**1. Battery capacity**1). Series and parallel output mode

In practical applications, the calculation of battery capacity is more important, because meeting the requirements of use mainly depends on the capacity of the battery. The power of the solar panels of the vehicle-mounted solar power station is determined by the vehicle body. Except for special customization, the commercially available battery modules are mostly 12V output and need to be used in series and parallel. The series and parallel connections and output modes are the same as those of solar cells as shown in Figure 1.

2). Battery capacity calculation and selection

(1) Calculation of battery capacity.

Bc=AQ1N1 T0/Cc

In the formula, A—— safety factor (1.1~1.4);

Q1——The average daily power consumption of the load;

N1——The longest number of consecutive rainy days;

T0——Temperature correction coefficient, 1 above 0C, 1.1 at -10C, 1.2 below -10C;

Cc——battery discharge depth (normally 0.75 for lead-acid batteries, 0.85 for alkaline nickel-cadmium batteries).

(2) Battery selection.

The main performance parameters of batteries include specific energy, specific power, cycle life and charging time. At present, the most commonly used valve-controlled maintenance-free lead-acid batteries and silica gel batteries, the best used are lithium-ion batteries and lithium iron phosphate batteries, super capacitors and hybrid super capacitors have begun to be used, hydrogen fuel cells and aluminum-air batteries are under development try out.

(3) Series and parallel applications of batteries.

Single battery I=E0/(Rb+R)

Where E0——open circuit voltage of battery;

Rb, R-internal resistance and external resistance.

n batteries in series: l=nEo/(nRb+R), increase the voltage.

Connect n batteries in parallel: I=Eo/(Rb/n+R), increase current.

**2. Calculation example of battery energy system of solar container car body**1). Load daily average power consumption Q1

The key to the calculation is to determine the daily average power consumption Q1 of the load.

Work procedures: the dealer-maintenance-inspection analysis and plan formulation-debridement and polishing before welding-welding-post-welding treatment and inspection.

Working hours/h: | 1.6 | 1.6 | 1.6 | 1.6 | 1.6 | Of 8 |

Rated power kW: | 4 | 0.5 | 0.5 | 4 | 1 | Of 10 |

Daily power consumption kw·h: | 8.4 | 0.8 | 0.8 | 8.4 | 1.6 | Of 20 |

2). Solar power output

The solar panels of the solar engineering vehicle are installed horizontally. Refer to Figure 2 for the output power. The month of high output is 4 months, which is 1 month less than before and after installation at a reasonable angle. The monthly output power is reduced month by month, down to about 40%. The amount of change in the power output in a day is also large, the maximum output time is 5 hours, and the output extends for hours, and the output power decreases to the minimum to 0 hour by hour. The output drops by 40%~50% in cloudy weather, and 80%~90% in rainy weather. In addition, the actual output of solar energy is only about 80%, but the actual power used is generally less than 80% of the rated power, so only the actual local weather conditions at the time can be considered in the calculation.

3). Sunshine time and the longest number of rainy days H1

For welding engineering vehicles, only daytime work is considered, so the power generation can be determined according to the ratio of sunny and cloudy days to cloudy and rainy days in the local area at that time, and the duration of sunshine. Taking Chengdu as an example, the three types of weather account for about 1/3 of each of the 30 days in a month, and the sunshine is sunny for 6 hours. A cloudy day is equivalent to 3.0h. It is equivalent to 0.6h on rainy days. Total 9.6h. Each year accounts for 121.7 days=1168h, which is consistent with the data of 1100h from Chengdu Meteorological Department.

4). Power generation of solar container car body

The annual power generation is 4.48×1168=5232kW·h. The power consumption of the whole vehicle is 20×250=5000kW·h. Theoretically, the power generation is slightly higher than the power consumption, but it cannot work without power generation on cloudy and rainy days. If the surplus power generation is not used in sunny days, it will be wasted. Therefore, a battery must be used to store the surplus energy in sunny days. It is used in rainy days, and the energy requirements for working in rainy days must be ensured. The power of the equipment used in this car is 10kW, but the driving and welding are running at the wrong time, so the maximum operating power is 4kW. If you want to use it all-weather, you must be equipped with a battery of sufficient power and capacity to ensure that it can work for a day in rainy and rainy days, that is 2.4×1.6=12.8 kw·h (48V/267A·h or 12V/1067A·h), if the longest number of rainy days is 3 days, it needs to be increased to 3 times. At present, the container solar power supply is only used for welding, so only 12V/420A·h lead-acid batteries (four groups connected in series into 48V) are used for direct output and 220V AC output by the inverter.