I have shore power with automatic battery charger. You probably know, as soon you hook the boat charger on 110 volts, you immediatly can hear a ''grrrrrrrrrrrr'' sound, just like with any big battery charger. There is a red light on.

I'm always wondering how is this thing really working. Each time I leave the batt charger on, either for 2 or 4 or 6 hours, I always hear the ''grrrrrrrrr'' sound, and the red light is always on...

So, I'm affraid to leave the Batt charger on and burn the batteries or even set the boat on fire with this thing. Is the battery charger light supposed to turn off sometimes if the batt are full? If ever it stops charging, would I still hear the ''grrrrrrr'' ? Or if the batt charger stops charging, then the ''grrrrrrr'' sound would also stop?

Any light on this subject would be appreciated!

What is the make of the charger?

Be Careful. They can raise hell!!

I don't know or can't recall... Boat has a tarp on it right now with snow on it so ... will need some sun so I can look at it... But it is the factory charger Formula supplied in these years. The red light is on top of charger, not on the sides...

That's why I'm asking before leaving it hooked for weeks...

If its on your 89 year boat you might want to put one of those small,new battery tenders from a store like boaters world.

Ditto on the battery tender. Been using it for years on all my toys. Small enought to fit anywere and not powerfull enough to toast the boat.