Lithium Polymer (LiPo) batteries are rechargeable batteries that have become increasingly popular in recent years due to their high energy density and lightweight design. They are commonly used in a variety of applications, including remote-controlled vehicles, drones, smartphones, and portable electronics. However, to get the most out of your LiPo battery, it is important to understand the common parameters that affect its performance. In this article, we will explore the most important parameters to consider when selecting and using a LiPo battery.

**OPEN CIRCUIT VOLTAGE**

The difference between the electrode potentials of the two poles of the battery when the battery is disconnected.The open circuit voltage is an actual measured value.For example, the open circuit voltage of a lithium-ion battery is 4.1V, and the electromotive force of a lead-acid battery is 2.1V. The electromotive force or open circuit voltage value of the battery depends on the electrode material and electrolyte of the battery. The activity and discharge temperature have nothing to do with the geometry and size of the battery.

**RATED VOLTAGE**

The standard voltage for the battery to work under specified conditions.Used to distinguish the battery system.3. Rated voltage: The standard voltage for the battery to work under specified conditions.Used to distinguish the battery system.Such as: lead-acid battery: 2.0V nickel-cadmium battery: 1.2V nickel-hydrogen battery: 1.2V zinc-manganese battery: 1.5V lithium-ion battery: 3.6-3.8V.

**DISCHARGE CUT-OFF VOLTAGE**

Refers to the minimum operating voltage value at which the voltage drops to the point where it is not appropriate to continue discharging during discharge.Is an artificially specified value.For example: when a lithium-ion battery is charged, the termination voltage is 4.2V, and when it is discharged, it is 3.0V or 2.75V.

**OPERATING VOLTAGE**

Also known as discharge voltage or load voltage, it refers to the potential difference between the two poles of the battery when the battery outputs current externally.The operating voltage is always lower than the open circuit voltage.The change of the battery discharge voltage is related to the discharge system, that is, the change of the discharge curve is also affected by the discharge system, including: discharge current, discharge temperature, discharge termination voltage; intermittent or continuous discharge.The larger the discharge current, the faster the operating voltage drops; with the increase of the discharge temperature, the discharge curve changes more gently; for secondary batteries, the discharge voltage is lower than the specified termination voltage is called over-discharge, over-discharge often affects the cycle life of the battery.Constant resistance discharge, constant current discharge, constant current discharge, continuous discharge, intermittent discharge.

**ENERGY & SPECIFIC ENERGY**

The electrical energy that a battery can output for external work under certain conditions is called the energy of the battery, and the unit is generally expressed in wh.

a.The discharge process of the theoretical energy battery is in an equilibrium state, the discharge voltage maintains the value of the electromotive force (E), and the utilization rate of the active substance is 100%. Under this condition, the output energy of the battery is the theoretical energy (W0), which can reverse the maximum non-expansion work done by the battery at constant temperature and pressure (W0=C0E).

b.Actual energy The energy actually output when the battery is discharged is called actual energy.The energy actually output when the battery is discharged is called the actual energy.

**CAPACITY**

Battery capacity refers to the power given by the battery under a certain discharge system (at a certain I discharge, T discharge, and V discharge). Characterize the ability of the battery to store energy in Ah or C. The capacity is affected by many primers, such as discharge current, discharge temperature, etc.

The size of the capacity is determined by the number of active substances in the positive and negative electrodes.

Theoretical capacity: The capacity given by all active substances to participate in the reaction. Actual capacity: The actual capacity released under a certain discharge system. Rated capacity: Also known as nominal capacity, it refers to the minimum power guaranteed by the battery under the designed discharge conditions. In practical applications, battery capacity = positive electrode capacity specific capacity: In order to compare different batteries, the concept of specific capacity is introduced. The specific capacity refers to the capacity given by the battery per unit mass or unit volume, which is called the mass specific capacity or volume specific capacity. The usual calculation method is：

Battery first discharge capacity/(active substance quantity*active substance utilization rate)

**Factors Affecting Battery Capacity：**

- The discharge speed of the battery (usually expressed in terms of current intensity mA): the greater the current, the less output capacity；
- Battery discharge temperature: the temperature decreases and the output capacity decreases；
- The discharge termination voltage of the battery: it is set by the definition of the electrical appliances and the battery itself. For example, when charging, the termination voltage is 4.2V, and when discharging, it is 3.0V or 2.75V.
- Battery storage time: After the battery is stored for a long time, the discharge capacity of the battery will be reduced accordingly.

**POWER & SPECIFIC POWER**

The energy output per unit time of the battery under certain discharge conditions is expressed in P and the unit is W. Theoretical power Actual power Actual ratio Energy mass ratio energy ratio Energy theoretical ratio energy volume ratio energy power is an important performance of the battery, it represents the size of the battery discharge rate, the greater the power of the battery, the battery can be discharged at high current or high speed.

**SELF-DISCHARGE**

Lio battery self-discharge refers to the phenomenon that the battery capacity decreases by itself when the battery is not loaded. The main reason is that the electrode material spontaneously undergoes a redox reaction; in the two electrodes, the self-discharge of the negative electrode is the main one, and the self-discharge causes the active substance to be consumed in vain. Battery self-discharge is closely related to battery storage performance. The storage performance of the battery must be good when it is stored, and the self-discharge is required to be small when it is stored, and there must be no leakage or alkali crawling. Various battery storage methods: full charge storage, partial charge storage, and discharge state storage.

**SOC & DOD**

SOC, State of Charge, is the state of charge, indicating the percentage of the remaining battery capacity to the total capacity. DOD, Depth of Discharge, is the depth of discharge, a measure of the degree of discharge, and is the percentage of the discharge capacity to the total discharge capacity. The level of discharge depth has a great relationship with the life of the secondary battery: the deeper the discharge depth, the shorter its life.

**CHARGE & DISCHARGE RATE**

Discharge time rate: Refers to the full rated capacity of the battery within the specified discharge time.

Discharge magnification: Refers to the discharge current as a certain multiple of the rated capacity of the battery.

Charge and discharge rate refer to the speed at which a battery is charged or discharged. It is usually measured in terms of the current flow, and it is expressed in amperes (A). The charge rate is the amount of current that a battery can accept while charging, while the discharge rate is the amount of current that a battery can deliver while discharging. The charge and discharge rate of a battery depend on various factors, including the battery chemistry, temperature, and capacity. Understanding the charge and discharge rate is crucial in determining the battery’s performance and lifespan.

To calculate the charge and discharge rate of a battery, you need to know the capacity of the battery in ampere-hours (Ah) and the current in amperes (A) or milliamperes (mA) that is being charged or discharged.

**Charge rate calculation:**

Charge rate = Charging current (A) / Battery capacity (Ah)

For example, if you have a 100 Ah battery and you are charging it with a current of 10 A, the charge rate would be:

Charge rate = 10 A / 100 Ah = 0.1 (or 10%) of the battery capacity per hour

**Discharge rate calculation:**

Discharge rate = Discharging current (A) / Battery capacity (Ah)

For example, if you have a 100 Ah battery and you are discharging it with a current of 5 A, the discharge rate would be:

Discharge rate = 5 A / 100 Ah = 0.05 (or 5%) of the battery capacity per hour

It is important to note that the charge and discharge rate of a battery may vary depending on factors such as temperature, age, and state of charge.

In conclusion, understanding the common parameters of a LiPo battery is essential for optimizing its performance and ensuring its longevity. By considering the capacity, voltage, discharge rate, and charge rate, you can select the right battery for your application and use it safely and effectively. With proper care and maintenance, a LiPo battery can provide reliable and efficient power for a wide range of devices and applications. However, it is important to follow the manufacturer’s recommendations and safety guidelines to avoid damaging the battery and risking injury or property damage. By taking the time to understand and respect the common parameters of a LiPo battery, you can enjoy its benefits and avoid its risks.