You might think the crack team of reporters at CleanTechnica would have bisected, dissected, and intersected every scrap of Tesla news there is to be had in the entire universe by now. Much to our astonishment, a significant piece of Tesla news — that bi-directional charging will be available in all Tesla vehicles by 2025 — cropped up during the Tesla Investor Day event on March 1, 2023, that we didn’t spend much time on. (Though, Jesper Berggreen did cover it briefly in his roundup article about Investor Day.)
In response to a question from the audience, Tesla Senior Vice President for Powertrain and Energy Engineering Drew Baglino said, “Bidirectional … it wasn’t like a conscious decision to not do it. It just wasn’t a priority at the time. We’ve found ways to bring bi-directionality while actually reducing the cost of power electronics in the vehicle.
“And at all things Tesla, the goal is usually to get more for less. And so, we are in the middle of a kind of power electronics retool, I would say, that would bring that functionality to all of our vehicles over the next two years. Most of the value comes in charging the car at the right time. It’s not really about sending the energy the other way.”
That conversation completely escaped my notice until a sharp-eyed reader brought it up, but the folks at WhichCar in Australia jumped on top of it at the time.
Bi-Directional Charging For Tesla
Image courtesy of Nissan.
For years, Tesla has shown little interest in bi-directional charging, which allows the battery in an electric car to export electricity back to the outside world, where it can be put to many uses.
- Vehicle To Load (V2L) — allows the battery to power external devices like power tools, outdoor lighting, or helping to charge another EV that is short of electrons.
- Vehicle To Home (V2H) — allows the battery to power selected circuits in the home during a power outage, things like air conditioners, heat pumps, refrigerators, and such.
- Vehicle To Grid (V2H) — allows the battery to feed electricity back to the electrical grid.
The specifics of bi-directional charging are fairly complex, depending on how it is used. How many amps will be needed and at what voltage? Is there a need for DC or AC current?
The central conundrum of EV charging is that batteries operate on direct current while the electrical grid uses alternating current. The two do not play well together. To charge an electric car, the AC supplied by the charger has to be converted to DC by a device called an inverter. Any time electricity is converted from one form to another, there are losses involved in the conversion process.
Fast chargers operate on DC, which means electrons can be added faster because the car’s inverter can be bypassed, but they are powered from the grid, which means they have to convert the electricity they receive before it gets passed on to a car.
Reverse the process and all sorts of obstacles occur. A power tool doesn’t draw many amps, so a system that exports electricity from the battery in a V2L scenario doesn’t need to be particularly robust. But a V2H use case requires considerably more complexity. Not only is the amperage much higher, but many electrical devices require the voltage to be within rather specific limits in order to operate properly.
The dream for many is a scenario in which millions of electric cars are all connected to the grid most of the time. They could absorb lots of renewable energy from solar panels during the day and feed it back into the grid after dark. The grid would become like the tides — distributing zero-emissions energy all day every day and reclaiming it at night. But the performance parameters that apply to the grid are much more stringent than those for residential use. Voltage and frequency have to meet strict standards in order for the grid to function properly.
[Note: the author is not an electrical engineer, nor has he ever played one on TV. He has, however, spent a lot of time doing things he shouldn’t inside the breaker box at his home!]
Ideally, utility companies would not need to build large battery storage facilities because there would be millions of GWh available in all those electric cars. The whole system would be managed by artificial intelligence, so every car would be fully charged when needed and the grid would have all the power required at all times. Did I mention that is the ideal?
There’s another factor at work as well. The world would need fewer battery cells. Instead of having two demand streams — one for electric cars and another for grid storage — there would only be one. Environmentalists would be happy because there would be less need for battery materials, so less lithium, manganese, nickel, copper, and cobalt mining would be needed, which most would consider a good thing.
Elon Demurs On Bi-Directional Charging
Bi-directional charging is the new, new thing in the world of electric cars. It’s been around for a long time, but it is just starting to get implemented by several major automakers. GM says its EVs will be ready, willing, and able to act as backup power supplies for homes. Hyundai, Ford, and Nissan have already been offering V2G capability. Volkswagen is experimenting with V2G technologies as well.
Elon Musk threw cold water on the idea during the Investors Day confab, however. He said the idea makes little sense unless it is paired with a residential storage battery like a Tesla Powerwall. “I don’t think very many people are going to use bidirectional charging, unless you have a Powerwall, because if you unplug your car, your house goes dark and this is extremely inconvenient. I think there’s some value there as a supplemental energy source down the road, where, if you have a Powerwall, you don’t diminish the convenience of the people in the house.”
Elon is correct. Relying on the battery in your EV to power your home or to sell electricity back to the grid only works if the car is stationary and plugged in. Otherwise, the house goes dark every time the car gets used to run to the Piggly Wiggly for more salsa and chips.
Tesla has just debuted a new universal home charger and acquired a wireless charging company. Will either of those be involved in bi-directional charging? And what about battery degradation? There is a lot of hoopla about V2H systems, but there is no data available yet that answers that question definitively. Some say bi-directional charging may actually be good for battery longevity, but those claims are also not backed up by real-world data.
The takeaway seems to be that just as the rest of the industry has embraced the Tesla NACS charging standard for North America, Tesla will embrace bi-directional charging. By 2030, it is likely all electric cars will come with V2L and/or V2H capability as standard equipment as EVs become the norm among new car buyers.
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