POWERTRAIN
cells largely constructed with only one or two strings in parallel. Both designs have their advantages/ disadvantages and depend on the vehicle application.
Battery chemistry-wise, most manufacturers (with the exception of Tesla) are moving towards high-energy NMC cathode chemistries, maximising the nickel content and increasingly, silicon doped anodes.
Q
HOW IMPORTANT IS TEMPERATURE CONTROL BECOMING?
It’s very important, and it depends on cost. For lower cost EVs passive or active air cooling is the most used approach. This is only applicable however if the battery pack is not required for high power outputs. For more high performance vehicles liquid cooling is the preferred approach, based on its superior cooling capability, and because it has less reliance on ambient conditions. However, it is likely that liquid cooling will become more prevalent as faster charge rates and higher overall pack capacities become more common.
Battery pack design is improving, particularly knowledge around optimum cell thermal management, which will have a large eff ect on lifetime. The most signifi cant challenge however, could lie in the battery management system, which needs to allow the required performance while delivering the maximum possible lifetime for a given cell.
Progress has been made in this area, with tailored charging profi les to avoid lithium plating, intelligent charge timing to reduce state of charge (SoC), and temperature compensation in operational strategies.
The environmental conditions of each market play an important consideration, and making an electric vehicle suitable to all is indeed a challenge. High temperature regions can cause considerable problems with accelerated battery pack degradation, and low temperature regions can come with reduced performance, and in particular, inability to charge without battery pack damage.
Therefore, we are now seeing more focus for OEMs to increase the AER at the temperature extremes (both hot and cold) through battery thermal
Power pack
makes it uniquely positioned to ponder the current state of the EV market. Over to you, Richard:
Q
WHAT’S HAPPENING WITH BATTERY PACK DESIGN?
It is moving towards higher voltage and higher capacity to meet demands with range and fast charging. In terms of cell confi guration, there are two distinct options that get preferred: a very large amount of small 18650 cells, connected with multiple strings in parallel, or large format, high-capacity prismatic/pouch
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