What the 2022 Toyota LandCruiser 300 Series' alternator means for off-roading in Australia

Carmakers invest years, billions of dollars and millions of kilometres of testing making sure their latest product is fit for purpose, but it’s often the details that set some makes and models apart from the rest. 

In the case of the new Toyota LandCruiser 300 Series, there’s a chance the vehicle has taken a backward step compared with the outgoing 200 Series.

And that’s in the electrical department; specifically, while the 200 Series had a factory dual battery set-up, no such option appears to exist for the 300. 

Given that the LandCruiser has always been a popular rig for outback touring where extra lights and a fridge are mandatory accessories (the latter, especially, requiring an auxiliary battery) the lack of a second battery from the showroom won’t please everyone.

But it’s not all bad news, as the new Cruiser’s charging system seems to be a preferable set-up to the increasingly common – and reviled in touring circles – smart alternator used by many of its competitors. 

As environmental concerns increase globally, carmakers are switching to smart alternators as a means of improving fuel economy and reducing tailpipe emissions. These units reduce the load on the engine by reducing the charge rate of the alternator. Less load means less fuel burned. 

In theory it’s a great idea. The problem for many owners who use their vehicles for outback touring, is that it’s not really the best alternator solution, and Toyota clearly knows this.

Also known as computer-controlled alternator or a variable voltage alternator, these units have caught out owners who have a lot of electrical accessories or dual-battery systems fitted. Those same owners have complained that while the clever alternator is great at keeping the main battery fully charged, it’s not so smart at getting the second battery to a fully charged state or keeping it there.

Fundamentally, the difference between a normal and a smart alternator is a simple one: The conventional alternator has an internal regulator that controls the charge rate, while the smart alternator takes its regulating cues from the ECU. What that means, in effect, is that the smart alternator obeys the ECU as a reflection of the charge condition of the vehicle’s main battery. As long as that battery is fully charged, the ECU is happy. The ECU can then decide whether to command the alternator to charge at the usual 14.4 volts or, once the main battery is fully charged, it can reduce the charge rate to somewhere between 12.5 and 13.5 volts. 

And this lower charge rate is simply not enough for a dual battery system with a fridge constantly draining the set-up. In fact, some specialists claim that the reduced charging rate results in the second battery only ever achieving a best of about 70 per cent of its charge potential.

This also has an implication for electrical accessories like extra vehicle lighting, camping lights, radios, and even details like a phone charger. For the ECU to recognise that they’re fitted – and to adjust the charge rate accordingly – these accessories must be earthed to the vehicle’s chassis or body, not the negative terminal of the car’s battery.

The smart alternator can also cause problems for vehicles that link their two batteries with a Voltage Sensing Relay (VSR). This device normally ensures that both batteries remain fully charged, but some experts tell us that a smart alternator that allows its output voltage to drop too far, say, below about 12.7 volts, will cause the VSR to disconnect the two batteries, allowing the auxiliary battery to go uncharged.

Even without a VSR, if the second battery is located outside the engine bay, the voltage drop inherent in a longer cable might also see that battery not receiving any charge, or at least not the amount it requires to become fully charged. 

The solution for many owners of four-wheel-drives fitted with smart alternators has been to have the ECU reflashed to remove this functionality. The catch here is that there may or may not be warranty ramifications in going down this road. 

But there are other solutions, including on-board battery-chargers (known as battery-to-battery chargers). Whether or not a dealership can reflash the ECU to return an alternator to conventional operation can vary from make to make and model to model. But perhaps the best hack is also the simplest one. In some cases, simply driving everywhere with the car’s headlights on will force the alternator to acknowledge the voltage drain and step up its game sufficiently to getting everything charging at a suitable rate. It mightn’t work in every case, but it’s probably worth a shot.

Off-roaders we know of that already use smart alternators include the Nissan Navara D40 from 2011 on, Nissan R51 Pathfinder from 2011 on, Range Rover 4 from 2011 on, Ford Ranger from 2011 on, Mitsubishi Pajero from 2012 on, Land Rover Discovery 4 from 2009 to 2016, Nissan Patrol Y62 from 2012 on and the Jeep Grand Cherokee from 2013 on.

Of course, it’s never that simple and what the new LandCruiser does have is a temperature compensating alternator. This unit looks at the temperature of the driveline and keeps the charge rate higher at lower temperatures typical after a cold-start when the start-battery may be slightly depleted. Then, once the driveline is up to temperature, the alternator backs off to as low as 13.2 volts. But experience has shown that this may not be enough for some touring rigs, so it’s worth keeping an eye on the voltage in that all-important second battery.

Toyota has used this type of alternator on just about every off-roader it has sold in Australia since about 2010 onwards, so it’s a well-known quantity in the trade.

Meantime, the subject of a dual-battery set-up is currently being furiously worked on by this country’s small army of four-wheel-drive accessory manufacturers. We haven’t heard of a system available just yet, but it won’t be far away. 

Unfortunately, it’s unlikely to be a cheap solution as the crowded LC300 engine bay is proving difficult to fit with a large, heavy second battery. Current thinking seems to be to move some of the factory fittings from behind the driver’s side headlight and mount the second battery there. Either way, it won’t be a simple conversion thanks to the complexity involved in making it physically fit.