Stop-Start technology - an overview

Modern cars possess a bewildering range of technologies to make them more efficient. While many of these systems work better under laboratory conditions, rather than those in real life, savings still result, if they are used correctly.

Fuel economy

Should fuel economy be high on your priority list, it may be worth choosing an older vehicle, equipped with automatic Stop-Start technology. New car buyers tend not to have a choice: virtually every new car has Stop-Start fitted as standard, whether you like it, or not. The latest vehicles also have no means to switch the system off.

What is Stop-Start technology?

Instead of letting it idle, Stop-Start technology cuts the engine, when the car is stationary in traffic. The engine is then restarted, when either the clutch pedal is depressed, or the brake pedal is released.

Are Stop-Start Engines More Efficient?

The jury is out in the long term, because the initial fuel savings are likely to be eclipsed by higher maintenance and repair costs, as the car ages. These include pricier batteries and starter motors.

Aside from saving money, becoming familiar with how the car's systems react is good for safety. For instance, so you ensure that the engine does not cut-out, when you need to execute a swift manoeuvre.

Start-stop technology disadvantages

Special 12-volt batteries are also requirements for most cars possessing Stop-Start. Basic systems need Enhanced Flooded Batteries (EFB) at least, whereas more

sophisticated versions require those with Absorbed Glass Mat (AGM) technology. Unsurprisingly, they are more expensive and more powerful than standard flooded batteries, which have been in use for many decades. Stop-Start vehicles also tend to need the charging systems programmed after the battery is replaced, adding to the cost.

Cars with Stop-Start should not have their battery technologies downgraded. Doing so is a false economy, which can damage both the battery and electrical system. It also can disable the Stop-Start system, so you also lose the fuel-saving potential as well.

Stop-Start not ready - battery charging

Sometimes, the Stop-Start will not activate. In this situation, some cars will flag an advice message, while others may not. When activated, Stop-Start considers a variety of factors, before it deploys. These include not just battery health and charge levels but also engine coolant temperature and even the status of the interior heating and ventilation system.

Yet, there could be a problem that prevents the Stop-Start from functioning. Therefore, you are likely to see a 'Stop-Start not ready – battery charging' message, or similar.

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