Boat has been in storage for 3 months. Charging batteries with 3 bank onboard charger. Turned on radio while charging, came on for a few seconds, then went off. Could not get back on. Now, when turn on key, no alarm, but gauges work. No start, no tilt/trim. Battery appears fully charged. Took out of boat, and put on manual charger, and did not move the needle, so assumed fully charged. What am I missing? Thanks for your help.