Quick Answer
For a 2000 watt solar system, a suitable battery bank would be in the range of 12-20 kWh, consisting of 12-20 deep cycle batteries in parallel, with each battery rated around 4-6 volts and 200-300 Ah.
Determining Bank Size and Depth of Discharge
When calculating the size of a battery bank, it’s essential to consider the system’s energy needs, solar panel output, and desired days of autonomy. A good rule of thumb is to size the bank to provide 2-5 days of autonomy during periods of low solar irradiance. For a 2000 watt system, a 2-day autonomy would require a bank of approximately 8-12 kWh. However, to account for periods of prolonged low solar output, we may want to increase the autonomy to 3-4 days, requiring a 12-16 kWh bank.
Choosing the Right Depth of Discharge
The depth of discharge (DOD) is the percentage of the battery’s capacity that can be safely discharged before it begins to degrade. Most deep cycle batteries are designed to operate at a DOD of 50% or less. For a 12V battery bank, this translates to a DOD of 25% or less per battery. To ensure the longevity of the battery bank, it’s essential to maintain a DOD of 50% or less per cycle.
Battery Bank Configuration
To configure the battery bank, we can use a combination of parallel and series connections. For a 12V system, we can use 12V batteries in series to achieve the required voltage, and then connect them in parallel to achieve the desired capacity. For example, to achieve a 24V system, we can connect two 12V batteries in series. To increase the capacity, we can add more batteries in parallel. A common configuration for a 12V system would be 2-4 batteries in series, with 4-6 batteries in parallel, resulting in a total bank size of 12-24 kWh.
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