B8.5 battery charging voltage. I am using an AGM battery. I appreciate that the charging cycle is quite complicated, with regen coming into play under certain conditions, but I was wondering whether anyone knew how to reprogram the relevant module using VCDS to limit the maximum battery charging voltage to 14.4V i.e. the maximum voltage specified by the battery manufacturer (Exide). At present, the voltage can reach 14.8 V (which is much too high) before it drops into regen mode.
Programming the battery charging voltage
- Thread starter Stan Butler
- Start date
Thanks for the reply. I have a calibrated voltmeter connected to the 12V outlet in the cabin. The voltage increases during charging, as you would expect. During a long journey (>1 hour) the voltage increases steadily and eventually reaches 14.8 V. After a further hour or so, when cruising with the battery almost fully charged, the alternator switches-off automatically and the voltage then drops to about 13.1 V (float charging). If I lift-off the accelerator or apply the brakes while driving in this mode, the alternator cuts-in again and the voltage increases to 14.8V. I expect this is an energy-recovery (regen) feature in software and quite normal for the TDi Ultra model, but I think 14.8 V is too high and likely to shorten the life of the battery unnecessarily. Therefore, I want to limit the voltage to something lower (14.4 V) by re-programming the relevant module, if possible. I have never seen any advice on this topic before.
Is the battery in the car the correct size?. If it's an exide than it's not the original battery as these are usually Varta items . VCDS will allow you to alter the battery chemistry and capacity of the battery and the charge voltage is determined to a certain extent by these values.
