Repairing an electric smart car

The 3rd generation smart electric drive is a very robust car. Usually it reaches 200,000 km without any noteworthy problems, neither it's high-voltage technology nor general.

For workshops, there is hardly anything to do that they are not familiar with from normal cars already. The high-voltage technology is practically maintenance-free and things like brakes, steering and suspension are nothing new for them. With this blog post I want to take away the fear from the independent workshops of working on electric cars.

As I learned myself, it's not difficult. It started with the teardown of the 22kW charger of an smart eMotion follower. At the same time, I also learned how to replace it and what is important. All in all, it is not as complicated as you hear regularly from inexperienced workshops.

Repairs to the electric smart are no rocket science, even if they involve high-voltage components themselves. In order to make it easier for independent workshops, I would like to give an overview below. In addition, you can now buy all high-voltage components of the smart ED3 as used parts in the smart eMotion Shop. This means that expensive HV repairs are a thing of the past with the smart ED3.

Thank you to all supporters:

I would particularly like to mention Thomas Rebele from Tom’s Garage. As a motor vehicle master with high voltage certificate, Thomas is a great help. His workshop in Stuttgart (Germany) has helped smart eMotion readers by repairing smaller and larger defects. In his private life, he is fully electric, with a smart ED3 convertible and a Tesla Model 3.

I would also like to thank the ElectrifyBW trio around the Spanish car2go. They bring almost 100 decommissioned car2go smarties back into shape. The exchange with them is beneficial for both sides and has also helped a lot for this post.

Be careful:

Nevertheless, electric cars are vehicles with up to 400V board networks, some even up to 800V. It is important to know what that means: Even if there are a lot precautionary measures in the car, there is a risk to life if handled incorrectly. Visiting an experienced workshop, whose employees have an HV certificate, is always advisable if you want to work on high-voltage components. For private individuals, this is only at their own risk.

Always pull the service disconnect before working on high-voltage components. The high-voltage electrical system is thus reliably de-energized. All high-voltage cables are clearly identifiable as these thanks to the orange plastic isolation.

What for are high voltage components used for?

As is generally known, the technical effort for an electric car is quite clear. Provided power must be rectified, if necessary, in order to be able to charge it. It then is being converted by an inverter onto the three-phase power for the motor. In addition, the 12V is provided by the large battery and the heater is supplied with high voltage as well.

An overview of the individual components

Schematische Überischt EN

Charging port

It starts with the charging connection, which is also visible to the end user. It has the type 2 (USA: type 1) plug and a cable harness that goes directly to the charger. It loops through the signals of the charging station and has no intelligence of its own. Even the connector is locked when instructed by the charger tell it to do so.

In contrast to many other electric cars, the smart only has the type 2 connector, no CCS. Accordingly, there is no direct DC connection to the battery.


The charger is responsible for receiving the signals from the charging station. On the one hand, the charging station specifies how much power it can provide and on the other hand, the charger and charging station also coordinate whether everything is OK and ready to charge.

The task of the charger is to turn the AC current into a DC current, with which the battery can then be charged. You can think of this as something like the power adapter of any computer.

You can find more information about AC chargers here, there are also information about DC chargers. You can find a detailed analysis of the grid feedback and efficiency of the 22kW charger here.

HV wiring harness

The HV wiring harness is responsible for connecting all HV components together. It also includes HV fuses. The HV wiring harness is also a "stupid" component. No information is exchanged about it, all of this happens via the CAN bus, which has its own cable.

Battery pack

The battery is the core of every electric car, while all other components are basically nothing new, it is still a technical achievement. Its main task is, of course, to store electrical energy. It also includes the high-voltage contactors and the BMS. Outside the high-voltage battery, there is only HV voltage when all systems are active and working correctly.

I will explain it in an upcoming post and go in to full detail about it. Follow smart eMotion on the social media plato forms so you won't miss it.

Inverter & DCDC converter

The inverter is responsible for ensuring that the DC current of the high-voltage wiring harness becomes three-phase current for the motor again. If you recuperate this process happens in reverse, then it works as a charger for the battery.

The inverter of the smart ED3 also contains the electronics, which are known as DCDC converters. This is responsible for delivering 12V from the 400V of the large battery to supply the 12V electrical system. More about this here.


The motor itself is not a high-tech component. Of course, it is relatively compact, but in the end it is just an electric motor. There is not much to say about it, it converts electrical energy into kinetic energy and when you use regenerative breaking it does this vice versa.

More information about the motor of the smart ED3 can be found here, also about the differences between the Brabus and regular smart ED3.


The heating in the smart ED3 is a usual PTC heating element. This means that it is connected to the high-voltage wiring harness and gets hot if it receives the signal from the CAN bus. Technically, it is more or less just a 4 kW and 400 V hair dryer.

Service disconnect

The service disconnect is on the left in the driver's footwell. It is the inconspicuous red connector. Once it is pulled, work can be done safely on the vehicle's high-voltage components. It is always required to be pulled when you plan to work on the electric car. Every electric car has a service disconnect.

I do not specifically explain all the 12V components. These hardly differ from those from a conventional vehicle. The same applies to the 12V block. The only extra that is worth mentioning is the battery heating on smarties with a 22kW charger, which runs via the 12V system and heats the vehicle's cooling circuit.

Incidentally, it is recommended to replace the 12V block every 3-5 years. Although it never has to deliver high starting currents for starting, it is practically continuously charged to 100% and has no BMS. The 12V are also required to "start" the large battery. You can find out how to replace the 12V block here.

Cooling and CAN bus

Modern electric cars have two cooling circuits: A normal one for air conditioning and one for the battery, as well as other high-voltage components. The one for the air conditioning is like in any other car. In the case of the electric smart car with 22kW charger, this is also connected to the cooling circuit for the high-voltage components via a chiller.

The cooling circuit for the battery also cools the motor, the inverter and the charger. A classic glycol-water mixture is used, which can be electrically conductive, but must be mixed so that it can never freeze. Every good workshop always has this coolant at hand.

The CAN bus in the electric smart has several levels. However, this is not uncommon in modern cars. There is the level at which diagnostic devices run, such as the battery readout tool for the smart ED3 and ED4 and "hidden" sub-levels. Even advanced users are better off leaving the sub levels alone.

Replacing high-voltage components is no different in itself than replacing control units of a combustion engine cars. Old part out, fresh part in and train on the vehicle. The following components are linked to the chassis number of the vehicle and cannot simply be installed using plug & play:

The fuse box is also linked to the keys of the vehicle, and the control unit for the air conditioning system can only be properly connected in the installed vehicle. In terms of content, both are the same as in combustion engines cars.

You can buy both the components mentioned here, as well as many more, as used parts in the smart eMotion Shop. Depending on how you want, including cloning the software of the defective part onto the used exchange part. If you already have an exchange part and only need someone to clone it for you, you will also find an offer for this in the shop as well.


Working on the electric smart is no rocket science. As with any other car, it is an advantage if you know what you are doing. Basically, you can't break much. In the worst case, the CAN bus detects that something is wrong, the car does not switch on and there is an error message. Of course, working on HV components is only permitted with a valid HV certificate.

In the smart eMotion Shop you can finde a large selection of used spare parts and also solutions to marry used parts to the smart. If a workshop is open to the topic, it can also easily maintain and repair the electric smart if necessary. As before, you have to deal with the technology.

It is particularly pleasant that about every part can be replaced within 1 - 2 hours. Of course, it is always helpful to have a star diagnosis / Xentry tool at hand. This has further helpful information on the various work on the electric smart. The service manual for the smart ED3 is also helpful:

[Download the service manual]

Do you have questions about smart and e-mobility or do you want to discuss the content of this page?

Then register today here in the smart EMOTION forum. The constantly growing community is happy to engage in expert discussions and share their experiences with you. I also participate and support you with my network and expertise.