Troubleshooting a low voltage
To identify the commonly low voltage and excessively low voltage, the
commonly low voltage mentioned here is the decrease of open-circuit
voltage of the module, which is caused by the temperature rising of
solar cells or lower irradiance. Excessively low voltage is typically
caused by improper connections of the terminals or defective bypass
diodes.
·First, check all wiring connections to see if it is not open-circuit or is not
connected well.
·Check the open-circuit voltage of each module
·Disconnect the wiring at both terminals of the modules.
·If the measured voltage is only half of the rate, this indicates a defective
bypass diode. By replacing or remove the diode, the issue may be
sorted. Removing the bypass diodes should only be done by a compe-
tent PV technician and the module has to be disconnected from the
system.
In the case of fine irradiance, if the voltage across the terminals differs
from the rated value by more than 15%, this indicates a bad electrical
connection.
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·Determine the short-circuit current (Isc) of every series circuit. It can be
measured directly by connecting the digital multimeter to the two termi-
nals of the series circuit or module. Attention, the rated scale of the am-
meter or the rated current of load should be more than 1.25 times of the
rated short-circuit current of the series module. You will find the rated
current data in the technical specifications sheet. The measured value
can vary significantly, depending on weather conditions, the time of day,
and the shading of the module.
