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Do you know about the battery parameters

Author: source: Datetime: 2021-04-07 10:12:26

Do you know about the battery parameters

lithium battery

     In the photovoltaic energy storage system, the function of the battery is to store electrical energy. Due to the limited capacity of a single battery, the system usually combines multiple batteries in series to achieve the designed voltage level and capacity requirements, so it is also called a battery group. In the photovoltaic energy storage system, the initial cost of the battery pack and the photovoltaic module are the same, but the life of the battery pack is lower. The technical parameters of the battery are very important to the system design. When selecting and designing, pay attention to the key parameters of the battery, such as battery capacity. , Rated voltage, charge and discharge current, depth of discharge, number of cycles, etc.

1. Battery capacity

The capacity of the battery is determined by the amount of active material in the battery, usually expressed in Ah or mAh. For example, the nominal capacity of 250Ah (10hr, 1.80V/cell, 25°C) refers to the discharge capacity when the voltage of a single battery drops to 1.80V by discharging at a current of 25A for 10 hours at 25°C.

The energy of the battery refers to the electric energy that the battery can give under a certain discharge system, usually expressed in watt-hours (Wh). The energy of the battery is divided into theoretical energy and actual energy: For example, a 12V150Ah battery, the theoretical energy is 12*150=1800Wh, which is 1.8 kWh, which means the battery can save the amount of electricity, if the depth of discharge is 70%, the actual energy is 1800 *70%=1.2 Wh, which is 2.1 kWh of electricity, which is the amount of electricity that can be used.

2. Rated voltage

The potential difference between the positive and negative poles of the battery is called the battery's rated voltage. Common lead-acid batteries have three rated voltages of 2V, 6V, and 12V. The single lead-acid battery is 2V, and the 12V battery is made up of 6 single batteries in series. 

The actual voltage of the battery is not a constant value. The voltage is high when there is no load, and the voltage will decrease when there is a load. When there is a sudden large current discharge, the voltage will suddenly drop. There is an approximately linear relationship between the battery voltage and the remaining power. This simple association exists only when there is no load. When a load is applied, the battery voltage will be distorted due to the voltage drop caused by the battery's internal impedance.

3. Maximum charge and discharge current

The battery is bidirectional and has two states, charging and discharging. The current is limited. Different batteries have different maximum charge and discharge currents. The battery charging current is generally expressed as a multiple of the battery capacity C. For example, If the battery capacity C=100Ah and the charging current is 0.15C, then 0.15×100=15A.

4. Discharge depth and cycle life

In the process of battery use, the percentage of the battery's rated capacity is called the depth of discharge. There is a deep relationship between the depth of discharge and the battery life. The deeper the depth of discharge, the shorter the charging life. The battery undergoes a charge and discharge, which is called a cycle (a cycle). Under certain discharge conditions, the number of cycles that the battery can withstand before the battery reaches a certain capacity is called the cycle life. The battery discharge depth between 10% and 30% is a shallow cycle discharge; the discharge depth is between 40% and 70% is a medium cycle discharge; the discharge depth is between 80% and 90% is a deep cycle discharge. The deeper the daily discharge depth of the battery during long-term operation, the shorter the battery life, and the shallower the discharge depth, the longer the battery life.

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lithium battery pack