I agree with shutting off DC main breakers while hauled out. The
problem is what to do about self-discharge of the batteries during long
intervals between recharging? The rate of self-discharge for a lead
acid battery is about 0.1%/day (of amp-hour capacity) at an ambient
temperature of 10C, and roughly triple that at a temperature of 30C.
So, a 6 month absence from a cold boat in a winter layup is no big
deal; at most 10-20% of battery bank capacity would be lost from self-
discharge. But in the Caribbean, for example, the layup of a hot boat
during hurricane season, maybe 50% or more of battery capacity could be
lost, which is beginning to be serious.
S/V Third Wish