I'm trying to design the electrical system
for my sailboat. The electrical
requirements are very modest--approximately 8.56 daily amp-hours: LED running lights, two LED cabin
lights, the compass
fan, and a VHF radio
. According to a book I have, the house battery
capacity should be about 2.5 times consumption
, in amp-hours, between charges. That would be 21.4 amp-hours of battery
My plan is for a 12v deep cycle house battery and a solar
panel to keep the battery charged. On another boat, I used two 6v Trojan T-105 golf cart batteries wired in series with good results. This has a capacity of 225 amp-hours (which seems like overkill for my new electrical
1. Is there any reason NOT to use a battery that has considerably more capacity than the 21.4 amp-hours required by my daily electrical needs?
2. To use a solar
panel to keep a battery charged that is supplying 8.56 daily amp-hours of electricity, does the panel simply need to put out at least 8.56 amps in a day? If so, that doesn't mean the panel has to have an output of 8.56 amps, but could have a lower output? For example, if it outputs 2 amps, and you have 4 hours of direct sunlight, then it will pump 8 amps into the battery, replacing what I used during the day. Yes? No?