To determine recharge time from the solar panels, just divide the utilized battery capacity (in kWh) by the daily solar harvest (in kWh/day). For instance, the MS-225 has a battery capacity of 25kWh and solar array has a daily harvest of 9kWh/day. Let’s assume you drain the battery down 80% (meaning 20% is left in the battery). The math: 25kWh x 0.80 = 20kWh. And 20kWh / 9kWh/day = 2.2 days of solar charge to bring the battery back up to a 100% State of Charge (SOC).