What is a split-pack battery for electric vehicles?

EVs have split batteries to increase charging compatibility and eliminate the need for a voltage booster.

Split battery pack Split battery pack

All electric vehicles have large battery packs that can hold tens of kilowatt hours of electricity, which are needed to power their powerful traction motors for hundreds of miles. However, in some EVs the battery pack is not one-piece and can be split into two or more battery arrays, usually to facilitate charging at a specific voltage.

This applies to the GMC Hummer EV and the Tesla Cybertruck, whose split battery packs make it possible to charge at 400 or 800 volts respectively. In both cases, the individual battery modules can operate in series or parallel, giving the vehicles more flexibility.

The GMC Hummer EV, which operates at approximately 400 volts in normal use, has a battery pack consisting of 24 separate battery modules with a combined gross capacity of 246 kWh, of which 212 kWh is the usable capacity. It weighs about 5,000 pounds, about as much as a compact car, and if you’ve ever seen a photo or a crop of it, you’ve probably noticed that it’s unusually long.

That’s because the two parts of the package are actually stacked on top of each other: twelve modules on top and twelve modules on the bottom. Everything is wrapped in a stamped steel housing that’s welded, and GM says that’s one of the reasons it took this approach (unlike, say, Ford, whose F-150 Lightning battery packs are made of lighter aluminum and composite materials) was to improve the structural rigidity of the vehicle.

According to GM, having a battery pack that thick with a solid steel shell makes the Hummer EV stiff enough to allow removal of the roof panels without compromising torsional rigidity.

Even though the GMC Hummer EV is a 400-volt EV, the split pack is specifically designed to be able to switch to 800 volts while charging. This allows the vehicle to charge its massive battery up to 350 kW via a suitably powerful Level 3 DC fast charger that supports 800 volts, or it can remain at 400 volts if plugged into a lower voltage station.

In normal use, the individual packs of the electric Hummer are connected in parallel and supply 400 volts. When the vehicle senses it is connected to a compatible charger capable of delivering 800 volts, it connects the two separate modules in series, doubling the voltage. When charging at 800 volts, the range can be replenished by up to 160 kilometers every 12 minutes, which is an impressive feat considering how many kilowatt hours that amounts to (more than 60 kWh).

The Tesla Cybertruck takes a similar split-pack approach to the GMC Hummer EV, but in reverse. The battery pack, which is also structural and has a capacity of just over 122 kWh in Cyberbeast trim with three motors, is split into four separate 200-volt modules. In normal use, they are connected in series, as the Cybertruck is the first 800-volt Tesla EV (with a rated operating voltage of 816 volts, to be precise).

Thanks to the double voltage of all previous Teslas, the Cybertruck can charge significantly faster, with a maximum charging speed of 350 kW. However, this is only possible if you connect it to a V4 Tesla Supercharger, which is designed to support 800-volt electric vehicles. If you connect a Cybertruck to a V3 or older Supercharger, it will only charge at 400 volts and will not reach the charging speed of approximately 250 kW.

By having multiple battery modules, Tesla will also be able to increase the voltage of the Cybertruck 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 to other vehicles, and the Cybertruck seems like the perfect candidate.

A major reason why both the Cybertruck and 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 connects its two battery modules together when it detects it’s plugged into an 800 volt charger.

Another vehicle that does it similarly to the Tesla Cybertruck, although the 800-volt battery is divided into two segments, not four, is the new 800-volt Porsche Macan EV. This makes it compatible with 400-volt charging stations, although the maximum charging power of 270 kW at 800 volts is halved and therefore does not exceed 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 electric vehicles come to market, as they will need to work with both 400 and 800-volt charging stations .

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