Most people consider batteries as energy storage devices. The more energy they contain, the better. In a car this translates into range. But range isn’t everything. A battery becomes useful when the energy can be charged and discharged rapidly. Often energy and power requirements are not compatible with each other. The more energy, the less power and vice versa. We examine this further using 3 real-world applications, some rather extreme but they highlight the issues.
What are extreme battery load scenarios?
Let’s first take the extreme driving profile of a race car. The race will last only 30 minutes, consuming about 130 kWh but as the race car has 4 motors of 400 kW each, it’s the equivalent of 1.6 MW on the wheels. Peak demand is 2 MW. If we use a 130 kWh lithium-ion battery, then about 60 to 80 % of the energy will be available but unless special precautions are taken, the maximum power output will be around 390 kW. We need 5 times more power. The reason is that a lithium-ion battery is limited in current and hence it will heat up too much and likely destroy itself. In order to meet the requirements, we would need a battery with more than 500 kWh. Such a battery would weigh more than 6 tons.
How to overcome this challenge? Let’s use hybrid powercapacitors. These cells combine a reasonable energy density with excellent power capabilities.
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