A guide to start-stop technology: Is it bad for my car?

HAMBURG: Anyone who often drives in city traffic is familiar with the problem of constant starting and braking.

In crowded streets, the car engine idles for between several seconds and minutes, especially at traffic lights and intersections.

The ubiquitous automatic start-stop system is intended to remedy this problem but many motorists worry that all the stop-and-start cycles may lead to increased engine wear.

By automatically switching off the engine, an automatic start-stop system can save around 15% of fuel on average. This saves money and benefits the environment too.

In order for this system to work, rows of sensors are installed in the car, which are coupled with the engine control unit. The system thus knows when the car is in neutral gear and activates the tech. However, this only works if the car battery has sufficient charge.

Temperatures that are too high or too low hinder the start-stop system, because a switched-on heater or air conditioner put too much strain on the car's battery.

The clear benefits of the start-stop tech come with several limitations. Wear and tear on components is increased and a more powerful battery is essential.

For once the battery on a car with a start-stop system is worn out, not just any new one will do.

You need an enhanced flooded battery (EFB) which can handle deep discharges and has a larger capacity.

Some larger vehicles will require an Absorbent Glass Mat (AGM) battery. These work just like standard batteries, except they have a fibreglass mat between the negative and positive plates. The electrolyte passes through the mat in a controlled manner without any danger of flooding it.

This also means that no liquid will come out if the battery casing is damaged.

A traditional lead-acid battery of the kind that used to be fitted to all cars will fail quickly and could cause damage in a car with start-stop.

Some drivers also find the start-stop tech irritating, as it can take too long to restart the engine spontaneously. In many cars the system can be manually deactivated.

There are also times when stop-start will not kick in. If the engine is cold, for example, the system is less likely to intervene and will allow the engine to warm up fully.

Experts reckon that a car without automatic stop-start will go through up to 50,000 manual stop-start cycles during its lifetime, compared to 10 times that amount for a car fitted with the technology.

This places a strain on the crankshaft, which is the key part of an engine which changes the up and down motion of the pistons into rotation. It runs on bearings which are supplied constantly with a thin film of oil.

Whenever an engine restarts it takes a moment before the oil takes the strain and this is when most wear occurs. Cars with start-stop tech have beefier bearings to cope with this and ensure durability.

By the way, automatic start-stop systems have been around since the 1970s. At that time, the oil crisis triggered the technological innovation.

Toyota is credited with having invented the first automatic start-stop system in the mid-1970s and Volkswagen and Audi introduced their versions in the 1980s. A new generation of start-stop systems followed in the 2000s.

Today, it is not only financial aspects but also ecological ones that are making the system more and more popular.