The one question that no one at the dealer seems to be able to answer is whether I can tender my battery when I am gone for 2 or 3 months. Most agree that it should not be done. Of course it can be jumped but not tendered. I would think that would hurt the life of the unit. I guess the vehicle is too new to have some of these things answered.
I believe similar "trickle charge" question was asked in the
"Special Insight 12 Volt Battery" thread.
The manual says an
AGM-compatible charger should be fine to use (p592): "AGM labeled batteries like those installed in your vehicle require a compatible charger to be properly charged. Damage to the battery can result if the battery is charged improperly or with the wrong equipment. For more information on how to charge your vehicle’s AGM battery, consult a dealer."
This
AGM article from Battery University says that AGM batteries have low self-discharge and can last longer in storage and/or between charges than conventional lead acid batteries. It also states that AGM batteries are sensitive to overcharging, and the float charge should be managed.
This
article and video were also helpful for info on AGM charging.
Net, I don't think it's an issue to tender your battery, so long as you use equipment compatible with an AGM battery. But the battery frankly shouldn't need it, given its better performance qualities.