Everything to do with repairing an electric smart EQ

Basically, the smart EQ is of course also a relatively reliable vehicle. With my first smart EQ I had covered more than 100,000 km in 3 years and had no significant defects or repairs to report. But if something is defective, it can be time-consuming to replace it.


Thank you to my loyal 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. His employees now also drive fully electric.

Hardly anything would be possible with the smart EQ without Vanja Katic. He is a Croatian electronics professional and can do everything that is smart and Tesla, from cell replacement to firmware correction. In the past he had already repaired the charger of my parents' Model S and supported Thomas with various repairs in the smart ED & EQ. His know-how regarding repairs is probably unique in the EV world.


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.



Get a hold of HV components at all


In an earlier article I already explained what all HV components are in the smart and what their function is. In addition, I have already shown in a teardown how the battery of the current fortwo looks from the inside. If you want to go even deeper, you can look around in the smart eMotion Lexicon, which also explains, for example, how you can read out the remaining capacity of the battery yourself.


Alles rund ums Reparieren eines elektrischen smart EQ


All that remains is the large HV block under the trunk. What was more or less separate parts in the previous model has now all grown together in the smart EQ. Still fundamentally modular, but can only be reached with a lot of effort. In our example we would like to go to the DCDC converter because it is defective. As with many other things, we first have to localize where it is. The rear axle looks like this:


Alles rund ums Reparieren eines elektrischen smart EQ


In the middle we have the electric motor (1), the reduction gear (2) flanged to it and above it the cooling fan (5) for the motor and inverter. To the right of this is the control unit for the charger (3) and what is known as the high-voltage control unit box (4). In this box we find the DCDC converter after removing the cover on the right.


Alles rund ums Reparieren eines elektrischen smart EQ


Here we can see the DCDC converter (2) we are looking for and at the bottom we find the inverter (4). As already said, we have to remove the side cover. But we have to dismantle half the rear of the smart 453. The apron has to go, the rear wheels as well, so that the drive shafts can be removed and the whole HV-block has to be lowered including the motor and reduction gear. Only then can we reasonably access the site cover.


Alles rund ums Reparieren eines elektrischen smart EQ


At first glance it looks quite easy and in fact it is not difficult at all. But it is very time consuming and we have to be careful. Especially with the HV connector. Of course, there is no risk of injury from them, but they all have different locking and unlocking mechanisms. These must not be damaged under any circumstances. Because with the help of the interlock circuit, they are checked by the car and if they are defective, it no longer drives. In such a case, the corresponding part of the wiring harness would have to be replaced.


At least the wiring harnesses are available individually as spare parts. Because the whole HV-block is available from smart as a spare part. Only the motor and reduction gear can be ordered separately, apart from the block. Since the whole block is practically a Renault part, individual components can be obtained from Renault (Twingo ZE). But then the software must also be adapted to the smart. Tom's Garage in Stuttgart can carry out such repairs and works closely with Vanja Katic from Croatia. Both are very competent experts in their field, whom I personally know and appreciate.

Arrived at this point, we can now replace the DCDC converter and put the vehicle back together. Due to the complex way to get there, you can easily schedule 8-16 working hours for such a simple job. Incidentally, this is a repair that smart itself unfortunately does not offer. They would only replace the entire drive block for a multiple of the value of the DCDC converter. The same applies to the 22 kW charger, as this is integrated into it. Only the 7 kW charger is a separate part and can be replaced individually.



The search for the HV fuses


As with the old smart, there are a few HV fuses to protect the individual HV components. A large and quite easy one to reach directly on the battery, this is integrated into the service disconnect. It's the big main fuse.


smart ED4 17,6kWh Akku - Accumotive E18-2evo Teardown & Analyse


If you lift the carpet in the trunk, you will also find the well-known service door of the smart fortwo and forfour underneath. Removing these takes you to the main fuse box. Depending on whether a 22 kW charger is installed or the standard 7.2 kW charger (throttled to 4.6 kW in European left-hand drive vehicles), either 4 fuses (7.2 kW) or 2 fuses (22 kW) can be found here. .


Alles rund ums Reparieren eines elektrischen smart EQ


In vehicles with a 22 kW charger, there is also a fuse between the type 2 socket and the charger. Unfortunately, this is not documented anywhere, which is why I mention it separately here.


Alles rund ums Reparieren eines elektrischen smart EQ



My personal conclusion


Working on the smart EQ is of course possible and anyone who specializes in it can repair a lot. In such cases, Tom's garage in Stuttgart and Vanja Katic from Croatia are worth their weight in gold. But repairability was definitely not a priority with the HV-block under the trunk. You have to invest a lot of time to get to the individual components, and the procurement of spare parts can be expensive or time-consuming, depending on the part. Hopefully that will get better with the smart #1. The repairability of the old smart was very pleasant.


Luckily, something rarely breaks and if something does cause problems, the community of the smart eMotion forum also helps. Because sometimes it's just a little thing on the 12 V system. This can also report incorrect errors in error-free operation. It's not for nothing that this FAQ article is one of the most viewed articles in my entire lexicon: What can I do about "Charging not possible - Visit workshop"?