All electric vehicles have big battery packs that can hold dozens of kilowatt hours of electricity, which are required to power their powerful traction motors for hundreds of miles. For some EVs, though, the battery pack isn’t a single unit, and it can be split into two or more battery arrays, usually to facilitate charging at a certain voltage.

This applies to the GMC Hummer EV and the Tesla Cybertruck, whose split battery packs allow them to charge at 400 or 800 volts, respectively. In both cases, the separate battery modules can operate either in series or in parallel, and they grant the vehicles more flexibility.

The GMC Hummer EV, which under normal operation runs at about 400 volts, has a battery pack made up of 24 individual battery modules with a combined gross capacity of 246 kWh, of which 212 kWh is its usable capacity. It weighs around 2,800 pounds, about as much as a compact car, and if you’ve ever seen a photo or a cutaway of one, you probably noticed that it’s unusually tall.

2022 GMC Hummer EV's Ultium battery pack

That’s because the two parts of the pack are actually stacked on top of one another—12 modules on top and 12 on the bottom. Everything is encased in a stamped steel case that is welded, and GM says one of the reasons it opted for this approach (as opposed to Ford, for instance, whose F-150 Lightning battery pack cases are made out of lighter aluminum and composite materials) was to improve the vehicle’s structural rigidity.

According to GM, having a battery pack this thick with a solid steel shell is what makes the Hummer EV stiff enough to make removing the roof panels possible without compromising its torsional rigidity.

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Even though the GMC Hummer EV is a 400-volt EV, its split pack has been specifically designed to allow it to switch to 800 volts while charging. This enables the vehicle to replenish its huge battery at up to 350 kW from a powerful enough Level 3 DC fast charger that supports 800 volts, or it can stay at 400 volts when plugging into a lower-voltage station.

Under normal operation, the electric Hummer’s separate packs are linked in parallel and provide 400 volts. When the vehicle detects it’s been hooked up to a compatible charger capable of delivering 800 volts, it links the two separate modules in series, thus doubling its voltage. When charging at 800 volts, it can replenish range at a rate of up to 100 miles every 12 minutes, which is an impressive feat given how many kilowatt hours that amounts to (over 60 kWh).

Tesla Cybertruck

The Tesla Cybertruck adopts a similar split-pack approach to the GMC Hummer EV but in reverse. Its battery pack, which is also structural and has a capacity of a little over 122 kWh in tri-motor Cyberbeast trim, is split into four separate 200-volt modules. They are hooked up in series under normal operation since the Cybertruck is the first 800-volt Tesla EV (with a nominal operating voltage of 816 volts, to be precise).

Having double the voltage of any previous Tesla allows the Cybertruck to charge considerably faster, with a maximum charging speed of 350 kW. However, this is only possible if you plug it into a V4 Tesla Supercharger, which has been designed to support 800-volt EVs. If you plug a Cybertruck into a V3 or older Supercharger, then it will only charge at 400 volts, and it won’t exceed a charging speed of about 250 kW.

By having multiple battery modules, Tesla will also be able to increase the Cybertruck’s voltage in the future. The EV manufacturer has confirmed that the 1,000-volt architecture it currently only uses in the Semi truck will make its way into other vehicles, and the Cybertruck seems like the perfect candidate.

One big reason why both the Cybertruck and the Hummer EV have this split pack design is to negate the need for a DC-to-DC converter or voltage booster to change the voltage depending on what is needed—eliminating this converter saves cost and weight. So the Tesla runs at a virtual 400 volts when charging from anything other than a V4 Supercharger, while the GMC links its two battery modules together when it detects that it’s been plugged into an 800-volt charger.

2024 Porsche Macan EV

Another vehicle that does it the same way as the Tesla Cybertruck, although it separates its 800-volt battery into two segments, not four, is the new 800-volt Porsche Macan EV. This enables it to be compatible with 400-volt charging stations, although its maximum charging rate of 270 kW at 800 volts will be halved, so it won’t go any higher than 135 kW.

Ford also has a patent for an 800-volt EV architecture that appears to split the battery pack into two or more arrays.

This approach of splitting an EV’s battery pack into two or more large modules to facilitate charging compatibility will become more popular as more 800-volt EVs are launched since they will need to work with both 400- and 800-volt charging stations.

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