Autoelectro uncovers rare find, a car engine that requires two alternators
Autoelectro has made a notable discovery: the Rolls-Royce 6.7 V12 engine, found in the latest Cullinan, Phantom and Ghost models (2018-onwards), requires two alternators!
While some heavy-duty trucks, commercial vehicles and public service vehicles have required two alternators for some time, for a standard passenger car, one alternator is usually enough – but, for the latest Rolls-Royce 6.7 V12 engines, that is not the case.
How did Autoelectro discover this?
During a routine new-to-range exercise, which results in at least two new part numbers being released every week, AEG1647 was introduced; however, Autoelectro’s production and cataloguing team later identified another OE number with identical vehicle details but differing specifications.
Curious about the discrepancy, Autoelectro procured an OE version of the alternator and conducted a detailed reverse-engineering process. This investigation revealed a key design feature of the engine: it utilises two alternators, one mounted on the left side and the other on the right. Consequently, Autoelectro developed and introduced a new part number (AEG1689).
Why are there two alternators?
Upon some research, it transpires that there are also two batteries fitted to the same engine. It was discovered that one is used for traditional vehicle electrical systems, while the other is for specialised equipment. Autoelectro believes the latter is likely tailored to the unique requirements of high-end Rolls-Royce technology – luxury items like fridge, wine cooler, heated and cooled seats, televisions and ‘ambient’ lighting.
Notably, during the same investigation, Autoelectro’s experts spotted that older Rolls-Royce 6.7 V12 engines – fitted only to 2003-2017 Phantom models – also have two alternators fitted; however, those are both water-cooled alternators. Autoelectro’s data shows that they are the same alternator (AEK2864), but because there’s such a high electrical load, two alternators are needed to manage it.
Contrastingly, the alternators mounted onto the older Phantom line up on top of each other; whereas, on the newer 6.7 V12 engines, AEG1647 and AEG1689 are fitted on opposite sides of the engine and are not water cooled – they are air-cooled and have vast air ducts attached to the rear to help with cooling and ventilation for heat dissipation.
The evolution of Rolls-Royce alternators
Interestingly, Autoelectro’s investigation also uncovered that a different Rolls-Royce 6.6 V12 engine from 2009 – used in models like the Wraith, Ghost and Dawn – was fitted with an air-cooled 220A alternator (AEK3692). This led Autoelectro’s engineers to conclude that the latest 6.7 V12 engine design took the best parts from both the previous 6.7 and 6.6 V12 engines.
By using two air-cooled 180A alternators (AEG1647 and AEG1689), it is possible that Rolls-Royce developed a solution to ensure optimal performance and efficient ventilation, eliminating the need for water-cooling systems.
Leading the way in availability and innovation
While the automotive aftermarket may not see many Rolls-Royce 6.7 V12 engines with two alternators fitted to them, this example from Autoelectro is not just a fascinating insight, but it also demonstrates the commitment and techniques the remanufacturer will go to in order to further expand its range, availability and pedigree in rotating electrics.