Enter the rated capacity of the battery and the current drawn from the battery, along with the Peukert’s constant into the calculator to determine the discharge time. This calculator can also evaluate any of the variables given the others are known.

## Peukert’s Law Formula

The following formula is used to calculate the discharge time of a battery according to Peukert’s Law.

T = C / (I^k)

Variables:

• T is the time for the battery to discharge (hours)
• C is the rated capacity of the battery (Ah)
• I is the current drawn from the battery (A)
• k is the Peukert’s constant, which is specific to each battery and typically provided by the manufacturer

To calculate the discharge time of a battery according to Peukert’s Law, divide the rated capacity of the battery by the current drawn from the battery raised to the power of the Peukert’s constant. The Peukert’s constant is a value that represents the inefficiency of the battery and is typically provided by the battery manufacturer. The higher the Peukert’s constant, the faster the battery will discharge at higher currents.

## What is Peukert’s Law?

Peukert’s Law is a mathematical formula that describes the rate at which a battery, specifically a lead-acid battery, will discharge its energy relative to its capacity. It states that as the rate of discharge increases, the battery’s available capacity decreases. This is due to the internal resistance and reaction inefficiencies within the battery. The law is named after German scientist Wilhelm Peukert who formulated it in the late 19th century.

## How to Calculate Peukert’s Law?

The following steps outline how to calculate Peukert’s Law:

1. First, determine the rated capacity of the battery (C) in ampere-hours (Ah).
2. Next, determine the current drawn from the battery (I) in amperes (A).
3. Next, gather the Peukert’s constant (k) specific to the battery being used.
4. Use the formula T = C / (I^k) to calculate the time for the battery to discharge (T) in hours.
5. After inserting the values of C, I, and k into the formula, calculate the result.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Rated capacity of the battery (C) = 100 Ah

Current drawn from the battery (I) = 10 A

Peukert’s constant (k) = 1.2