1. What is Battery Internal Resistance?

Internal resistance is the opposition to the flow of current within a battery, causing voltage drop under load. It's a key indicator of battery health and performance.

2. How Does the Calculator Work?

The calculator uses the internal resistance formula:

Where:

• \( r \) — Internal resistance (Ω)
• \( V_{no} \) — No-load voltage (V)
• \( V_{load} \) — Voltage under load (V)
• \( I \) — Current (A)

Explanation: The voltage difference between no-load and loaded conditions divided by the current gives the internal resistance.

3. Importance of Internal Resistance

Details: Lower internal resistance means better battery performance, higher efficiency, and less voltage drop under load. It increases with battery age and degradation.

4. Using the Calculator

Tips: Measure voltage without load (V_no), then with load (V_load) while measuring current (I). All values must be positive and current must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a good internal resistance value?
A: It varies by battery type and capacity. Generally, lower is better. Compare against manufacturer specifications or new battery values.

Q2: How does temperature affect internal resistance?
A: Resistance typically increases at lower temperatures and decreases at higher temperatures (within safe limits).

Q3: Why does internal resistance matter?
A: High resistance reduces available power, causes voltage sag, and indicates battery wear or problems.

Q4: How often should I measure internal resistance?
A: For critical applications, regular monitoring (e.g., monthly) helps track battery health over time.

Q5: Can I use this for all battery types?
A: Yes, the formula works for all battery chemistries (Li-ion, Lead-acid, NiMH, etc.), but interpretation of results varies.