If you occasionally dry camp and are looking for a solar power solution to charge your 220Ah battery bank then this post is for you.
Here, you’ll find how many watts of solar are suited to keeping a 220 Ah battery consistently charged, and what you should consider in sizing the solar panel size. You’ll also find how long it takes to charge so that you have the right expectations when using solar as a charging source.
How Many Watts of Solar you Need?
Note: These calculations assume a 12V battery bank
This depends on the depth of charge (recommended available capacity of the battery) and how much of the battery capacity is used on average in a day.
Using a 220Ah AGM Battery Bank
With AGM batteries as an example, you need at least 300 watts of solar panels assuming they have been installed in a location that receives an average of 4 hours of sunshine each day.
How Many Solar Panels?
You can use a single 300 or 320-watt solar panel or 3 pcs of 100-watt solar panels connected in parallel for 300 watts of solar.
How Many KWh from the Solar Panels?
With 4 hours of sunshine on average, the 300 watts of solar panels generate about 1,200 Wh or 1.2 kWh of energy. The calculation: 300 watts of solar x 4 hours of sunshine.
Using a 220Ah Lithium Battery Bank
If it is a Lithium battery bank (80% usable capacity), you’ll need at least 600 watts of solar (double the solar panel capacity with AGM) to recharge them in a location with an average of 4 days of solar.
This assumes that they are discharged to 80% of the available capacity.
How Many Solar Panels?
You can use two 300 solar panels, 3 pcs of 200-watt solar or 6 pcs of 100-watt solar panels connected in parallel for 600 watts of solar.
How Many KWh from The Solar Panels?
With 4 hours of sunshine on average, the 600 watts of solar panels generate about 2,400 Wh or 2.4 kWh of energy. The calculation: 600 watts of solar x 4 hours of sunshine.
If the average usage of the battery capacities is less than 50% in the case of AGM battery bank or 80% for Lithium, you can use fewer watts of solar.
For example, if the 220Ah AGM battery bank is only discharged to 25% of its capacity (25A) then a minimum of 150 watts of solar panels is sufficient.
Is 400 Watts Enough?
If the AGM battery bank is discharged to 50% of its capacity, then 400 watts of solar is enough to fully charge a 220Ah AGM battery bank on a daily basis.
The estimated daily charging capacity of 400 watts of solar is about 130 Ah from (400 watts of solar)/(solar panel voltage) x average hours of sunshine. If the daily draw on battery capacity at 12V is less than 130 Ah then 400 watts of solar is enough.
How Long to Charge a 220 Ah Battery?
The estimated charging time for a 220 Ah AGM battery bank with 300 watts of solar is about 6 hours.
This assumes it is discharged to only 50% of its capacity. This is longer than the calculated 4 hours because in practice the charging current can vary depending on how much sun is available.
Closing Thoughts
With 300 watts of solar, you can consistently keep a 220Ah AGM battery bank charged. This assumes on average 4 hours of sunshine and that the battery is discharged to 50% of its capacity.
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