Originally Posted by Kistler
I just want a trickle charger for maintenance!
Are you going to disconnect the LP detector, which isn't disconnected when you shut the master battery switch off? Or do you need to power it 24 X 7 also? If so, you need to multiply its current draw by 24 hours to get daily amp-hour usage you'll have to replace.
Do you have AGMs (self-discharge 2-3% per month) or flooded cells (2-3% per week)? How many total amp-hours do those percentages apply to? For example, at 3% for 200 amp-hours, that's 6 amp-hours per week for flooded cells and the same per month for AGMs.
Solar cells laid flat provide about 25% of their wattage in amp-hours on a good day in the summer, about 17% in spring and fall, and as low as 5% in winter. This is reduced more by cloudy or rainy days, so allow for the appropriate number of days per week of that for your area.
Also keep in mind that charging efficiency is less than 100%. You'll need to supply about 110% of what's used.