With an extra 110Ah battery, you can set up an off-grid solar system to power a few low-power electronics in your caravan, cabin, or even shed.
The battery is important but only just one of the components you’ll need. In addition, there’s a solar panel and possibly a charge controller too.
Here, you’ll find what size of solar panel and charge controller to use with a 110Ah battery and estimated charge time so that you have a solid foundation for your system.
Solar Panel Size (watts) to Charge Battery
You can use a 200-watt solar panel to keep a 110Ah AGM battery charged up with daily use assuming it is discharged to 50% of its capacity.
The solar panel has an ideal output of about 800 watt-hours (solar panel peak power 200 watts x the average number of sunshine hours, 4 hours).
This is more than sufficient to replenish the AGM battery’s usable capacity of about 660 watt-hours (battery capacity of 110Ah x battery voltage of 12V x recommended depth of discharge of 50%).
With a 110Ah LiFePO4 battery, you have about double the available capacity of an AGM battery. Use a 400-watt solar panel to keep a 110Ah LiFePO4 battery charged up with daily use assuming it is discharged to 80% of its capacity.
If the battery draw is considerably less than the recommended depth of discharge, you may be able to get by with a solar panel with a lower capacity (watts).
However, there is a danger that the battery will be discharged more than you expect if not carefully monitored and not fully charged which in turn can shorten its life.
Estimated Time to Charge
The estimated duration to charge a 110Ah AGM or LIFePO4 battery with the recommended solar panel sizes above is about 6-8 hours.
This mainly depends on the hours of sunshine received at the location, if the solar panels are clear and properly mounted to face the sun, and to what extent the battery has been discharged.
Connecting Solar Panel Directly to the Battery? Is a Charge Controller Necessary?
The Dangers of Connecting a Solar Panel Directly
No, use a charge controller to avoid overcharging or over-discharging the battery which shortens the battery life.
With a 200-watt solar panel charging a 110AH AGM battery, you can use a 20 amp charge controller or larger though manufacturers will usually provide a 30 amp charge controller.
You can use a 40 amp MPPT charge controller with a 400-watt solar panel system.
What Charger to Use for the Battery?
You can use a 10 amp smart charger or higher. The estimated charging time with a 110Ah AGM battery discharged to 50% is about 7-8 hours.
Use a 200-watt solar panel to charge a 110Ah AGM battery. With a LiFePO4, use a 400-watts solar panel array.