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Discussion Starter #1
Hi guys, quick question. My battery is dying on me and want to change it. I need to buy the wrenches through as I don't have them. I think I'd need a 10mm and a 13mm if I am correct? It is difficult to find exact info online. 66 plate btw.
Many thanks
 

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Get this set

 

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Get this set

That's a lot cheaper than anything I had found on Amazon. Haha, I'll pick it up though because it seems a nice set to have. I've probably for this time decided to just take it to halfords and have the battery changed there as I have a bit too much on my plate right now to deal with and their OEM seems to be of quite decent quality. I have a couple of questions though regarding the batteries in these cars if someone can help me:

1) In the future if next time I do end up changing it myself, does it need a software calibration after it does? I've read that in some Mercedes you have to update the SAM module so it knows it has a new battery etc but I am not sure if we have to do something like this at all in the W176, or if it's advised but not necessary or something that ideally SHOULD be done

2) Does anyone know with certainty what that small auxilliary battery does? I've read from some random electronics to some saying that it's for the start/stop function (which I can't imagine that small battery is able to start the engine all the time). Since those ones are quite cheap I am thinking of changing it as well as not really got much to lose in case it's also not up to par

3) Does the car battery charge only with regenerative braking or the conventional way as well? Because my work commute is just 9 miles each way and I am contemplating whether my main battery got weak through the years just because it never gets enough driving time to properly charge.
 

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1. No need for any special calibration when new battery is fitted.

2. In the event that your main starter battery dies, the small aux battery keeps alive certain functions like alarm and central locking etc. so that you can still get into the car etc. The main starter battery is responsible for the starter motor (hence start/stop), but if the aux battery isn't in good condition, this can inhibit the start/stop system working.

3. If 66 plate likely to be EU6, so will have "smart alternator" technology fitted, so yes, if your journey is only 9 miles consider getting a CTEK battery charger just to keep the main starter battery in top condition, put it on overnight every 3 months or so. Maybe more frequently in winter months as you will be using a lot of battery (heated rear window, heated seats, lights at night etc.) so entirely possible your battery won't have time to fully charge with the short journeys.

See
 

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1. No need for any special calibration when new battery is fitted.

2. In the event that your main starter battery dies, the small aux battery keeps alive certain functions like alarm and central locking etc. so that you can still get into the car etc. The main starter battery is responsible for the starter motor (hence start/stop), but if the aux battery isn't in good condition, this can inhibit the start/stop system working.

3. If 66 plate likely to be EU6, so will have "smart alternator" technology fitted, so yes, if your journey is only 9 miles consider getting a CTEK battery charger just to keep the main starter battery in top condition, put it on overnight every 3 months or so.

Cheers thx for the quick reply. The past few weeks that I've noticed that the main battery "struggles" a bit more to start the car and at the same time on quite a few occassional the keyless go wouldn't work i.e I touch all the right places and get no response and then I am forced to unlock by pressing the buttons on the key. I thought it might have been related to the main battery but if that's the case then more likely to be the auxilliary's fault for that specific aspect I guess?
I've had the car since Nov 2019, and a week since having it the start/stop pretty much never worked since which gave me the indication of a possible battery growing weaker but then again there's a fair chance it sat at the dealership for god knows how many weeks/months until I got it. Both main and aux batteries though are still highly likely the original ones (they are both Mercedes branded) and as they are approaching 5Y old I guess no harm is done changing them both since even if my driving had some part in it they would still probably needed to be changed in the near future.
 
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