I have a AGM battery in our E53. Not sure whether the E70 comes stock with a standard lead battery or AGM.

Every 2 months or whenever I remember, I will put our chargers on it, mainly because AGM's are supposed to be charged up to 14.7 versus a traditional battery, 14.4. Whether those .3 volts is a big difference on whether these AGM's sulphate or not, I don't know. I just try to be proactive about it...