Tesla's Multi-Vehicle Charging Patent Dissected
By Bill Moore
As long as there are a few hundred thousand electric cars scattered across a country of a quarter million motor vehicles, most EV owners are likely to not have much of a problem getting recharged from public chargers. In a few communities, some chargers go unused for weeks, raising the ire of the more fiscally conservative in the town. Then you have situations like Silicon Valley and southern California where instances of 'charger rage' have appeared: EV drivers finding there aren't enough chargers at their workplace.
In the perfect world, a single charging station could handle more than a single car at a time. In addition, it would be able to prioritize charging depending on a host of different factors and contingencies. That perfect world may be just around the corner.
Permit me to introduce you to U.S. Patent 8,643,330.
The patent has been awarded to Tesla Motors on Feb. 4, 2014 and covers a "method of distributing charging power among a plurality of charge ports of a battery charging station…" In layman's language, the system offers the ability to charge multiple electric cars from a single charging station using prioritization algorithms, several of which hold some surprises.
Reason for the Patent
Tesla's patent includes an explanation of why they see a need for this new technology, stating:
Often when discussing the transition between a society dependent upon combustion vehicles and one that relies heavily on electric vehicles, the discussion turns to the need for a charging infrastructure that would make it easy for the electric vehicle owner to charge their vehicle when they are away from their primary charging station (e.g., home charging station). Unfortunately, the current charging infrastructure is quite limited. For example, in a large parking lot or structure, at best there may be one or two parking stalls that provide access to a charging system for recharging an electric vehicle's batteries. While this situation may be adequate for the current number of electric vehicles, as electric vehicles gain wider acceptance the need for better charging station access will become more essential.
During a Tesla owner's Q&A session in Oslo, Norway, Elon Musk revealed that it's his long range aim to eventually be able to manufacture a half-million electric cars annually. Of course, he won't be the only one producing cars and while he was answering owner questions, he let it be known that the company was developing an adapter that would enable Tesla owners to also make use of Nissan's CHAdeMO fast charging system in Europe. Presumably, with the introduction of a multi-charge port station, owners of not only Tesla Model S, X and Y cars, but also other EVs might be able to make use of the new system.
Tesla's patent explains that...
[I]n a conventional multiport system simultaneous charging is accomplished by incorporating four charging circuits within the single system. Charging circuits are coupled to source (e.g., power grid) and coupled to different vehicle ports, respectively. In a conventional multiport charging station, charging circuits are independent of one another, i.e., the operation or power output of one charging circuit does not impact the operation or power output of the other charging circuits within charging station. While this approach may be used to significantly improve vehicle access to a charging source, it is a relatively inefficient and costly approach due to the duplication of charging circuits…
Figure 2 in the patent illustrates this approach. What Tesla's patent offers is a way to handle more than one vehicle at a time. The patent currently stipulates four vehicles per charger, and seems to leave open the possibility of more.
The patent describes what happens when cars plug into the Tesla charge station in four steps, which at the fourth step, then either repeats until the car's battery is charged or the car is unplugged. These are:
(1) monitoring battery charging station conditions and operating conditions for each charging port;
(2) determining current battery charging station conditions which include current operating conditions for each charging port, and where the current battery charging station conditions vary over time;
(3) determining power distribution for the battery charging station and the charging ports in response to the current battery charging conditions and in accordance with a predefined set of power distribution rules, where the power distribution may couple between zero power and the maximum available charging power to any port by coupling between zero power stages and all of the power stages to any port of the plurality of charging ports;
(4) coupling the power stages to the charging ports in accordance with the power distribution, for example using a plurality of contactors or semiconductor switches.
These steps are controlled by a priority system based on a number of interesting criteria that include fees paid, customer priority, and reservation position, as well as battery state of charge, arrival time and planned departure time.
Specifically, here are three of the priority criteria as spelled out in the patent:
(ii) charger usage fees paid for coupling a vehicle to a charging port, where the step of determining power distribution includes the step of awarding priority on the basis of monitored charger usage fees;
(iii) vehicle priority information, where the step of determining power distribution includes the step of awarding priority on the basis of the monitored vehicle priority information;
(iv) customer priority information, where the step of determining power distribution includes the step of awarding priority on the basis of the monitored customer priority information;
Up to this point, using Tesla Superchargers have been free to all Model S owners. Find a charger, plug-in, top-off the battery in half-an-hour, and off you go, free of charge. Obviously Tesla engineers are thinking ahead and looking for ways to monetize the network in the future. The patent specifically talks about a credit card, debit card reader as part of the design. [See figure 3 below] Rates, of course, are not discussed, but we can assume that if you want to move higher on charge priority, you'll have to pay for it.
Also, the 'customer priority' category suggests a future 'frequent chargers' program with various categories of status, not unlike airline frequent flier programs. Will owners of $80,000 Model S sedans get a higher priority than, say, $40,000 Model Y? Or will any Tesla owner find themselves higher in the charging cue than, say, a Chevy Spark or BMW i3 driver who plugs in? Talk about an interesting sales incentive over the competition.
U.S. Patent 8,643,330 is more than allowing more than one car per charge station, it's about changing the landscape of electric car charging, taking advantage of the inherent human dynamics of electric car ownership that we're starting to see emerge, from 'range anxiety' to 'workplace rage' to 'charger obsession.'
It's the essence of entrepreneurship: find the pain, offer the relief.
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