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What is the Charge and Discharge of Solar Charge Controller?

Views:77     Author:Site Editor     Publish Time: 2020-02-26      Origin:Site

The solar charge controller is an automatic control device, which is  used in solar photovoltaic system to control the charging of batteries by multiple solar cell arrays and the power supply of batteries to the load of solar inverters.


(1)Power regulation function.

(2)Communication function, simple indication function and protocol communication function.

(3)Perfect protection function, electrical protection, reverse connection, short circuit, over current.

2.Topological Structure

According to the topological structure, solar controllers can generally be divided into DC/DC and direct-through type. DC/DC can also be divided into resonance type and MPPT type. However, due to the existence of large inductance components in DC/DC controllers, its volume and weight will increase rapidly after high current. These shortcomings make its practical application in the high-power field limited. The direct-through controller has more advantages in high-power applications. Even if the photovoltaic current reaches several hundred amperes, its volume and weight will not be too large. Therefore, in the high-power areas such as mobile communication base stations, the direct-through controller has been widely used.

3.Charging and Discharging

(1)Direct Charging Protective Point Voltage

Direct charging is also called emergency charging, which belongs to fast charging. Generally, when the battery voltage is low, it charges the battery with high current and relatively high voltage. When the battery terminal voltage is higher than the protective values, direct charging should be stopped. Otherwise, it will cause overcharge and damage the battery. The voltage of direct charge protection point is also "overcharge protection point" voltage. 

(2)Equalization Control Point Voltage

After the direct charge is finished, the battery will be statically set by the charge and discharge controller for a period of time, so that its voltage will fall naturally. When it falls to the “recovery voltage” value, it will enter the equalization state. Because after the direct charge is completed, there may be some batteries of the terminal voltage is relatively low. In order to make all the battery terminal voltages have uniform consistency, it is necessary to recharge the batteries with high voltage and moderate current for a short time, which is called "balanced charging".

(3)Floating Charge Control Point Voltage

Generally, after the balanced charging is completed, the battery is also left to stand for a period of time, so that its terminal voltage naturally falls. When it falls to the "maintenance voltage" point, it enters the floating charging state. At present, PWM (Pulse Width Modulation) mode is adopted, which is similar to small current charging. When the battery voltage is low, it charges a little bit, one by one, in order to avoid battery temperature continues rising, which is very good for the battery, because the internal temperature of the battery has a great impact on charge and discharge. In fact, the PWM mode is mainly designed to stabilize the battery terminal voltage, by adjusting the pulse width to reduce the battery charging current. Specifically, when the residual capacitance (SOC) of the battery is more than 80% at the later stage of charging, the charging current must be reduced to prevent excessive discharge due to overcharging.

(4)Over-discharge protection termination voltage

Battery discharge should not be lower than the termination voltage, which is stipulated by the national standard. It should be noted that for the sake of safety, the overdischarge protection point voltage of 12V battery is usually artificially added with 0.3V as temperature compensation or zero drift correction of control circuit, so that the overdischarge protection point voltage of 12V battery is 11.10V. So the overdischarge protection point voltage of 24V battery is 22.20V. At present, many manufacturers of charge and discharge controllers adopt 22.2V standard.

With the rapid development of the economy, the energy shortage is getting worse. As a representative of new energy generation, solar power system has been formally applied to production practice.

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