[asphaltgambler]

If this is indeed a AGM battery - their discharge rate is not linear like a lead-acid battery. After some use the available amperage will fall off a cliff.

AGM's are great in many aspects but do not tolerate repeated over charging, deep cycling and vibration.

Lithium ion batteries for automotive use are the answer but are still too expensive ...............for now.

Conventional automotive batteries in good condition, should be able to supply a radio, lights, door open for a while - maybe an hour or more and still have reserve to start the vehicle.