For those of you that are considering using AGM or gell cell batteries, please be advised that many battery chargers, including some onboard chargers, are not compatiable with these batteries. I did a lot of research on these several years ago because I was switching to AGM batteries. At my advanced age my memory isn't what is used to be and I don't remember all of the details, but the bottom line is many battery chargers put out voltage over 14.4 volts and will damage this type of battery. You must use a "smart charger", one that has a separate setting for AGM/gell cell. Apparently the higher voltage of many chargers will damage these batteries( over time ), regardless of the amount of current flowing.
I stopped using my onboard charger and now charge with a portable charger that is compatable with AGM batteries. Even though this is a pain to do, the AGM batteries are worth the extra effort to me.
I don't want to argue with anyone or sound like a know-it-all. I just want to advise everyone to make sure your charger will not fry your new high dollar AGM/gell cell batteries....................Al