TOEd wrote:Forgot to mention that during past 40 years I have owned probably 20 agm batteries. They were used in a car, snowmobiles and a motorcycle. They usually lasted a year or two.
Maybe your AGM batteries were low quality or were being charged at too high a voltage. The charging voltage of an AGM battery is lower than that of a flooded-cell battery.
The Odyssey AGM battery in the 2000 Honda Insight that we sold in July was 7 years old, so under the right conditions, an AGM battery can have a long life. Our Insight's original flooded-cell battery failed after 3 years, possibly because the Insight's rather low-voltage 12 V charging system was better suited to an AGM battery.
Maybe the i3's AGM battery is low quality as well. If after the battery warranty expires and if the life of BMW's replacement AGM battery is no better than 3 years, I'll install a high-quality Odyssey AGM battery.
TOEd wrote:So I can appreciate your dealer suggesting a flooded battery. Not a bad option for those wanting long life from their battery.
The i3's 12 V charging system is set to charge an AGM battery, not a flooded-cell battery, so a flooded-cell battery might not last as long as it should.