Vehicles fitted with a smart alternator in Australia

They’re called variable voltage alternators, but the car-making world has started calling them smart alternators. But if you’re an off-roader, or drive a car with lots of accessories, the tech mightn’t seem very smart at all.

Smart alternators are one of many recent technologies aimed at squeezing a few more metres out of every drop of fuel, but as many car owners have found, there are some serious side-effects to this nth-degree fuel saving stuff.

So what does a car alternator do and what is a smart alternator?

Because an alternator is (traditionally) driven via a rubber belt from the engine, it consumes a small amount of engine horsepower to operate.

The idea is the alternator produces electricity to run the car’s electrical systems and keep the battery charged up. The more power the alternator produces, the more engine power it consumes, and that equals those precious drops of fuel.

So, the theory developed by carmakers is that if you can reduce the amount of voltage the alternator produces, you can reduce the amount of power, and therefore fuel, it consumes.

So, what a smart alternator does is it charges at a slightly lower rate than a conventional alternator. Then, when the driver lifts their foot off the throttle, the alternator senses this and suddenly ramps up the charge rate to quickly charge the car’s battery using momentum in the driveline versus the engine’s power.

At which point, it’s charging the battery with no extra fuel being consumed by the engine. It’s a bit like the way an EV uses braking regeneration to charge its battery. Smart, right? Maybe.

The problems start when you have a vehicle that has electrical accessories or a second battery (a very common addition to a touring four-wheel drive) to power, say, a fridge, that the smart alternator doesn’t recognise.

So, it continues to charge at its slightly lower rate which is not enough to keep that second battery charged. And suddenly, you have a fridge that doesn’t keep stuff cold any longer. Not ideal.

And its not like you can just add a bit of wiring to join the two batteries, as the smart alternator is controlled via the car’s ECU (on-board computer) and isn’t that easily hacked.

That said, one solution is to fit a DC to DC charger system which should keep both batteries charged.

Also, some owners of vehicles with smart alternators don’t report any shortcomings, and will claim a smart alternator dual battery system will work perfectly. But for others, a flat fridge battery is the end result.

Some vehicles can be switched to a non-smart (for want of a better term) alternator at the dealership come service time, too, so it’s worth asking about this.

So when did smart alternators come out in mainstream makes and models? We first started seeing them around 2010 and by 2015 they were getting pretty common as carmakers were trying harder and harder to reduce fuel consumption and achieve the latest emissions standards around the world.

There’s no definitive list of vehicles with smart alternators Australia wide but we do know of plenty of brands that do fit them.

Those include a lot of the Chinese made utes like the LDV T60, and plenty of Thai-made utes. That said, a lot of them don’t, either, and the MR Triton is one that uses a conventional – or fixed voltage – alternator. But the Holden RG Colorado, Ford Ranger and Nissan Navara NP300 do have smart units.

We’re also seeing a lot of European-sourced commercial vehicles - Ford Transits, Mercedes Sprinters and Renault vans - with smart alternators, too.

The 200 Series LandCruiser didn’t have a smart alternator but the newer 300 Series does, and the Prado 150 also used a fixed-voltage unit, probably in deference to the type of use to which these vehicles were commonly put.

But what about the more utilitarian Toyotas that are more workhorse than plaything? Does the 79 Series have a smart alternator? No, it doesn’t. Again, for really sound reasons.

So, with no published list that we could find, plenty of owners are asking: Does my car have a smart alternator? And the good news is there’s a pretty sure-fire way to find out.

The smart alternator is defined by its preference to run at a lower voltage. So, once you know how to check alternator output, you’re on your way to finding out what type of alternator you have under your bonnet.

The best way to test alternator output is to use a multi-meter set to volts. Start with a cold engine, preferably one that has been sitting overnight. Switch off all electrical gear like fans, radios and lights.

With the engine started and the multi-meter probes placed across the terminals of the battery, alternator output should read about 14 volts or perhaps a little more.

Now, either take the car for a quick drive or let the car idle for five to 10 minutes. Check the reading again across the battery terminals.

If the alternator voltage output has now fallen to 12.5 volts or so, you have a smart alternator. If it stays between 12.8 and 14.4 volts, you have a fixed voltage unit.