The difference between lithium-ion battery capacity and rated capacity. What is the difference between lithium-ion battery capacity and rated capacity? Battery capacity refers to the amount of electrical energy a battery can store. Rated capacity is measured in mAh. Rated capacity refers to the capacity a battery can achieve after being designed and manufactured.
The difference between lithium-ion battery capacity and rated capacity.
Capacity is a crucial indicator of battery electrical performance. Lithium-ion battery capacity is typically categorized into rated capacity, actual capacity, and theoretical capacity. The capacity of a lithium-ion battery is determined by the capacity of its electrodes, particularly the positive electrode material. Improving the performance of the positive electrode material can significantly increase lithium-ion battery capacity and reduce battery size. Lithium-ion battery capacity is a critical indicator in lithium-ion applications, and commonly used methods for calculating and evaluating lithium-ion battery capacity include chemical methods, voltage methods, and current integration methods.
Battery capacity:
It is one of the important performance indicators for measuring battery performance. It represents the amount of electricity that the battery can release under certain conditions (discharge rate, temperature, termination voltage, etc.) (discharge test can be performed using -150D), that is, the battery capacity, usually expressed in ampere-hours (abbreviated as A·H, 1A·h=3600C).
Battery capacity is categorized into actual capacity, theoretical capacity, and rated capacity under different conditions. The formula for calculating battery capacity C is C = ∫t0It1dt (integral over the current I over the time interval t0 to t1). Batteries have positive and negative terminals. Battery capacity is generally calculated in AH (ampere-hours), but another method is to calculate it in CELL (watts per unit plate).
Rated capacity:
This refers to the capacity of a motor or electrical appliance, as indicated on its nameplate, to operate continuously under rated operating conditions. Typically, for transformers it refers to apparent power, for motors to active power, and for phase-shifting equipment to apparent or reactive power. Units include VA, kVA, and MVA.
Actual battery capacity:
The ampere-hour (Ah) is the unit that reflects the actual amount of electricity a battery can store. A higher Ah indicates a larger battery capacity and a longer driving range for the electric vehicle. During use, the actual capacity of a battery gradually decreases. National standards stipulate that a newly manufactured battery with an actual capacity greater than its rated capacity is considered a qualified battery. For example, the batteries in electric bicycles currently on the market, when discharged at a constant current of 5A for more than 2 hours (120 minutes), exceed (2 hours × 5A) 10Ah. This is equivalent to an electric vehicle continuously driving on a flat road for more than 2 hours.
What aspects are included in the capacity of a lithium-ion battery?
1. Nominal capacity
Lithium-ion batteries deliver different amounts of electricity under different discharge regimes. The actual capacity of a battery under these unspecified discharge regimes is called its nominal capacity.
2. Rated capacity
When designing and manufacturing batteries, the minimum amount of electricity that a lithium-ion battery should release under certain discharge conditions is specified.
3. Theoretical capacity
The capacity assuming the active substance is 100% utilized.
4. Design capacity
The capacity value used in the design of lithium-ion batteries takes into account various influencing factors. The design capacity is generally larger than the rated capacity.
5. Actual capacity
The actual output capacity of a lithium-ion battery under specified conditions.
In summary, lithium-ion batteries have two types of capacity: rated capacity and actual capacity. The rated capacity refers to the amount of electricity the battery should supply when discharged to its termination voltage at an ambient temperature of 20℃±5℃ and a 5-hour discharge rate, denoted by C5. The actual capacity refers to the actual amount of electricity the battery discharges under specific discharge conditions, and is significantly affected by the discharge rate and temperature.
