Sailors and RVers have a lot in common, not the least being a prediliction for house banks of Trojan T-105s wired up in pairs to make 12 volts. A boat may sport a big array of solar panels while a camper van charges off the engine as it eats up the highway miles, but either way, the batteries need to be full when night comes, whether it is in a secluded anchorage or a primitive campground deep in the forest.
An RVer friend returned home from a week of camping with a few grocery items left in the reefer. He hooked up to the shore power (an outlet in his garage), confident that the charger would keep the battery bank topped off, the battery bank would power the inverter, and the inverter would keep the beer cold until the next trip, planned for a few days later.
Like a good, prudent person, he had a GFCI outlet in the chain. Something tripped it, probably just a transient power surge. The charger went off, but the fridge kept on keeping the beer cold, and it didn't take more than a couple of days to drain those Trojans flat. Lead acid batteries will put up with a lot, but if the voltage ever gets down below 11.5, they're damaged, and below 10.5 they are dead for good.
So that's how my friend ruined an expensive set of Trojans. The moral is, don't go off and leave a load on your house bank. If you're not convinced, see Cautionary Tale II.
Text by Paul Clayton.
Copyright © 2025 Paul M. Clayton