 is connected to a CTEK battery when parked in the garage. The starter battery (under the hood) is not connected.

Periodically, the SL500 displays a malfunction during which a) the hardtop cannot be raised or lowered and/or b) the cigarette lighter is similarly not operative. After driving for a period, the malfunction disappears and everything functions normally.

Has anyone else experienced this situation? Is the convenience battery due for replacement? I have replaced the starter battery once during my seventeen years / 11,000 miles of ownership.

skmorgansr

I’ve had the same issues on my 04 SL500. Finally I had service call and AAA guy said the consumer battery was fully charged. I’m getting the consumer battery replacement tomorrow. At some point I don’t think the battery will hold the charge.

ph1958

Did replacing the battery solve the issue?

Thanks!

skmorgansr

No, it’s currently at the dealership. I questioned the service writer why they insist on replacing the gear box with OEM which is still using the cheap plastic part.

A1EK

Batteries are low, your voltage maybe okay but the current maybe weak, check your alternator is giving out 14.1 V.

Replace the battery with a genuine Mercedes battery or Varta, I did this and never had the issue again, I do not use a trickle charge as its not required, I can leave the car for a month and it will start right up .

ph1958

Thank you to all for the suggestions. I will look at replacing the battery...which is the original battery...

tonylinc

It's almost unimaginable that a 2004 could still be using an original battery, that's what, 17 years?!
The battery you buy is your choice, of course. All the Mercedes I've put batteries in over the past several years, I've bought Duracell AGM batteries, and never had any trouble after that.
I just thought, who knows batteries better then Duracell? And the coppertop black and copper color looks good to me. Naturally they have a good warranty.
Obviously a Mercedes brand battery is going to perform perfectly as well. I wonder what the price difference is, if any.
The giant trunk batteries I've bought have ranged around $200-230 USD. Best of luck, to all!

MBCO

Just replaced both my batteries which were 7 and 9 years old MB OEM with same from local dealer. Shopped all the parts stores for batteries and discovered that many were available and prices were within 10% of MB. In addition 1 stop not 2 as not all stores carried both in stock. I asked for a discount and MB parts gave me 10% off which helped.
starter $ 216 trunk $185 less core 22.50 ea. plus sales tax, $431.00 out the door. Ez diy.

m60kaf

In specific answer to your question ... No I havent and I say that constructively in that I've owned the car over 10 years had 3 boot batteries and 1 starter and that has NEVER happened. Get "convienience functions not available" think US cars say "consumers unavailable" with low battery issues. So you may be barking up the wrong tree.

What is the message on the malfunction if you arrow up

You could have a fault with K75, or N10/10 driver SAM but those do have a supply from the starter battery so you may be right