How battery capacity is measured and what is Wh? (Watt Hour)

About this Video

• Video Title: How battery capacity is measured and what is Wh? (Watt Hour)
• Channel: Currentium Power
• Speakers: None specified in transcript.
• Duration: 00:05:13

Introduction

This video explains how battery capacity is measured, focusing on Watt-hours (Wh) as the most accurate measure. It contrasts Wh with less informative metrics like amp-hours (Ah) and milliamp-hours (mAh), often used in marketing. The video also details several reasons why a battery's actual delivered power is often less than its theoretical Wh capacity.

Key Takeaways

• Watt-hours (Wh) is the most accurate measure of battery capacity. It represents the total power a battery can deliver.
• The simplified calculation of Wh (Volts x Amps x Hours) is always higher than the actual delivered power. Several factors contribute to this discrepancy.
• Voltage decreases as a battery discharges. This means the available power diminishes throughout use.
• Voltage conversion losses occur. Batteries may need to convert their internal voltage to match external requirements (e.g., USB power banks boosting voltage), leading to power loss.
• High discharge rates cause additional voltage drops and energy loss as heat. This can significantly reduce the usable power.
• Battery aging and damage reduce capacity. Older or damaged batteries deliver less than their original rated capacity.