Steve Zim­mer­man

Passage Maker - - Ask the Experts -

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?

—Bob Ste­wart

Christina Sophia

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.—

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