1. What is the Battery Size Calculation?

The battery size calculation determines the required capacity (in ampere-hours) of a car battery based on the starting current, required runtime, and a derating factor. This ensures your vehicle has adequate power for starting and electrical systems.

2. How Does the Calculator Work?

The calculator uses the battery size formula:

Where:

• Car Start A — Starting current required by the vehicle (in amps)
• Time — Desired runtime before recharge (in hours)
• Factor — Derating factor (typically 0.7 for lead-acid batteries)

Explanation: The equation accounts for the total energy requirement divided by a factor that compensates for battery efficiency and discharge characteristics.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing ensures reliable vehicle starting, prevents premature battery failure, and supports all electrical systems. Undersized batteries may fail to start the engine, while oversized batteries add unnecessary weight and cost.

4. Using the Calculator

Tips: Enter the starting current (typically 200-800A for cars), desired runtime, and appropriate factor (0.7 for lead-acid). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical car starting current?
A: Most passenger cars require 200-500 amps for starting, while larger vehicles may need 500-800 amps.

Q2: Why is the factor typically 0.7?
A: This accounts for lead-acid battery efficiency and the fact that batteries shouldn't be fully discharged for longevity.

Q3: How does temperature affect battery size?
A: Cold weather reduces battery capacity. In freezing temperatures, consider increasing calculated size by 20-30%.

Q4: What about additional electrical loads?
A: For vehicles with high accessory loads, add those amperage requirements to the starting current.

Q5: Does this work for deep cycle batteries?
A: Yes, but the factor may be different (closer to 0.5) for true deep cycle applications.