The automatic start-stop system automatically shuts down the engine after the vehicle stops without requiring a change in the forward gear or other operating modes. To resume driving, simply press the accelerator. Shutting down the engine while stopped can reduce fuel consumption, but most car owners dislike this feature, primarily because the drawbacks outweigh the benefits. Each time the engine starts, the vehicle's starting battery is drained. During the start-up process, the battery needs a high current discharge, resulting in significant power usage. If the commute involves heavy traffic and short distances, the battery will lose capacity due to frequent start-stop cycles.
While driving can recharge the battery, short trips often fail to compensate for the consumption from the start-stop system. This makes the battery more prone to power loss, which damages the lead-acid battery. Today's lead-acid batteries cannot use cadmium, leading to shorter lifespans. A battery is considered high-quality if it can handle more than 300 full charge and discharge cycles. Thus, using this system does not protect the battery, and vehicles with an automatic start-stop function require enhanced batteries, costing thousands of yuan to replace.
In fuel vehicles, the air conditioning system depends on the engine. Cool air requires the compressor to operate the refrigerant, which is powered by the engine through a belt. Warm air relies on the engine's antifreeze coolant heating up in the heat exchanger and is unavailable when the engine is off, leaving only the blower running. In simple terms, only the "fan" can be used.
The purpose of using a car for commuting is to improve travel quality, yet if the air conditioner cannot run while the engine is off, travel quality is compromised. In conditions with large temperature differences between the car's interior and exterior, windows may fog up, requiring the air conditioner to defog, which can prevent start-stop activation.
Consider this scenario:
There's a traffic jam on the highway, with a large vehicle ahead and unknown vehicles approaching from behind. You need to share at least half a parking space with the vehicle in front to avoid heavy vehicles behind that may not brake in time. In low visibility, the best option is to accelerate and switch lanes, but this requires the engine to start first. This slight delay could mean very different outcomes, making the automatic start-stop function impractical.
So why do automakers keep it?
Automakers are aware of the poor real-world experience of the automatic start-stop system, yet by 2024, many fuel vehicles still have it. Reducing this feature would allow the use of cheaper batteries and cut hardware costs, but carmakers are unlikely to simplify and reduce costs here.
The reason is clear: any technology that reduces fuel consumption will be favored by automakers. Even if the real-world fuel-saving effect of automatic start-stop is minimal, it is effective in fuel consumption tests. In WLTC/NEDC or CLTC energy consumption tests, simulating urban driving conditions includes stops and waits.
Idling fuel consumption for one hour is roughly half of the engine's displacement without additional load in an ideal temperature environment. Turning on the air conditioner doubles this, and extreme temperatures increase it further. Idling fuel consumption explains why city driving has higher fuel use than highway driving. Thus, any technology that reduces idling fuel consumption during testing will be embraced by automakers, as lower test fuel consumption can earn them points to ease the financial pressure of compliance with dual-credit policies.
For these reasons, the automatic start-stop system won't be eliminated until fuel vehicles are phased out.
If you dislike the automatic start-stop, you can consider flashing the firmware. Most vehicle brands allow this feature to be permanently disabled by modifying the system settings.