What is Bidirectional Charging And Why Isn’t It the EV Game-Changer You Might Think… Yet!

The topic of bidirectional charging is as popular in the e-mobility enthusiast community as the “Last Christmas” song every December—you literally can’t escape it. But whenever you try researching some information behind the basic definition of what bidirectional charging actually is, you might get inundated with an overwhelming array of Wikipedia articles with dubious sources at the bottom. We say it’s time to clear the fog around this topic.

The name doesn’t lie. Bidirectional EV charging involves the two-way flow of power: from the grid to the vehicle and from the vehicle back to the grid. In contrast, the conventional method of charging, where power flows only from the grid into the vehicle, could be termed unidirectional charging.

As we explained in one of our previous blog posts, charging an electric car is a lot about converting power from AC (alternating current) to DC (direct current).

When you are charging your electric car, AC coming from the grid is converted into DC. This conversion occurs either within the charger itself, as is the case with DC charging stations, or within the vehicle when you use an AC charger. And if you want to move power back to the grid, it needs to go through a reverse conversion process, which isn't possible with a regular charger.

Electricity generated by a PV system, on the other hand, starts as DC power. In theory, a DC charger could directly charge a battery without additional conversion, potentially offering an advantage. However, the costs associated with this, such as the bidirectional wallbox Quasar priced at around 6,000 euros, often outweigh the benefits.

Normal AC chargers are not able to perform any power conversion. So how does bidirectional charging work? AC and DC bidirectional chargers ensure transforming power back from car-friendly electricity (DC) back to normal home electricity (AC). This way, you can take the energy stored in the car's battery and use it to power your house or give some back to the grid.

• Improved energy demand management: Bi-directional EV chargers help balance local power demand by utilising stored car energy, preventing surges at peak times.

• Energy resale opportunity: Homeowners with bi-directional chargers may potentially sell excess energy in the future to local utilities, benefiting a wide range of users.

Bidirectional charging can be used for things like providing power to your house appliances, selling it to the grid, or powering an isolated reindeer farm as Hyundai did. Here are three main ways you can take advantage of two-way charging:

So far, this is the most developed method of bidirectional charging. It allows you to use electricity from your electric car battery for charging low-consumption devices. Imagine making your morning cup of delicious cappuccino just by connecting a coffee machine directly to your vehicle when camping. To use Vehicle to Load bidirectional charging, you need a normal Schuko socket in the electric car to which you can connect electrical devices on the go. Or you need an adapter for the type 2 charging port of your car, such as Hyundai offers for the IONIQ 5 and IONIQ 6. Its maximum power output is only 3.7 kW, but for powering up a hairdryer or a kettle it’s plenty enough. 

With V2G, electric vehicles can collect power when the demand is low and send it from their batteries back to the public power grid during peak hours. Consider people coming back home from school and work, cranking up their air conditioners, turning on the lights, and maybe firing up the blender for a refreshing smoothie. All in all, it's like a power party where the public grid is the one getting a hangover. Simply put, the electrical system in the entire area suffers from high loads. 

Solution? When electricity demand is high, EVs can supply electricity to the grid, acting as a distributed energy source. Conversely, during off-peak hours, they can recharge. 

The goal of bidirectional charging, in this case, is to contribute to grid stability and reduce the need for additional power plants. The maximum power output of the energy returning to the grid has not yet been established, but one of the manufacturers, sun2wheel, offers pre-orders for bidirectional DC chargers with a maximum power rating of 10 kW in both ways. Bidirectional AC chargers are slowly entering the market, but it is still a challenge to find one to order.

V2H enables your electric car to supply electricity from its battery to your home or any other building. Similar to V2G, this process involves a DC-to-AC converter in the EV charger. The difference is that in this case, the energy is supplied to the electrical system of a particular building. 

Accordingly, one practical use is optimising energy consumption at the residential level. For instance, you can charge your EV during the night when your TV, blender, and washing machine are all taking a nap and electricity demand is low. Then, you can use that stored energy to power your own home during the day when electricity usage is higher. This way, you not only contribute to power grid stability but also save money due to fluctuations in electricity prices.

Another possibility is to combine excess photovoltaic power with a bidirectional charger. By doing so, you can generate electricity, store it in your vehicle and receive a bonus from the grid operator for supplying electricity during peak demand periods. Although this remains a theoretical concept for now, it has promising potential for the future.

So the situation is as follows: A whole range of electric cars are now being launched on the market with the hardware for bidirectional charging, but without the appropriate software or suitably priced wallboxes, you unfortunately don't get much out of it.

Bidirectional EV charging development is slow because theoretical profitability doesn’t always translate to real-life gains. In addition, it can potentially reduce the lifespan of the car battery. Currently, a smart charger is enough to provide you with a power safety net. 

Let’s dive into details!

• Legal questions unanswered

How should the electricity that is fed back into the grid be taxed? After all, an electric car owner could charge his car at his employer's office with tax benefits and even for free, and then feed it back into the network at home for money. 

• Shortens the life of the car battery

It’s not like energy is leaving your car's battery without it noticing anything. Constant charging and discharging ages the battery, potentially leading to it having to be replaced sooner. This would mean a considerable amount of avoidable waste, as the battery cannot be fully recycled or reused, at least not at the moment.

In addition, the battery of an electric car is one of the most expensive components of the vehicle. Who guarantees the battery's service life in the case of bidirectional charging and what happens if the battery has to be replaced prematurely? It is still completely unclear who will pay for the costs of a possibly necessary early battery replacement in this case. Will it fall upon the car manufacturer, the grid operator, the electricity provider, or the vehicle owner? Until these uncertainties are addressed, practical implementation of bidirectional charging will face significant challenges.

• A regular smart charger is enough

A lot of EV owners are interested in bidirectional charging because it is like a safety net, ensuring that they won’t be caught off guard by power outages and pay less for electricity. 

However, it's essential to note that this promising technology isn't quite ready to deliver these advantages just yet. While a few bidirectional charging stations are available for pre-order (though not currently on sale), promising V2H and V2G capabilities, they might come at a premium price point, with some costing upwards of 20,000 EUR, making them a costly gamble for early adopters. And who knows, maybe in some years, when the technology is all set, these chargers will be considered outdated because they won't have some of the features added as bidirectional charging evolves.

The good news is, though, if you have a smart wallbox that controls the charging current to prevent overloading the grid, many features of bidirectional charging become unnecessary. 

• Sounds more profitable in theory than it is in real life

When it comes to discussing bidirectional charging, most people talk about grid stability without mentioning making money with it. At the end, it feels like there is an elephant in the middle of the room. Well, yes, in theory, you can profit from selling electricity back to the grid when it’s more expensive. But before that, you will have to buy an expensive bidirectional charger and select an electric car according to whether it supports this type of charging. Also, the car battery may need to be replaced sooner than if it was not used for two-way charging. And let's remember the main thing: none of this is possible yet, as the components required for this type of charging have not yet been fully developed.

At the moment, you don’t need bidirectional charging. Despite the exciting potential of bidirectional charging, there's a simpler and more immediate solution available: a smart wallbox with dynamic load balancing and flexible tariff charging like our go-e Charger. 

The go-e Charger, especially when paired with the go-e Controller or another compatible energy management (EMS) system, offers numerous practical advantages:

• Power reliability: Dynamic load balancing ensures a steady power distribution, eliminating power outages.

• Cost efficiency: Flexible electricity tariffs help reduce charging costs by charging your car when electricity is cheapest.

• Grid stability: Load shifting and peak shaving contribute to a more stable grid. Moreover, with the go-e Charger and the go-e Controller or other EMS, you can take advantage of excess photovoltaic charging and supply excess solar energy to your electric vehicle's battery.

• Enhanced comfort: You can easily control both the go-e Charger and the go-e Controller via a dedicated app. In addition, the combo offers automatic phase switching, energy monitoring and full control over power flows in your building for a smoother charging experience.

Why is it stealing the spotlight? 

Well, the problem that bidirectional charging is trying to solve is power balancing. And one of the great challenges for the power grid at the moment is the mass charging of electric vehicles, which often happens simultaneously. Many people come home from work and start charging their cars. Accordingly, this puts a heavy load on the power grid.

The energy consumption when charging an electric vehicle is higher than that of washing machines, air conditioners or other household appliances that most people have at home.

Smart chargers, including our go-e Charger Gemini and Gemini flex, rely on static load balancing to keep things in check. Static load balancing involves applying predetermined limits within your charger's settings. For instance, you (or your electrician) can establish a maximum power consumption threshold of, say, 10 kW. You definitely should take this into account when charging with several charging stations simultaneously. This way, you balance the load, trying not to draw more than the network can offer at one time.

But the true magic happens when you team up the go-e Charger with the go-e Controller or another compatible energy management system.