Autoelectro provides a look at smart charge alternators, exploring the complexity of their design and how they have evolved over time.
Smart charge – or intelligent charge – alternators have been available in the automotive aftermarket for some time. However, the complexity of their design has evolved over time. Consequently, rotating electrics remanufacturer, Autoelectro, has invested heavily in the latest test equipment, to ensure it stays ahead of the technological curve and offer the latest applications to the marketplace as quickly as possible.
Vehicle manufacturers, under pressure from governments and environmental policies, have had to find ways to reduce emissions and increase fuel efficiency, according to Autoelectro UK Sales Manager, Nick Hood. He believes the introduction of engine control units (ECUs) has allowed for closer interaction between the different vehicle components:
“Sensors can now constantly monitor the performance of all the critical areas of the vehicles, such as air flow, engine speed, manifold pressure, fuel burn performance, temperature and voltage. All of this information is collated by the ECU to maximise the performance of the vehicle and reduce emissions.”
Smart charge alternators can usually be identified from their regulator plug type – LIN, BSS or COM, for example.
Essentially, a smart charge alternator is controlled externally by the ECU, with information communicated between the two via a cable. The output of these alternators can vary, depending on the information sent to the ECU from the various sensors: the condition of charge of the battery, demands from the vehicle’s electronic parts and accessories, such as heated screens/seats and infotainment systems. The benefit of the smart charge system is it can output a lower voltage over a longer period, thus reducing the drag upon the engine, leading to improved fuel efficiency.
A battery accepts charge more efficiently when it is cold. For this reason, a smart charge alternator will charge at a higher rate to maximise the performance and bring the battery back to optimal operating level. Once this level is achieved, the ECU will reduce the alternator output to supply the vehicle’s demands.
It should be noted that the battery charge light affiliated with smart charge alternators is no longer actuated by the alternator itself – but via the ECU. The battery charge limit can illuminate for various reasons, and the vehicle should always be checked for underlying faults before condemning the alternator.
Nick provided an example of this scenario: “This is common on three-pin regulator Ford type alternators fitted to Fiesta, Focus, Kuga and other similar models (AEK2815). A common fault exists on the vehicle’s wiring loom, which is around 40cm long, in that it has been found that corrosion can occur and can interfere with the connection between the alternator and ECU.
“This can lead to the battery charge light illuminating and possibly low or no output from the alternator. Removing the three-pin plug from the back of the alternator will slip the affected part into ‘limp’ mode and should produce between 13.4 and 13.8V, which signifies that the alternator is functioning correctly, and the problem lies elsewhere in the circuit. A vehicle should never be run for a long period of time with the ECU communication cable unplugged.”
Autoelectro’s website allows visitors to check if an individual application has a smart charge and contains information on the plug regulator and pin functions.
Tips for diagnosing a smart charge alternator
When testing a smart charge alternator, the communication between the alternator and ECU is in a ‘wave’ and requires a suitable device to read the pattern, such as an oscilloscope. Technicians should use the VM’s guidelines for assessing wave patterns.
The signal from the ECU to the alternator should be a square wave pattern that will change with load request; if there is no change in the pattern, it is likely there is an ECU communication fault.
The signal from the alternator should remain a constant square wave pattern; if this pattern mirrors the signal from the ECU, the issue may lie with the smart charge alternator.
