The 2024 Chevy Equinox EV Tells Us A Lot About Why Voltage Issues

The Chevy Equinox EV is among the most necessary new autos in Common Motors’ lineup. Earlier than the reborn Bolt EUV arrives subsequent yr, this crossover would be the most cost-effective electrical car the automaker sells—and one of many most cost-effective lithium-ion-powered EVs on the market proper now, interval. What’s particular concerning the Equinox EV’s battery is the way it reveals off each the strengths and weaknesses of GM’s Ultium platform, particularly with regard to the modules it produces now. 

Briefly, it’s a monster for its vary and worth combo. However one tradeoff is voltage, and I’m about to dive into what which means for consumers.

The Equinox EV battery module is similar one present in each Ultium-based EV produced thus far. Its nominal voltage sits at round 28.8V, which is necessary. Even in bigger pack Ultium vehicles just like the 12-module Cadillac Lyriq, all of those teams of cells are wired in sequence, which means the pack voltage out of the terminals is totally depending on what number of modules are current. 

This implies the Equinox EV’s 85 kWh pack needed to lose voltage to attain the decrease capability essential to convey down the car worth. It has simply 10 modules, mounted within the ground of the car. This provides the automobile an 80S pack, which means a nominal voltage of 288V. So, the Equinox does probably not have a 400V structure; it’s extra like a 300V system. (As an fascinating facet observe, the Corvette E-Ray’s hybrid battery can also be 288V nominal, though not a lot of that pack’s true capability is getting used.) 

The Corvette E-Ray’s 80S pack, nestled into the car’s structural middle tunnel.

However what does this imply within the grand scheme of issues? Nicely, the Equinox EV can’t cost as quick because the bigger Blazer EV with its 102 kWh battery or the Lyriq; the Equinox EV maxes out at 150kW in comparison with these vehicles’ 190kW. Larger voltages are inclined to imply sooner cost speeds, and shedding voltage means a slower cost except the amperage, the opposite part of energy together with voltage, is introduced as much as compensate, which isn’t potential right here. 

Charging is all about voltage and present. Wattage is simply the 2 figures multiplied. A automobile that may cost at 50kW—50,000 watts—has some mixture of voltage and present to attain that determine. 

Forgive the technical rationalization under, however belief me after I say this may all make sense quickly. 

Particular person battery cells have a charged, nominal, and discharged voltage. For lithium-ion Nickel Manganese Cobalt (NMC) cells, it’s round 4.2V charged, 3.6V nominal, and a couple of.8V discharged. You’ll be able to take these cell limits barely greater or decrease, however it normally shortens the cell’s life. Some automakers cost their battery cells all the best way as much as 4.25V to chase that little bit of additional vary, for example. The brand new electrical Dodge Charger does this (if its spec sheet is correct.) GM doesn’t do that.

To cost a battery cell, you apply its charged voltage throughout the terminals at a sure present. If you need it to cost sooner, you apply extra present, however the voltage stays the identical. Cells have scores that let you know how a lot present may be utilized to them for the way lengthy. For those who exceed these limits, you enter the hazard zone. Cycle life may be decreased, cells could passively discharge a lot sooner than regular, and extra seen hassle like enlargement, smoking, or fireplace is feasible. The latter is unusual with out excessive abuse.

Battery pack voltage is set by how the cells are wired up internally. The Equinox has three parallel teams of 80 cells in sequence. This interprets into the automobile’s 288V nominal pack voltage (3.6V multiplied by 80). If we needed to cost it fully, we might apply 336V (4.2V multiplied by 80) throughout the pack’s terminals. Once more, GM doesn’t do that; it costs the automobile to a decrease voltage to boost cell longevity.

If we apply extra present the automobile can theoretically cost sooner, however we run into the aforementioned cell scores. Extra present means extra warmth which should be dissipated, and at a sure level the cells, pack cooling system, or each can’t deal with it.

So GM is aware of its charging voltage for the Equinox EV’s pack and the way a lot present the cells can absorb a steady cost. Say, for the sake of argument, that GM did cost the pack at 336V. If we put a measly 5 amps into the pack, it could cost at 1,680W (336V multiplied by 5). If we as an alternative put 400 amps into the system at this voltage, we might get 134,400W (134.4 kilowatts). That’s how cost charges work.

The Equinox pack’s three parallel teams increase the quantity of present that may be absorbed, however the automobile’s low voltage basically limits the facility that the pack can absorb. You would possibly perceive now why high-voltage architectures can cost a lot sooner. If we improve the voltage we don’t get practically as massive of a rise in warmth below charging and the mathematics tells us our wattage is now a lot greater if the present stays the identical. Extra kilowatts.

The essential Ultium battery module which underpins each GM electrical car as we speak, besides the Cadillac Celestiq

For this reason vehicles with 800V-nominal packs can sometimes cost at nearer to 350kW. Many Hyundai and Kia merchandise, the Lucid Air, and the Tesla Cybertruck, function natively at round 800V. The GMC Hummer EV operates its drive items at round 350V however can cost at round 800V by wiring the 2 halves of its large pack in sequence; that is referred to as a “break up pack setup.”

Decrease voltage additionally theoretically interprets into much less top-end efficiency, however this is a bit more difficult. You’ll be able to design a everlasting magnet motor’s windings in order that it spins at a sure velocity for a given voltage. This is named the motor’s kV ranking. kV is solely motor RPM per volt of enter. A 100kV motor will spin at 100 rpm when a single volt is utilized to it, 500 RPM at 5V, and so on. Electrical drive items have a discount gear to attain wheel speeds so you’ll be able to tailor all the system—motor, discount, voltage—to attain the precise compromise you need.

Electrical motor stators from GM’s Ultium drive items

For those who suppose the car will spend most of its time at excessive speeds, it’s your decision a decrease gear ratio to be able to have energy up high earlier than the motor runs out of steam. This can value you torque, although, which may solely be made up by including amperage, which is an entire can of worms.

The compromise was clearly made for a decrease vary of working speeds within the Equinox EV. Its entrance drive unit has an 11.59:1 ratio as in comparison with the RWD Lyriq/Blazer’s 11.63:1 (virtually an identical). If the motor KV ranking is comparable—which I sadly can solely assume—the top-end efficiency will undergo. 

In observe, this isn’t a lot of an assumption. Driving the FWD Equinox EV, we observed that above 75 mph it will get critically quick on energy. This phenomenon is a mixture of all of those elements.

On the flip facet of this, we are able to have a look at the AWD Cadillac Lyriq. Its entrance and rear drive items have ratios of 9.87:1 and 10.49:1, respectively. The Lyriq’s pack has a better voltage and two drive items, so the present dealing with functionality of the drivetrain is elevated. This implies extra torque, greater potential velocity, and higher energy. 

All of this results in an fascinating conundrum. GM will very probably be producing autos with lithium-ion NMC packs smaller than the Equinox—85 kWh is terribly huge for an automaker’s smallest battery—however in case you take away extra modules the voltage turns into very low. A 53kWh pack utilizing six normal Ultium modules interprets into simply ~172.8V nominal. That’s solely acceptable for one thing like a metropolis automobile; certainly, many small Chinese language EVs function on this vary and even decrease. (The usual Nissan Leaf has solely a 40 kWh battery, for instance.)

The one method round this downside is to make a brand new module or rewire the prevailing one. From the skin, it might look like GM has backed itself right into a nook right here. 

The format of the fundamental Ultium module may resolve this downside, although. Its configuration is 8S 3P for twenty-four cells complete, a pleasantly divisible quantity. It could possibly be rewired to a 12S 2P configuration which affords greater voltage per module. I’ve seen a chart laying out how GM could plan to do that, however I’m undecided how official it’s anymore.

The chart in query

With a hypothetical 12S module (roughly 43.2 volts nominal), a 53kWh pack with this new 72S configuration shouldn’t be 172.8V, however 259.2V, which is within the vary of current architectures.

I offered the aforementioned chart to one in every of GM’s representatives, however I used to be instructed this info was “outdated.” Automotive firms additionally dislike speculating on future merchandise they haven’t formally introduced. As such, I used to be instructed that, at the least proper now, “there aren’t any smaller or bigger modules.” 

Getting extra info on this entrance will in all probability be robust as a result of clarifying the existence of a higher-voltage Ultium module successfully pronounces that smaller EVs are in improvement, which we have no idea of past the up to date Bolt EUV.

So the Equinox EV tells us rather a lot about GM’s electrical technique and the way it plans to navigate numerous sizes and courses of autos. The automaker determined to commercialize its bigger EVs first and the modules that energy them.

The Equinox is the smallest EV to make use of these lower-voltage modules, which implies it was the corporate’s first small-ish Ultium EV to be launched. Going even smaller means altering the module by way of rewiring.

Within the case of the upcoming Ultium Bolt EUV, this may imply switching chemistries to lithium-iron-phosphate (LFP) for higher value financial savings. How the automaker plans to do that is but to be seen. It can probably want a brand new battery cell and module. The automaker refused to make clear these particulars at the moment. 

Producing each in quantity proper off the bat shall be troublesome, and with the Bolt EUV’s reveal date set for subsequent yr, the corporate is doubtlessly speeding to get the entire items in place.

[Correction 6/11/24 at 5:14 p.m.: This article originally stated that two of the vehicle’s 10 battery modules are mounted under the hood. That is incorrect, the entire battery pack is structurally integrated into the floor of the vehicle. We regret the error.]