What is an electric car onboard charger? EV onboard chargers explained
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What is an electric car onboard charger?

What is an electric car onboard charger? EV onboard chargers explained

Electric vehicle charging comes in various shapes and sizes – slow, fast and rapid charging, Type 1 and Type 2 connectors, 3-pin plug charging, smart home charging and public charging – there are numerous ways to power your electric car.

However, there’s one crucial EV component that plays a pivotal role in the functionality of electric vehicle charging – the onboard charger (OBC).

But what is an electric car onboard charger?

We’re here to provide all the answers. In this blog, we will explain what an electric car onboard charger is, how onboard chargers for EVs work, and provide maximum onboard charger rates for some of the most popular electric vehicle chargers.

What is an onboard charger for an electric vehicle?

An electric vehicle (EV) onboard charger (OBC) is an essential part of every electric vehicle.

Since electric car batteries only charge with direct current (DC), and electricity from the grid is always alternating current (AC), an electric car onboard charger’s main responsibility is converting AC into DC so that you can charge your electric car’s battery.

Your electric car’s onboard charger only converts energy when you are plugged into an AC source, such as when you plug in to charge at home or certain lower-rated public charging points. This conversion process doesn’t occur when you plug into a DC charger, such as Rapid or Ultra-Rapid EV charging points, as there’s a pre-existing off-board charger inside the DC charging point that converts AC into DC before the power reaches your car.

But that’s not all; your electric car’s onboard charger also undertakes other operations, such as monitoring the charging rate of your EV.


Important – Make sure you don’t get EV onboard chargers mistaken for an actual electric car charging point that you plug in.


Where is an electric car onboard charger located?

The onboard charger is located within the electric vehicle itself, as shown below, and its primary job is to manage and control the charging process, ensuring safe and efficient conversion and delivery of direct current to the EV battery.

Tesla onboard-charger

Source: Tesla

How does an EV onboard charger work?

When an EV is plugged into an AC charging station, the onboard charger within the EV communicates with the electric car charging station to determine the available power, voltage, and charging capacity. It then converts AC into DC power before regulating the flow of electricity into the battery, successfully charging your electric car.

Each electric vehicle’s onboard charger has a maximum charging rate – the fastest it can charge with alternating current. For example, if your EV has a maximum charging rate of 7kW, you won’t be able to charge any faster than 7kW, even if you used a 22kW AC charger.

Maximum charging rates depend on the EV make and model.

What is an EV onboard charger

How do I know what size kW onboard charger my electric car has?

As previously mentioned, electric cars come equipped with onboard chargers that determine their maximum AC charging rate, often measured in kW (kilowatts). To find the specific maximum onboard charging rate for your electric vehicle (EV), make sure you refer to your EV’s manual.

On the whole, the available maximum charging rates for electric cars range between 3.7kW and 22kW. However, the most common maximum onboard charging rate for many electric cars is around 7kW – specifically 7kW, 7.2kW or 7.4kW – making 7kW home EV chargers a popular choice.

Smaller electric cars generally have maximum charging rates of around 6kW or 7kW, with slight variations like 6.6kW. On the other hand, some electric cars, particularly premium models with larger batteries, offer higher onboard charging rates of 11kW or 22kW.

For instance, Tesla vehicles are renowned for their unique maximum charging rates:

  • Tesla Model 3 onboard charger – 11kW
  • Tesla Model S onboard charger – 11kW
  • Tesla Model Y onboard charger – 11kW

But, it’s essential to note that no electric car currently exceeds a maximum AC onboard charging rate of 22kW.

Don’t get your maximum AC onboard charging rate confused with your DC charging rate, either. Since electric car batteries charge with DC only, you can use high-power DC rapid charge points of up to 150 kW to charge your EV if you want to – maximum charging rates are only for AC.

Popular electric cars and their maximum onboard charging rates:

Model Maximum onboard charging rate (kW)
Honda e 6.6kW
Nissan Leaf 6.6kW
Mazda MX-30 6.6kW
Kia e-Niro 7.2kW
Hyundai Ioniq 7.2kW
Kia Soul EV 7.2kW
Volkswagen e-up! 7.2kW
Fiat 500e 7.4kW
Vauxhall Corsa-e 7.4 kW
Vauxhall Mokka Electric 7.4kW
Jaguar I-Pace 11kW
Polestar 2 11kW
Mini Electric 11kW
Audi Q8 e-tron 11kW
Porsche Taycan 11kW
Skoda Enyaq iV EV 11kW
Renault Zoe R135 22kW
Polestar 4 Long Range Single Motor 22kW


Are there any other versions of an onboard charger?

Yes, two-way onboard chargers are in their infancy. A two-way onboard charger converts AC from the grid to DC within the EV while also allowing DC to be converted back to AC when it’s sold to the grid. Converting DC from your EV to AC and sending it back to the grid is commonly called ‘Vehicle to Grid’ charging.

As we mentioned, ‘Vehicle to Grid’ technology is not a widespread practice in the UK, but with future advancements, it’s likely to become more well-known in the next decade.

Do plug-in hybrids electric cars have onboard chargers?

Yes, plug-in hybrid electric cars have onboard chargers. However, since hybrid electric cars have both an internal combustion engine (similar to petrol and diesel vehicles) and an electric motor, the onboard charging rate is significantly lower – typically between 3.3kW-3.6kW.


What is an electric vehicle onboard charger

What is an offboard charger?

Unlike an onboard charger, an offboard charger is outside of your electric vehicle and is located in the EV charger that you’re using, not the vehicle itself. The difference between onboard and offboard chargers is that an offboard charger converts AC from the grid to DC before feeding the electricity back to your battery, as touched upon before.

EV charging points with offboard chargers are usually rapid or ultra-rapid public EV charging points. You’ll usually know when you are at a DC charging point as the rates will be significantly higher – typically over 50kW, but some reaching 150kW – and they’ll also be considerably bigger than AC chargers. Since the EV onboard charger isn’t needed, DC rapid chargers allow for faster charging sessions with higher rates since it feeds DC energy straight to your electric car’s battery, bypassing the need for conversion.


  • An electric vehicle onboard charger (OBC) is a crucial component responsible for converting alternating current (AC) from the grid to direct current (DC) to charge an electric car.
  • The OBC is located within the electric vehicle and manages and controls the charging process, ensuring safe and efficient delivery of DC power to the EV battery.
  • Different EVs have varying maximum onboard charging rates due to the onboard charges, ranging from 3.7 kW to 22 kW.
  • Typically, electric cars have a standard maximum onboard charging rate of around 7kW, making them a popular choice for home chargers and referred to as fast charging.
  • Premium electric vehicles may offer higher onboard charging rates, commonly around 11kW.
  • Tesla Model 3 and Tesla Model S both have a maximum onboard charging rate of 11kW.
  • Two-way onboard chargers, also known as ‘Vehicle to Grid’ chargers, are in the early stages of development, allowing DC to be converted back to AC and sold back to the grid.
  • Hybrid electric vehicles have lower maximum onboard charging rates, typically around 3.6kW.
  • Offboard chargers are external to the EV and located in the EV charger used for rapid or ultra-rapid public charging points. They convert AC to DC before delivering it to the EV’s battery, allowing for faster charging sessions.


Interested in a 7kW or 22kW charger?

As OZEV-approved installers, we can install single-phase and three-phase compatible electric car chargers at rates of 7kW, 11kW and 22kW. And with installers across the UK, we can install nationwide – in as little as 8-10 working days from DNO approval.

Contact us at 03333 44 96 99 to discuss your options. We are open seven days a week, including bank holidays, and ready to give free, unbiased advice and EV charger quotes.

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Tethered charger

This type of electric charger has it's own cable to charge your car.

Socketed charger

This type of electric charger requires a seperate cable to charge your car.

Spread over a 60 month period.

Tenants and homeowners are eligible for finance.

You decide the amount of months.

Minimum of £1000.

We will contact you to process the credit application. Approval is subject to application, financial circumstances and borrowing history. 13.9% APR representative. T&Cs apply.

Your order is not confirmed until your application has been approved.

Underground cable

We lay SWA cable laid at 600mm deep, with a protective cable warning tape laid 150mm above the cable. These are laid on a sand or sifted sand soil bed then backfilled.

Overhead cable

We position overhead cables at a minimum height of 3.5m and are run along a catenary wire. The cable run should not be accessible to vehicles.

Standard Installation
Our instant price is fixed if it falls within our standard installation package plus any additions that you have selected (extra cabling for example). This package covers the majority of homes in the UK. Before we undertake your installation we will carry out a digital survey to check that nothing has been missed. After reviewing the survey results some additional work may be required in order to complete your installation safely and to the required standards. If this is the case, we will contact you well before the installation date and advise the cost of any required work. You can then continue with your installation, or alternatively we will refund you in full if you do not want to proceed.

Included in our standard installation is :
• Fitting of a single phase charge point to a brick or plaster wall or other suitable permanent structure
• Up to 10 metres of cable, run and neatly clipped to the wall between the electricity supply meter / distribution board and the charge point.
• Routing of the cable through a drilled hole in a wall up to 500mm (20 inches) thick if this is needed.
• The fitting and testing of electrical connections and protections required for the charge point.
• An additional three way consumer unit, if required
• Installation of a Type A RCBO in an RCBO enclosure
• Up to 3 metres of plastic trunking to conceal interior wiring.
• An O-pen earth protection device if the charge point requires it. (This is NOT an earth rod)
• Up to 4 hours of labour from your installer to complete the work.
• Electrical testing of the whole installation.
• Handover and setup of the charge point and any app that may be needed.

Not included in our standard installation (additional work) :
• Where the installation requires additional cabling over and above the amount you have told us about.
• Upgrade/replacement of the main incoming supply fuse where the local DNO (eg Northern Powergrid) would need to attend site.
• If the charge point is to be mounted on a post/pedestal rather than an existing wall and where you have not selected a post as an extra cost option in your order.
• Installation of a charge point to a three phase supply.
• Where gas and water mains bonding (earthing) is not in place at your property. If this is not in place, additional work would be required before installation of the charge point.
• Any groundwork that has not been selected during the order process.

A Surge Protection Device is not included in our standard installation. 

What else you need to know :
• On the day of installation, please ensure that the area around your consumer unit (fuse box), incoming electricity supply meter and proposed charge point location (including where the cable is expected to be run) is clear and free of obstructions.
• We will need your WiFi password as part of the installation process in order to connect your charge point to the internet. Please have this available for the installer. Details will not be kept.
• The charge point must be on your own designated off road parking.
• The charger will be fixed in line with current guidelines at a height where it cannot be hit by a vehicle.
• Our installers are not able to enter loft spaces; lift floorboards or flooring; take apart any furniture of work above a height of 2m. If you anticipate that any of this may be required, then please contact us and we can discuss in more detail and provide you with a quotation.
• Should there be extreme weather conditions our installers may not be able to continue with you installation if it is not safe to do so (for example flooding). They will always do their best to complete the work where they can.

If you have any questions then please contact our customer service team who will be happy to help. Please also read our terms and conditions.