A single piece of aluminium
While the battery modules and e-boxes are being assembled, in another part the aluminium can forming the body of the battery is prepared. Most of the handling work here is done by robots, but at some stations they have a manual backup in case the robot is unable to do the job for some reason.
The massive aluminium case also comes from a supplier. Here on the line it is fitted with all the necessary components such as various connectors, seals, stops and screw bushes, but also the external heat shield that passes through the centre of the case. This shield protects the entire battery from the heat from the exhaust that runs beneath it.
Assembled batteries head off for rigorous testing.
When the case is fully assembled, it is the turn of a perhaps unexpected assistant to do its bit: a robot that uses a vacuum cleaner to make sure that the case is free from any impurities that might cause problems during operation. After being vacuumed, the case is ready for what is known as the “marriage”. While in automobile manufacture this has traditionally meant the phase when the body is joined together with the chassis and engine, here it means putting the assembled battery modules into the case, which is done by a robot. Another robot takes care of the fairly complicated process of screwing bath and module together. The seal lies on a mount. The complexity lies in the fact that the screw and the mount are automatically connected first.
Once the case and modules have been put together, other components are fitted, primarily the cooling circuit. The installation of the low-voltage cabling is completed and the case is given filler material and support braces. One smart solution is applied when these are screwed together on the line. “The screws for attaching braces are on a special trolley with scales, which can tell whether the worker used the right number of screws and didn’t take one more that fell into the case, for example,” says Otakar Mašek.
At the start of assembly battery modules are paired up; the complete battery blocks are made from multiples of these pairs.
Another control practice might seem unexpected as well: after all the connectors have been attached inside the battery, the employee at the next station uses a felt-tip pen to make a dot on the place of the given connection to show that he performed a second visual check of the connection. “This requirement forces the employee to actually look at the connection,” Mašek says. All that’s left to do after that is to connect the module to the control unit, and the battery is ready to be sealed. The lid on the case is secured with a double seal: rubber and a special glue. The lid is screwed on by a robot.