mAh vs mWh • Design Capacity vs Full Charge Capacity • What counts as a charge cycle
Quick recap
Battery capacity is how much electrical energy a battery can store and deliver. Laptop packs usually show capacity in mAh (milliampere-hour) or mWh (milliwatt-hour). Higher numbers generally mean longer runtime, assuming the same device and voltage.
What is battery capacity?
Battery capacity is how much electrical energy a battery can store and deliver. For laptops it’s typically shown as
mAh or mWh.
mAh vs mWh — what’s the difference?
- mAh measures current over time.
- mWh measures energy and is often more comparable across different voltages.
Higher mAh or mWh usually means longer runtime (same device & voltage).
What is “Design Capacity”?
Design Capacity is the capacity the battery was engineered to hold at the factory and is printed on the pack/box.
It’s a useful reference but does not reveal how much energy the battery holds today.
What is “Full Charge Capacity (FCC)”?
Full Charge Capacity is the amount of charge the battery actually holds at a full charge right now.
FCC can differ from Design Capacity even when new and will decline with usage and aging.
What counts as a charge cycle for lithium batteries?
One cycle equals a cumulative 100% discharge, not each plug-in.
Example: use 40% on Day 1 and 60% on Day 2 → 40% + 60% = 100% = one cycle.
Why does FCC matter when buying a replacement battery?
FCC reflects real-world capacity. A quality new battery’s FCC should closely match its Design Capacity.
A large gap may indicate lower-quality cells or poor matching.
How do I check Full Charge Capacity on Windows?
- Open Command Prompt (Admin).
- Run:
powercfg /batteryreport - Open the generated battery-report.html (usually in your user folder) to see Design Capacity and Full Charge Capacity.
Any tools to monitor capacity over time?
Yes—battery utilities for Windows (e.g., BatteryMon) can track capacity and health trends over time.