Is 15 volts too high for charging alternator output? - BIMMERPOST E92 m3 from 09 2011, competition packet I have the OEM battery w 90 Ah Its Varta brand, 90Ah w 900A AGM Battery looks close to death I trying to recharge it but it doesn't hold the voltage (after full recharging to 14,5V and 890A goes again low in few hours to cca 12,3 V and 600A and then hold this values) So I have to buy a new battery, probably this one: Varta Silver Dynamic G14 AGM