The battery size calculator calculates required the battery rating in ampere hour (Ah) based on load, duration and discharge level.

**Parameters:**

**Load type (ampere or watt):**Select the unit in which the load will be specified, ampere or watt.**Load (watt)**: If the load type is watt, specify the load in watt, for example 100 W. Use and average value if its a cyclical load.**Load (ampere):**If the load type is ampere, specify the current in ampere, for example 10 A.**Voltage (V)**: Specify the battery voltage, if the load type is watt.**Required duration (hours):**Specify the duration that the load must be supplied for.**Battery type:**Select the battery type, lead-acid or lithium-ion.

**Required battery size (Ah)**: The recommend battery size in Ah.

**Current calculation:**

- If the load is specified in watt, the current
**I**is calculated as:

\(I=\dfrac{P}{V}\)

where, **P** is the power in watts, and **V** is the voltage in volts.

**Lithium****-ion batteries:**

- The required battery size \(B_{li-ion}\) for litium-ion batteries is calculated by the battery size calculator as:

\(B_{li-ion}=\dfrac {100 \cdot I \cdot t}{100 – Q}\)

where, **I** is current in ampere, **t** is the duration in hours and **Q** is the required remaining charge in percentage.

**Lead-acid batteries:**

- The battery rating of a lead-acid batteries is proportional to the discharge rate. They are typically rated for a discharge rate over 20 hours. For example, a 20 Ah battery can deliver 1 A for 20 hours, which amounts to 20 Ah.
- The rating of the battery reduces by approximately 62% if it is discharged in 1 hour. For example, if the same 20 Ah battery is discharged in one hour, it can only deliver 12.4 A for one hour, which amounts to 12.4 Ah. The battery size calculator derates the battery linearly based in this characteristic.
- The required battery size \(B_{lead-acid}\) for lead-acid batteries is calculated by the battery size calculator as:

\(B_{lead-acid}=\dfrac{100 \cdot I \cdot t}{(100-Q) \cdot (0.02 \cdot t+0.6)}\)

where, **I** is current in ampere, **t** is the duration in hours, and **Q** is the required remaining charge in percentage.