SL/R230: How long should a starter battery last?
Thread Starter
Member
Joined: Feb 2024
Posts: 77
Likes: 37
From: California
2005 SL55 (past), 2021 E53 (present)
How long should a starter battery last?
There must be a parasitic leak. Because my 2005 SL55 consumer battery can't go more than a day without the voltage dropping well below 11V. But that doesn't explain why the starter battery won't start the car. It should be able to sit idle for several weeks without losing charge (Because there is no load on it other than starting), but it can't. It can start the car after a few days but not after a few weeks. I do have a charger and use it on the consumer battery. But that doesn't explain the starter battery losing charge so quickly.
Both batteries are MB and were replaced in 2023.
Both batteries are MB and were replaced in 2023.
Super Member
Joined: Sep 2018
Posts: 746
Likes: 185
From: Melbourne, Australia
2005 SL 500 R230
There must be a parasitic leak.
More likely you have a dodgy-from-new battery - it happens. There are two options: Dying from new, or you have a drain, which can be only through the BCM, presuming no aftermarket mods.
First get a deep test on the battery with a dummy load. If it proves good, then you'll have to hook up a meter to check for quiescent current draw - it should be zero so if there is drain, there is a fault.
Mine sits for weeks and weeks and always cranks quickly.
More likely you have a dodgy-from-new battery - it happens. There are two options: Dying from new, or you have a drain, which can be only through the BCM, presuming no aftermarket mods.
First get a deep test on the battery with a dummy load. If it proves good, then you'll have to hook up a meter to check for quiescent current draw - it should be zero so if there is drain, there is a fault.
Mine sits for weeks and weeks and always cranks quickly.
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,329
Likes: 365
From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
Yeah, you should be good for months with a healthy battery. I would check for parasitic drain. Also, check to see if anything has been tapped off of the front battery. Like Tom said, the only potential for drain as it came from the factory is the BCM, but someone installing an aftermarket alarm or some other accessory could have tapped into the front battery.
Senior Member
Joined: Jul 2013
Posts: 448
Likes: 48
From: Europe, but from Norway
89 SL500 Silver ,97 SL500 Carlsson 04 Mercedes SL55 AMG , 07 Mercedes SL55 AMG convertedBlack series
should last 6 years starter batteri, is not any drain on thoose. 2 different cars i changed them after they died 6 years on the clock
MBWorld Fanatic!
Joined: Dec 2005
Posts: 4,057
Likes: 341
From: NJ
2009 SL63 AMG
5+ years easily on a healthy system.
My starter battery has a Aug-2018 mfg. date and I purchased / installed it in May-2019.
The battery is disconnected from the car and on a tender during Winter storage, and I load test it every Spring before re-installation.
Still showed 100% health / capacity this year.
My starter battery has a Aug-2018 mfg. date and I purchased / installed it in May-2019.
The battery is disconnected from the car and on a tender during Winter storage, and I load test it every Spring before re-installation.
Still showed 100% health / capacity this year.
