dis6933

Hi

If I do not drive the car (2005 SL500) for a few days, the display in my gauge has a statement that "accessories are not on" or similar. I do not notice any non operational items, and the notice goes away after I drive a mile or two. My trunk battery is the original battery - 8 years old -- is it possible that the battery does not hold charge which keeps some accessories off till the battery get to a normal voltage level?
Any suggestions on replacement batteries?
Thanks
Don

TwinCam

Most likely your trunk battery is on its last leg after a long and prosperous life. Eight years has to be close to a record! Given the unique size of the battery, you may have to get the battery from your Mercedes dealership. Hope your next battery lasts as long.

vtvette

+1 dis6693

My original starter battery just gave up the ghost a few months ago in my 2005 SL55. I went straight to the dealer as I hear there is really no aftermarket alternative due to the size.

Now, my accessory battery (in the trunk) gives me the "accessories not available" notice for several minutes after I start the car, even when it's only sat overnight.

dis6933

The MBZ dealer wants $250 fort the trunk battery, while an Interstate 76 Mo battery is priced at $150. Guess which one I will purchase.
Don

vtvette

Thanks Don for the info!!

cal1

The trunk batteries seem to be busy discharging slowly whenever the engine is off. It is not a bad idea to trickle charge the trunk battery if the car won't be started for a number of days. Doing so will likely increase the life of the battery and stop the annoying electronic consumers offline message from popping up. Mine has been worse ever since installing an ELM lowering module. I hook up my trickle charger if I am not going to be driving the SL from more than a few days.

ilovemaui1

My SL is rarely driven, so I keep a trickle charger on my accessory battery.

Dave in VA

What is the battery number for the trunk battery? Checking Interstates web site it has two batteries listed one is a MT7 AGM (primary - length 10.91, height 7.47) and one is a MT5 AGM (alternate - length 11.00, height 7.50), I not sure but it appears this is the size of the one under the hood.

Also as I understand if you use a battery tender on the battery in the trunk it also keep the one under the hood charged.

Dave

dis6933

Hi

I purchased an AP48 battery, but not an Interstate, as it does not have the amp ratings that MBZ requires. This is not a "water" battery, so it does not need
any attention. It is a Part Master Platinum, 72 months warranty.
I do not know about the interconnections between the batteries, but I do know
that MBZ requires that you disconnect the trunk battery first, before disconnecting the engine located battery.
I do have a trickle charger for the trunk battery, but not sure that gets to the engine start one.

cal1

Hopefully someone else will answer regarding the part number for the trunk battery as i do not know.

Regarding the trickle charge on the trunk battery, I am not sure if it actually keeps the engine battery charged. I have been told by others that it is not necessary to trickle charge the engine battery. I put my SL to bed by the end of November and don't start it again until early April. The engine always cranks over with good power after all of that time.