Are there benefits to using deep cycle batteries in solar systems?

Sizing a Battery Bank for Deep Cycle Batteries

When sizing a battery bank for a deep cycle battery system, it’s essential to consider the total energy storage required. This depends on the system’s load, the amount of energy generated by the solar array, and the duration of the discharge. A general rule of thumb is to size the battery bank based on a 3-5 day reserve capacity, which accounts for periods of low sunlight and high energy demand.

For example, a 3-day reserve capacity would require a battery bank that can supply at least 3 days’ worth of energy for the system’s load. This can be calculated by multiplying the daily energy demand by 3. If the system’s daily energy demand is 10 kWh, then the battery bank would need to be sized to supply at least 30 kWh of energy.

Deep Cycle Battery Bank Configuration

Deep cycle battery banks are typically configured in a series-parallel arrangement to achieve the desired voltage and capacity. Series connections are used to increase the voltage, while parallel connections are used to increase the capacity. For example, a 24V system could be configured with 8 batteries in series to achieve a total voltage of 192V, and then 4 of these series strings could be connected in parallel to achieve a total capacity of 192Ah.

Battery Bank Depth of Discharge

Deep cycle batteries can handle repeated deep discharging, but it’s essential to maintain a safe depth of discharge (DOD) to prolong the battery’s lifespan. A DOD of 50% is considered safe for deep cycle batteries, and it’s recommended to charge the batteries back up to 100% as soon as possible after a discharge event. This helps maintain the battery’s capacity and prevents degradation over time.