Leave the panel size at 0 to get the wattage needed to refill the battery in the number of days you set.
How it works
Energy to replace (Wh) = Ah × volts × share to recharge. Sun hours = energy ÷ (panel W × efficiency).
Example: refilling 80% of a 12 V 100 Ah battery in 1 day at 4.98 sun hours takes about a 227 W panel.
At a glance
Same settings as the calculator, changing only the battery.
| Battery | Energy | Panel for 1 day |
|---|---|---|
| 50 Ah | 480 Wh | 113 W |
| 100 Ah | 960 Wh | 227 W |
| 200 Ah | 1,920 Wh | 454 W |
| 300 Ah | 2,880 Wh | 680 W |
| 400 Ah | 3,840 Wh | 907 W |
Common questions
How long does a 100 W panel take to charge a 100 Ah battery?
Half-charging a 12 V 100 Ah battery takes 600 Wh. A 100 W panel at 85% efficiency delivers 85 W, so about 7 hours of full sun.
Do I need a charge controller?
Yes. It stops overcharging. MPPT controllers get more from the panel than PWM types.