1. The 20a charger puts out 20a at 12vdc. That translates into only 2a (plus losses) on the 120v side (ohm's law). Figure the 12v amps are roughly 10x the 120v amps. So no, the 10a breaker does not ever trip. I could have used a 5a breaker, but the 10 was on the shelf.
Since the single group-31 battery is about 130 amp-hours (we try not to drain it below 70%), a full recharge is done at the dock in under 6 hours. The original setup from the factory used a small group-24 battery, which wasn't adequate for two-week cruising, especially if you throw in some night sailing. You don't want to drain the battery all the way down, or it really shortens its life.
2. The anchor light is an old Forespar unit, but I replaced the festoon bulb with an aftermarket LED array when it burned out. Pops right in -- direct replacement lamp. Sea-Dog makes some economical LED units as well. Kerosene would work OK, and accidentally leaving it on during the day wouldn't run down the battery.
3. The AC breaker panel is a cheapie, maybe Ancor brand, that has provision for 4 "world" breakers (the standard marine units). The inlet must feed a double breaker (like a 220 breaker in a house), that trips both wires, to meet ABYC standards, because there is always the possibility that you plug into a reversed outlet at someone's dock. So when it's tripped off, the AC is definitely off, regardless of bad shore wiring. That leaves exactly room for the 2 other breakers, which are fed from the Black leg of the double. The panel is installed in a bulkhead, and the back is covered (per ABYC standards) to keep everything neat and safe.
While on that topic, the shore inlet is a standard Marinco 30a twist-lock, wired to the panel with 10 awg Ancor marine-grade wire (yes, you need 10 awg or bigger to safely accommodate 30 amps). Do not run residential wiring anywhere on the boat. You must use marine-grade, stranded wire, preferably fully-tinned, with proper marine-grade terminations on the ends.
Long story short, by running only one battery, the maintenance is a lot cheaper and easier. If I already had a 2-battery switch, I would probably still just run one battery bank -- either two batteries, with the switch set to "both", or one large battery. Amp-hours for the buck, one big battery is much more economical.
BUT, If it was an inboard, then I would want a "start" battery that could not be run down by the cabin lights and accessories. In that case, I would either run a switch, or an isolator, to allow parallel charging from the OB.
Paul Van Voorhees
Certified Tohatsu TLDI Technician
Mgr, Obersheimer Sails
Buffalo, NY USA