Tools: battery sizing

Battery sizing table for lead acid batteries in a solar application requires careful consideration of several factors. These include the total daily energy consumption (in watt-hours), the system voltage (in volts), the maximum depth of discharge (DOD) for the batteries, and the number of days of autonomy (sunless days) you want your system to support.

Let’s break down the formula into simple terms for understanding and then create a template for the table:

1. Total Daily Energy Consumption (Wh/day): This is the total amount of energy in watt-hours that your solar system needs to provide each day.

2. System Voltage (V): This is the voltage of your battery bank, typically 12V, 24V, or 48V.

3. Maximum Depth of Discharge (DOD): For lead acid batteries, it’s recommended not to discharge them completely to prolong their life. A 60% DOD means you plan to use 60% of the battery’s capacity before recharging.

4. Days of Autonomy: The number of days you want your system to run without sunlight. In this case, it’s 3 days.

5. Battery Capacity Needed (Ah): This is the total ampere-hours of battery capacity required to meet your energy needs during the specified days of autonomy without exceeding the maximum DOD.

The formula to calculate the battery capacity needed is:

Battery Capacity (Ah)=Total Daily Energy Consumption (Wh/day)×Days of AutonomySystem Voltage (V)×Maximum DOD

Battery Capacity (Ah)=System Voltage (V)×Maximum DOD

Total Daily Energy Consumption (Wh/day)×Days of Autonomy

Let’s create a template for the table based on the formula:

Please replace “User Input” with your specific values to calculate the Battery Capacity (Ah) needed for your application. This table will help guide you through understanding and computing the necessary battery capacity for a solar application considering a maximum depth of discharge of 60% and 3 sunless days of autonomy.