New Battery, Bad BMS Code, cleared codes, low battery charge

[Vorlockfoss]

Hi, I'm looking for help with installing my new battery.

I have just replaced the old Exide battery on my 2009 Audi A4 B8 2.0 TFSI Quattro as it was showing 20% charge, 0Ah and only 11.6 volts available, seemingly no matter how long I drove for.  I did try charging it with a slow charger, and got it to 40%, but no more.  At this time my car had gone into 'energy management active', and although my engine would crank apparently easily, it would not fire at all.

The battery suggested by Varta, and bought, is a "Varta A7 - E39 - MPN 570901076 - 70Ah/760A - AGM Battery", which is the same specification as the Exide I've just removed.  Now, according to the sticker in my Audi Service Schedule, the 'Starter' battery for my car was 'J0B', which was a "92Ah/520A AGM Battery", according to what I've learned online anyway; I'm open to correction if I'm wrong.  Anyway, I fitted the new Varta battery, changed the last digit of the serial number of the previous BMS Code via VCDS, saved and cleared the error codes.

I have to say that I have no idea what values the current code in the BMS represents, but it may be incorrect.  Obviously I can't use the original Starter Battery BMS code, otherwise my car may try to charge the new Varta battery to 92Ah and damage it, IMO.  I am trying to establish the correct code for my new Varta Battery, but it's proving quite difficult.  As is known, the code needs to be 10 or 11 digits long, but the MPN on my new Varta is only 9 digits long.  I have searched high and low, but each time I'm presented with the same manufacturer part number '570901076', which is only 9 digits long as I stated.  I have tried adding 3 spaces to fill the missing digits between it and 'V0A', but no go, VCDS will not allow it; a 10 digit serial is tagged on the end as required.  As I previously stated, the code installed may not be the correct code because, even though there is no error code showing in the log (see next paragraph), the dashboard is still displaying a 'low battery charge' and my car still will not start; it just turns over & does not attempt to fire.

Just to add some context to the above, I was having issues with very rough running, which came on all of a sudden last week, rendering my car undrivable.  Aside from the reasonably violent engine vibrations, I was seeing a considerable amount of white smoke leaving the exhaust and drastically reduced power.  After thorough investigations I was satisfied my head gasket is intact.  Incidentally, the white smoke did not smell very nice, but not 'eggy' as would be expected with the CAT; it was a combination of bad smell & petrol I think.  I also smelt petrol in the oil filler, and coupled with a low fuel pressure error code and much research I concluded the High Pressure Fuel Pump needed replacing.  I installed a brand new Hitachi HPFP, which has made a difference to the consistency of the rough running, i.e. less erratic.  After further investigations I concluded the PCV had most likely failed, maybe in relation to the HPFP failing.  I therefore installed a new PCV (oil separator), and a fuel pressure sensor while I was at it, but my engine has not started since; the installation of the PCV & Sensor/Sender is around the time my car power state changed to 'energy management active'.

My opinion is, I need to install the correct code for my new battery & car combination, or at least equivalent code i.e. 70Ah / 700A / AGM.  As I've previously mentioned, I suspect the code installed may be incorrect as I have been seeing power issues on my car for over 2 years; I don't know in what context the code may be wrong, but it would make sense, especially considering the persistent low battery charge error on my dashboard.  To add, the battery is only 4 years old and I've only driven an average of 4k miles each year.

Any help, thoughts or opinions would be gratefully appreciated, and a correct code would be blooming marvellous...!!!

Thanks for your time.

Paul.