These batteries hold roughly 5700-watt hours of power, and depending on your power usage you'll need a lot of panel power to recharge the battery every day. Based on usage of 10kWh per day, here are some examples: 10kWh x 2 (for 50% depth of discharge) x 1. 2 (inefficiency factor) = 24 kWh 10kWh x 1. 05 (inefficiency. . Our rule of thumb is to size your battery bank to have a usable capacity 3 times your daily watt-hour needs. 7v 1000mAh and three different solar panels. That's what the specs says and I confirmed it myself at a full sun and no load, just the multimeter. What Size Solar Panel to Charge 12V Battery? 12 volt batteries are the most common voltage I see people using in their solar power setups.