Frequently Asked Questions
What is mAh?
mAh stands for milliampere-hour. It is a unit of electric charge that describes the energy storage capacity of a battery. For example, a 1000mAh battery can theoretically provide 1000mA (1 Amp) for 1 hour, or 100mA for 10 hours.
How do I convert mAh to Wh?
The formula is: Wh = (mAh × V) / 1000.
For instance, a 10,000mAh power bank at 3.7V is: (10,000 * 3.7) / 1000 = 37 Wh.
What is the 85% Efficiency Rule?
Batteries are not 100% efficient. Energy is lost as heat during discharge and voltage conversion (boost/buck converters). A safe "real-world" estimate for most Lithium-Ion power banks and devices is 85% efficiency.
Battery Chemistry Types
Common voltages for different chemistries:
- Alkaline (AA/AAA): 1.5V nominal. Non-rechargeable.
- NiMH (AA/AAA Rechargeable): 1.2V nominal.
- Li-Ion (18650, Laptops): 3.6V - 3.7V nominal. (4.2V fully charged).
- LiFePO4: 3.2V nominal. Safer, longer life.
- Lead Acid (Car Battery): 12V (actually ~12.6V).