Maintaining a car on a daily basis relies on regular mechanical checks and thoughtful purchasing decisions. The lifespan of a vehicle depends as much on the quality of its maintenance as on the relevance of the model chosen initially.
12 V Battery: the invisible failure that also affects electric cars
Classic maintenance guides detail fluid levels and tire pressure, but overlook a component whose failure can immobilize the vehicle without warning. The 12 V starter battery powers the onboard electronic system, locks, dashboard, and the starting of the powertrain, even on a 100% electric model.
On an electric car, this battery is separate from the high-voltage traction battery. Therefore, a vehicle can display a correct range and refuse to start because its 12 V battery is flat. According to reliability data reported by Sud Radio in September 2026, the 12 V battery remains a major cause of breakdown across all types of drivetrains.
To monitor its condition, a simple multimeter is sufficient: a voltage lower than 12.4 V with the engine off indicates a tired battery. In winter, low temperatures accelerate capacity loss. Replacing it preventively every four to five years avoids most unexpected immobilizations. Owners of electric cars that do not travel long distances must be particularly vigilant, as short trips do not always allow for a full recharge of this auxiliary battery.
The comparators available on the site lunion-auto.fr allow you to cross-reference the technical characteristics of models, including the type and accessibility of the 12 V battery, even before purchase.
SoH Certificate: the document to request for a used electric purchase
The French market for used electric cars is growing rapidly. With this growth, a new reflex is necessary when purchasing: ask for the battery health certificate, called SoH (State of Health).
This document indicates the residual capacity of the traction battery compared to its initial capacity. A SoH of 85% means that the battery retains 85% of its original range. Unlike mileage, which informs about overall mechanical wear, the SoH directly reflects the functional value of the vehicle’s most expensive component.
According to Le Dauphiné libéré (September 2026), the SoH has become as crucial as the maintenance history in negotiating a used electric vehicle. A seller unable to provide this certificate should raise caution.
Points to check before signing
- The SoH certificate must be recent (less than three months) and issued by a manufacturer diagnostic or a recognized third-party tool, not simply declared by the seller
- The history of repeated fast charges, which accelerate the degradation of lithium-ion cells on certain models
- The correspondence between the displayed mileage and the data recorded in the battery’s computer, to detect any potential tampering with the odometer
In a market where the demand for used electric vehicles reaches record levels and prices are rising, requiring this document protects against unpleasant surprises at resale.
Tire Pressure and Oil Change: two often underestimated maintenance tasks
Tire pressure influences fuel consumption, road handling, and tread wear. An under-inflated tire increases rolling resistance and heats the sidewall, reducing its lifespan.
Checking the pressure when cold once a month is the most cost-effective gesture in terms of regular maintenance. Reference values are found on the label affixed to the driver’s door frame or in the maintenance booklet. Adjusting the pressure according to the load (empty trip or full trunk) avoids unstable behavior in turns.
Oil Change: stick to the interval, don’t delay it
Engine oil lubricates, cools, and cleans the internal parts of the engine. Over time, it loses its properties and accumulates metal particles. Exceeding the oil change interval recommended by the manufacturer accelerates internal wear and can lead to costly breakdowns.
For a thermal vehicle, the frequency of oil changes depends on the type of oil, the engine, and the driving style. Short urban trips put more strain on the oil than long highway journeys, as the engine does not always reach its optimal operating temperature. An up-to-date maintenance booklet with oil change invoices is also a strong argument during resale.
Vehicle Repairability: a purchasing criterion too often ignored
Choosing a car is not just about comparing the purchase price, the engine type, or the level of equipment. The ease of repair affects the total cost of ownership over several years.
A model with readily available spare parts at reasonable prices will cost less to maintain than a vehicle with rare or proprietary components. Some brands incorporate glued or welded elements where others use standard mechanical fasteners, increasing labor time in the workshop.
- Check the availability and average price of wear parts (brake pads, filters, shock absorbers) before purchase
- Favor models whose mechanics are shared with other vehicles in the same group, as common parts are more accessible
- Consult specialized forums to identify recurring faults specific to a model and their average repair costs
A vehicle that is easy to repair retains its value better because the next buyer knows they will not pay a premium for each intervention. This criterion weighs more as the vehicle ages, precisely when maintenance costs increase.
The choice of a vehicle and its maintenance form a whole. A well-prepared purchase, with verification of the SoH for electric vehicles or repairability for thermal ones, reduces unexpected costs. On a daily basis, the 12 V battery, tire pressure, and adherence to oil change intervals remain the three areas where a few minutes of regular checks can prevent disproportionate bills.
