Lithium-ion batteries are characterized by small size, lightweight, high voltage, no memory effect.
Batteries are generally 18650 and are compared in units of volume and weight energy density. Volume energy density is expressed in units of [Wh/m3] or[ Wh/L].
It shows the battery capacity per unit volume, and the unit of energy density is expressed with [Wh].
This represents how many hours it will last with constant power, and although the power is voltage × current, in the case of batteries the voltage changes depending on remaining capacity so it is necessary to check the item of rated voltage for rating of the battery.
This represents the voltage toward the total energy when discharging at 1C current, and the total energy of the lithium-ion battery can be obtained by multiplying the average voltage at 1C discharge and the current capacity value.
For example, if the nominal voltage of a battery is 3.6V and the nominal capacity is 3400mAh, the energy of the battery is derived as 3.6×3.4=12.24Wh.
The 18650 lithium-ion battery is small and light secondary battery toward energy.
It can lose against lithium primary batteries, but lithium primary batteries cannot be charged.
Battery voltage is nearly three times that of dry cell, Ni-Cd, and Ni-MH, and it can respond to semiconductor’s standard voltage 5V with 2-direct, and to 3.3V with 1-direct.
In the days when lithium-ion and Ni-MH batteries were both used in a notebook computer, lithium-ion batteries had a capacity of 2000mAh or less for 18650, whereas Ni-MH batteries had that of 5000mAh for the same size, so the same capacity could be secured.
However,in terms of weight, the weight of lithium-ion is 1/2.
Although the difference in price and the difference in weight plus whether or not there is memory effect were chosen, currently lithium-ion batteries win the game.