Starter Battery

[Warwickduo]

Hi, I need to change the starter battery on my 2019 C43. Will I need to follow any particular method or it just a case of disconnecting the old battery and reconnecting the new one?
I recall reading somewhere that the ecu needs resetting when the battery is replaced?
Any advice/comments would be most appreciated.

 

[Germgh0st]

You need to reset the battery monitor so that it knows you've fitted a new battery, this is done by plugging into the OBD.

I went to Halfords to have my battery replaced. I was glad I did because it's a hell of a fiddly job - took them a while and scraped all their knuckles. Plus they had the doodad to reset the battery monitor.

 

[rf065]

I recall reading somewhere that the ecu needs resetting when the battery is replaced?

I've replaced both C Class & SLC batteries, never reset anything, just disconnected and refit the new ones. Never had any problems with them since and that was 3 or 4 years ago.

 

[Germgh0st]

If the battery management reset, using a scan tool, is not done when a new battery is installed, the system believes that the old battery is still installed and treats it as a weak, aged battery. This means that the various modules in the car will not receive full voltage even though it has a new battery. This can lead to driveability concerns, charging light coming on, check engine light, abs light, airbag light or other warning lights coming on, and it will set various fault codes in each module. It can also reduce the life of the new battery by a year or more. So it's better to get it done.

 

[rf065]

My experience with two different Mercedes says that is does not matter a jot if you just change the batteries without doing anything else.

 

[Germgh0st]

My experience with my C43 a year or so ago was that when the battery was replaced the dash went mad with warnings until the battery monitor was reset. You may have gotten away with it, others may not. It takes two minutes so not exactly a hardship.

 

[OneForTheRoad]

Would charging the old battery overnight before swapping them over , con the system into not seeing a change over . ?

Asking for a friend.

 

[Germgh0st]

Would charging the old battery overnight before swapping them over , con the system into not seeing a change over . ?

Asking for a friend.

I don't think it's all about charge - it's about condition.

 

[rf065]

Pretty sure there was a post from someone who deals with these cars on a daily basis who also said it does not matter, although BMW''s were different and did need it done.

 

[Germgh0st]

Pretty sure there was a post from someone who deals with these cars on a daily basis who also said it does not matter, although BMW''s were different and did need it done.

My experience kind of sets an argument against that. Maybe it depends on car, software version, etc. I'd rather be safe than sorry and just get someone to do it.

 

[Skd884]

I've replaced both C Class & SLC batteries, never reset anything, just disconnected and refit the new ones. Never had any problems with them since and that was 3 or 4 years ago.

+1 ^

 

[MikeInWimbledon]

Hi, I need to change the starter battery on my 2019 C43. Will I need to follow any particular method or it just a case of disconnecting the old battery and reconnecting the new one?
I recall reading somewhere that the ecu needs resetting when the battery is replaced?
Any advice/comments would be most appreciated.

Apologies for asking the question, but it's an old issue. Why change a five year old battery? Have you tried charging, or conditioning the battery, if it's let you down a couple of times?

Again, apologies, but a lot of people do replace batteries just because they use their vehicles lightly for occasional short runs, and then find that the car isn't driven enough to charge the battery

 

[rf065]

Since stop/start was invented, even if you switch it off and never use it, some batteries now fail after 3 or 4 years. Don't know why, but I'd never replaced a battery in any of my cars, my last CLK was 13 years old and still on the original. But lately my C Class and SLC needed new batteries before they were 4 years old, wifes and daughters Nissans both had theirs replaced under warranty before they were even 3 years old. Too many for it to be a coindidence.

 

[OneForTheRoad]

Since stop/start was invented, even if you switch it off and never use it, some batteries now fail after 3 or 4 years. Don't know why, but I'd never replaced a battery in any of my cars, my last CLK was 13 years old and still on the original. But lately my C Class and SLC needed new batteries before they were 4 years old, wifes and daughters Nissans both had theirs replaced under warranty before they were even 3 years old. Too many for it to be a coindidence.

The battery in my 17 reg e350 needed changing in 2021 , it refused to take charge . 115 from Halfords fitted , no BMS involved.