When I got my FG out of storage before starting my current trip, the batteries were dead. After quite a while on the charger, they took a charge. The difficulty of getting the batteries charged up seemed odd but I ignored it and I thought I was back in business. But while on this trip I'd noticed some oddities. I have a cigarette lighter digital voltmeter. At the end of the day it would show 12.x voltage. The next morning it would show 11.x voltage. Starter also did not sound as snappy as I thought it should. Yesterday, after stopping for fuel shortly after starting out for the day, engine would not crank. Tried jumping it with the camper battery, no luck. Got towed to a parking lot and I swapped in a spare starter I had aboard. At first it clicked, then it started. I thought I was back in business again but due to some exigent circumstance, I didn't want to take a chance on shutting off the engine since we had to drive a few hundred miles to catch a ferry. After driving for a couple of hours, I pulled over to fuel up and opened up the box door to check the batteries. I immediately smelled acid. Right battery was bulging, boiling acid fumes were coming out the fill holes and it was too hot to touch. Obviously it was overcharging. Since I didn't want to shut down the engine in case it wouldn't start again, I decided to disconnect the hot battery and continue. Probably not a wise thing to do. Working on an object bulging with pressure from boiling acid fumes is not that safe. Nonetheless, I disconnected the negative post. Voltage jumped up to 14.5 from 13.8 after disconnecting. When we got to a campground with electricity where I could plug in my battery charger, I shut off the engine. Left battery showed only 9 volts and would not start. Obviously the left battery was bad. I switched the batteries over, connecting the previously hot right battery and disconnecting the low voltage left battery. Voltage showed 12.4 Truck started. I concluded left battery has been bad, drawing down the right battery and calling for constant voltage/amperage to charge up. This constant high amperage had overcharged the right battery. Put the right battery on a 2 amp charge overnight. This morning, voltage showed 11.x on right battery but truck started snappily. But driving to the ferry, I began to smell acid again. Right battery is hot again. No visible discharge of acid fumes but it smells. Perhaps I boiled off enough of the battery liquid that the remaining is getting hot on a normal charge.
But the lesson of the story (for me) is that diagnosing electrical/battery problems with a constantly connected dual battery set up is not simple. When my starter failed to work, I should have separated out the batteries and checked the condition of each separately. I probably could have jumped the starter if I had disconnected the low voltage bad battery. The voltage at the cigarette lighter is giving some kind of average of both batteries and is not a true indication of the condition of each battery.
It also points to the problem of lack of full instrumentation on the FG. My $5 cigarette lighter voltage meter was very helpful in figuring out the situation but an ammeter would have been even more helpful since it would have showed the high charge amperage as a result of the bad battery. I may install an ammeter near the batteries.
I still don't know why the batteries went dead initially. Was something drawing them down or did one (pretty new) battery just go bad and suck down the other one.
But in any case, for a guy like me, used to working on single battery cars or dual battery sailboats with a selector switch, diagnosing electrical problems on a constantly joined dual battery set up is more complicated than normal.
Right now, I'm on the ferry back to Nova Scotia. I disconnected the one functional battery for the ferry trip in case there is a draw on the system. I planned to continue the rest of the trip with the one remaining battery. Perhaps this will be possible by refilling the battery with fluid. Perhaps I will pick up a spare battery in case I irreparably damaged the good right battery by severely overcharging it.
But the lesson of the story (for me) is that diagnosing electrical/battery problems with a constantly connected dual battery set up is not simple. When my starter failed to work, I should have separated out the batteries and checked the condition of each separately. I probably could have jumped the starter if I had disconnected the low voltage bad battery. The voltage at the cigarette lighter is giving some kind of average of both batteries and is not a true indication of the condition of each battery.
It also points to the problem of lack of full instrumentation on the FG. My $5 cigarette lighter voltage meter was very helpful in figuring out the situation but an ammeter would have been even more helpful since it would have showed the high charge amperage as a result of the bad battery. I may install an ammeter near the batteries.
I still don't know why the batteries went dead initially. Was something drawing them down or did one (pretty new) battery just go bad and suck down the other one.
But in any case, for a guy like me, used to working on single battery cars or dual battery sailboats with a selector switch, diagnosing electrical problems on a constantly joined dual battery set up is more complicated than normal.
Right now, I'm on the ferry back to Nova Scotia. I disconnected the one functional battery for the ferry trip in case there is a draw on the system. I planned to continue the rest of the trip with the one remaining battery. Perhaps this will be possible by refilling the battery with fluid. Perhaps I will pick up a spare battery in case I irreparably damaged the good right battery by severely overcharging it.