Moving knowledge forward on low -voltage hybrids While there is nothing to fear from low-voltage technology, be wary of complacency. Rob Marshall, therefore, discusses the pertinent issues with remanufacturing exponent, Autoelectro, to establish the reasons why To reduce CO2 emissions (and, therefore, take advantage of taxation benefits) start-stop technology stalls the engine and restarts it promptly. These micro-hybrids were refined into mild-hybrids, the majority of which utilise 48-volt combined belt-driven starter-alternators. Autoelectro reports that, because these costly units are tricky to copy accurately, remanufacturing is essential to introduce quality aftermarket replacements quickly. The company argues that quality remanufacturing is a preferable option over a copy
Be familiar with the low voltage micro/mild-hybrid application (i.e., under 48 volts), with which you are faced. Pictured is an early Bosch Stop-Start application for non-manual gearbox vehicles.
part that has not been produced by the original manufacturer. Therefore, a removed faulty unit is still valuable as core. A further issue is that some rotating electric components are becoming bespoke to certain models, so copy parts may not be viable, due to too low a production run. Even so, being familiar with the application on which you are working, adopting a logical diagnostics process, and addressing the fault, not just the symptom, will stand you in good stead.
Smart alternators
1. Some micro-hybrids can possess smart alternators, which charge at variable voltages. Between 10 and 18 volts are typical. Should the unit be found not to be charging at an expected constant voltage, or even not at all, something else on the vehicle may be responsible, instead of a faulty alternator. (Image courtesy of Bosch).
2. Communication between the alternator and engine ECU is via Pulse Width Modulated (PWM) data signals. Pictured are both LIN (Local Interconnect Network) and BSS (Bit Synchronous Interface) connections, which you are most likely to encounter. Alternatively, the Digital Field Monitor (DFM) connection sends an alternator load signal to the ECU. 'FR' directs a variable output of between zero and 11 volts to the ECU to assess the battery charge rate. Never introduce test voltages into these data wires.
Combined starter/alternators
1. Low-voltage mild-hybrids can employ these units, mounted to the FEAD drive. A separate starter motor may be fitted for cold-start purposes. Valeo's StARS was the first massproduction combined starter-alternator unit, although OEMs use their own terminology. Ford uses the acronym, 'B-ISG', (Belt-driven Integrated Starter Generator), for instance.
ROTATING ELECTRICS
3. An oscilloscope displays real-time smart alternator responses to loading the electrical system. Yet, Autoelectro advises that you can disconnect the alternator-to-ECU communication wires (See Step A2), which enables the alternator to run independently of the ECU. The resultant voltages should measure between 14.5 and 14.8. Consider, however, that you may create the StopStart system to log a fault code, which you must reset afterwards. (Image courtesy of Pico Technology.)
"Because these costly units are tricky to copy accurately, remanufacturing is essential to introduce quality aftermarket replacements quickly"
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