After the Audi 48V light hybrid electric vehicle (MHEV) appeared on the market, I would like to further study the advantages of 48V MHEV compared with the traditional 12 V engine system.
Audi A8 is proven over the vehicle such comparative experiments because it is both possible to use conventional 12 V from moving engine machine , it can be used 48V starting system . From the starting point of view, during the stop/start phase, the 48 V system can provide greater torque and power without the hysteresis of the 12 V system.
With this in mind, I think it would be helpful to compare the data of the two systems over time with the mathematical channel.
First, start with the 12 V system, and then we will use a traditional starter motor to start the V6 3.0 TDI engine.
Figure 1 RPM curve of 12V system
As shown in Figure 1, I have calculated the starting power through the mathematical channel voltage * current, and calculated the engine RPM from the crankshaft sensor signal (using low-pass filtering). In Figure 2, I added multiple math channels to calculate torque (N·m) based on power and engine speed, calculate power consumption in watt hours (Wh) based on power and time, and integrate power to calculate it in watts Power consumption in seconds (Ws). Adding some measurements, we can get the waveform and value of each event during the 460ms period required to start the engine.
Figure 2 12V system torque and electric energy curve
Next, we observe the difference between starting the same engine with 48V system. The torque (N·m), the energy consumption in watt-hours (Wh), and the energy consumption in watt-seconds (Ws) are still calculated through mathematical channels, so as to directly compare the two systems .
Figure 3 RPM curve of 48V system
Figure 4 48V system torque and electric energy curve
The most obvious difference between the first term is, 48 V system from actuation time only as 277 ms, 12 V system and from actuation time of 460 ms. Although 460ms is already a very good data, it should be noted that when using a 48 V system, the starting speed quickly increases from zero to idling conditions, and it reaches a speed of 600 rpm or more in a quarter of a second!
Summarize the test results:
Figure 5 Comparison of results
I need to review the data of the power (mWh) consumed by the 12 V system because they don't look correct! This may be because three start events were collected in one waveform buffer, and the 48 V system only contains one start event. I will give feedback as soon as possible.
All in all, the increase in power , torque and speed of all these data is due to the completely independent 48 V power supply system, so the impact of the start-stop phase on the 12V system is minimized. In addition, fuel consumption, emissions and energy recovery have all been improved.