racerjack

Hello again,

Have 2020 SL450 with OEM batteries almost 48 months old. Car has 4K miles.
Should I replace the batteries before they leave me stranded?

toolguy4u

My 2015 sl OE battery was replaced 1 year ago. No symptoms but like you, I figured 9 years and 30K miles was pushing iti. I still have the orig Aux battery

jmattioni

That's very low mileage! The starter battery should last about 5 years. Less if it's ever gone flat, like when sitting in the garage for long stretches. The aux battery can last up to 10 years, but probably only in a car that's being driven so it's kept charged. Otherwise, I would change the aux at the same time as the starter battery.

A car full of computers can have strange glitches if the main battery voltage isn't steady. It's normally capable of detecting a failing battery and reporting it, but that's not 100% reliable. Sometimes you just start to get strange fault codes. Preventative battery replacement is definitely worth it.

Markrtn7

2017 SL450 50k miles, still have both original batteries. Not a daily driver, but use a CTEK on main. Am I pushing my luck?

docjoe

At 37000 miles and 8 years I replaced the main battery, although it was still functioning. The Auxiliary battery is still functioning normally at 9 years. Impressive.

This is in my 2015 SL400. My experience with MB’s batteries has been good.

jmattioni

Your miles are above the typical, which is good for the battery (and for you!). Plus, the CTEK helps extend battery life. But I'd say you're about due for a new main battery within the next year. I know some people have gotten as much as 10 years out of their main battery, but I say why push it? That's especially true if you drive it at all in the winter, when colder temps reduce battery efficiency.

Bitbytr

I live in Florida with my 13 SL550 and still running the OEM main battery. No issues so far but six months ago started to noticed weird things with the ECO functioning. I replaced the Aux battery and all's back to normal. This is not meant as advice but simply FYI as, obviously, YMMV!

Montreal300

On a 2014 SL550, both batteries were showing faults so they got replaced.

rmorin49

When the main 12V battery in the trunk is replaced what settings are lost? Anything else affected? I have always replaced the batteries in my vehicles. I think my SL main battery was replaced when it was CPO certified. Not sure but I did replace the auxiliary battery at 8 years. Car was CPO certified in 2019. I should see if there is a date code on the battery. I'll also review the CPO work order which I received from my local dealer that lists all the parts that were replaced. I do keep it on a CTEK when it's parked in my garage.

WLP624

My 2015’s original battery didn’t start showing its age until recently, and then only slightly slower cranking on start. It was an easy diy to replace with no lost settings.

Keon

I got 10 years out of the battery under the fuse panel (I think that's the auxiliary one). Even then, all I got was a warning that the battery was malfunctioning every now and then. The OEM batteries in these cars are really great.

rmorin49

OEM battery? Who makes it? Is it German? In the US I have read that only 2 or 3 manufacturers make most of the batteries for a multitude of different brand names. I've seen photos of batteries coming down the assembly line with different brands labels.
Johnson Controls
Stryten
East Penn

Markrtn7

My main is a Varta (Germany), aux is Fiamm (Italy). Curious what brands were supplied by the MB dealer for those of you who went that route (in the U.S.).