Retrofitting the 22 kW charger

With the standard 3.7 kW charger, the smart needs 5 hours to recharge its 100 km. Accordingly, we had not left the federal state with it in the past. My father drove it across Germany for a week just to have fun and a few years later I also drove it from Stuttgart to Berlin and back. And once 400 km in 24 hours, to the smart plant in France and back. A little later my father also made the 400 km in 24 hours. But that was well above what the 3.7 kW car was intended for.

In everyday life, however, we missed the 22 kW charger on the smart very much. Years ago, my father asked the Maushardt car dealership in Bruchsal whether they could retrofit the charger. With a pure parts price of over 8,000 €, that was off the table again. It would be much more economical to sell the smart and buy one with 22 kW. What is not an option for us, it grew too dear to our hearts for the last 250,000 km.

Instead, the main car was then replaced by a Renault Zoe, it had 22 kW and was perfect in 2015 in terms of price / performance. But in the long term, that didn't change the fact that we were missing the 22 kW charger in the smart. Now I was finally able to correct this mistake from the last decade. Here's how it's done.

smart eMotion would be nothing without supporters and community:

I would particularly like to mention Thomas Rebele from Tom’s Garage. As a motor vehicle master with a high-voltage license, Thomas is a great help. His Stuttgart workshop has already helped many smart eMotion readers to repair smaller and larger defects in the past and he is really into the topic of electromobility. In his private life, he is fully electric with a smart ED3 convertible and a Tesla Model 3. Even his employees are now all fully electric with smarties.

I would also like to thank the ElectrifyBW trio for the Spanish car2go. They brought almost 100 discarded car2go smarties back into shape. Thanks to their help, I was able to see how the 22 kW chargers were installed and had access to everything I needed.

And last but not least, Janusz Piwiński and his son Marek Piwiński. The two had already converted a smart to 22 kW some time ago. When I made my road trip through Poland and Lithuania this summer, they showed me and my parents around Warsaw and also explained how the upgrade should be carried out. Fortunately, there were no surprises on what I already knew. Together with Hybrid Serwis Ługowski, they are happy to help with any renovation work in the greater Warsaw area.

Parts list and procurement

Before you start you need all the parts. Since the 22 kW charger was also available by the factory, the conversion is carried out with 100% original parts. Roughly speaking, you need a new HV wiring harness, a new type 2 charging socket, of course the 22 kW charger and also new cooling hoses and brackets into which the charger is then screwed. A full list is available here:

The parts cost around € 7,800 from the dealer when new. Together with the article numbers, you should be able to buy them from any smart and Mercedes dealer. But since that is of course a proud penny, I carried out the conversion with used parts. My parts are from a Spanish car2go that had an accident. If you want to do it with used parts, you can order them in my shop.

Important when buying used parts:

There are 22 kW charger with different AC connections for the type 2 socket. There must have been some change in 2015, make sure that the type 2 socket also fits into the 22 kW charger. It's best to buy both together.

This is what the 3.7 kW charger and 22 kW charger look like, together with the matching type 2 socket. The 22 kW charger is on the right, the 3.7 kW charger on the left:

smart 451 von 3,7 kW auf 22 kW aufrüsten

These are the two wiring harnesses next to each other. The lower one is for 22 kW:

smart 451 von 3,7 kW auf 22 kW aufrüsten

The conversion

The conversion itself is quite simple in theory, but time-consuming and exhausting in practice. First the theory:

You have to replace the charger, the 3.7 kW charger has to go out, it is no longer needed. The 22 kW charger will take over its job in the future, it can charge anything from 1.4 kW (0,7 kW @ 110 V) to 22 kW. In addition, the type 2 socket must be replaced by a 3-phase one. Last but not least, almost the entire HV wiring harness has to be replaced. The 22 one has a different plug for the charger and also a larger fuse for the charger.

Now to practice:

First pull the ServiceDisconnect so that the vehicle is voltage-free. The smart then has to get on the lifting platform and the rear panel needs to be removed. This is the only way to get the necessary screws to replace the type 2 box.

smart 451 von 3,7 kW auf 22 kW aufrüsten

Now we can lower the entire rear chassis, which simplifies our work and the brackets for the 22 kW charger canl not be attached any other way later.


On this occasion you can also have a look at the motor mount and the axle mount. Both are not particularly expensive and the driving comfort as well as the straight-line stability will be better if you renew them. We'll have to readjust the wheels (axle bearing) later anyway.

Now the 3.7 kW charger has to go, the type 2 socket was plugged directly into it. It is located between the gearbox and the rear bumper. You can also use this opportunity to unscrew the brackets for the 3.7 kW charger, they are no longer needed. The left bracket is attached to the gearbox, the other to the motor bracket.

smart 451 von 3,7 kW auf 22 kW aufrüsten

Now we also get to reach the two cooling hoses rather easy, which have to be exchanged. Loosen the mechanism and remove the hose from the manifold.

smart 451 von 3,7 kW auf 22 kW aufrüsten

smart 451 von 3,7 kW auf 22 kW aufrüsten

You can use this opportunity to install the new hoses directly. The short one on the left, the long one on the right. Next up are the brackets: These have to be screwed to the vehicle, as shown in the following picture. In addition, threaded sleeves are missing in the vehicle's chassis You can use the brackets to mark the positions and then use the appropriate tools to set the threaded sleeves. Some of them are also screwed tight with existing screws for the bumper.

Now it's time to replace the HV wiring harness. All orange cables go into a box, which was screwed onto the inverter from the right. Releases all plugs that connect cables to the individual components. Then you unscrew it from the inverter and take out the whole wiring harness. The new wiring harness is installed like the old one, only backwards of course. Make sure that you also plug the cable for the battery into the battery. Do not confuse it with the one for the 22 kW charger, the plugs are the same. But the cable for the 22 kW charger does not reach down to the battery and the fuse in the fuse box would also be too small for the battery.

smart 451 von 3,7 kW auf 22 kW aufrüsten

Now you can connect everything, install the 22 kW charger and screw it on. Later you can no longer reach the screws so nicely. When that is done, you can attach the chassis to the smart again with its 4 screws. Since the chassis was removed, you can't avoid having the track re-measured.

Now you can finish everything, install the rear panel and check again that all plugs are correctly seated and nothing has been forgotten. If you've done everything correctly, the smart should now be fully functional and also able to charging, but only with up to 3.7 kW. The 22 kW still have to be activated and the chassis number entered in the charger.

Before you put the charger into operation, it is advisable to check the level of the cooling fluid and, if necessary, to refill it. A 50/50 mixture of water and glycol is used. In addition, the cooling circuit must be bleeded. It is best to use the venting process from the Daimler workshop device, otherwise by letting the smart slowly charge for 30-60 minutes at the socket. However, I would strongly prefer the venting program from the Daimler workshop device.

It took us 2x 8 hours for the whole process.

Activation of the 22 kW charger

As always, I'm holding back a little here because you can do a lot very wrong here. Please leave that to someone who knows which programs he needs for this and who can use them accurately. Unlocking the 22 kW charger is no rocket science for experienced workshops, anyone who can unlock parts on the smart 451 can also unlock the 22 kW charger. In addition, the chassis number of the vehicle must be entered in the 22 kW charger. Ask a professional about the activation or come to Tom's Garage in Stuttgart. There I did the exchange and had everything activated.

Congratulations, now the 22 kW charger is installed and your smart is much more flexible.

What you can also do if you cannot activate it: Install the 22 kW smart engine control unit in the smart. Then the loader is unlocked. If possible, I would still recommend unlocking it in the classic way and leaving the original engine control unit in the vehicle.

95 PS Brabus-Software freischalten

What else is there to say?

Vehicles that have a 22 kW charger installed by the factory also have a cooling circuit in which they can also use either the air conditioning or a 600 W heater for the coolant. European vehicles with 3.7 kW do not have this. Fortunately, this is hardly needed, if at all. Should the smart nevertheless get so warm or cold that this extra function is necessary, the smart will reduce the charging power. During my 500 km test drive (30 ° C outside temperature) the battery temperatures stayed within reasonable limits and nothing was throttled. Only the charging limit has been reduced a bit, which is normal with the smart ED3 and is now also part of the FAQ: Why did my smart only charge to about 90 percent?

Of course, such conversions are at your own risk, I do not take any liability for the statements made here.

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.

Do you like smart EMOTION, maybe saved time and money with it?

Then support the site with a membership and get exclusive rights.

You can find out more about this here.