The batteries are produced in a straight line inside the bright and spacious hall. Production consists of three main parts, with finished batteries coming out roughly in the middle. The first part is used for the assembly of battery modules and requires a high degree of accuracy. In the second, the aluminium tub, which forms the battery body, is equipped with internal and external components. And in the third part, a set of control electronics – the so-called e-box – is created.
Modules move in two parallel streams in the first part of the line – for the battery’s left and right parts. Each module arrives from the supplier charged to about 20 percent of capacity, so everyone must pay close attention to safety.
The aluminium container, which forms the battery body, is simultaneously created in the second part of the line. It is most often robots that handle it, but with a manual back-up behind them. The sturdy container is fitted with all the necessary connectors, seals, stops, screw bushings, as well as an external thermal shield that protects the entire battery from the heat generated by the exhaust pipe.
Then comes the robot that removes any dirt from the container with a vacuum cleaner. After being vacuumed, the container is ready for the so-called “wedding” – that is, the coupling of the container and the assembled battery modules.
The installation of other components, especially the cooling circuit, is next. The installation of low-voltage cabling and high-voltage jumpers is also completed, and panels and braces are added to the container.
Before closing the battery with the cover, the e-box is installed. It is prepared on a smaller assembly line nearby, and in thus is continuously supplied to the main assembly. The e-box is one of the parts that must be protected against electrostatic discharge (ESD). “The floor, clothing and shoes must all comply with the requirements of the ESD protected area in order to prevent this risk. Before arriving at the workplace, each worker is measured at a special station to ensure that their clothing and footwear provide the required function”, explains Otakar Mašek, a battery assembly specialist from PKM/3 –Assembly Battery, Small-lot Assemb.EA 111.
The battery is tested after assembly. First, the tightness of the cooling circuit and of the entire battery is tested separately. Then it can go to one of the 13 test benches for a series of electrical tests that check both HV and LV (communication) parts and the insulation functionality. At the end, the battery is charged to around 38 percent of its capacity directly on the test bench. Next, warning labels and other markings are added, and off to the warehouse it goes.