Roy RitchieCar and driver
When GM launched the Chevrolet Volt plug-in hybrid in 2010, the auto industry talked about a battery cost of around $ 1,000 per kilowatt hour of energy storage. At that price, the Volt’s 16.0 kWh pack was probably more expensive than all of the other components in the car combined.
Now, with GM’s latest battery, dubbed Ultium, the company says it is approaching 90% lower cost, a point where it may finally pay off to move away from internal combustion engines. The automaker has pledged to do just that, launching 30 new electric vehicles around the world by 2025. By 2035, its only vehicles with tailpipes will be heavy trucks.
The building block in this plan is a large, pocket-type lithium-ion cell, approximately 23 x 4 x 0.4 inches. It weighs around three pounds and contains 20 times more energy than Tesla’s small cylindrical cells. (Teslas currently has thousands of battery cells in its packs, while electric vehicles from GM and most other automakers have hundreds of them.) The gross energy capacity of 0.37 kilowatt hours in each cell is enough for propel the first Ultium-powered vehicle, the mammoth 2022 GMC Hummer EV Pickup — just over half a mile. These cells will be produced in a joint venture with LG Chem at two massive new facilities in Ohio and Tennessee. When the two factories are operational by the end of 2023, they will be able to create a combined value of 70 gigawatt hours of batteries each year. That’s the equivalent of about 190 million cells, or enough for about 750,000 vehicles, by our estimate.
LG has been GM’s preferred battery supplier for more than a decade, during which time cell size and chemistry changed dramatically. Compared to the battery used in the Bolt EV, the Ultium battery, a nickel-cobalt-manganese-aluminum blend, contains 70% less cobalt, a key to reducing costs. However, any LG customer can purchase this cell, so any competitive advantage GM gains will have to come from how it integrates the components into a complete package. The packs will have net capacities of between 50 kilowatt-hours (144 cells) and 200 kilowatt-hours (576 cells), power between 235 and 1,000 horsepower, and a range of up to 450 miles.
GM claims it’s the only automaker today that can either lay the cells flat or stand them upright. This gives engineers the flexibility to shape a pack to follow the floor of a vehicle. GM groups cells into groups of 24, creating a module. In the Hummer, 12 modules are wired in series to form a 400 volt, 100.0 kWh layer of a dual stack battery. The two layers are connected in parallel to arrive at a total net capacity of 200.0 kWh.
Here’s the trick: On some Ultium vehicles, such as the Hummer, the top and bottom layers can be temporarily switched from a parallel connection to a series connection, doubling the voltage to 800. This allows it to take full advantage of the. highest output 800. -volt Electrify America fast charging stations. Fittingly, the Hummer’s ability to charge at 350 kilowatts means it can use up electricity faster than any EV on the market today. By switching the pack from 400 to 800 volts for fast charging, GM avoids paying for the more expensive components needed to get an EV to run at the highest voltage all the time, like the Porsche Taycan does. The Taycan is currently the only EV capable of charging at 800 volts, albeit at a lower peak of 270 kW.
Fast direct current charging, along with repeatedly charging a battery to 100 percent, is the most common cause of degradation that reduces a battery’s capacity over time. This fast charging can cause fast lithium ions to crystallize in cells, preventing them from moving back and forth as the battery charges and discharges. But Tim Grewe, GM’s global director of electrification and battery systems, is making some bold statements for the Ultium pack. He says that no amount of fast DC charging will degrade its capacity, and unlike Tesla and others, GM won’t suggest that the pack be charged less than 100% during normal daily use. He attributes the breakthrough to the careful development of chemistry, including the addition of aluminum to the cell. Grewe also promises that the Ultium pack “will outlast the Bolt EV,” which he says hits between 150,000 and 250,000 miles in the real world, comfortably exceeding its 100,000 mile guarantee.
Typically, automakers need a multitude of wires to monitor the hundreds of individual cells in a pack. But GM has found a way to monitor the Ultium wirelessly. Each group of two or three cells wired in parallel broadcasts key information such as temperature and voltage several times per second. This reduces the wiring of the pack by 80% compared to that of the Bolt, eliminating a source of warranty claims, improving packaging and simplifying the wiring harness. Additionally, GM says this setup does not consume more power than a wired system.
GM develops and tests the packs at its 100,000 square foot battery lab in Warren, Michigan. The company’s 75-ton megashaker looks like a 10-by-10-foot oven perched on top of a platform. It jostles a battery while varying the temperature and humidity to the extreme. In a matter of days, this drill mimics the abuse a battery takes from a life of driving over potholes. Elsewhere in the huge lab, packs are repeatedly loaded and unloaded to simulate a full life cycle. They go through puncture testing and are dropped from a height of six and 16 feet to make sure, among other things, that Hummer owners can confidently do a peacock off-road. Engineers are also learning from the competition: the day we visited, we saw a workbench filled with components from Tesla and Jaguar batteries.
While GM has yet to sell a vehicle with an Ultium pack, the lab is already working hard on the second-generation airframe. Grewe suggests he could double the energy density of this new cell. With costs now under control, the next big challenge in battery technology is to extend runtime and reduce the weight of today’s packs.
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