Lithium-ion cells are popular for their high energy density, long cycle life, and low self-discharge.
Few essential parameters to check from lithium-ion cell "data sheets" to help you choose the most suitable cell for your specific requirements are:
a) Nominal Capacity:
The nominal capacity, typically measured in ampere-hours (Ah) or milliampere-hours (mAh), represents the amount of charge a cell can store under specified conditions. This parameter is critical as it directly relates to the cell's energy storage capability. Higher capacity values correspond to longer runtimes, but may also mean increased size and weight.
b) Nominal Voltage:
The nominal voltage is the average voltage at which a cell operates during discharge under normal conditions. This value, usually around 3.6-3.7V for lithium-ion cells, is essential to ensure compatibility with the intended application's voltage requirements.
c) Energy Density:
Energy density, expressed in watt-hours per kilogram (Wh/kg) or watt-hours per liter (Wh/L), indicates the amount of energy stored per unit weight or volume, respectively. A higher energy density means more energy can be stored in a smaller, lighter package. This parameter is especially important for applications with strict size and weight constraints, such as electric vehicles or portable electronics.
d) Discharge Rate (C-rate):
The discharge rate, or C-rate, represents the cell's ability to deliver current relative to its capacity. Higher C-rates mean the cell can deliver more power at once, which is important for high-drain applications like electric vehicles or power tools. It is essential to check the maximum continuous discharge rate and the pulse discharge rate to ensure the cell can meet the application's power demands without risking damage or reduced lifespan.
e) Cycle Life:
The cycle life represents the number of charge-discharge cycles a cell can undergo before its capacity degrades to a certain level, often 80% of its initial capacity. This parameter is crucial for applications where long service life and low maintenance are essential, such as grid energy storage or electric vehicles.
f) Temperature Range:
Lithium-ion cells can be sensitive to extreme temperatures, which can affect their performance, safety, and lifespan. Checking the recommended operating temperature range, as well as the storage temperature range, ensures the cell will function optimally in the intended application's environment.
g) Internal Resistance:
The internal resistance of a lithium-ion cell, measured in milliohms (mΩ), represents the opposition to the flow of current within the cell. Lower internal resistance values result in less energy wasted as heat during charge and discharge, leading to improved efficiency & reduced temperature rise.
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