1. What is Battery Run Time?

Battery run time is the estimated duration a battery can power a specific load before needing recharge. For 12V batteries, this depends on the battery's capacity (in Ah) and the power consumption of the connected device (in Watts).

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \text{Battery Ah} \) — Battery capacity in amp-hours
• \( 12 \text{V} \) — Nominal voltage of the battery
• \( \text{Load W} \) — Power consumption of the device in watts

Explanation: The formula converts battery capacity to watt-hours (Ah × V = Wh) then divides by load power to get runtime in hours.

3. Importance of Run Time Calculation

Details: Accurate run time estimation helps in battery sizing for applications like solar systems, RVs, boats, and emergency power backups.

4. Using the Calculator

Tips: Enter battery capacity in Ah and load power in W. Both values must be positive numbers. The calculator assumes 100% efficiency (real-world results may be 10-20% less).

5. Frequently Asked Questions (FAQ)

Q1: Why multiply by 12 volts?
A: This converts amp-hours to watt-hours (energy capacity). 1Ah × 12V = 12Wh of stored energy.

Q2: What's a typical Ah rating for car batteries?
A: Car batteries typically range from 40Ah to 100Ah. Deep cycle batteries for RVs/solar may be 100-300Ah.

Q3: How does temperature affect run time?
A: Cold temperatures can reduce effective capacity by 20-50% in lead-acid batteries.

Q4: Should I derate the calculated run time?
A: Yes, for lead-acid batteries, multiply by 0.8 (80%) to account for depth-of-discharge limits.

Q5: Does this work for lithium batteries?
A: Yes, but lithium batteries can typically discharge deeper (90-100%) and maintain capacity better in cold.