If you’re venturing into the world of solar, it may not always be necessary to buy a complete solar system kit including solar panels, a charge controller, and even an inverter because you already have the battery. You’d need to know the capacities of the solar system components to use so that the system works reliably.
How many solar panels do you need for a 150Ah battery? How many watts of solar are required?
This post provides some guidance on how many solar panels, their watts, charge controller, and even an inverter rating (watts) you can use with a 150Ah battery.
Number of Solar Panels and Watts to Charge Battery
Using 150 Ah AGM Battery
You can use 1 x 300-watt, 2 x 150-watt, or 3 x 100-watt solar panels to keep a 150Ah AGM battery charged up with daily use assuming it is discharged to 50% of its capacity.
Note: This is just a selection of the possible solar panel size and configurations you can use.
The 300 watts of power from the solar panels has an ideal output of about 1,200 watt-hours (solar panel peak power 300 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 900 watt-hours (battery capacity of 150Ah x battery voltage of 12V x recommended depth of discharge of 50%).
Using a 150 Ah Lithium Battery
With a 150Ah LiFePO4 battery, you have about double the available capacity of an AGM battery.
Use 600-watts of solar, (2 x 300-watt solar panels, 4 x 150-watt solar panels, or 6 x100 watt solar panels) to keep a 150Ah LiFePO4 battery charged up with daily use assuming it is discharged to 80% of its capacity.
You may be able to use fewer watts of solar if the energy draw from the battery is considerably less than the recommended depth of discharge.
Doing so, however, carries a danger of not being able to fully charge the battery with the limited solar if not energy usage is not carefully monitored which in turn can shorten the life of the batteries.
Estimated Time to Charge
The estimated duration to charge a 150Ah 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.
Solar Charge Controller Size
The Dangers of Connecting a Solar Panel Directly
Always use a charge controller to avoid overcharging or over-discharging the battery which damage the battery. For a 300-watt solar panel charging a 150AH AGM battery, you can use a 30 amp charge controller or larger.
You can use a 60 amp MPPT charge controller with a 600-watt solar panel system.
Related Questions
#1. What Charger to Use for the Battery?
You can use a 10 amp smart charger or higher. The estimated charging time with a 150Ah AGM battery discharged to 50% is about 7-8 hours or longer depending on how deeply discharged the battery is.
#2. What Size of Inverter to use with the Battery?
Inverter size generally depends on the combined capacity of the AC loads that need to be powered. That said, depending on the power consumption of connected appliances, a 1,000-watt 12V to 110V AC inverter can be a good size to consider.
Closing Thoughts
Use 300-watts of solar to charge a 150Ah AGM battery. With a LiFePO4, use at least 600-watts of solar to keep the battery bank fully charged.
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