Solar Battery Bank Size Calculator
Solar Battery Bank Size is evaluated from Daily Energy Consumption, Days of Battery Backup and Depth of Discharge. The calculation reports Total kWh Needed, Required Usable Capacity and Required Gross Battery Capacity.
Results
About the Solar Battery Bank Size Calculator
The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.
Formula basis:
_dk = parseFloat(daily_kwh)
_bd = parseFloat(backup_days)
_dod = parseFloat(dod) / 100
_sv = parseFloat(system_voltage)
_bv = parseFloat(battery_voltage) || 12
_bah = parseFloat(battery_ah) || 100
total_kwh_needed = _dk * _bd
usable_kwh = total_kwh_needed
gross_kwh = total_kwh_needed / _dod
total_ah = (gross_kwh * 1000) / _sv
_batt_kwh = (_bv * _bah) / 1000
_batts_per_string = Math.ceil(_sv / _bv)
_strings = Math.ceil(gross_kwh / (_batt_kwh * _batts_per_string))
batteries_needed = _batts_per_string * _strings
approx_cost = batteries_needed * _bah * 1.50
Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.
Formula & How It Works
The calculation applies the following relations exactly as recorded in the metadata: _dk = parseFloat(daily_kwh) _bd = parseFloat(backup_days) _dod = parseFloat(dod) / 100 _sv = parseFloat(system_voltage) _bv = parseFloat(battery_voltage) || 12 _bah = parseFloat(battery_ah) || 100 total_kwh_needed = _dk * _bd usable_kwh = total_kwh_needed gross_kwh = total_kwh_needed / _dod total_ah = (gross_kwh * 1000) / _sv _batt_kwh = (_bv * _bah) / 1000 _batts_per_string = Math.ceil(_sv / _bv) _strings = Math.ceil(gross_kwh / (_batt_kwh * _batts_per_string)) batteries_needed = _batts_per_string * _strings approx_cost = batteries_needed * _bah * 1.50 Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.
Worked Examples
Example 1: Small cabin: 5 kWh/day, 2-day backup, 80% DoD
Inputs
With Daily Energy Consumption = 5, Days of Battery Backup = 2, Depth of Discharge = 80 and System Voltage = 24 as the stated inputs, the result is Total kWh Needed = 10 kWh, Required Usable Capacity = 10 kWh and Required Gross Battery Capacity = 12.5 kWh. Each value corresponds to the declared output fields.
Example 2: Home battery backup: 30 kWh/day, 1-day backup, LiFePO4 90% DoD
Inputs
With Daily Energy Consumption = 30, Days of Battery Backup = 1, Depth of Discharge = 90 and System Voltage = 48 as the stated inputs, the result is Total kWh Needed = 30 kWh, Required Usable Capacity = 30 kWh and Required Gross Battery Capacity = 33.33 kWh. Each value corresponds to the declared output fields.
Example 3: RV/van solar system: 3 kWh/day, 3-day autonomy, AGM 50% DoD
Inputs
With Daily Energy Consumption = 3, Days of Battery Backup = 3, Depth of Discharge = 50 and System Voltage = 12 as the stated inputs, the result is Total kWh Needed = 9 kWh, Required Usable Capacity = 9 kWh and Required Gross Battery Capacity = 18 kWh. Each value corresponds to the declared output fields.
Example 4: Small business/commercial: 100 kWh/day, 1-day backup
Inputs
With Daily Energy Consumption = 100, Days of Battery Backup = 1, Depth of Discharge = 85 and System Voltage = 48 as the stated inputs, the result is Total kWh Needed = 100 kWh, Required Usable Capacity = 100 kWh and Required Gross Battery Capacity = 117.65 kWh. Each value corresponds to the declared output fields.
Common Use Cases
- Size a battery bank for off-grid solar system
- Calculate battery backup for home solar
- Determine number of batteries needed for solar setup