The Chicken & Egg Problem with Electric Vehicle Charging

Electric vehicles (EVs) are a disruptive technology-  that’s reaching its tipping point toward market dominance. At which point, they’re almost certainly a technology that will, with time, become dominant over their predecessor. In this case, the predecessor is the internal combustion car, EVs have the potential to revolutionise the way we move and transport goods, and it is likely that they will become the standard in the automotive industry.

Chances are, though, when asked, you’d say that your next car will not be electric, and you’re right—the average consumer, according to surveys, would not even consider purchasing an electric vehicle, demonstrating that the technology is not yet at that tipping point where it’s on a certain path towards market dominance. But again, that path is almost certain. EVs are not there yet—right now, they’re too expensive, and too slow to charge—but they’re close.

Taking a look at the prices of the base-models of the world’s bestselling electric vehicles, they’re already roughly there, so we know that that’s not what’s holding mass-market consumers back: The cost of the battery is a significant factor in the overall cost of an electric vehicle (EV). In recent years, the industry has made efforts to lower the cost of EV batteries through innovation and scale.

The average price per kilowatt-hour (kWh) of an EV battery has decreased significantly in recent years. As the cost of batteries decreases, it becomes more feasible for manufacturers to sell EVs at a lower price point. It is expected that the price per kWh will continue to drop in the future.

Neither is range what’s significantly holding mass-market consumers back, and it won’t be at all within a few years. What is, though, is charging. It's currently possible to get an EV with just about what the mass-market requires for cost and range but reaching that charging time—that’s just a lot tougher. What this research can lead us to conclude is that the largest barrier right now to mass-market adoption is, in fact, the charging problem.

The tipping-point just will not happen without widespread fast charging, but widespread fast charging is just difficult because of the very way our electric grid works. You see, back when Thomas Edison, with his direct current electric system, battled it out with George Westinghouse, and his alternating current system.

As the names suggest, direct current electricity flows consistently and unidirectionally, while alternating current oscillates in magnitude and rapidly changes direction. The exact details of how each works isn’t that important in this context, but what is to know is that, for a variety of reasons, AC power won, it’s now the standard for power grids, but there are certain technologies that still need DC power.

The most widespread example of that is batteries—you cannot charge a battery using AC power. That’s why you don’t plug your smartphone directly into an outlet—you plug it into a power brick that plugs into an outlet, and that power brick is an AC to DC inverter. A standard iPhone charging inverter outputs 5 watts of electricity, which is plenty enough to charge the phone’s 11-watt hour battery in a few hours. A generic electric car, meanwhile, has a 50-kilowatt hour battery 4500 times larger.

Therefore, it needs a much higher wattage power inverter to charge with any speed. It solves this in two ways: There’s a 7.7-kW inverter that can take AC power from common sources, like a standard wall outlet, and convert it into DC power to charge the battery.

At its max rate, this can charge the car fully in under ten hours and has the advantage of allowing consumers to charge using regular wall plugs or by installing relatively inexpensive chargers on existing domestic AC electric circuits. The disadvantage, though, is that, while 7.7 kW is plenty fast enough for regular, overnight, at-home charging, it’s not fast enough to compete with the convenience of filling up an internal combustion car at the gas station. It’s not fast enough if you’re on a long-distance trip and need to be able to gain hundreds of miles of range in a matter of minutes.

So, if you need more electricity faster, you need a higher wattage inverter. To be able to take your electric car  from almost empty to almost full in thirty minutes, you want between 120 and 250 kW. So, for faster charging, one needs to offboard the inversion process. That’s exactly what a DC-fast charger does—it supplies a huge quantity of DC power to the car, which bypasses the onboard inverter and charges the battery directly.

But here’s something counterintuitive: using a 250 kW charger versus a 150 kW one doesn’t really impact how fast you charge. Batteries charge slower the fuller they are, so the first 20% will pass far faster than the last 20%. In the context of EV charging, this means that quite quickly into the charge, the speeds are impacted not by how much power the station is putting out, but by how much electricity the battery can accept.

So, it’s actually faster to charge to 50%, drive until empty, charge to 50%, and drive until empty again than charging to 100% and driving to empty. So, combining two charges from empty to 50%, in two stops, you could effectively reach the tipping point speed of 100% charge in 31 minutes with existing 250kW chargers. Therefore, what the industry needs is not faster chargers, but more chargers.

EVs are comparable in cost to internal combustion cars, their range is about what consumers demand, but what’s lagging behind is the charging infrastructure. This isn’t an exclusively Singaporean problem, around the world, as we progress.