Internal resistance
Also: source resistance
An equivalent resistance representing voltage loss and heating inside a real source.
Terminal voltage falls approximately by I·R_internal under a simple local model; resistance varies with charge, temperature, age, and frequency.
- Units
- ohm (Ω)
Example 0.2 Ω at 2 A predicts 0.4 V sag and 0.8 W internal heating.
Common misconception Internal resistance is not always constant or the only cause of battery voltage sag.