W453 (2017-2024) · 17.6 kWh battery · Electric motor 60 kW (82 hp)
The ultimate urban electric runabout with minimal range but clever packaging. Perfect second car for city commuting but range anxiety is real - expect 60-80 km in winter. The electric drivetrain is simple and reliable, but watch for expensive charging system failures (DCDC converter, onboard charger), 12V battery drain issues, and high-voltage battery control problems. Service costs are low thanks to minimal maintenance needs and regenerative braking extends brake life significantly. Not a practical only-car due to 58-mile EPA range, but unbeatable for tight parking and zero-emission city driving.
12V battery drain and HV battery damage€150 - €8,000
Weak 12V battery can drain HV pack to zero volts, potentially destroying electronics · more· less
This is a serious design flaw. If the 12V auxiliary battery weakens, the car cannot charge or top it up unless driven. For unexplained reasons, a weak 12V battery can cause the high-voltage battery pack to drain all cells to zero volts, throwing irreversible error codes and potentially destroying the BMS and other electronics. Multiple owners have experienced this catastrophic failure mode. Smart service requirements state you lose your HV battery guarantee if the 12V battery is not replaced every 3 years. Replacement 12V battery costs €150-200, but if HV pack damage occurs, repair costs can reach €8,000. Always maintain 12V battery health and consider replacing it preventatively every 3 years.
The DCDC converter (located at bottom of inverter assembly) converts high-voltage battery power to charge the 12V battery. When it fails, the car won't charge or drive. Mercedes dealerships quote €5,500-8,000 for repair because they replace the entire powertrain assembly (inverter, DCDC, HVJB, PTCU) rather than just the DCDC converter. Access requires removing rear apron, wheels, drive shafts, and lowering the motor/gearbox - 8-16 hours labor. Independent specialists can repair just the DCDC converter for €500-800, but Smart/Mercedes dealers typically refuse this approach. The 8-year battery warranty does NOT cover DCDC failures.
Onboard charger (N83) failure€1,000 - €16,000
Car won't charge beyond 20% or displays "Charging not possible" warning · more· less
The N83 onboard charger (OBC) converts AC power to DC for charging the battery. Common failure modes include charging stopping at 20%, sporadic malfunctions (fault code P085249), or complete charging failure. Some owners report charging starts then stops immediately. Mercedes dealerships quote $14,000-16,000 for replacement. However, the OBC is plug-and-play with no programming required, so sourcing a used unit from a salvage yard and self-installing can reduce costs to €1,000-1,500. Always check if the issue is actually low 12V battery voltage first (11.86V or lower) - charging the 12V battery externally may resolve the error. Not covered by battery warranty.
Inverter/motor controller failure€2,000 - €7,000
Power electronics failure causes limp mode or no drive · more· less
The inverter (power electronics module) controls the electric motor. Failure symptoms include limp mode, complete loss of drive, or error codes. Often confused with DCDC converter issues since they're integrated in the same assembly. Mercedes quotes approximately €7,000 for inverter replacement. Specialists charge around €2,000-3,500 for used inverter plus €2,000 labor. Since the drivetrain is essentially a Renault part (from Twingo ZE), components can be sourced from Renault but require software adaptation. Not covered by the 8-year battery warranty - only the battery pack itself is covered.
Battery capacity degradation€0 - €8,000
17.6 kWh battery typically retains 90% capacity after 200,000 km · more· less
The Smart EQ fortwo uses a 17.6 kWh battery pack (16.7 kWh usable). Real-world degradation is relatively mild - one 2013 Smart electric drive with 200,000 km still retained 90% capacity. However, some owners report 15% capacity loss after aggressive use (deep cycling twice daily). Battery is warranted for 8 years/100,000 km with replacement if state of health (SOH) falls below 70%. Battery replacement costs approximately €8,000 at Mercedes dealers. Important: warranty covers the battery pack only, not DCDC converter, inverter, or onboard charger. Regional variations: US warranty is 8 years/62,000 miles; Europe is 8 years/100,000-125,000 km depending on market.
PTC electric heater failure€1,200 - €1,600
400V PTC heater provides cabin heat - expensive when it fails · more· less
Since the electric motor produces minimal heat, the Smart EQ uses a 400-volt PTC (Positive Temperature Coefficient) electric heater for cabin warming. This heater draws power from the main battery, reducing range in winter. Replacement PTC heater costs nearly €1,400. Normal operation: heater takes 5 minutes to warm up after starting, and on very cold days the HV battery gets heating priority before cabin heat. If no heat at all, check fuse R5 on driver's side. Complete heater failure requires expensive PTC unit replacement.
Front suspension bushings wear€400 - €800
Anti-roll bar and control arm bushes deteriorate from water/salt ingress · more· less
Front suspension bushings (particularly anti-roll bar bushes) are susceptible to water and salt ingress, causing creaking, cracking, and banging noises as suspension moves. 9 out of 10 times, noise is caused by contaminated anti-roll bar bushes with increased friction. Also affects control arm drop links, wishbone bushes left and right. Bushings are not sold separately - entire control arm assemblies must be replaced. Polyurethane replacement bushes are more resistant to water/salt damage. Typical replacement cost €400-800 for both sides with labor.
Range anxiety (limited real-world range)N/A
EPA 58 miles - real-world 60-80 km summer, 45-65 km winter · more· less
This is not a defect but a fundamental limitation. Official WLTP range is 130 km (81 miles), EPA certified range is 93 km (58 miles). Real-world range: Summer 90-130 km (55-80 miles), winter with heater 60-100 km (40-65 miles). Extreme cold with continuous heater use can drop range to 50 km (30 miles). Multiple owners report worrying about charge on trips as short as North London to Watford. The 17.6 kWh battery is small by modern EV standards. Range makes intercity travel impractical - this is strictly an urban/commuter vehicle or second car. However, for daily city use within its range envelope, it excels at parking, maneuverability, and zero emissions.
Simple drivetrain, but electrical failures are expensive
The electric motor itself is robust with minimal maintenance needs, and the battery pack shows good longevity (90% capacity after 200,000 km documented). However, when electrical components fail (DCDC converter, onboard charger, inverter), repair costs are disproportionately high because Mercedes dealers replace entire assemblies rather than individual components. The 12V battery drain issue is a serious design flaw requiring preventative 3-year replacement. Budget for potential electrical system repairs and maintain the 12V battery religiously.
Pre-Purchase Inspection Checklist
General checks
Service history
Complete Smart/Mercedes dealer or specialist records essential. Verify 12V battery replacement history.
Tires
Check tread depth, age (date codes). Front 185/50 R16, rear 205/45 R16. Budget tires €40-50, premium €90-100 each.
Test charging
Verify car charges properly with both Level 1 and Level 2 chargers. Watch for "Charging not possible" warnings.
Battery health report
Request diagnostics showing battery state of health (SOH). Should be above 80% for cars under 100,000 km.
Test drive minimum 20 minutes
Check acceleration smoothness, regenerative braking operation, no warning lights.
Specific for this vehicle
Check 12V battery voltage
Must show 12.4-12.8V when off, 13.5-14.5V when "on". Low voltage (below 12V) indicates imminent failure - replace immediately to prevent HV pack damage.
Verify charging functionality at multiple charge levels
Start at low state of charge (below 30%) and verify charging continues beyond 20%. Onboard charger failures often limit charging to 20%.
Test cabin heater in winter
Turn heater to maximum and verify warm air within 5 minutes. Complete failure means €1,400 PTC heater replacement.
Listen for suspension creaking/banging
Drive over speed bumps slowly. Creaking or banging indicates worn suspension bushings (€400-800 repair).
Check warranty status and documentation
Battery warranty is 8 years/100,000 km in Europe. Verify no warning lights and no stored fault codes via OBD scanner.
Verify 2017 steering knuckle recall completed (if 2017 model)
110 vehicles affected - left front axle steering knuckle may fail. Contact Smart with VIN to confirm.
Check for battery lease agreements
Early models sometimes had battery leasing arrangements. Verify battery is owned, not leased.
Test real-world range
If possible, charge to 100% and drive until range anxiety sets in. Real range should be 60-100 km depending on conditions.
Recalls and Technical Service Bulletins
Steering knuckle failure - 2017 models only (110 vehicles)Verify completed
High-voltage battery weld defect - single 2019 vehicleRare issue
Contact Smart/Mercedes-Benz with VIN to verify all recalls completed. The steering knuckle recall (Campaign 17V447000) affects only 2017 models. The 2019 battery weld recall affected just one vehicle. Smart EQ fortwo has an iSeeCars Recall Rating of 9.3 (good).
Warranty Status
Factory warranty (3 years unlimited mileage)Expired on 2017-2021 models
High-voltage battery warranty (Europe)8 years / 100,000 km
High-voltage battery warranty (US)8 years / 62,000 miles
Battery warranty coverage thresholdReplacement if SOH below 70%
Battery warranty covers the high-voltage battery pack ONLY if state of health falls below 70%. It does NOT cover DCDC converter, inverter, onboard charger, or 12V battery. Smart requires 12V battery replacement every 3 years to maintain HV battery warranty validity. UK market has 8 years/125,000 miles battery coverage. Check warranty status with Smart/Mercedes-Benz using VIN.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.