1: First calculate the current:
Example: 12V battery system; 2 lights of 30W, total 60W.
Current＝60W÷12V＝5A
2: Calculate the battery capacity requirement:
For example, the cumulative lighting time of street lights needs to be 7 hours (h) at full load every night;
(For example, open at 8:00 pm, close 1 at 11:30 at night, open 2 at 4:30 in the morning, and close at 5:30 in the morning)
It needs to meet the lighting needs of 5 consecutive cloudy and rainy days. (5 days plus lighting the night before the rainy day, 6 days)
Battery=5A×7h×(5+1)day=5A×42h=210AH
In addition, in order to prevent the battery from being overcharged and overdischarged, the battery is generally charged to about 90%, and the remaining 20% is discharged. So the 210aH is also only about 70% of the real standard in the application.
Three: Calculate the peak demand (WP) of the battery panel:
The cumulative lighting time of street lights needs to be 7 hours per night (h);
★: The average daily effective light time for the solar panels is 4.5 hours (h); at least 20% of the reserved amount for the solar panels needs to be relaxed.
WP÷17.4V＝(5A×7h×120％)÷4.5h
WP÷17.4V＝9.33
WP=162 (W)
★: 4.5h daily sunshine time is the sunshine coefficient in the vicinity of the middle and lower reaches of the Yangtze River. The middle and upper reaches of the Yangtze River are generally 5 hours.
In addition, in the solar street light assembly, the line loss, the loss of the controller, and the power consumption of the ballast or constant current source are different, which may be about 5%-25% in practical applications. Therefore, 162W is only a theoretical value, and the configuration parameters need to be increased or decreased according to the actual situation.