Improving autonomy, capacity or maximum power delivery are not the only aspects to improve in electric car batteries. If they become structural elements, the chassis engineering will have considerable improvements, but that is not all.
The improvement of the steels and materials used in the automotive industry have resulted in vehicles becoming more rigid and resistant. We are not only talking about passive safety, especially in the passenger compartment, also in comfort, dynamic behavior in curves or NVH levels.
Under the current prism, the batteries of electric cars are not structural elements, so the chassis / platform must provide the necessary robustness to protect the battery packs at a level similar to that which protects the occupants from body deformations and penetrations. of own or other mechanical organs.
The next evolutionary leap is the concept of structural batteries, which are actually part of the chassis / platform, making the latter can be lighter while maintaining rigidity. The mere reduction in weight already implies an improvement in autonomy.
NIO CTP batteries with a capacity of 100 kWh
From here, different approaches to how to distribute cells and modules within batteries can be considered. At the moment the motor industry has not agreed on a common format, since each one is waging war on their own, the same with regard to battery manufacturers.
Under the CTP (cell to pack) mode, the cells are directly part of the batteries, avoiding the need to divide them into modules, thus saving weight on components and there is more space to store energy. Batteries do not have a good energy / mass ratio when compared to petroleum derivatives deposits, with this design that improves a lot.
The main problem with this approach is that modularity is lost, with implications when designing different battery sizes / capacities, as well as taking into account future maintenance needs. For example, it is easier to replace a module than entire batteries.
GMC Hummer EV Pick-up
We have several manufacturers that are making progress in the field of structural batteries, such as General Motors, Tesla or Volvo. The latter announced that they are working, together with the Swedish Northvolt, on batteries that provide autonomies of the order of 1,000 kilometers.
In the case of General Motors, the Ultium platform batteries that we will see working in the GMC Hummer EV are structural elements, very important in an off-road vehicle, although the hierarchy of cells and modules is maintained. The Chinese BYD and CATL have designs in which there are no modules, only cells.
Another interesting architecture is the one that develops One Next Energy (whose acronym is ONE), with a double battery pack design, a structural one without modules that is complemented by another with more capacity and that powers the previous one. According to its creators, this design provides more safety and is more environmentally friendly by not using nickel or cobalt. In addition, it greatly facilitates its manufacture at logistical levels (raw materials).
ONE bets on batteries in series, where some recharge the other
As we can see, the advances that can be made only in the packaging part are important. We have seen it in the past in models such as Renault ZOE, BMW i3 or Nissan Leaf, which have substantially improved their autonomies within the same generation compared to the first models, almost doubling them, and occupying the same space.
However, classic design issues must be taken into account when batteries have higher capacity. First, the higher the capacity, the longer it takes to recharge given the same power. Large batteries therefore imply very high charging powers. That brings us to the second problem: temperature.
Batteries must maintain an acceptable temperature range, neither too cold nor too hot, so that their cells maintain capacity and the nominal and maximum power delivery. The closer the cells are, the more complicated their cooling becomes. Finally, do not avoid cost, which is the one that ends up making the difference, as the batteries are the most expensive in the car.