The *mAh rating on a battery is an indicator of the maximum amount of current that the battery can deliver per hour and is generally an indicator of the capacity of the battery. However, this also depends largely on the voltage of the battery. The Watts (Wh) rating is a better indicator of capacity as this factors in the voltage as well.

Some batteries are rated in Ah and others mAh. 1Ah = 1000mAh

(Wh) = mAh x V / 1000 which abbreviates the formula utilized by the calculator in executing the conversions from milliamp-hours to watt-hours.

(mAh)= Wh x 1000 / V

For example,

If you have 150 mAh and 45 V the calculation will be;

(Wh) = 150 x 45 / 1000 = 6.75 (Wh)

(mAh) = 6.75 x 1000 / 45 = 150 (mAh)

It is quite safe to use a battery with a lower or higher Ah / mAh rating. However it may affect how long your device lasts on a single charge.