A 3500mAh battery is a high-capacity power source, meaning it can store a significant amount of energy, with common examples being the rechargeable lithium-ion 18650 cell or non-rechargeable AA lithium batteries.
Specifications
This high capacity translates to longer runtimes for devices like flashlights, cameras, or laptops. While some are disposable, many are rechargeable and feature safety protections against overcharging and short circuits.