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Powering up with stop-start batteries

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Updated 6 Sep 2021

Paul Tugwell

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Stop-start systems on new vehicles are becoming a common feature these days and it’s a fairly easy system to understand.

When your car comes to a stop, instead of running idle the system cuts the engine.

Take your foot off the brake, the engine comes back to life and off you go. Simple.

It takes a bit of getting used to – for the uninitiated it can feel very odd for the engine to be completely dead when all you’ve done is stop at the traffic lights – but there’s no doubt it is a clever system.

It’s designed to have two major benefits – save fuel and reduce pollution. Makes sense.

If your engine isn’t running, then it’s not consuming fuel or producing pollution.

There are plenty of people who will argue that these reductions and savings are so small as to be insignificant, but every little bit helps, right?

Now, while it is designed to be friendlier on your wallet and the environment, the start-stop system is not on as good terms with the battery.

In fact, it is asking the battery to work quite a bit harder.

A standard car battery – a lead-acid flooded battery known as an LSI (lighting, starting, ignition) battery – is designed to give the engine a decent starting jolt a handful of times a day.

A stop-start system demands the same task be performed dozens of times a day. That’s hard work.

And it’s not just that constant stop-start power that’s needed either.

Just as in any other vehicle, when the engine is not running, everything else you want to use – from the infotainment systems to lights, from the air conditioning to a phone charger – gets its juice from the battery.

That sort of heavy lifting requires a battery with some extra oomph. And that’s where the start-stop batteries come in.

Types of Stop-start batteries

ECM (Enhanced Cyclic Mat) battery:

Also known as an Advanced Flooded Battery (AFB) or Enhanced Flooded Battery (EFB) is designed to meet entry-level stop-start technology requirements.

This battery is an improved version of the standard lead-acid flooded technology found in LSI batteries.

It is more durable, allows for a more consistent flow of power, has deep cycle capabilities (meaning it can dip deeper into its capacity without losing performance), faster recharge capabilities and an improved cycle life (the number of times it can be charged and discharged before it expires).

Absorbent Glass Mat (AGM) battery:

The most advanced example of lead-acid technology, with the acid absorbed into a fibreglass material rather than remaining as a free-flowing liquid.

The AGM battery is maintenance-free, fast charging, has a high power output, improved cycle life, excellent deep cycle properties and can continue to deliver high cranking power (the kind of power needed to kickstart the engine) even with a low state of charge.

AGM batteries can also be used with regenerative braking systems – a system in electric and hybrid vehicles which allows the energy created through braking with electric motors to be diverted to recharge the battery.

While both of these battery types can be used with stop-start technology, they are not interchangeable. ECM batteries can be replaced with an AGM battery, but vehicles designed to take AGM batteries should only ever use AGM technology. Standard LSI batteries should not even be considered.

As always, check with your vehicle’s manufacturer for guidance, or use the services of a qualified mechanic or auto electrician to make sure you’re installing the correct tech.

If you’re looking to replace or inspect the battery in your car, AutoGuru can help!

We connect you with high-quality local battery specialists for hassle-free battery check-ups and replacement.

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Written By

Paul Tugwell

Paul has been working in the automotive industry for 50 years and since 2004 has been training apprentices and students across Queensland in the dark arts of the auto-electrical trade and hybrid/electrical power sources and systems.