You have two 225-watt solar panels which is equal to 450-watts, for a close estimation of battery size, you need to include the average sunshine duration in your region. So, suppose the average sunshine duration in your area is around 6 to 8 hours.
Now, calculate the total energy produced by solar panels during sunshine, to get an idea about which battery type is perfect for the combination.
Here is the calculation:
Solar panel capacity- 225-watt * 2 (nos. of solar panels)
Sunshine duration: 6 to 8 hours
Solar panel capacity * Sunshine Duration = Total Energy
= 450- watt (225-watt*2) * 6 hours
=, 2700-watt*hours or 2.7kWh = 2.7 units of an electric meter.
By calculation, we were able to find out that the total energy production is around 2.7 kWh during 6 hours of sunshine period.
But this value can only be on paper. On the ground, the value varies by a considerable margin as 4% energy production decreases due to overheating of solar panels, The shadow of an object, and lack of sunlight for some periods also can affect the value of total energy production.
Best Battery for daily 2.7 kWh solar energy production
Generally, the size of the battery is not depending on the size of the solar system, it is up to your backup need. But to get the perfect battery size for your solar system you need to buy it according to the capacity of the solar system. According to our calculation, a 450-kW solar panel can charge up to five 40AH/12v batteries during sunshine.
40Ah/12v Lithium battery
Loom solar CAML 40 Ah/ 500 Watt-hour Lithium Battery is suitable for Homes and Small Shops and comes with faster charging technology- the battery gets charged 100% in just 2-4 hours. It is lightweight and has a longer life span - Compared to Lead acid and SMF, Lithium battery has around 2,000 cyclic life which translates into 10 years.
With two solar panels of 225-watt each and 40Ah/12v lithium battery is suitable to run for Coolers, Fans, led bulbs, TVs, or other low-power rating devices. It can provide 4 hours of backup on a 100w load.
To get a more accurate assessment, it's advisable to consult with a solar energy system installer or an expert who can design a solution tailored to your individual needs.