You need around 200-300 watts of solar panels to charge most of the 12V lead-acid batteries from 50% depth of discharge in 6 peak sun hours with an MPPT charge controller. . Pretty much any solar panel will be able to charge a 100Ah battery. It just depends on how long it will take. 8 peak sun hours (or, realistically, in little more than 2 days, if. . To get there, use the following formulas; 1 Amp AC = 10 Amps DC. (example, 2AC amps =20DC amp) Add 10% (22 amps) DC amps x 12v = DC watts. (22 x12 =264 watts) 264 would be entered in field # 3 Fields #6 and #12 are for how many hours you expect your equipment to run in a 24 hour period, and your. . Estimate how long it takes your solar panel to charge a battery based on panel wattage, battery capacity, voltage, and charge efficiency. Formula: Charging Time (h) ≈ (Battery Ah × V × (Target SOC / 100)) ÷ (Panel W × (Eff% / 100)). Enter. . Does a 20 watt, 24 volt system have enough amps to charge? I am a VERY newbie to solar, although I have been consider it for my RV! A few weeks ago I had a driveway gate installed and it came with a solar kit, but it just isn't charging the batteries and I don't know if it's the panel or the charge. . Number of solar panels x wattage of individual solar panels = total wattage of solar panels For example, assuming you have 20 units 200w solar panels in your solar system, according to the above formula, you can enter 4000 into the solar panel wattage column of the calculator.