Talk to me about W221 batteries
Discussion
2013 late model W221 S350 Bluetec on 90,000 miles.
Noticed that the ECO (start-stop) function just doesn’t seem to want to kick in recently and there are some journeys where it will not change up above a certain (often 4th) gear and shifting behaviour seems a bit odd.
Does this sound like it could be a battery issue?
I have a multimeter and will try and get a voltage tomorrow.
I see the main battery in the engine compartment but believe that there an aux battery in the rear bulkhead that may also be worth checking?
I had expected to see some warning messages pop-up, but nothing so far (with the exception of a couple of CEL codes P0171 cnf & pnd so I’m beginning to think replace a battery first, then see if these CELs disappear).
Noticed that the ECO (start-stop) function just doesn’t seem to want to kick in recently and there are some journeys where it will not change up above a certain (often 4th) gear and shifting behaviour seems a bit odd.
Does this sound like it could be a battery issue?
I have a multimeter and will try and get a voltage tomorrow.
I see the main battery in the engine compartment but believe that there an aux battery in the rear bulkhead that may also be worth checking?
I had expected to see some warning messages pop-up, but nothing so far (with the exception of a couple of CEL codes P0171 cnf & pnd so I’m beginning to think replace a battery first, then see if these CELs disappear).
At that age if might be worth changing the auxilliary as well.
I recently changed mine, (on an E-class, not S) couldn't source a genuine MB-Varta one (online MB dealers wouldn't post/courier the main battery), so opted for an AGM one from Halfords (made by Yuasa), with 5-year warranty. Sourced the auxilliary one from MB.
I recently changed mine, (on an E-class, not S) couldn't source a genuine MB-Varta one (online MB dealers wouldn't post/courier the main battery), so opted for an AGM one from Halfords (made by Yuasa), with 5-year warranty. Sourced the auxilliary one from MB.
Did you see any warning messages appear about the aux battery, or did you just replace it as a precaution?
One alarming quirk of the W221 with its LCD speedometer which Inhave seen once or twice and I which I imagine will battery related is that when you start it up, the speedo display screen can look like it’s buggered with a mess of vertical lines and digital noise…before the alternator kicks-in and the voltage rises and it all comes back to normal within a couple of seconds!
One alarming quirk of the W221 with its LCD speedometer which Inhave seen once or twice and I which I imagine will battery related is that when you start it up, the speedo display screen can look like it’s buggered with a mess of vertical lines and digital noise…before the alternator kicks-in and the voltage rises and it all comes back to normal within a couple of seconds!
Edited by Mogul on Tuesday 15th February 21:01
No warning messages, I just decided that as the main battery was past its best I'd change both at the same time.
As with most modern cars, so many 'glitches' seem to be related to batteries and as the car is 9-years old and I've had from new, so knew that they were original (plus they're dated), I decided to do both: car is kept on a trickle charger in the garage.
I don't know which auxilliary battery is in yours but the replacement for mine was a different part number to the original (possibly slightly different A/hr rating).
As with most modern cars, so many 'glitches' seem to be related to batteries and as the car is 9-years old and I've had from new, so knew that they were original (plus they're dated), I decided to do both: car is kept on a trickle charger in the garage.
I don't know which auxilliary battery is in yours but the replacement for mine was a different part number to the original (possibly slightly different A/hr rating).
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