The capacity of lithium battery cells is measured in amp-hours (Ah) or sometimes milliamp-hours (mAh) where 1 Ah = 1,000 mAh. Lithium battery cells can have anywhere from a few mAh to 100 Ah. Occasionally the unit watt-hour (Wh) will be listed on a cell instead of the amp-hour. Watt-hour is another unit of energy, but also consider voltage.
Occasionally lithium battery cells are marketed with just a C rating and not a maximum current rating. This can make it easier to compare the power level of battery cells of different capacities. As long as you know the capacity of the cell, you can use the C rate to quickly calculate the maximum current rating of the cell.
Almost all lithium-ion batteries work at 3.8 volts. Lithium-ion 18650 batteries generally have capacity ratings from 2,300 to 3,600 mAh. C-rate is used to express how fast a battery is discharged or charged relative to its maximum capacity. It has units h−1. A 1C rate means that the discharge current will discharge the entire battery in 1 hour.
Lithium-ion and lithium-polymer batteries should be kept at charge levels between 30 and 70 % at all times. Full charge/discharge cycles should be avoided if possible. Exceptions to this can be made occasionally to readjust the charge controller and battery capacity meter.
You need to know the current and the time to calculate the lithium-ion battery capacity. The current, usually measured in amperes (A) or milliamperes (mA), is the amount of electric charge that flows through the battery per unit of time. The time, usually measured in hours (h) or fractions of an hour, is the charge or discharge cycle duration.
Here we will look at the most important lithium ion battery specifications. The capacity of a cell is probably the most critical factor, as it determines how much energy is available in the cell. The capacity of lithium battery cells is measured in amp-hours (Ah) or sometimes milliamp-hours (mAh) where 1 Ah = 1,000 mAh.