AGM Battery

[Bunka]

I don't recall any discussion about this. I replaced the original lead acid battery in Feb, 2016 with an AGM battery. I started experiencing hard starting at least a year ago until a couple of days ago when it wouldn't start. The battery is a couple months shy of 4 years old. I have since learned that my 2008 Cayenne does not have the software to differentiate between an AGM and a lead acid battery. An AGM battery needs to be charged slower and at less power. The result is that my AGM battery has been constantly overcharged for close to 4 years and that has led to premature failure. I just had a factory correct lead acid battery installed. I do not know when Porsche started to install software that can differentiate and provide the correct charging, but they did. Maybe someone can tell everyone after what year it is OK to use an AGM battery. I suspect it was only a few years after 2008. Also, if you check the various web sites of the battery makers, you will see that they all have AGM batteries for a 2008 Cayenne. They are all of the right size and CCA, however, they are not the correct battery for older Cayennes.