Ask HN: What technologies made the electric car practical?
Electric cars have existed for over a century.
What technologies made the electric car "practical". For the sake of discussion, I am going to define "practical" here as having a range of at least 200km.
I can think of 2:
1. The insulated gate bipolar transistor. This allowed the creation of AC induction motors, which offer less friction and are thus more efficient than traditional DC motors.
2. The Lithium Ion battery.
What other technologies am I missing?
12 comments
> This allowed the creation of AC induction motors, which offer less friction and are thus more efficient than traditional DC motors.
AC induction motors were not created for the modern electric car. The squirrel cage induction motor is the standard motor design used in most every AC motor.
It's not that DC motors have more friction, the issue is electrical losses and maintenance of the commutator. The commutator both transmits current to the armature (spinning part) and acts as a mechanical switch to continually energize the next set of coils maintaining a magnetic chasing effect which causes the armature to spin.
The brushes are made from carbon or graphite and stay in contact with the spinning commutator via a spring so they both wear out and wear down the commutator bars and the springs can wear too. Any dirt or contamination on the commutator will cause arcing which can cause rapid destruction of the commutator. Worn brushes and/or bad springs cause poor contact leading to destructive arcing. Worn brushes and commutators create dust that can cause other problems. They are very maintenance intensive.
Since the the commutator uses carbon or graphite brushes to transmit current to the commutator bars there is a voltage drop through the brush as carbon and graphite aren't great conductors but have awesome lubricity when paired with metals. This voltage drop can be as high as 2 volts and that power is lost as heat. Heat generated by brushes places an upper limit on how large commutated machinery can grow as the power lost through the commutator will grow beyond what can be dissipated by normal air cooled convection. This limit is something like 2-3 megawatts.
An AC induction or permanent magnet induction (dc brush-less) motors have no need to transmit current to the armature so they avoid all these pitfalls.
AC induction motors were not created for the modern electric car. The squirrel cage induction motor is the standard motor design used in most every AC motor.
It's not that DC motors have more friction, the issue is electrical losses and maintenance of the commutator. The commutator both transmits current to the armature (spinning part) and acts as a mechanical switch to continually energize the next set of coils maintaining a magnetic chasing effect which causes the armature to spin.
The brushes are made from carbon or graphite and stay in contact with the spinning commutator via a spring so they both wear out and wear down the commutator bars and the springs can wear too. Any dirt or contamination on the commutator will cause arcing which can cause rapid destruction of the commutator. Worn brushes and/or bad springs cause poor contact leading to destructive arcing. Worn brushes and commutators create dust that can cause other problems. They are very maintenance intensive.
Since the the commutator uses carbon or graphite brushes to transmit current to the commutator bars there is a voltage drop through the brush as carbon and graphite aren't great conductors but have awesome lubricity when paired with metals. This voltage drop can be as high as 2 volts and that power is lost as heat. Heat generated by brushes places an upper limit on how large commutated machinery can grow as the power lost through the commutator will grow beyond what can be dissipated by normal air cooled convection. This limit is something like 2-3 megawatts.
An AC induction or permanent magnet induction (dc brush-less) motors have no need to transmit current to the armature so they avoid all these pitfalls.
It might be worth thinking about where there were successful electric vehicles before cars. All the scenarios I can think of are times the vehicle purchaser is willing to deal with charging infrastructure in return for the benefits.
Milk floats were quiet and didn't need to haul heavy loads, which was convenient for early morning deliveries. Distribution point/dairy can be the charge point.
Golf karts/utility vehicles. Never stray far from their chargers. Being quiet makes them more comfortable.
Forklifts are majority electric, and that was before lithium. Cheaper to run than fuel equivalents. They're still majority Lead Acid. A lead acid battery is heavy (a positive for a forklift) and lasts a shift before charging cheaply at overnight rates or swapping out the battery if there's another shift needing to use it. Lack of combustion fumes for an indoor warehouse or factory is real nice.
On technology specifically, range is next to useless if you can't tell how much you've left. I understand that tracking energy in and out the battery to a high level is not easy for a BMS - sample at the wrong rate and the potential error in over/underestimating range is quite large.
Milk floats were quiet and didn't need to haul heavy loads, which was convenient for early morning deliveries. Distribution point/dairy can be the charge point.
Golf karts/utility vehicles. Never stray far from their chargers. Being quiet makes them more comfortable.
Forklifts are majority electric, and that was before lithium. Cheaper to run than fuel equivalents. They're still majority Lead Acid. A lead acid battery is heavy (a positive for a forklift) and lasts a shift before charging cheaply at overnight rates or swapping out the battery if there's another shift needing to use it. Lack of combustion fumes for an indoor warehouse or factory is real nice.
On technology specifically, range is next to useless if you can't tell how much you've left. I understand that tracking energy in and out the battery to a high level is not easy for a BMS - sample at the wrong rate and the potential error in over/underestimating range is quite large.
Eons ago I've driven one such forklift through a high rack warehouse for a year. It had 2 batteries, weighing about 4 metric tons each (Lead-Sulfuric acid). They made it about 4 hours (half shift), then had to be exchanged with another forklift at the loading station. Always had to check for levels of sulfuric acid, watch out for oxyhydrogen/electrolytic gas, and whatnot else. But was fun to ride, because up to 35kph on the ground for the whole 12 metric tons, wobbly cabin/platform at 12meters up, and deadly fast fork. So...very niche, I guess?
Another thing similar to milk floats comes to mind from the time the railways used to deliver post and packets. Those things always trundled along the platforms, to where the post/baggage car would be. Sometimes with several small trailers.
Another thing similar to milk floats comes to mind from the time the railways used to deliver post and packets. Those things always trundled along the platforms, to where the post/baggage car would be. Sometimes with several small trailers.
Well, percent state of charge (how full the battery pack is) is not so hard to calculate, you just have a look up table for battery voltage vs %SOC. Although you may need to calibrate for the voltage drop caused by the internal resistance of the battery cells. The hard part is converting that into a "miles remaining" estimate, which requires a good estimation of how many kWh your vehicle uses per mile. I think some manufacturers even link this into the GPS and take into account the elevation change on the route you selected.
High power motor controllers have been made with plain old BJTs, as well as thyristors and FETs. So I don't think IGBT's are an enabling item for EVs. Would it save $100 in gate-drive/base-drive circuitry? Also you could use induction motors, synchronous motors, and DC motors, and the friction would be a very small loss mechanism, so I don't think there is any enabler here either. DC motors might have an extra maintenance step by replacing the carbon brushes every once in a while, but even then, for the low number of hours a car runs, you might never need to replace brushes. I think it is mostly like the real estate motto: batteries, batteries, batteries.
SCR's were the beasts of burden for DC motor control using phase angle firing when fed off AC. You can even use them in DC systems, e.g. rail traction motor control using forced commutation. SCR's once triggered don't turn off until the conducted current drops below the turn-on threshold so you wire a circuit across it using one or two more smaller scr's to apply a pulse of reverse flow current across it to force it off. Way slower switching times than IGBT mind you.
I don't think the "practical" was a problem of technology but of economy.
It's really interesting to read some very early accounts of cars. EVs were the original "practical" and "reliable". The earliest accounts of range anxiety were from ICE owners. EVs had a predictable range and you could charge just about anywhere with electricity. ICE were loud and impractical and unreliable (especially accounting for how much they were prone to breakdowns or worse explosions) and you couldn't just get more fuel at any corner drug store, it had to be very specific corner drug stores of which there were very few.
From the long view of history, it may turn out that we'll look back on the epoch of "reliable" and "practical" ICE as the anomaly of a curious economic over-investment in baroque infrastructure, at best. (At worst, given what we've known about climate change for too many centuries now, it may be looked back upon as criminal and deceitful.)
It's really interesting to read some very early accounts of cars. EVs were the original "practical" and "reliable". The earliest accounts of range anxiety were from ICE owners. EVs had a predictable range and you could charge just about anywhere with electricity. ICE were loud and impractical and unreliable (especially accounting for how much they were prone to breakdowns or worse explosions) and you couldn't just get more fuel at any corner drug store, it had to be very specific corner drug stores of which there were very few.
From the long view of history, it may turn out that we'll look back on the epoch of "reliable" and "practical" ICE as the anomaly of a curious economic over-investment in baroque infrastructure, at best. (At worst, given what we've known about climate change for too many centuries now, it may be looked back upon as criminal and deceitful.)
Good points, this makes me think of the tradeoffs between AC and DC electricity and how DC has many advantages despite AC being more "common" with infrastructure
Not too familiar with electric motors personally but would assume a lot of it is battery technology (both chemistry and manufacturing).
My parents converted a Honda to electric in the 80s (cool!) but mentioned it was not practical for regular daily use because of the tremendous weight (assume it was all from lead) and low range (would assume dozens of miles). Charging doesn't seem too easy (on the go) either. But they had other friends who seemingly used their also-converted EVs quite extensively locally.
Maybe it was always "practical" for folks who wanted to endure but that's different than a mass-produced off-the-shelf Unit.
My parents converted a Honda to electric in the 80s (cool!) but mentioned it was not practical for regular daily use because of the tremendous weight (assume it was all from lead) and low range (would assume dozens of miles). Charging doesn't seem too easy (on the go) either. But they had other friends who seemingly used their also-converted EVs quite extensively locally.
Maybe it was always "practical" for folks who wanted to endure but that's different than a mass-produced off-the-shelf Unit.
Besides the lithium ion battery issue, were they really that "impractical" before? Or was there just not anyone making ones that people wanted to buy...? Charging station availability as well?
Caring about the environment just wasn't an issue back then.
Tesla (Nikola, not the car company) made induction motors over 100 years ago. They have nothing to do with IGBT's, which have been around for over 20 years themselves.
Basically it was increased battery life/power to weight ratio and the development of easy charging. The impetus was really more of a technology application than an underlying technology itself.
Basically it was increased battery life/power to weight ratio and the development of easy charging. The impetus was really more of a technology application than an underlying technology itself.
It's not just the lithium battery, it's the ability to make it at scale fairly cheaply, and the ability to recharge it hundreds of times. We basically needed hybrid cars to happen first to build up battery demand and bring down costs and encourage research.
And then, from an adoption perspective, you needed to make them accelerate faster than gas cars. Prior efforts failed from lack of demand because the cars were (perceived as) extremely slow.
Are you talking about the pre-model T ones ? (But then the first Porsche was electric and overwhelmingly won a race ??)
The 1996 GM EV1 already had a fan following thanks to it's high acceleration.
The 1996 GM EV1 already had a fan following thanks to it's high acceleration.
I was thinking of the GM EV1. It went 0 to 60 in 7.7 seconds[1], which is slightly slower than a 1996 Ford Taurus SHO [2]. A modern BMW 328 is 5.3 seconds. The original Tesla roadster was 4.6.
1 https://www.motortrend.com/features/1997-gm-ev1/
2 https://www.zeroto60times.com
1 https://www.motortrend.com/features/1997-gm-ev1/
2 https://www.zeroto60times.com
Ah, but it might not as simple as that one single number :
> Driven like a regular car, GM's "voltswagen" is quite adept in traffic. Its 7.7-second 0-60-mph ability equals that of potent performers such as the '69 Camaro SS 350. And since the electric motor produces the same 110 pound-feet of torque at one rpm as at 7000, response is instantaneous.
> With more than a half ton of batteries low in the chassis, the car is very stable and handles remarkably well despite the ultranarrow, low-rolling-resistance tires. Darting from light to light along L.A. 's bustling La Cienega Boulevard, the car would easily spurt ahead from intersections for uninterrupted lane choice.
However :
> Of course, this driving style meant I was sucking amps like the Las Vegas strip, and the battery state-of-charge gauge used everything but sarcasm to get me to slow down. However, I'm a performance driver first, an environmentalist second-so I decided that while my trip up the coast may be brief, it would be without accelerative compromises.
[...]
> Driving smoothly is the key to efficiency (read: more mileage) in any vehicle, but given the current limitations, it's all-important in an electric car. So, to make my way through the 36 urban miles to my home, I was a virtual rolling roadblock, easing into the throttle with such delicacy that within the first few miles I knew I'd be late for my wife's lovingly prepared dinner.
That would explain my confusion after reading this :
https://www.energy.gov/articles/history-electric-car
> With a range of 80 miles and the ability to accelerate from 0 to 50 miles per hour in just seven seconds,
-which I took to mean that they were much better than average-
> the EV1 quickly gained a cult following.
> Driven like a regular car, GM's "voltswagen" is quite adept in traffic. Its 7.7-second 0-60-mph ability equals that of potent performers such as the '69 Camaro SS 350. And since the electric motor produces the same 110 pound-feet of torque at one rpm as at 7000, response is instantaneous.
> With more than a half ton of batteries low in the chassis, the car is very stable and handles remarkably well despite the ultranarrow, low-rolling-resistance tires. Darting from light to light along L.A. 's bustling La Cienega Boulevard, the car would easily spurt ahead from intersections for uninterrupted lane choice.
However :
> Of course, this driving style meant I was sucking amps like the Las Vegas strip, and the battery state-of-charge gauge used everything but sarcasm to get me to slow down. However, I'm a performance driver first, an environmentalist second-so I decided that while my trip up the coast may be brief, it would be without accelerative compromises.
[...]
> Driving smoothly is the key to efficiency (read: more mileage) in any vehicle, but given the current limitations, it's all-important in an electric car. So, to make my way through the 36 urban miles to my home, I was a virtual rolling roadblock, easing into the throttle with such delicacy that within the first few miles I knew I'd be late for my wife's lovingly prepared dinner.
That would explain my confusion after reading this :
https://www.energy.gov/articles/history-electric-car
> With a range of 80 miles and the ability to accelerate from 0 to 50 miles per hour in just seven seconds,
-which I took to mean that they were much better than average-
> the EV1 quickly gained a cult following.
Dunno the technology behind it specifically, but the various types of fast charging has really unlocked the potential in EVs, IMO. Making an EV act more like an ICE car is what made them pop in terms of viability.
I don't know much about electrical engineering but I have a feeling that advancements in the inverter technologies were quite important!
Wheels and tires would definitely be part of it.