EV Bi-directional charging – Everything you need to know

As electric vehicles take over the world, they continue to bring exciting technologies with them. One such technology is bi-directional charging, which opens the door to so many possibilities.

This article is a guide to everything you need to know about bi-directional charging.

What is bi-directional charging?

Also known as vehicle-to-grid (V2G) or vehicle-to-home (V2H), bi-directional charging is the ability of an electric vehicle to reverse the process of taking power from the grid, ie, the vehicle can supply energy back to the grid. 

However, the grid is not the only source that can draw power from an electric vehicle’s battery; the energy can power a home, another electric car, power tools, etc.

Essentially, your vehicle becomes a mobile power bank that you can tap into at any time.

How does bi-directional charging work?

You can get an understanding of bi-directional working by considering how charging an electric vehicle works. When you plug in your car, it takes AC from the grid, which is then converted into a DC by the internal charger or converter before being stored in the battery.

To bring out energy from the battery, you need a bi-directional charger that will convert the DC from the battery into AC before sending it to say, a home or a power tool.

Is bi-directional charging worth it in actual terms?

Yes, bi-directional charging is practical. Electric vehicles are essentially moving banks of energy with their batteries. For example, a 70 kWh battery can power an average home for more than two days. An average driver covers less than 30 miles per day, which may be less than one-eight of many modern EV battery capacities. This means workers can rely on their bi-directional vans to get to worksites around town, power their tools, and still have enough battery to drive home at the close of work.

Bi-directional charging has other practical applications. For example, it may power appliances during picnics or camping trips in remote locations.

Financially, bi-directional charging may save you some money. For instance, if you have access to free charging at your place of work, you could go off-grid when you get home by plugging into your battery and save on your electricity bill. You might even be able to sell some of the energy in your car battery, depending on electricity regulations where you live.

Can every electric vehicle do bi-directional charging?

The answer is no, but more vehicles are getting the ability.

Vehicles that use CHAdeMO charging standards can include bi-directional charging. However, CCS standards will soon incorporate the technology as well.

Tesla, one of the most popular electric vehicle brands, has promised that its future models will come with the technology. Volkswagen has been testing the hardware needed for the technology as it has plans to incorporate it into its home energy system. Hyundai too has included bi-directional charging in the platform it has used to build the Ioniq 5 and Kia EV6.

What effect does bi-directional charging have on the battery?

Some people may be apprehensive of the effect of bi-directional charging on the battery. However, there is no negative impact attributable to bi-directional charging overtime. This is because the discharge rate is less intensive than when you drive, meaning your battery may even be safer when it discharges through bi-directional charging. 

Similarly, there is no danger of overloading a bi-directional electric vehicle. This is because, just like solar inverters, there are sensors that monitor the load of the house, for instance. If too much power is drawn, they shut down the supply or the battery level drops below a preset percentage.

What are the benefits of bi-directional charging?

We know how bi-directional charging works. But what is the practical benefit for you as a user? 

Save money – Benefitting from flexible energy prices

If the charging time of the vehicle is linked to the energy prices, we can charge the battery cheaply and when the energy prices increase again, we can use the energy from the vehicle battery to reduce the energy costs.

Thereby the owner of a bi-directional charging vehicle and bi-directional charging station gains independence from energy providers.

Reducing the load of the grid

With lots and lots of bidirectional charging vehicles, the grid can benefit from a mass effect. The load of the grid can be reduced for peak hours, such as 4 pm-8 pm, when workers and students typically come home and start cooking or using other electrical devices. With many bi-directional charging vehicles connected to the grid, this peak load can be reduced for the grid. Consequently, the risk of grid outages can be reduced for all.

Use of wind-power and solar-power

For wind and solar power, power generation is highly dependent on daily conditions. Having many bi-directional charging vehicles connected to the grid, the vehicles can be charged when the weather conditions allow for a high power generation. If the weather conditions change and the power for the grid needs to be generated by other technologies, the vehicles can support the grid while starting up the other power plants.

Powering homes during extreme weather conditions 

With climate change, many regions experience more extreme weather conditions. Hard snowfalls or extreme Winds can lead to power lines collapsing. One example of this was the extreme weather condition in Texas in 2021. With the grid broken down, many customers were stuck with flexible energy prices skyrocketing.  

How long could a household run on the car battery?

An average US household consumes about 877kwh per month. Which roughly equals 30kWh per day. Here you can find an overview showing how many days a household could be run on the energy stored in the battery.

The less energy is used and the bigger the battery is, the longer a household could be covered by the vehicle battery.

Battery SizeDaily energy consumption of 35 kWhDaily energy consumption of 30 kWhDaily energy consumption of 25 kWh
70 kWh2 Days2.33 Days2.8 Days
85 kWh2.43 Days2.83 Days3.4 Days
100 kWh2.86 Days3.33 Days4 Days

Conclusion

Bi-directional charging is an excellent technology that lets electric vehicle owners use the power from their car battery to power their homes and other applications. While not all existing vehicles have the capability, newer and future models are increasingly getting bi-directional charging built-in.