still feed the onboard circuits with grounded power? If not, what is the problem and how do we get around it? (If relevant, the AC, fridge, ice maker, microwave, etc., are off for the winter and only the chargers and air circulators are drawing power; the low annual anode wear suggests no stray current.)
Another unrelated question concerns the dual-purpose start/house battery. It is six years old, originally installed to power the engine start, house and thruster, which has since been repowered with the glass mats. Now it is not holding a charge well, testing only marginally acceptable and in need of replacement. Given its dual purpose, can I replace it with three 24-series batteries in parallel for easier installation?
Should they be a combination of one start battery for high CCA/ MCA and two deep cycles for their reserve capacity? Connected in parallel, would they charge at the same rate, and do they have to?
Mainship 430 Dartmouth, Nova Scotia, Canada
Bob, electrical code now states that outside outlets need to be protected by GFCI outlets or breakers. GFCIs trip at only 5 milliamps (.005 amps). While they certainly protect people from faults, they were never designed to have boats with all their complicated wiring plugged into them.
You should never disable a ground to get around a GFCI tripping or for any other reason. But I understand the dilemma.
Sometimes there is one device on board that is causing the issue and you can try shutting off every breaker and then turning on each piece of equipment to see if one circuit causes the trip. There may actually be a real problem that can be found this way.
Salt drops across terminals or contacts are notorious for bridging and tripping GFCIs. If you have an inverter, that also might be the cause due to its internal transfer switch and could be indicative of incorrect wiring related to the neutral bus. The other solution would be to use a portable charger plugged into just a 15-amp extension cord once or twice a month throughout the winter. I wouldn’t leave this plugged in when you’re not on the boat.
I also would not parallel start batteries and deep-cycle batteries within the same bank. The thin plates of the start batteries and the thick plates of the deep-cycle batteries have different charging characteristics and I would not expect a long life for the bank. I’d recommend continuing the use of dualpurpose batteries. You can use multiple smaller batteries as long as their collective CCA meets the engine’s starting requirements. Typically, you lose some capacity with smaller cases in parallel from additional resistance. Be sure to cross tap the bank such that the load is pulled from the negative post on one end of the battery and the positive on the other end battery.—