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Electric EQ453 (2017-2022) – DCDC Inverter defect


Smart 453 EQ – A Costly and Challenging Repair Landscape

After extensive testing and repeated analysis, we have found that this vehicle presents some of the most complex and costly repair challenges in recent automotive history. Many critical components are integrated in such a way that even minor malfunctions require the removal of the entire electric powertrain—a time-consuming and expensive process.

For instance, if the DC-DC buck converter (which charges the 12V battery from the high-voltage system) fails, accessing it requires dismantling a significant portion of the vehicle, including 350 bolts, cables, connectors, and covers. However, what makes the situation more problematic is that, instead of replacing just the defective component, the standard repair procedure at authorized service centers involves replacing the entire drive unit at a cost of approximately €5,500.

Bundled Replacements & High Repair Costs

If a failure is diagnosed in the DC-DC converter, the entire RLC filter, DC-DC converter, onboard charger (OBC), and VFD inverter are all replaced simultaneously—every time. Similarly, if the onboard charger (OBC) fails, the entire assembly is replaced again because all components are integrated into a single aluminum housing on the electric motor.

  • No individual component sales: The manufacturer does not offer separate replacements for these parts, making every repair a full powertrain replacement at a minimum of €5,500.
  • Drive motor issues: We have also observed instances of electric motor failures (buzzing, scraping, rattling, etc.) appearing at approximately 100,000 km, though further analysis is needed.
  • Warranty limitations: The warranty for these crucial components is only 2 years or 20,000 km, meaning many owners encounter major repair costs early in the vehicle’s lifespan.

Battery Management & Programmed Faults

Beyond powertrain replacements, we have identified multiple recurring issues affecting the high-voltage battery system, including:

  • BMS hardware failures (serial defect)
  • Firmware-related BMS errors
  • Crash lock & counter limitations
  • Recurring warranty disputes over repair eligibility

Over the past two years, EV Clinic has researched and documented every possible failure mode, as well as all available solutions and repair methods. Unfortunately, these issues significantly impact the reliability and long-term sustainability of the Smart 453 EQ, which otherwise serves as an excellent urban EV.

Industry Trends & Manufacturer Strategy

These challenges are not exclusive to the Smart 453—we have observed similar powertrain issues across multiple electric models from this manufacturer since 2010. While we remain committed to finding sustainable repair solutions, it is evident that these design choices lead to high long-term ownership costs for EV drivers.

Part number: A4533404500, 292A05698R

Error: P0852F1, P085296

OEM Workshop: 5500 euro

EV Clinic: 1500 euro

What we offer:

-Full powertrain disassembly training

-Full DCDC Repair training

-Full OBC Repair training

-Full Drive inverter cloning, programming and repair training

-Full Battery repair training

-Full BMS software reading, writing and programmed defect reset training

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Electric EQ Smart 453 – Problematic EV

If you’ve never stood as a guarantor for a questionable loan, never had a less-than-pleasant experience in a high-security facility, never borrowed money from a less-than-official lender, or never owned a temperamental Citroën, VW, or BMW hybrid but want to experience all of that at once—this exceptional vehicle might be your perfect introduction.

German engineering, once renowned for its excellence, hasn’t just declined slightly—it seems to have reached an entirely new dimension. To perform a simple task like inflating the tires, one must first remove the entire engine, as the valve is ingeniously placed inside the motor’s stator. But before even attempting that, you’ll need to split the car in half—yes, literally!

Repair costs for this masterpiece don’t start at €1,000, nor €2,000, or even €3,000. Instead, every significant issue demands an eye-watering €5,500, because the solution is always the same—replace the entire powertrain module. If your windshield wipers stop working, you might as well contact an industrial machinery specialist to weld a whole new front end of the car—because, apparently, that’s the more practical approach.

But wait, there’s more! This vehicle boasts not just one, but four distinct faults that require full module replacements, two of which appear to be software-related. And the fun doesn’t stop there—battery defects? Of course! Not just a minor issue, but six different recurring serial faults. Out of those, three are seemingly software-triggered (contactor counter, impact detection, and cell imbalance OTP error), leading to the inevitable replacement of a perfectly functional battery—at a staggering cost of €15,000.

Truly, a marvel of modern automotive engineering!

The challenges associated with this vehicle remained unresolved until it arrived at EV Clinic. Over the course of 12 months, we conducted extensive research across three different fleets and multiple vehicles, identifying and addressing numerous technical issues. Through this process, we uncovered a range of design choices that significantly impact repairability and maintenance.

For instance, the high-voltage cable incorporates integrated cylindrical 40A fuses, meaning that if a fuse fails, the entire cable must be replaced instead of a simple fuse swap. Additionally, we observed a recurring issue with the internal instrument in the Battery Management System (BMS) responsible for measuring insulation resistance. In its current design, the standard repair approach requires replacing the entire battery pack rather than just the affected BMS component.

One notable aspect of this vehicle is that body parts are relatively affordable, which may provide some cost benefits in certain repair scenarios.

Let’s go through the serial defects:

DCDC hardware defect: €5500
DCDC programmed fault: €5500
Inverter: €5500
Charger: €5500
Motor bearing: €5500
Fuse in the type 2 cable port: €800
Battery after a crash – programmed fault: €15,000
Battery “unable to charge” internal bug never resolved by the manufacturer: €25 million
BMS ISO error: €15,000
BMS programmed fault P18051C: €15,000
Front headlight Daylight LED DCDC: €350

All these slippery problems arise by 30,000 km.

To highlight the positives, this car is an excellent choice for city driving. Its compact size makes parking and maneuvering effortless, making it a practical urban vehicle. However, when it comes to long-term ownership and maintenance, it is best suited for those with deep expertise—like us at EV Clinic—or for someone with close ties, such as a family member, trusted friend, or colleague. For the average owner, maintaining this vehicle can present significant challenges.

At EV Clinic, this model will serve as our future replacement vehicle for clients, but we do not recommend purchasing it unless the price is low enough to account for the potential high repair costs. If there’s one thing we firmly stand against, it’s unreliable vehicles—regardless of whether they are electric, hybrid, or combustion-powered. In contrast, the first-generation Smart 451 ED is a well-designed and durable electric vehicle, offering far better engineering solutions and fewer faults, making it our recommended choice.

EV Clinic’s Perspective on Repairability:

While electric mobility has great potential, certain design choices can make repairs unsustainable. Models such as the Smart 453 EQ, Renault Twingo, and Renault Zoe R240 appear to have been designed in a way that leads to recurring failures, often at intervals as low as 50,000 km—or, in some cases, as little as 10,000 km. While we cannot change the original design, our goal is to help customers avoid unnecessary spending on non-sustainable repair solutions.

A particularly concerning issue is the use of non-repairable onboard charging (OBC) systems. Instead of using commercially available and serviceable components, these models incorporate the FS200T12A1T4 Infineon HybridPACK1 IGBT—a component typically designed for driving electric motors but repurposed here for handling 22kW charging power. Unfortunately, this IGBT is not available for purchase separately, nor is the Battery Charger Box (BCB) module itself. As a result, when a fault occurs, the only option offered by the manufacturer is to replace the entire powertrain box, leading to excessive costs.

Additionally, testing repairs on these systems requires full disassembly and reassembly—an intricate process that can take up to eight labor hours just to verify whether the fix was successful. Our mission at EV Clinic is to introduce sustainable repair solutions where possible, even when the original design does not prioritize serviceability. While this is not always easy and can be time-consuming, we are committed to making electric vehicle repairs more practical and cost-effective.