Ask the Experts

However, this depends on the absorption voltage (the regulated voltage once the initial bulk charge phase of charging is over) and how long this is sustained before the charger trips to float. The more aggressive the cycling, the higher the absorption voltage should be, and the longer the absorption charge should continue before the trip to float on those occasions where extended charging is possible.

In your situation I would think an absorption voltage of 14.4 volts would be appropriate (in some applications with very limited charge times and only intermittent full-charge cycles, it pays to go as high as 14.7 volts). If the tripto-float parameter is based on time, you might want to set this as high as eight hours. If it is based on the charge rate (amps) into the batteries, something as low as a trip threshold of 200 milliamps per 100 amp hours of battery capacity would be appropriate (as opposed to the more conventional 2 amps per 100 amp hours of capacity). If you set the amps this low, you will definitely also want a time limit on the absorption charge in case the battery charge rate does not fall this low.

This will keep the charger from boiling the electrolyte out of the batteries on those occasions when you are plugged in for days at a time.— Nigel Calder

WINTER POWER

My 2002 Mainship 430 has two Cat 3116 diesels and an electrical setup consisting of one 8D 1200 MCA start battery with a 55-amp alternator and one dual-purpose 8D 1450 CCA start/ deep-cycle house battery charged by a 105-amp alternator that also charges the two 1000 MCA AGM thruster batteries through a Victron isolator. There is also an 8kW generator with its own 27-series start battery and a Xantrex 3000 inverter/charger with a bank of three 8D batteries. At our marina dock we have 50-amp power to both the boat battery charger and the inverter/ charger, and all is well.

However, when we haul the boat for the winter, our yard power is only 110 volts/15 amps through a GFCI socket. I change the inverter power share from 30 amps (the max) in the water to 15 amps on shore, but every time we put power on, the shore socket GFCI trips. The only way we can keep power to the boat to feed the chargers, air circulators, etc., is by bypassing the shorepower ground, which I don’t like to do.

One possible theory is that the boat has several internal GFCI sockets fed by either shorepower or the inverter. So the overall system has onboard GFCI sockets fed from a shorepower GFCI socket, and you can’t have one GFCI downstream from another. Is that right?

If so, how do we get around that and