posted 5 hours ago
A 17-18 Vdc solar panel is just barely enough to charge a 12 Vdc battery, and even then, it's going to be (maybe painfully) slow. Depending on how fast you need to use the system, you may find you need/want more power or need more charging speed.
It may help to convert everything to the same units?
100 Ah 12.8 Vdc battery = backup 1280 volt-amp-hours, which = 1280 watt-hours, which = 1.28 KWh. A 100 watt panel in ideal conditions would need nearly 13 hours to fully charge that battery from 0.
Your probably not in Death Valley, California, or a desert in southern Arizona, so you probably won't have access to "ideal" solar conditions, and may only get 50% of the nameplate rating from your panel, which will mean it takes almost 26 hours of sunlight to charge your battery... How much patience do you have??
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