What’s going on with the battery in the Chevy Equinox EV?

No one seems to be able to figure out how much capacity there is in the new Chevy Equinox EV and GM isn’t exactly helping.

We got our Chevrolet Equinox EV 2RS AWD a few weeks ago and have loved it so far. We haven’t done any long trips yet and have barely charged it, but I had noticed that it seemed to squeeze out more range than expected. Then recently, Tom Moloughney of the excellent StateOfCharge channel ran his similar FWD model in a 70 mph range test and it not only went further than expected, but seemed to pull far more than the 85 kWh of energy than GM claims it has. In his test, he saw usage of around 90 kWh. Since GM hasn’t yet responded and there’s a lot of interest and confusion, I took things into my own hands and bought a Bluetooth OBD2 scanner to check what the vehicle itself reports at 100%.

First up, I had to ensure that the battery monitoring system (BMS) is properly callibrated as our Equnox has only been charged once in it’s lifetime and never to 100%. After doing so, I hooked up the OBD2 scanner from Topdon and measured the high voltage battery stats to get the full data.

GM’s EVs all the way from the Equinox EV up to the Cadillac EscaladeIQ and GMC Hummer EV Pickup utilize a platform GM calls Ultium. The magic of Ultium is that it relies on a series (literally wired in series) of battery pack modules that can be sized appropriately for the class of vehicle and to tune range and power. The Hummer EV Pickup and Chevy Sierra EVs for example use 24 modules while the Equinox uses a mere 10. Because they are wired in series, the voltage of the battery pack itself is determined by the number of modules. Each battery cell has a nominal voltage of 3.6 V, and with 80 cells (8 per module, 10 modules), this means a nominal voltage of 288 V. This is unique as it’s a very low number for an EV. The issue is that power (whether it’s charging power or driving power to the motors) is determined by the voltage times the current (amperage). This explains why the Equinox EV requires a high amperage charger to reach even the relatively low peak charging rate of 150 kW (at about 300 volts, it needs a beefy 500 amps to hit 150 kW). The downside is that power losses increase linearly with voltage increases, but exponentially with current (due to the i^2r calculation), meaning it’s more wasteful than a car achieving 150 kW at something like 800 volts and 187.5 amps. This is also why the Equnox EV has a fairly low power output compared to other similar sized EVs, though adding a second motor as in the case of the AWD helps.

Per these numbers, the actual capacity of the Equinox EV (or any 10 module Ultium vehicle) should be about 89 kWH which is closer to what the range tests found. However, as was noted in these tests, the battery wasn’t run to completely empty, and the guess was that it might be closer to 100 kWh.

The data I pulled at 100% seems to confirm this.

At 100%, I see a High Voltage Battery Pack Voltage of 331.29V. The Total Battery Storage Capacity measured at 316.44 Ah (this didn’t change at 80% state of charge and appears to be the measured maximum). That compares to the 309 Ah that GM claims is the capacity of these battery cells in this configuration. That’s 7.44 more Ah than promised. This would mean that the Equinox EV has an actual total battery power storage of 104.833 kWh. Even if calculated at the 288V nominal rating, that would still be 91.134 kWh.

It’s unclear exactly why this discrepency exists. First, it might just be a mistake in GM’s materials. GM doesn’t specifically publish the gross versus usable ranges of the batteries in the Equinox EV, so it could be that they are leaving more room to play with the buffers in future software updates of vehicle production. It could also be a case of under-promise and over-deliver. If GM promises less usable capacity, that’s better than saying there is more and having a potential law suit if people get less. GM probably also realizes that the customers of the Equinox EV care less about battery capacity and more about the range which is why they focus on the range in all their marketing. It could also be for warranty purposes. If GM says that the battery has less actual capacity, when the batteries degrade over time, it will appear that they actually lost less capacity so they may have to deal with fewer warranty claims. These numbers don’t tell the whole story either as it’s not clear all together how much is usable and how much of a buffer this is above the true 0% SoC. Interestingly, the OBD2 data shows that my vehicle is still at a measure 96% SoC even after fully charging it and allowing it to pull as much energy as possible.

All of this said, I’m not an expert in this area, so please let me know if I got any details wrong or there is other data you’d be interested in.

I’ll definitely do a full range test in the future to measure this data against the real world, so make sure you’re subscribed to the channel.