As many of you know, I am very interested in understanding how the car works. For that purpose I bought a ScanGauge last summer and recently purchased a cheap Android tablet from Amazon and a Wi-Fi ELM 327 scanner to communicate with the tablet and Torque Pro app. The tablet setup is not very useful to look at data while moving to adjust my driving style, but it is very useful to log data to analyze offline. The ScanGauge does not log data to be able to analyze after the fact. I also bought a splitter cable so that I could use both the ScanGauge and the tablet at once, but they don't work together in the Fusion. In the Prius I can use both devices at the same time. Special thanks to larryh for explaining many things to me and getting me setup!
I am going to use this thread as my overall summary of everything that I have learned about the FFH powertrain operation to date. I will also continue to post future knowledge gained in this thread.
ICE Operation Observations
- Horsepower - the generator often places about a 15 horsepower load on the ICE when the battery is low and the ICE is doing maximum recharging. This is good for about 35 amps of current flowing into the HVB. In other situations it seems that each hp of ICE output to spin the generator is good for slightly less than 2 amps of current flowing into the HVB. In these situations the Generator Torque is consistently about 30 newton-meters. Torque shows this torque as a negative number. I think that's the unit of my data at least. Unfortunately, I don't have a way to track HP with Torque (just LOD) so I cannot calculate how much of each HP of engine output becomes 1 kW of electricity generated unless someone else can see something that I'm missing that would allow me to do so.
- With the ScanGauge II two of the most useful gauges I've found are the Horsepower and LOD (Load) gauges. Below is a BSFC chart for the 2nd Gen Prius (1.5L engine) and 3rd (current) Gen Prius (1.8L engine). BSFC = Brake Specific Fuel Consumption. If you aren't familiar with what that means you can read more here. Do take the time to read the explanation. Understanding this concept is crucial to maximizing your fuel economy.
Notice how the Prius is most efficient, a low g/kWh, at a fairly high power (kW) output but a low engine speed (less than 3650 RPM). To get such a high power output a such a low speed the computer must be placing a high load on the engine. As described in the link above, in a normal gas car you're often operating at only about 25% throttle which is a light load on the engine. In the hybrid, the generator places a load on the ICE to increase the load and get the car to run in a more efficient BSFC region. For the Prius, which has a smaller engine, the kW output is a maximum of about 30 kW in the peak BSFC region. 30 kW = 22.37 hp. That isn't a lot of power demand. Unfortunately I don't have a BSFC graph for the FFH 2.0L engine. However, based on my observations of hp and LOD readings on my ScanGauge I have a pretty good idea where it is...When the FFH SGII output shows 33-42 HP (24.6-31.3) I have observed a LOD of 95+. This is typically a 2 bar acceleration on the Empower screen. The FFH acceleration coach considers this to be efficient and returns the maximum score on the acceleration coach bar. If I accelerate more slowly, I only see LOD numbers in the low seventies to low eighties. When accelerating harder than this I still see a high nineties LOD but the ICE is too far off to the right on the graph and is out of the most efficient range. This leads me to believe that the peak BSFC region for the Ford 2.0L Atkinson-cycle engine is somewhere around 20-35 kW of power. I have asked Ashley a few BSFC related questions and have been told that this info is proprietary and that Ford will not share that info with me.
- Warm up stages - when the ICE is in S1a the power demand on the ICE is very low, less than 10 hp and a LOD less than 60, this is quite inefficient and shows why skipping stage S1a improves fuel economy so much as discussed here.
- Transmission/battery storage efficiency appears to be about 95% when the ICE is generating electricity. I will continue to calculate more data for this as I have time to confirm the 95% efficiency and to check if other factors affect that efficiency. For example, Torque allows me to log the amps and volts at 1 second intervals. During a prolonged stretch of ICE on HVB charging I used the amps and volts from Torque to calculate the kW generated each second. I then converted this to kWh. Then I summed the kWh from my second-by-second calculations of kWh - ((amps x volts)/1000)/3600. I then looked at the percent change in absolute SOC according to Torque/ScanGauge. The car displays this data to 8 decimal places on the Torque app, this is very precise data. I took that delta in SOC and multiplied it times 1.4 since that's the kWh capacity of the pack. Then I could compare the data. Here is a set of sample calculations:
kWh used SOC change SOC calc kWh Efficiency
0.10368587 7.78199768 0.108947968 95.170%
EV Operation Observations
- Amps - the maximum regen braking charge seems to be about 65-70 amps. I've never seen the regen braking charge go above 75 amps while still getting 100% brake score. That seems to be the limit for using the traction motor as a generator (when braking the traction motor recharges the battery, when the ICE is charging the battery the electricity is generated by the generator motor). When driving in EV 1 bar on the Empower screen is about 40 amps of current flowing out of the battery. The max current I have seen flowing out of the battery has been about 110 amps. This happened when I was accelerating in EV at 1.5 or 1.75 bars and then it kicked over to the ICE. Since one motor/generator must spin the ICE up to speed (like a starter motor in a conventional car) there is a momentary spike in amps flowing out of the battery to start the ICE. There is also a momentary positive value of Generator Torque of about 18-21 newton-meters right when spinning the ICE up to speed.
- Recharging - The computer likes to charge the battery with a ~30 amp current flow when the battery SOC is low to maybe about 75% of the display. This seems to be in the most efficient range of the ICE as well as the LOD will often be 85+ when this load is placed on the ICE by the generator while accelerating. When the battery SOC is higher than 75% of the battery icon the amps from the ICE generator drops to 10-20 amps. If the battery is almost full the current flow drops to about 5 amps. Note: the car will aggressively charge the HVB if the useable SOC is less than 40%. From 40-50% useable SOC it will slowly charge the HVB as mentioned above.
- Coasting - when coasting with your foot off the gas pedal the generator places about a 5-10 amp load to gradually slow the car down.
- Idling - when idling the current draw to run the computers and charge the 12V battery is about 1.1-1.2 amps. This amount of current is drawn whether the car is in Park, Reverse, Neutral or Drive as long as you are not moving. The brake lights pull a minimal amount of current, but enough to make this range 1.2-1.3 amps when you are stepping on the brake.
- Lights - the headlights/taillights draw about 0.5 amps (140 watts). The park lights and fog lights draw the same amperage as the headlights. If you combine headlights and fog lights the current draw is about 0.9 amps (260 watts). This means that the headlights and fog lights each draw about 0.4 amps (110 watts) and the park lights draw about 0.1 amps (28 watts)
- Current draw when off - after turning off the car in the few seconds before the SGII turns off the power draw shows 0.08 amps. This is likely to run whatever computers are still active to display the Trip Summary and Lifetime Summary screens.
- Battery display on dash without charge/discharge arrows - It is very hard to get the battery display to show no arrows for charging or discharging. It appears that while moving the car displays no arrows when the current flow is less than 2 amps in or out of the HVB. However, sometimes the current flow will be less than 2 amps and the dash will still display arrows for charging or discharging. Also, when stopped a current flow of less than 2 amps displays as the HVB is discharging. No matter how hard I've tried I have never been able to get the display to show 0.00 amps as the current flow. With steady pedal pressure it is possible to keep the amp flow steady for many seconds though while driving as long as the slope of the road doesn't change.
High Voltage Battery Pack Observations
- HVB temps - the HVB temp quickly increases when driving from the current flow in and out of the battery. In the winter, the HVB fans kick on when the HVB exceeds 70oF. The fans will stay on even when the HVB temp drops as low as 68oF. I haven't had any trips where the HVB temp has gone above 70 to trigger the fans and has then dropped lower than 68 with the fans operational to see if the fans will shut back off.
- It seems that the useable SOC will jump around when the HVB temp changes while the car is off. If the HVB cools then the useable SOC jumps. If the HVB temp rises from having been cold, the SOC seems to fall.
- The max power limit for the HVB is normally 35 kW. When the battery is very cold this drops. This also appears to drop when the HVB is very warm, but I don't have hard data to support this. This post shows data that an Energi owner gathered. The FFH should roughly compare.
- AC amp draw - the AC will draw 30-40 amps from the HVB when first turned on with a hot car. Once the car has cooled down the AC continues to draw an extra 4-7 amps minimum that we observed. This puts some numbers to the effect of AC on gas mileage. That is a lot of current that must be replaced by burning gasoline. 30-40 amps is roughly 8.4-11.2 kW of power draw to run the AC at first. This is a huge power draw.
- HVB Volts vary from 255-305 in my observations. Low voltages happen when the HVB is discharging and at a lower SOC. Higher voltages happen when the HVB is being charged and the SOC is higher. Volts are most commonly 280-290 and I typically use these numbers in my calculations.
- The battery icon on the dash is not linear. A 75% useable SOC equates to a battery icon that is ~8/10-9/10 full. A 60% useable SOC equates to a battery icon that is roughly 2/3 full. A 40% useable SOC equates to a 1/2 full battery icon. And a 20% useable SOC equates to a battery icon that is roughly 1/4 full. The 5% useable SOC that triggers the ICE to run and charge the battery while idling appears as roughly 1/8 full on the dash icon.
- The battery icon displays a rough estimate of the useable SOC of the battery. You can convert the useable SOC to the absolute SOC since the ScanGauge/Torque apps will allow you to access both data points. The linear equation is: y = 0.3837x + 0.312. y is the overall SOC and x is the useable SOC. This provides us some interesting data:
- The intercept is 31.2%, this means that if the useable SOC showed 0% the actual battery SOC would be 31.2%
- If we plug in 100% for x we get a result of 69.57% (0.3837 x 1 + 0.312)
- When idling the car will not let the useable SOC drop below 5% (33.12% absolute SOC) before turning on the ICE to charge the HVB. The ICE will run until the useable SOC reaches 30% before turning off again
- This means the limits for HVB charge are 33.12% and 69.57%
- Since the car doesn't really allow the useable SOC to go much below 15% and doesn't often let it go much above 60% we can see that in normal driving the range is 36.96%-54.22%
- However, most trips don't see the useable SOC get as low as 15%, it's very hard to keep the car in EV mode once the useable SOC gets below 20% unless you're cruising on flat ground at low speeds with a minimal power demand. A typical useable SOC range while driving is 20-60%, this equates to 38.87%-54.22%
- The r2 is 0.998 indicating that the linear trend line is very accurate.
Power Flow Screen Observations
- Charging HV Battery
Here you have blue flow from the electric motor to the battery. There is also blue flow from the electric motor to drive. There is white flow from fuel to engine to drive and from engine to electric motor. This seems to be one of the most common powertrain options chosen by the FFH computers. This screen often shows when traveling at highway speeds. In this mode both the Generator & the Traction Motor are consuming mechanical energy from the ICE and are sending electrical energy to the HVB. In this mode the wheels are only receiving power from the ICE.
- Hybrid Drive
In this case the HVB is also often being charged. When the HVB is being charged in Hybrid Drive the Generator is consuming mechanical energy and is converting it to electrical energy. Some of that electric energy is then consumed by the Traction Motor and converted back into Mechanical Energy to propel the car. The remaining electrical energy is sent to the HVB
Sometimes the HVB is not being charged when in Hybrid Drive. Most often this occurs on the freeway when the HVB reaches a high level of charge. Sometimes the Traction Motor consumes mechanical energy and converts it to electric energy, then the Generator consumes electrical energy and converts it to mechanical energy to assist the ICE is propelling the car.
Grille Cover Observations
- With 100% grille blocking and ambient temps below 20 degrees F I see that the coolant temp peaks at 185 F, Motor Inverter Coolant temp peaks at 120 F and Generator Inverter Coolant temp peaks at 140 F. These peak temps have been very consistent. I have never seen temps exceed the aforementioned values with 100% grille blocking. Highway driving generally keeps the Inverter temp between 100 F and 130 F (it cools to 100 F when driving short stretches of EV mode and then spikes quickly when the ICE is on and charging the battery). The Motor temp seems to usually hover between 100 F and 110 F when driving long freeway stretches. In city driving the Inverter temp quickly falls to the 60s or 70s since the ICE runs less and thus the generator does less work. In the city the Motor temp tends to be higher than the Inverter temp since the Motor is doing more work. Long stretches of city driving seem to keep the Motor temp between 65 F and 80 F. Regen braking causes the biggest spike in Motor temp, much more than accelerating in EV causes the temp to spike.
- As the weather warms I will slowly increase the air flow into the engine compartment to monitor these temps. These temps were a concern about grille covers prior. Now I am not concerned because I expect that temps will be much hotter in the summer with 0% grille blocking than they are now.
- As the weather has warmed the grille blocking has led to coolant temps exceeding 200 F. The peak I have observed has been about 230 F. This is still right at the midpoint of the temp gauge on MyView. The temp gauge is no higher with a coolant temp of 230 F compared to 180 F. This tells me that 230 F is a good operating temp. I will slowly begin removing foam now with increasing ambient temps and will report back.
Edited by hybridbear, 19 May 2014 - 12:36 PM.