Brake light warning came on after brief spirited driving

[JulianHicks]

Originally Posted by Mechcanico Lee

See on the coding at the end the 105A im assuming that means 105 amp hour because thats what was on the orginal battery

1. Easy to see why you thought this Lee but actually the 105 A is the last two parts of the part number. The original Audi battery just happened to have a part code that matched its 'Amp Hour' value.

VAG parts are xxx yyy zzz nn = vehicle subsystem part version

2. The Battery Meter % and its associated SOC values in the ECU that you read out with VCDS is one of the mysteries of life. The ECU calculates it and its value is shown in the MMI display but no-one knows what formula is used to determine it. I think Audi gave up on it, which is why it was removed at one of the MMI updates. After problems, I've seen the number 'stuck' at 10% on my car for three days before it magically returns to 100%, so don't trust it.

3. Best bet for working out the battery SOC is to use a volt meter across the battery. - 100% is 12.6V, 75& is 12.4V, 50% is 12.1V, 25% is 11.9V - all approximate values for 'normal' temperatures - Spring in the UK!