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Solar Wattage vs Battery charge rate.
Cheap Flooded batteries have a slow charge rate. AGM is better. Lithium is best. It's also poor, better, and best in terms of allowable depth of discharge. Know what you have.
Adding solar wattage can be a diminishing return for lead acid (esp flooded).
For better performance consider a MPPT solar Charge controller. It works like a transformer preserving the wattage while stepping down the voltage. So 5.5 amps at 18 volts becomes 7.25 at 13.8 volts. Also higher voltage (i.e. series wiring) can be used allowing better "scavenging" in low light conditions.
100W in sunny AZ was good enough for 2 flooded group 27 batteries, but it took all day to recharge if I used the furnace at night. It's still good enough for my 2 new group 31 Outback Nano-Carbon AGM. It hits max boost voltage in hour(s) and is done in half a day.
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Linear Mode
