So, I have four fairly new (< 6 mo) 6-volt batteries wired in series/parallel to form my house bank, plus a separate starting battery. The house bank has a theoretical 470 ah. There is also a battery monitor but probably not a very good one, and two 85-watt solar panels. Under the protocol I believe I was introduced to in this forum the useful "tidal range" of the house bank is between about 85% and 50% SOC assuming one does not wish to "murder" the batteries in the manner described by Maine Sail in his previous posts. So, 0.35 x 470 = 164.5 ah to work with. My daily needs appear to be near 50-60 ah (the fridge alone is near 30 @ 4 amps x 1/3 hr/hr x 24 hr = 32 ah). The Espar heater runs at 40 W; so, 40 W/12 v = 3.3 amps. Runs of 5 hr/day = 16.5 ah/day. Put the rest in the miscellaneous category for now. Due to high cliffs around there was only 7 hr of direct sunlight on my best day last week, generating 30 ah of charge from BOTH panels; only 4 days not clouded over, so maybe 120 ah total there. The rest of the charging had to come from the diesel. When we pulled up to come home yesterday the monitor read 53% SOC. That adds up to about 340 ah [120 + (0.47 x 470)]. Could my diesel running on average about 2 hr/day with 55-amp Hitachi alternator (output at 14.20 v) supply the difference, i.e., 55 ah demand/d x 8 d = 440 ah demand, then minus 340 ah = 100 ah?
In any case, the estimated 8-day demand of 440 ah divided by 220 ah = twice what I could generate on site, which ultimately brought the batteries to 53% SOC. Moreover, the admiral would have been much happier if we had run the Espar nearly continuously. Another few days of overcast, and we'd be running the diesel 4 or more hours per day to keep up the charge. How do others solve this problem short of the installation of a generator? Having a larger bank just kicks the can down the road.
In any case, the estimated 8-day demand of 440 ah divided by 220 ah = twice what I could generate on site, which ultimately brought the batteries to 53% SOC. Moreover, the admiral would have been much happier if we had run the Espar nearly continuously. Another few days of overcast, and we'd be running the diesel 4 or more hours per day to keep up the charge. How do others solve this problem short of the installation of a generator? Having a larger bank just kicks the can down the road.
Last edited: