In practical applications, solar cells usually form components in series, parallel or series-parallel phase mixing to meet the required current and voltage. However, due to the inconsistent parameters of the solar cells, the output power of the components after series-parallel connection may be smaller than each individual. The sum of the maximum output power of the solar cells.
When the batteries are connected in series, the voltage at both ends is the sum of the voltages in the individual cells, and the current is equal to the minimum current in each battery; when connected in parallel, the total current is the sum of the currents of the individual cells, and the voltage is averaged. Common components are generally connected in series. If a low-current battery is mixed in the normal battery in series, according to the principle of small current, the output current of the component is determined by the battery of the smallest battery, and the output power of the component is reduced. High package loss. To reduce the battery matching loss and obtain the maximum output power, it is necessary to select the battery with the same or similar electrical performance parameters in series to form a component. This requires that the appropriate binning mode should be selected during battery sorting to prevent battery mismatch.
The solar cells in the assembly are connected by a solder ribbon, the solder ribbon is generally a tinned copper strip, and the tin layer contains Sn/Pb, Sn/Pb/Ag or Sn/Pb/Bi. The resistance of the solder ribbon is mainly affected by the copper strip. If the resistance value is too high, part of the output voltage of the component will be consumed on the solder ribbon, resulting in electrical packaging loss. The resistance of the metal is equal to the resistivity multiplied by the length of the metal divided by the cross-sectional area of ​​the metal. Since the resistivity and length values ​​are fixed and difficult to change, it is necessary to increase the width and thickness of the ribbon to reduce the resistance of the ribbon. If the width of the ribbon is wider than the main grid of the battery, it will increase the shading area and reduce the efficiency of the battery, so the width of the ribbon should not change. Therefore, it is considered to increase the thickness of the copper strip, and the thickening of the solder ribbon causes battery chipping problems during soldering. Therefore, it is necessary to select a solder ribbon to suit the width and thickness to prevent excessive component power loss on the solder ribbon.
The welding process also seriously affects the power of the component. If there is a problem of poor soldering, soldering, etc. during the soldering process of the component, it will cause high contact resistance and reduce the output current of the component; improper soldering process may also cause the battery. The electrodes are detached from the silicon wafer and cannot collect current, resulting in an increase in package loss.
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