Auxiliary battery

[Les Merc]

Hi , I have recently replaced the Auxiliary battery which is in fact a voltage converter containing 4 capacitors. I changed the unit and took the back off the old unit to see a small area of black which indicated that it had failed and that it was not something else. After this the stop start display on the dash display is still yellow with a line through it even though it had done over 100 miles . I did wonder if the fuse had gone but the suggested fuses namely 438,448 and 455 are all ok and so I wonder if the fuse description is correct. In fact the fuse box in the boot does not even relate to the pamphlet inside it and there are no references to the Eco start or stop start.
Any info would be appreciated.

 

[Malcolm Johnson]

My start stop i thought was going to start when i replaced the auxiliary battery which told me it needed replacing. But it was the main battery when replaced created immediate start stop.

 

[Les Merc]

Thanks for that ,I never considered the main battery and the car is 7 years old . I have not had any other problems with the normal starting etc but it’s useful info . Thanks again

 

[Malcolm Johnson]

My starting crank was perfectly fine. But the battery didn't hold enough voltage so no start stop.

 

[Les Merc]

I will get my battery checked out next time I’m near a trusted garage . It was serviced last week but I don’t know if it would flag up on that service.your info is much appreciated.

 

[Botus]

My start stop i thought was going to start when i replaced the auxiliary battery which told me it needed replacing. But it was the main battery when replaced created immediate start stop.

sorry to hear - oh well lets hope not too much damage from that rubbish till you can get it disabled correctly

 

[AMGeed]

I will get my battery checked out next time I’m near a trusted garage . It was serviced last week but I don’t know if it would flag up on that service.your info is much appreciated.

A cheap multimeter can measure the voltage before you start the car. Always handy to keep one in the car for testing.

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The best test for a battery is a load test to see if the CCA is within a certain parameter.
Any battery sales outlet can do this.
If the battery is the original one at 7yrs old I'd suspect its failing.

 

[Les Merc]

Thanks , great info because it’s an angle I had not even thought of .

 

[Les Merc]

Thanks , great info because it’s an angle I had not even thought of .

 

[Les Merc]

Hi , I’ve been pricing up batteries and a guy has told me that if it’s an AGM battery for a stop start the car needs programming ? Is that correct

 

[Malcolm Johnson]

I changed the aux first then start stop on the S tank. Three weeks between. Both Varta. No programming.

 

[rf065]

Hi , I’ve been pricing up batteries and a guy has told me that if it’s an AGM battery for a stop start the car needs programming ? Is that correct

I've changed two, none of them were programmed and they are both going strong 3 years later.

 

[malcolm E53 AMG]

Hi , I’ve been pricing up batteries and a guy has told me that if it’s an AGM battery for a stop start the car needs programming ? Is that correct

BMW replacement batteries need programming to the BMS, the alternator has variable charging capability dependent on the age of the battery and Amp rating

As far as I’m aware MB don’t for 12V battery replacement

 

[Les Merc]

Thanks for that info , I went to Halfords today to buy a battery, it’s a £200 plus unit so should be decent. I was told that I needed to have it fitted by then because it needed to be programmed but when I got there I said I would fit it myself. The guy said that if I did the guarantee would not stand so I said ok fit it . He then said that their machine did not have my car listed ! So they couldn’t fit it so he said unless I could get Merc to say it didn’t need programming they wouldn’t guarantee it ? . I now think their machine didn’t have the car listed because it doesn’t need programming, I was going to hook up a 12v supply to the car whilst the battery was out to maintain power to all the systems as shown on Utube which I now think is an option. Cheers again

 

[rf065]

Thanks for that info , I went to Halfords today to buy a battery, it’s a £200 plus unit so should be decent. I was told that I needed to have it fitted by then because it needed to be programmed but when I got there I said I would fit it myself. The guy said that if I did the guarantee would not stand so I said ok fit it . He then said that their machine did not have my car listed ! So they couldn’t fit it so he said unless I could get Merc to say it didn’t need programming they wouldn’t guarantee it ? . I now think their machine didn’t have the car listed because it doesn’t need programming, I was going to hook up a 12v supply to the car whilst the battery was out to maintain power to all the systems as shown on Utube which I now think is an option. Cheers again

Did you not check Tayna.com? Next day delivery and usually cheapest.

 

[Les Merc]

I must admit I’ve never heard of Tanya.com so I will check that out but the question of the programming is still outstanding. Thanks for the input

 

[rf065]

I must admit I’ve never heard of Tanya.com so I will check that out but the question of the programming is still outstanding. Thanks for the input

It's https://www.tayna.co.uk/