A4 B8 2.0ltr Diesel Battery Change

[jdragon]

Hi all,

I hope everyone is keeping safe during these challenging times.

Unfortunately a period of not driving my car has expedited the demise of the battery in my A4.

 

It's currently fitted with the original Moll 8k0 915 105 E

12V 450A 95Ah DIN (760A EN/SAE)

I have (currently) selected a Bosch S4013 12V 95Ah (800A EN/SAE) at a reasonable(?) price of £99.99

The car does not have stop-start functionality, so presumably the original battery is LA? Although I appreciate the improvements of moving to AGM I'll have the car no longer than 3 years, so paying the extra £2x/3x seems unnecessary?

 

A bit of research has led me to understand the replacement needs to be programmed to the car with a BEM code:

Part Number (10 Digits)
Vendor Code (3 Digits)
Battery Serial Number (10 Digits)

Talking to the supplier, the Bosch battery does not have this info. I have read that in instances like this, I can simply increment the battery serial number and leave everything else the same in VCDS. Does anyone have experience doing this?

 

[audiA4carpet]

Unfortunately, another example of Audi designers trying to make basic DIY'ing as difficult as possible.

Solar trickle charger may help while we are off the road.

Never done the battery myself, but if you can find someone local with VCDS software, they maybe able to program the new battery for you for a fiver (£5) or  a pint of beer.

[audiA4carpet]

If you can get a spare car battery for a short while, then connect the spare battery before taking out old battery, to avoid disconnection of power.

Fit new battery. 

Then disconnect the spare battery.

Hopefully the car computer will never know that the battery has been replaced, and may just start charging after "learning" for a week or so.

[jdragon]

Quick update: I went for the Varta G3 Blue Dynamic 12V 95Ah 800A in the end delivered for £98.94

I didn't bother with connecting a backup power source, so there was about 10 minutes or so with no power in the system which didn't cause any issues later. Once the battery was connected, I checked the power meter in the MMI but it was greyed out; curiosity go the better of me so I started the car and still greyed out.

I had borrowed my mates VCDS setup and coded as follows:

[19 - CAN-Gateway]
[Long Adaptation-0A]
[Channel] 004
[Read]

VCDS populated the instructions in a pop up window with the formatting:

For my car, I did the following:

Part number remained the same

Changed the manufacturer code to VA0

Entered the date and last 4 digits of the number etched into the battery

8K0915105E  VA0 YYMMDDSSSS

[Test]
[Save]
[Done, Go Back]
[Close Controller, Go Back - 06] 

Started the car and the MMI battery state was at 100%

I Checked measuring blocks 018, 019 & 020 showed the battery SOC was 86% and the MMI was displaying 100% (original battery was something like SOC 25%, MMI 40%)

Lots of people had success with just changing the last digit of the serial number but I thought it was a bit cleaner to add the date, which is the format of the original BEM.

[Steve Q]

Glad you got sorted 🙂 great advice for others in a similar situation. 

Cheers

Steve

[Adam B]

Hi, 

Do we know if this can be done on the Exide EB 740 starter battery 74 Ah

I have recently changed mine and can’t get the batter serial number as it doesn’t have one? I have someone with the equipment to programme the code however don’t know what to put?

Any help appreciated 

Thanks

Adam

[jdragon]

The short answer is yes, this will work for any battery even if the manufacturer is not listed in the VCDS menu. You can simply change the last digit if the serial number currently logged to your car for it to recognise the new battery. I did this when fitting mine and it worked - the system is not that intelligent.

 

The long answer:

From my research I concluded the coding is extra Audi fluff to prevent people with cars under warranty from swapping their batteries with a mates duff one, to get a free replacement. When you scan the QR on an Audi original battery you get something that looks like this:

205# 8K0 915 105 F
#1#315472985#170712 *205
MLA1C7HBAF%*=

If you take the MLA plus the last 5 before "*=" and then drop the last symbol you have: MLA HBAF

Then reverse the pairs between # and *205 to give 120717 (the date when battery was manufactured likely)

The code you will have is MLA120717HBAF

This is the unique BEM that is printed on the battery and is precisely how Audi can reverse code to know if it has been changed.

I cannot remember the source of the above info but I applied the method to my own battery (as did others in the post) and it works.

 

Interestingly, I removed my original battery to fully charge it and when I fitted it again it was recognised in the MMI and showed it had been charged. So why did it not instantly recognise my new battery? My assumption here is charging alone will not reduce the resistance (Ohms) of an old/aging battery and this is probably the only thing the ECU/battery element of the system will recognise as changed (original battery was 7.0 mOhms, new was 4.2 mOhms).

I hope this helps.