All "Ultium" EVs use the same battery module. Except for bolts, and that may be its biggest advantage. At the heart of all General Motors EVs equipped with "Ultium" is a clever choice. Whether it's a big honking' GMC Hummer EV or an affordable, base model Chevy Equinox EV, all of the common electrical products rely on the same basic pillars: the same basic cells placed in 24 cell modules. All of them, that is, except for the new bolts. And it is also the one with the best 10-80% charging time. Coincidence? Not quite. The description requires some basic knowledge of the battery pack, a little bit of chemistry, and a dash of geopolitics. Let's get into it.
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Module Approach
These are the main reasons why many EVs are expensive. Economies of scale are not just kicking in as they have for gas vehicles. Over 100 plus years of building dinosaur burners, we got pretty good on every individual piece. There are many companies that can build fuel pumps, turbochargers, alternators and radiators at scale and take advantage of hundreds of thousands of units of volume to reduce costs per unit.
With EVs, automakers need to build an entire supply chain for scratch. Finding a supplier to manufacture automotive grade DC-DC converters is much more difficult than finding a supplier of fuel pumps. This is not surprising, because only one of these technologies was in demand 10 years ago. With most of these components, the supply base is built, so it is not a problem. But the biggest cost and the biggest challenge is the battery.
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Automotive-grade batteries are highly specialized and are not all-purpose models that fit all. But at the same time, the more you build multiple products, the more you can reduce costs in economies of scale. So, if you can't use the same pack for all cars, different vehicles have different range requirements, and you want to offer different models, you will be in a pinch. How do you build a variety of batteries without thinning the economy of your size?
For GM, the answer was to make everything common at the sub-pack level. Each pack is built from the same core component: 29 cells running at 24 volts, 103 amp-hour cells arranged into modules. Using its core building blocks, GM can build a variety of packs. The Chevy Equinox EV, Blazer EV LT and Optiq are 10-module, 85-kilowatt-hour packs, while the Cadillac Lyriq and Blazer EV SS are 12-module, 102-kWh packs. If you step up to the Big Dog trim of the Hummer EV and Chevy Silverado EV, you get 24 modules, or 205kWh of power.
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Voltage Problem
But if you know how the battery works, you can already see the problem. The core cells that make up large automotive batteries do not work at 400 or 800 volts. In this case, they run between 3.6 and 4.2 volts, as Motor1 described in an excellent deep dive. Getting a higher voltage requires wiring all these batteries together to raise the overall peak voltage of the pack.
Cars like the Equinox EV and Blazer EV will get 10 modules, each with a nominal voltage of 29 volts, and the overall pack voltage of about 290 volts. This explains why both vehicles have a rather unbearable charging curve. Both peak at 150kW, but to get 150kW from such a low voltage you need more than 500 amps — because the charging power (kW) is equal to voltage × current (amperes). Existing 150kW charger designs can't output that much current, so you need to find a 250kW or 350kW charger to get the peak count.
Even if you do, a 10-80% sprint will take a lethargic 40 minutes in the best scenario. And while larger GM packs can peak at higher speeds, the Silverado EV can charge up to 350kW. That means a small bolt with a 65kWh battery is the charging champion. It charges from 10-80% in 26 minutes. So why is the bolt not having this problem?
New LFP Pack from China, Straight
This is because Bolt does not use Ultium batteries, even though it uses broader Ultium architecture and software stack. Instead, get GM's first lithium-iron-phosphate (LFP) pack. LFP batteries are cheaper, more durable and longer lasting than nickel-mangnanese-cobalt batteries that power all other Ultium vehicles. Also, the pack did not require the use of GM's modular approach, which allowed Chinese suppliers to bring the nominal voltage significantly closer to 400. That is, it can peak at 150 kilowatts from a relatively low state of charge and hold a high charging speed for a long time. It has a large, fleshy charging curve that can fill up faster than other cheaper EVs like the Ford Mustang Mach-E and Volkswagen ID on the base model.
With that, GM has turned Bolt's biggest weakness into a major strength. The old one had a painful, hour—long charging stops on road trips, but the new one is more expensive than the Tesla Model Y or Rivian R2 when it comes to going from at least 10-80%. That's a big improvement. But the new bolt has one big catch.
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