What does the mAh refer to with batteries?
Batteries are typically listed with a value of mAh (milliamp hour), which is the batteries capacity measurement.
It represents the amount of current in milliamps the battery can provide per hour. An example will be a battery with a mAh of 1000mAh. The battery can theoretically provide 1000mA for 1 hour, 2000mA for 1/2hr or 500mA for 2hrs or any other combination based on the current load being used.
Of course electrical components are not perfect so there is always some power waste. A good rule to follow is the larger the mAh value the longer the battery charge will last vs. a lower mAh value used under the same conditions.