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Proterra Does a Tesla, Makes Rapid Charging Patents For Electric Busses Open Source

[EDIT] Since the original article was published, we’ve been contacted by Proterra with a few clarifications on its overhead charging technology, resulting in a few corrections to the article below.

When a new, revolutionary technology comes to market, the company which developed that technology usually works hard to protect its intellectual property through a series of carefully-worded patents. Any company seeking to use that technology in its own products must either license the technology from the patent holder (an additional revenue stream for the original patent holder), develop their own alternative, or face an expensive and lengthy court battle over patent infringement.

Traditional business logic states that protecting your patents means you have a chance of having an edge over your competitor. Sharing your patents means that you have to find some other way to stay ahead of the game.

The patents are for Proterra’s ‘FC’ DC quick charging technology.

In the past few years we’ve seen that wisdom challenged multiple times, as both Tesla Motors and then Toyota announced that they would make their respective zero emission vehicle patents available for competitors to use as a way to try to accelerate the development of electric vehicles and hydrogen fuel cell vehicles respectively.

Now, we can add a third company to that list: California company Proterra.

Known for its range of electric busses, Proterra has just announced that it will be making all of its patents relating to its overhead on-route fast charging technology available royalty-free to other companies in the public transportation sector. Just like the release of patents by Tesla and Toyota, Proterra says that it hopes making its technology available on an open-source basis will make it easier for more bus companies to switch from internal combustion engined vehicles to 100 percent electric vehicles.

In total, three patents are being made available on the royalty-free basis: U.S. Patents 8324858, 8829853 and 9352658. Each relates specifically to the overhead single-blade that sits atop Porterra’s busses and the matching DC overhead docking station that Proterra uses to rapidly charge its busses while passengers alight and mount the vehicle.

Proterra's unique charging system helps buses recharge quickly en-route.

Proterra’s unique charging system helps buses recharge quickly en-route.

How quick is the rapid charging technology? Quick: according to the patents, Proterra’s system can support voltages of between 250 volts and 1,000 volts at at currents of up to 1,400 amps. That translates to a charging power of up to 1.2 megawatts in theory, although at the moment Proterra’s current production vehicles operate at power rates of around 500 kW — equivalent to adding a full charge to Proterra’s specially-designed TerraVolt FC on-board battery pack in less than 10 minutes.

For comparison, Tesla’s Supercharger technology currently peaks out at around 135 kilowatts in ideal situations. The Combo CCS charge standard favored by most European and U.S. automakers and the most recent proposed upgrade to the CHAdeMO DC quick charge standard peaks out at a theoretical 150 kilowatts, although for now, most public charging stations using either standard are restricted to 50 kilowatts.

We should note however that at the time of writing, Proterra’s rapid charging technology isn’t designed for busses fitted with its XR long-distance battery pack. Instead, Proterra’s rapid charging technology While Proterra’s overhead charging technology can be used with busses fitted with both XR and XC battery packs, its headline 10-minute quick charge to full relates specifically to busses fitted with its FC battery pack. Smaller in capacity, chemistry and range than the XR long-distance battery pack, the 105 kWh FC battery pack is specially designed to allow rapid DC quick charging at rates of up to 500 kilowatts in 10 minutes, offering a real-world in-service range of around 63 miles per 10-minute quick charge.

We're curious to see how many companies take up Proterra on its offer.

We’re curious to see how many companies take up Proterra on its offer.

Proterra’s longer-range battery pack — which can offer 194 miles of range per charge from 330 kWh of storage can be used with the overhead charging system as a form of opportunistic charging, although with the battery pack being much larger, you can’t get the same 10-minute full charge from the system.

As we’ve seen from both Tesla and Toyota’s patent giveaway however, simply making the technology available doesn’t necessarily mean that it will be adopted by other companies. For that to happen, there has to be a lot of faith put in a rival’s technology, especially when such agreements usually come with some pretty strict requirements that must be met on both sides.

It’s not clear at the moment if Proterra intends to make more patents available in the future, but we think it’s a smart move that could, if we’re lucky, see a growth in electric buses around the world. And that has to beat today’s smelly diesel-powered models, right?


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  • Martin Lacey

    Imagine what 1.2MW would reduce BEV car charging times too. If only!

    • If only. 😉

      Consider this tradeoff. Would you be willing to pay three times as much for electricity and half as much for your ZEV, without giving up any range, if you could refuel at 2.4 MW? That’s twice what you were imagining.

      That’s the basic tradeoff made by Californians whose out-of-state travel is by air when they buy a Toyota Mirai instead of a 290-mile-range Tesla. Travel in-state is painless: a week ago I drove my Mirai down US-101 from SF South Bay to Santa Barbara without having to stop along the way to refuel. Refueling in Santa Barbara took 5 minutes to add 710 MJ. That’s 710/(5*60) = 2.37 MW. For a top-of-the-line Tesla to do that it would have to charge to 100% at the start and run down to 0% by the end. Not good for the battery.

      Toyota makes it even more painless by paying for the fuel. Tesla does the same. Very sensible of both.

      • Martin Lacey

        Why on earth would you buy a Mirai when you could have got a Tesla?

        • “Why on earth would you buy a Mirai when you could have got a Tesla?”

          Excellent question. I presume you’re referring to the Tesla S 90D with its EPA range of 294 miles, only 18 miles less than the Mirai’s. Although I’d set 300 miles as my lower limit I’m willing to contemplate cars like the S 90D that come sufficiently close.

          If money were no object, and I was fine with spending $1015/mo (before taxes, insurance, etc.) for 36 months, with $3500 down after the $2500 CA rebate, and I didn’t mind the tank-like inertia of a car with a curb weight of 4,824 lb, and I didn’t mind being obliged to retreat to an In-N-Out Burger for a very slow recharge every now and then on a long trip, then with the Tesla S 90D’s 0-60 time of 4.2 seconds and 155 mph top speed it would have been a no-brainer.

          As it was, I asked myself if all those wonderful things that I would have killed for when I was 24 were worth $613/month more now that I’m three times older. In the end I decided I’d rather spend $499/mo with nothing down after the $5000 CA rebate, and spend the $613/mo that this decision would free up on something more worthwhile than cheap hedonism. And I can drive down US-101 from SF South Bay to Santa Barbara (see my earlier post on that exciting trip) without having to stop along the way. Refuelling in Santa Barbara took me 5 minutes. What would it take me if I drove a Tesla 90D nonstop from the Bay Area to Santa Barbara? Don’t forget to take into account that topping up to 100% takes a lot longer than from 30% to 80%.

          Driving those 300 miles from SF to Santa Barbara non-stop would not be wearying in a Tesla because it has Autopilot, letting you watch a Harry Potter movie on that wonderful 17″ screen. The Mirai won’t let you do that: it insists that you remain in your lane and buzzes angrily if you leave it without signaling, but does not go beyond that: unlike the Tesla it does not steer for you.

          It does however allow you to set a fixed distance to the next car so that you can go for miles without touching the accelerator or the brake. Since the next car is unpredictable while the road ahead is very predictable (only an earthquake can move it), steering becomes the relaxing task of staying in your lane as long as no vehicle does anything more weird than speeding up or slowing down. As I need to keep my eyes on the road to keep the Mirai in its lane, if a semitrailer the color of the sky crosses my path I will notice it immediately and brake to avoid driving under it, unlike Tesla the car, which according to Tesla the company is unable to distinguish sky-colored semitrailers from the sky. Had the Mirai freed me up to watch Harry Potter movies I probably wouldn’t have noticed it myself.

          As we will learn in due course from cars let loose on US roads with Autopilot-like capabilities, automation has many ways to kill us besides an inability to distinguish sky-colored semitrailers from the sky. Expect a long litany of such excuses in the coming years from companies selling “autopilot” technology to unsuspecting drivers thrilled at the opportunity to film themselves on youtube playing the role of taxicab passengers.

          I don’t mean to be a pessimistic Luddite here. Some day robots will be much better drivers than humans and reduce the 30,000 road deaths per year to just a few hundred. Meanwhile please feel free to list all the wonderful reasons why my selection of a Mirai was a serious personal mistake (and I emphasize “personal”—different people have different needs). While I can’t think of any right now I’ll be more than happy to acknowledge those personal mistakes that I’ve overlooked. 😉

          • Martin Lacey

            Whilst you make a compelling case based on your own requirements perhaps you need to be a little more upfront about the cost of ownership… Fuel costs, heavily discounted purchase price, projected maintenance.

            ICE is cheapest, but more polluting.
            BEV is cheaper than FCEV, but on the go recharging can be time consuming.
            FCEV is prohibitively expensive and under supported with fuel stations.

            Model 3 is set to kill the ICE is cheapest argument if you look at whole life cost of ownership.

            I give FCEV about 10 years to go mainstream or die as a great idea, but a complicated and expensive one!

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