The Chevrolet Silverado EV Has One Of The Biggest Batteries Ever. Here's How It Works

You need a big battery to make a naturally inefficient class of vehicle, like a pickup, work as an EV. Ford, Rivian, and Tesla all have packs larger than 100 kilowatt-hours to give their respective trucks the range, payload, and towing capacity necessary to compete in the realm of their internal combustion counterparts. The new Chevrolet Silverado EV wants to beat them, and it’s doing so not with extreme efficiency—a considerable challenge considering the class of vehicle—but with a heck of a lot of battery under the floor. 

General Motors has been somewhat cagey about stating the capacity of this monster pack used in the long-range versions of its full-sized electric pickups and the top-trim Hummer EV. But because of an extensive conversation with one of the Ultium platform’s chief architects, Jerry Beemer, we can extrapolate its exact capacity, voltage, and other interesting things about it. 

I feel like this pack needs a name. I have been calling it the Acid Mattress, but that concept doesn’t seem to really apply to lithium-ion batteries. It’s definitely as big as a mattress, and just like what we sleep on, it’s a pain in the ass to move. Maybe just Lithium Mattress will work. (InsideEVs editor Patrick George called it a “big ol’ beef boy of a battery,” but we can stick with my bedding metaphor instead.)

GM’s lithium mattress, which sits under the floor of all of its full-size EV trucks, is the only pack configuration the automaker has so far that wires modules in parallel. In cars like the Cadillac Lyriq or Chevy Equinox EV, the Ultium building blocks are all wired in series, meaning the voltage out of the pack’s terminals is entirely dependent on how many modules you have. 

A single module from GM’s Ultium battery system, which contains 24 slender pouch cells

This is not the case in the Silverado EV RST. GM’s Ultium inverters operate at around 350V nominal or less, meaning that adding more than 12 modules will require some parallel wiring between them. The higher available current means more potential torque while driving, but also much faster charging when the two pack halves are wired in series.

That’s one of the most interesting features of the Silverado EV’s big battery: Its ability to charge at ~800 volts despite running on ~400 volts, thanks to a “split back” battery design. Internet commenters everywhere take issue with GM’s low drive voltages—just don’t mention many Teslas are still operating slightly lower, even the new 4680 cars—but the big advantage to high-voltage architectures is charging, and the mattress battery enables that.

The two halves of the pack can be series-wired when the car is connected to a capable charger, which enables faster charging speeds. The Tesla Cybertruck does this in reverse for lower voltage chargers, as it’s an 800V-native architecture.

The Silverado EV can, at least theoretically, charge even faster than its 350 kW rating. If we extrapolate how quickly we know the Cadillac Lyriq with half the battery (but still the same cells and modules) can charge—up to 190kW—we can reasonably assume that if there was a high enough current charger to support it, mattress-equipped full-size GM EVs could juice up as fast as 380 kW.

The automaker won’t reveal the actual charging buffer on each cell, i.e. their peak charge voltage in practice, so we can’t calculate the exact current that would be required. It’s a lot, though. Even at around 800V peak, it’s over 400 amps continuous. What we have seen in other testing is that the Silverado EV is a high-speed charging monster, but we’re eager to see how it holds up in wider use.

As a short aside, I want to mention an advantage of doing a bi-voltage pack like GM does here. Hyundai’s 800V E-GMP architecture rightfully gets credit for its innovative features, but that platform requires a boost converter to get power from lower-voltage chargers. It actually uses the motor windings themselves as a giant inductor as a part of this system, which means the motor appears to have four phases. GM’s system of using contactors (high power relays) to obtain higher/lower charging voltages seems a lot more elegant from a number of perspectives, as smart as Hyundai’s solution is. As I previously mentioned, Tesla does effectively the same thing as GM in the Cybertruck.

In any case, we can deduce a theoretical burst charging figure for the Silverado EV, better known as a peak regenerative braking number, based on the Lyriq’s battery performance. An AWD Lyriq can regen as hard as 240kW. Could an electric Silverado theoretically absorb up to 480kW from the road? I only observed around 220kW, for the record. I wonder how many kilowatts it would take to lock up all four wheels. 

Having this much energy enables all sorts of cool stuff like endless vehicle-to-load possibilities, especially if the truck is tied in with something like a solar array. In hindsight, these massive packs will seem ridiculous, but they’ll probably be a grand slam for people looking to live off-grid. Heck, even just having one of these things up on blocks in your backyard would be a viable way to store energy for your whole home. With a bed cap on a Silverado EV and the midgate down, you’re basically looking at an all-electric sleeper cab.

Motor1 editor Peter Holderith takes a break from testing gas-powered cars every now and then to geek out on the latest battery tech, including for his own project cars. Got a battery you want him to dive into? Contact the author: peter.holderith@motor1.com