A 10kW solar system is enough to meet my home's electricity needs. It is the ideal solution for living off-grid and being completely independent of the power company.
How I calculate the batteries needed for the system
A 10kW solar system that generates 40kwh per day requires 6 units of 300ah 24V cells to store all the energy generated. Dividing the daily solar panel watt output by the battery voltage, then I had the minimum battery capacity I needed.
Calculate the battery demand of 10kW solar system
Figuring out solar cell needs is a bit complicated because they vary from home to home. Here is a simplified process.
Solar array total output/cell voltage = number of cell amperes required
A 10kW solar system produces 40kW, or 40,000 watts, per day. Divide the wattage by the battery voltage. The battery has different voltages, but we will use 48V as it is most practical for large PHOTOVOLTAIC systems.
40,000w/48v = 833.3ah
I need a 48V battery pack of at least 833 amps.
So I can buy 3 x 300AH 48V batteries, 4 x 200ah, 2 x 450ah, any combination, as long as at least 833AH.
Of course, I can also use 24V or 12V batteries. They are connected in series to increase the voltage so that they can handle the system output. The only downside is that I have to double the number of batteries I need.
If I use a 24V battery, I will need 1666 amps. The best choice is 24V 300AH capacity, such as the Maxworld LiFePO4 battery, because it can handle electricity. A 10kW solar system requires 6 of these.
If the 48V battery requires 3 x 300ah, 6 units of 24V batteries and 12 units of 12v batteries are required. Batteries take up a lot of space and are heavy. More of them also means more wiring, which adds to the cost.
How many batteries do you really need?
The calculation given above is simple. But it assumes that you want to store all the power produced by a 10kW system in a single day.
If you want to store only the excess solar energy generated, subtract the extra amount from the total output.
Example: If you use 30kW per day, the system produces 40kW:
40kw-30kw = 10kw
10 kilowatts = 10,000 watts
You need a battery pack that can hold 10,000 watts.
10000 / 48 = 208ah
10000 / 24 = 416ah
10000 / 12 = 833ah
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