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As Volvo goes electric, here’s how it’s making its batteries top-notch


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As Volvo goes electric, here’s how it’s making its batteries top-notch

How do you make sure a lithium-ion battery pack can last the lifetime of a car?


Electric cars are becoming much more important to automakers, and that means those companies are having to learn how to get good with batteries. That was baked into Tesla from day one, but for existing automakers, batteries have to become a new core competency. Recently, Volvo opened its doors in Gothenburg, Sweden, to show us how that's happening, ahead of the launch later this year of its new battery EV, the XC40 Recharge.


Volvo was an early advocate for going electric, announcing a plan for its model range shortly after it told us that it was ending development on diesel engines. That plan calls for 50 percent of its sales to be BEVs by 2025, but actually implementing that plan is more involved than just holding a press conference, and it's a transformation that affects the entire company. Engineers are being retrained to work with electric motors instead of internal combustion engines. Supply lines and purchasing have to get to grips with responsibly sourcing a new range of materials. The carmaker even has to think about what its new EVs should sound like.

Volvos have to be safe

Volvo has built its reputation on safety, and obviously the move to electric powertrains can't be allowed to compromise that.


"You may think that it's an advantage to have something smaller like an electrical motor compared to a combustion engine in the front [of the vehicle]. But the way that we design for frontal crashes, taking into consideration the real world accidents where you have angles, different speeds, different offsets, the engine itself is actually part of the system to help distribute the loads," explained Thomas Broberg, one of Volvo's senior technical advisers for safety.


Consequently, don't expect a voluminous Tesla-style cargo frunk between the front wheels of an electric XC40. While there is a storage space under the hood, underneath that (and below the inverter and control electronics for the front motor) is a large steel crash structure that distributes frontal impact loads away from the car's occupants in the same way Volvo's internal combustion engines are designed to do.


The battery pack, like just about every EV since General Motors' AUTOnomy concept of 2002, lives between the front and rear axles, and it contributes significantly to the car's structural rigidity and crashworthiness. One doesn't envy the engineers, for the pack has to satisfy two potentially competing demands. Obviously a collision can't compromise the integrity of the pack itself, because lithium-ion cells don't react well to being short-circuited. But equally, you can't design an indestructible pack unless you want the vehicle occupants to absorb all the kinetic energy of a crash instead.

It’s building its own battery packs

But Volvo's electrification isn't starting at day one with the XC40 Recharge. There was a very short-lived electric version of the diminutive C30 hatchback, and of course there have been plug-in hybrid versions of its larger 90 and 60 series vehicles since the Scalable Product Architecture first debuted with the XC90 SUV back in 2015. But that old BEV and even the newer PHEVs all required bought-in batteries. For the XC40 onwards, Volvo decided to bring battery-pack production in-house.


"Up until now, we have bought complete battery systems," said Ulrik Persson, who leads traction-battery development at Volvo. For the current PHEVs, that supplier was LG Chem, which designed the battery packs according to requirements it got from the carmaker. "Starting with the BEV, it's a whole different ballgame," Persson told us. "Of course, it's possible to outsource that as well, working very closely with the supplier, but from our side we felt it was a strategic decision to take ownership of this new component. It's definitely the most expensive component in the vehicle, and as it's integral to the crash structure of the vehicle it really makes sense."


That means there's no shared components or cells between the 10.4kWh pack in a Volvo PHEV and the 78kWh pack that will power the XC40 Recharge (as well as the Polestar 2). For European and US XC40s, those packs will use LG Chem pouch cells, but China-bound BEVs will contain prismatic cells courtesy of CATL.

On the left, a module made up of lithium-ion pouch cells. In the middle, the blue thing is a prismatic lithium-ion cell, and to the right is a single pouch cell lying flat.
Enlarge / On the left, a module made up of lithium-ion pouch cells. In the middle, the blue thing is a prismatic lithium-ion cell, and to the right is a single pouch cell lying flat.

The rapid pace of technology development has led to changes in procurement. "You want a car to be refreshed on a constant basis, and especially with your software part, and even on the hardware. You want this to be more flexible," said Martina Buchhauser, head of Procurement at Volvo. "We haven't set up 10-year contracts anymore. It's a maximum three years, and then see how we can re-source and refresh," Buchhauser told Ars. Her team's job even includes ensuring that the company's commitment to CO2 reduction extends throughout Volvo's supply chain, as well as making sure that raw materials like cobalt are mined responsibly and without the use of child labor. "We've made it very clear to our suppliers that this is part of our sourcing process and part of our business, as important as technology, cost, and quality," she said.

Testing cells for up to two years

The rapid pace of development applies equally to software—just witness how many more miles Tesla can eke out of a kilowatt-hour today compared to a few years ago. Persson confirmed that Volvo will use the same approach of collecting real-world data and using it to roll out improvements via over-the-air updates. Well before that stage, his team engages in extensive testing of battery tech at the factory, using Volvo's new $60 million in-house battery testing lab.


"You could ask 'Is this investment really necessary—couldn't you just go out and buy the service?'" Persson told us. "But if you look at the market, all the labs in Europe are full—there is no capacity. And if you start testing [batteries] on that level, it is quite complex, and we want to have that in-house. We want to get the knowledge out of doing that—within our team.


"The trick with automotive batteries is that they need to last the lifetime of the vehicle. That's quite a difficult task, and in order to master that, we need to really focus on durability testing, and it starts on the cell level. Testing the cells in different temperatures, different currents, different types of cycles," Persson said. Much of that testing occurs in large temperature-controlled chambers that let Persson's engineers run tests that can last for months or even years, charging and discharging the lithium-ion cells repeatedly to mimic life on the road in a range of environments.


"The challenge is really that, every second or third year, we get offered upgraded chemistry," Persson told me, either for cheaper cells or ones with better energy density. "So you have to go in and redo the testing again and again and again, and some of the tests run for up to two years. The really long durability test is an accelerated test simulating 10 to 15 years." Beyond testing cells, Persson's group also has to run similar tests on complete battery packs.


"You have your cells going into modules, and the modules sit on the cooling system," Persson said. "You interconnect the modules with copper or aluminum busbars, and then you have the software control system with slaves. So you monitor each and every cell. You have a high-voltage disconnect unit so you have relays to open or close the circuit, and you have your fuses. So when we are at system level, then again cooling becomes of high interest to understand early on the distribution of heat in the pack—you want to have a uniform distribution. You need to understand this in a very good and controlled way; the narrower the delta between temperatures in different cells, the better the design, then it's easier to control and get the right durability," he explained.


Listing image by Volvo



Source: As Volvo goes electric, here’s how it’s making its batteries top-notch (Ars Technica)  


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