Three 350 watt solar panels connected in a series can charge a 48V 100ah battery in a day. For cold areas, the panel VOC should be between 67 to 72 volts, and for hot conditions it should be from 80 to 82 volts. An MPPT charge controller works best for 48V systems. If you have a 48V battery like. As a general guide, a 48V 100Ah lithium battery may need around 1,500W to 1,800W of solar panels for a strong full-day recharge in typical Canadian conditions. To calculate how much energy a battery stores, convert it into watt-hours (Wh) using this formula: Watt-hours = Volts × Amp-hours Examples: π For lead-acid batteries, only 50% of the capacity is usable.