First, the cell format and chemistry for the battery must be selected. There are three cell formats: cylindrical, pocket and prismatic. Each of these has different features which allow it to adapt to the vehicle’s functions. For example, the pocket format is designed to assist in heat transfer. It is the format that was selected by our engineers for the design of the battery for the Lion school bus prototype.
Then, a choice must be made between a self-managed (intelligent) or a non-self-managed battery management system (BMS). For a simple vehicle without much on-board management, like a lift truck, the self-managed system is usually preferred.
Also, the mechanical housing that holds, among other things, the heat management system, must be well thought out. In fact, it is important to determine if the battery must withstand hard vibrations or impacts in order to optimize its level of strength. The weight can also be a major issue, as some types of vehicles must remain light, such as planes. In a different vein, as the heat management system must cool or heat the battery, it must be suited to the vehicle’s requirements. For example, a battery with a powerful cooling system will be preferred if the vehicle operates near a heat source. One in a plane, however, will have to switch very fast between hot and cold, as the external temperature can change by tens of degrees Celsius during takeoff.
In short, the battery’s design is a crucial step in the vehicle’s electrification. As the IVI’s Director of R&D, Frederick Prigge, P. Eng., explains:
“The cost of designing a battery is significant, often more than the design of the rest of the vehicle. It is therefore important to put in the required energy in order to ensure that the battery not only complies with the desired performance, but that it is viable in production for years to come.”
My country isn’t a country, it’s winter!
Everyone knows that vehicles in Quebec have specific energy requirements because of winter conditions. Do you know why cold is an issue where it relates to batteries? It’s because, in general, the cells don’t want to recharge below 0°C, and to discharge below -20°C. Batteries must therefore be winterized in order to compensate for the cells’ whims!
There are a number of strategies to winterize a battery, such as adding insulation or heat sources to the external housing. The objective is to correctly manage the heat transfers with the ambient in order to maintain an optimal temperature. There are numerous methods used, and they must all be adapted to each system. As Pierre-Luc Lapointe, Eng. states:
“The challenge is to optimize the battery’s design in order to get the best energy density, without cannibalizing its energy. For example, the addition of numerous heat sources will increase the cells’ temperature to allow for recharging in winter, but at the cost of parasitic energy use. Also, adding too much insulation will limit the exchanges with the ambient during cold days, but will impair cooling during hot summer days.”
Expertise and a state-of-the-art laboratory
At IVI, the engineers can depend on a quality infrastructure that allows them to complete the required tests. Equipment that lets them weld the cells, with a bidirectional DC power source that allows for the simulation of a battery’s life cycle, or the environmental chamber that is used to test the batteries at various temperatures; they have everything to design powerful batteries.
It goes without saying that IVI’s engineers are electrification experts; they must have been energized when they were children!