Problems with accessory batteries and electronic systems are a common source of frustration in modern electric cars. These faults often show up as unexpected symptoms such as resetting infotainment systems, lost seat settings and failing navigation. Find out why these problems occur and how to recognise and resolve them.
The 12V battery system as the main cause
Many electric car owners immediately think of the large traction battery (the main battery that supplies power for propulsion) when problems arise. In reality, however, the culprit often turns out to be the 12V battery. This small auxiliary battery pack powers the computers, relays and electronic systems needed to activate the main battery safely. When it becomes weak, faults appear that seem to mimic major technical defects.
The Nissan Ariya regularly suffers from this problem. Even new examples fail within a few weeks, with symptoms ranging from a car that will not go into ready mode to warnings such as “Service EV System” or “Power Reduced”. The cause almost always lies in insufficient charging voltage from the accessory battery.
This also explains why seat memory settings suddenly disappear. These functions constantly use a small amount of power to store settings. With a weak 12V battery this information is lost, which for many drivers is the first noticeable symptom.
Why the infotainment system keeps restarting
A constantly rebooting infotainment system often points to voltage spikes or interruptions in the power supply. This happens when the 12V battery struggles to provide a stable voltage during start-up or during demanding tasks. The system detects the instability and tries to restart itself to prevent damage.
The problems often worsen after software updates or in cold weather. Updates can temporarily draw extra power, while low temperatures further reduce the capacity of a weakened battery. App connections then drop out and charging sessions are interrupted, especially during DC rapid charging (high-power direct-current charging), where the system places higher demands on the electronics.
Recognisable symptoms of battery problems
- Car will not go into ready mode after standing still for a few days
- Intermittent charging problems with both AC (alternating current, at home or on public chargers) and DC (direct current, rapid charging)
- Error messages that appear after parking and disappear again while driving
- Infotainment screen that goes black or restarts during use
- Loss of personalised settings such as seat positions and climate preferences
Navigation that gives up on long journeys
Navigation systems that fail during long trips often have the same cause. The 12V battery is continuously loaded by the infotainment system, climate control and other electronics. With a weak battery, the voltage during intensive use can drop below the minimum level the navigation unit requires.
This problem occurs mainly on journeys with heavy air conditioning use or with frequent short trips where the 12V battery does not get enough time to recharge. The system switches itself off to prevent further damage, which can happen at the worst possible moment during a route.
Diagnosis in three steps
Checking the battery health can help prevent costly repairs. Start with a visual check of the dashboard bars that show the battery status. Low bars immediately after start-up indicate problems.
Then measure the 12V voltage after a period of standing still. A healthy battery should show at least 12.4 volts. Values below 12 volts point to weakening or parasitic current draw. This is particularly important after a cold night or several days of parking.
Use an OBD2 scanner (a diagnostic device that you connect to the car to read out extensive system data) to check the State of Health (SOH, a percentage indicating the remaining capacity compared with a new battery) of the traction battery. A new car should show 100 per cent, while values of 95 to 98 per cent are normal after one to two years of use. Larger drops can indicate degradation, although this is rare with modern electric cars.
Practical solutions for owners
If warnings keep coming back, you should charge or replace the 12V battery. Many owners opt for a more robust, higher-capacity battery to extend its lifespan. This proves to be an effective measure, especially for one-year-old cars that are already showing signs of weakening.
Prevent degradation of the main battery by not always charging to 100 per cent. Also limit frequent short trips with heavy air conditioning use, as this places extra load on the 12V battery without giving it enough time to recharge. When buying a used electric car, an SOH check (State of Health check, a measurement of the remaining battery capacity) via an OBD2 app is a sensible precaution.
Tips for acute problems
- With a “Service EV soon” message: jump-start the 12V battery and monitor behaviour afterwards
- Power Reduced mode that limits speed to 40–50 kilometres per hour: have the 12V battery tested immediately
- Problems at external DC rapid chargers: try a different charger first before assuming a defect
- After software updates that cause problems: check the 12V voltage before looking for other causes
Distinguishing between the 12V and the traction battery
The traction battery generally performs reliably and rarely shows major problems. Early models may show a capacity loss of 0 to 5 per cent after 10,000 to 20,000 kilometres, but this stabilises afterwards. Larger 87 kWh battery packs hold up better than smaller variants.
A failing 12V battery, however, imitates major defects. Warnings that appear to point to the high-voltage battery often turn out, when checked, to be caused by insufficient voltage in the auxiliary system. Always check the small battery first before starting costly diagnostics on the traction battery.
When professional help is needed
If replacing the 12V battery does not solve the problems, there may be a deeper cause. Parasitic current draw from defective modules or a fault in the 12V battery charging system requires specialist diagnostics. A dealer can use professional equipment to read which component is consuming an abnormally high amount of current.
Software-related issues sometimes require a reset of the entire system or a firmware update. Some faults are caused by bugs in the control software that can only be fixed via official updates. Keep this in mind when infotainment problems persist that do not correlate with the 12V voltage.
On the Carnews website you will find much more information about electric cars, common problems and maintenance advice. Discover more tips and experiences to help you get the most out of your electric driving experience.
Frequently asked questions
You can often recognise a failing battery or electronic system by a car that is hard to start or will not start at all, dim lights or flickering dashboard warning lights and error messages such as “Service EV system” or “Power reduced”. Also watch for unexplained faults in the infotainment system, charging problems or the connection with apps dropping out. Regular voltage checks of the 12V battery (with a meter or at the workshop) can reveal ageing at an early stage. If the behaviour worsens in cold weather or after the car has stood still for a few days, that is an extra indication of a weak battery or an electronic problem.
The most common electronic faults in modern sports cars and performance cars are problems with sensors and ECU software (for example engine management, ABS/ESP), infotainment and connectivity errors, faults in adaptive damping/driving modes and electronically controlled transmissions. They manifest themselves in error messages, power limitations (limp mode), jerky or delayed throttle response and unexpected intervention from stability or traction control. This can make the driving experience less predictable and less involving, because systems intervene when it does not seem necessary or functions temporarily fail. At the same time, these faults often cause uncertainty and frustration for the driver, as they are difficult to reproduce or can only be traced using specialist diagnostics.
Keep the 12V battery in good condition by having it tested regularly, replacing it in good time if error messages keep returning, and avoiding long periods of inactivity by using an external trickle charger or driving regularly. Avoid routinely charging to 100% and, for normal daily use, set a charging limit of around 70–80% to protect the traction battery. If possible, install the latest manufacturer-approved software updates to minimise electronic glitches. In the case of recurring electrical faults (dashboard warnings, charging problems, infotainment failures), always have the 12V battery, the charging system and the earth connections checked preventively by a specialist.
Aftermarket modifications (such as non‑original alarm systems, audio upgrades or additional consumers) can significantly affect a car’s electronic system because they interfere with wiring, the CAN bus or the load on the 12V supply. Incorrect installation can cause voltage drops, short circuits or faults in sensors and control units. This may show up as random error messages, starting problems, failure of charging or safety systems and hard-to-trace “ghost faults”. The more complex the vehicle and the more deeply the modification interferes with existing circuits or software, the greater the chance of unexpected problems.
Essential are a good OBD2 diagnostic tool (scanner) with an accompanying app or software to read fault codes (DTCs) and monitor live data. In addition, a digital multimeter is indispensable for measuring voltages, resistances and continuity in the 12V system and sensors. For advanced users, manufacturer-specific diagnostic tools or dongles with brand-focused software are valuable for reading brand-specific modules and codes. Finally, a battery tester or charging/starting system tester can help objectively assess the health of the 12V battery and alternator.