Battery Reserve Capacity Calculator

Reserve Capacity Formula:

\[ \text{Reserve Capacity (min)} = \frac{\text{Battery Capacity (Ah)} \times 60}{\text{Discharge Current (A)}} \]

Reserve Capacity:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Battery Reserve Capacity?

Reserve Capacity (RC) is the number of minutes a fully charged battery can deliver a specified constant current (usually 25 amps for automotive batteries) before the voltage drops below a minimum threshold (typically 10.5 volts).

2. How Does the Calculator Work?

The calculator uses the reserve capacity formula:

\[ \text{Reserve Capacity (min)} = \frac{\text{Battery Capacity (Ah)} \times 60}{\text{Discharge Current (A)}} \]

Where:

Battery Capacity — The total charge capacity of the battery in amp-hours (Ah)
Discharge Current — The constant current drawn from the battery in amps (A)
60 — Conversion factor from hours to minutes

Explanation: The formula calculates how long (in minutes) a battery can sustain a given discharge current before being fully depleted.

3. Importance of Reserve Capacity

Details: Reserve capacity is crucial for understanding how long a battery can power essential systems (like vehicle electronics) if the charging system fails. It's particularly important for automotive and marine applications.

4. Using the Calculator

Tips: Enter battery capacity in amp-hours (Ah) and discharge current in amps (A). Both values must be positive numbers. Typical car batteries range from 40-100Ah capacity.

5. Frequently Asked Questions (FAQ)

Q1: How does reserve capacity differ from amp-hour rating?
A: Reserve capacity measures time at a fixed current (usually 25A), while amp-hour rating measures total charge capacity at a specified discharge rate over 20 hours.

Q2: What's a good reserve capacity for a car battery?
A: Most automotive batteries have RC between 90-180 minutes. Higher is better for vehicles with many electronic accessories.

Q3: Does temperature affect reserve capacity?
A: Yes, capacity decreases in cold temperatures. A battery might have 100% RC at 80°F but only 60% at 0°F.

Q4: How often should I check my battery's reserve capacity?
A: Have it tested annually after 3 years of service, or if you notice starting difficulties.

Q5: Can I increase my battery's reserve capacity?
A: Only by installing a battery with higher capacity or connecting additional batteries in parallel.