Chevrolet Bolt EV Traction Motor – Deep Dive: Video


Class is in session.

If you have ever been curious about the drive unit that puts the Chevy Bolt in motion, well, wonder no more. Located under the hood of the car, this component actually contains an electric motor, gears, and some other components — including two smaller electric motors — needed to make the wheels of the car turn. In the video above, Professor John Kelly of Weber State University (WSU) takes the block apart for our enjoyment and edification.

Now, you may be thinking this just might be the most boring idea for a video ever. If so, you’d be wrong. Although it can, admittedly, be a bit dry here and there, you’ll quite possibly find yourself totally drawn in after the first couple of minutes. Sure, there are no car chases, sight gags, or other gimmicks. But, there is a certain beguiling quality to the simple act of discovery and learning that can mysteriously keep you engaged. The WeberAuto YouTube channel didn’t manage to attract over 100,000 subscribers by accident.

Before the disassembly action begins, Professor Kelly discusses the motor and some of its performance parameters in relation to the unit in the Bowtie brand’s previous all-electric, the Spark EV. The Bolt’s motor produces less torque, has a lower peak amperage draw, and a higher RPM. Yet, we’re informed, it actually offers more torque and is a more efficient design.

The professor then takes us on a complete tour of the unit’s exterior, explaining all the various parts and pieces that are visible from the outside. With everything clearly labeled, the learning experience begins.

If you enjoyed this video, we would encourage you to take a look back at another recent video from Professor Kelly in which he teaches us all about the in and outs of the Bolt’s battery coolant system. While at first blush it may not sound especially interesting, but we suspect, as with the video here, once you get started you’ll be fascinated. Enjoy!

Source: YouTube

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28 Comments on "Chevrolet Bolt EV Traction Motor – Deep Dive: Video"

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Hat tip to GM EV Engineerinyg Team… very elegant design work on Bolt traction motor!

Too bad GM and Chevy dealer franchise network not more supportive of promoting and selling EV in volume. Hopefully that changes over time.

I thought LG did all the work?

GM designed the motor and inverters according to info from a while back

@David said: “I thought LG did all the work?”

GM designed the Bolt’s electric traction motor which LG factory builds for GM per GM’s design specifications.

LG also builds other Bolt parts some of which are designed by GM, some designed by LG, and some collaboration design GM & LG.


Yeah, here this ‘Gear Motor’ assembly is planned to be used in several vehicles. And then we have someone like Mary Barra at the Helm who will probably discontinue everything.

Mary Barra being electrical engineer, she probably wants to see EV come to fruition. Can’t say the same for the board, but if they have any sense, they’ll let Mary do her thing.

A straight line in terms of evolution from original Volt/Spark/Bolt. The story of the Volt was one of being an independent program free from interference of other GM divisions and engineering. I doubt that changes.

The point being the simplicity of manufacturing as demonstrated by the teardown. Battery technology and cost is likely to evolve to new and better materials.

You had me 😂

Yeah, so is Pamala Fletcher supposedly – with her “Reactionary Forces” (that make all the other engineers in the room cringe).

Thanks Prof, very informative, thanks much!

That motor is a work of art!

It is the Remy design, a good one.

Great! I’ve always marveled at the ‘beefiness’ of the exploded diagrams of this thing, but the drive pinion connecting to the Jack-Shaft (what he calls the ‘counter gear’, and the even larger output stage (the ‘low speed’ side of things – is even beefier as you’d expect)).

The Shaft-Encoder also seems quite solidly mounted (what he calls the ‘resolver’). Since the oil is kept at a relatively low temperature by the ‘water cooler’, this unit should be easily good for several hundred thousands of miles – especially since it is so ‘BUILT’ for only 200 hp.

It definitely looks impressive. I wonder what the cost and weight are compared to a standard engine/transmission. Certainly this piece of the pie is much lower cost. One of the factories shuttering in the big GM move makes transmissions. Think about the incredible impact on the entire supply chain of engines and transmissions. Holy cow. Also mentioned is that this will be the new Chevy ‘small block’. How long did that block go essentially unchanged? 50 years? And used nearly universally. Obviously that’s what Tesla is doing with the model 3 motor too. Want a powerful pickup truck? Fine. Just put one on every corner. AWD SUV? Sure. One in front, one in rear. Repairs can become almost like changing starters or alternators. Don’t bother tearing it apart. Just swap it out and have 20 rebuilt copies in stock. Then later have it rebuilt/recertified. I wonder how fast you can swap one of these out? Also he does a great job explaining final drive ratio and torque. Very seldom is that given any space and usually just ‘more is better’.

John Kelly’s videos are among the best about mechanics and cars found on YouTube.

Interested to see it does have an ATF filter after all, since Model 3 has a canister one the outside of the case.

With the relaxed duty those helical gears will see, I don’t think you’ll have to filter out many chips or broken teeth.

So when’s Quaiffe going to make a limited slip diff for that!

SparkEV was better

Right. That’s probably why they stopped selling it.

Bolt EV more torque to the wheels, more power with less amperage. Much more efficient design.

It’s not clear if Bolt motor is more efficient. SparkEV tops out about half the RPM of Bolt. Looking at torque curve, it looks like voltage limited. If the voltage is doubled to spin at Bolt motor RPM, SparkEV motor would produce about 280 HP.

But SparkEV motor being so torquey, it spins about half the RPM of Bolt at same speed. Lower RPM when all else being equal means more efficient. But there are other losses and the video did not cover SparkEV motor to make comparison.

Yes the video covers it. He clearly explained by the Bolt delivers more torque and is more efficient.

This guy’s videos are the freaking best, can’t stop watching.

And he is in a wheelchair? Wow.

I especially liked the minimalist oil cooling system. The glycol/oil “heat exchanger” is just the external surface of the oil-sump in the main cast-aluminum housing, with pre-cast baffles and heat exchange fins. One glycol pipe in, one glycol pipe out, and a bolt-on cover. No other parts to assemble or buy. If we are scoring GM vs Tesla for elegant engineering simplicity, this is a +1 for GM. The Model 3 has an external brazed-plate oil/glycol heat exchanger.

I like the comments about the six deep copper hairpin conductors in the stator to improve high speed efficiency. This is probably why despite the higher Cd of the Bolt EV it still gets pretty good highway efficiency. I look forward to seeing this motor design in many more GM EV’s.