Battery Reserve 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 usable level (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 amp-hour rating of the battery
Discharge Current — The constant current draw from the battery
60 — Conversion factor from hours to minutes

Explanation: The formula calculates how long a battery can sustain a given current draw before being depleted.

3. Importance of Reserve Capacity

Details: Reserve capacity is crucial for understanding how long a battery will last under load, especially in automotive and backup power applications. It helps in selecting the right battery for specific power needs.

4. Using the Calculator

Tips: Enter battery capacity in amp-hours (Ah) and discharge current in amps (A). Both values must be positive numbers. The result shows the estimated runtime in minutes.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between Ah rating and reserve capacity?
A: Ah rating measures total charge capacity, while reserve capacity measures runtime at a specific discharge rate (usually higher current).

Q2: How does temperature affect reserve capacity?
A: Cold temperatures significantly reduce reserve capacity, while moderate heat can slightly increase it but may shorten battery life.

Q3: What's a good reserve capacity for a car battery?
A: Typical automotive batteries have 90-180 minutes RC at 25A. Higher is better for vehicles with many electrical accessories.

Q4: Can I use this for lithium-ion batteries?
A: The calculation works similarly, but lithium batteries typically maintain voltage better until nearly depleted, so actual runtime might be slightly longer.

Q5: How does battery age affect reserve capacity?
A: As batteries age, their reserve capacity decreases due to sulfation and other degradation processes.