Dan
08-27-2009, 07:10 PM
I had another thread on this, but wanted to expand on the subject of efficiency without taking that Gauge thread in a tangent.
As I mention below I'm interested in an Enginer.us PHEV kit. To test how I would do, I choose a completely unscientific method.... I drove it ;). There is a way (*wink*) to top off a Prius battery to any level you choose. So I did the following.
Top off Battery for segment A
Reset Gauge for segment A
Record start SOC for segment A
Drive segment A (until charge is depleted)
Record end SOC for segment A
Record how much fuel was burned since reset (exclude top off exercise) for segment A.
Top off Battery for segment A
Reset Gauge for segment A
Record start SOC for segment A
Drive segment A (until charge is depleted)
Record end SOC for segment A
Record how much fuel was burned since reset (exclude top off exercise) for segment A.
etc...My thoughts were to get a feel for what the MPG delta would be (which I did)Now for the numbers. Keep in mind this was COMPLETELY unscientific (kinda like the VOLT figures). I ignored LOTs. The top-offs heated the engine allowing it to operate more efficiently. The gauges also only read to 1/10th of a mile and 1/100th of a gallon, which is not nearly as discrete as it needs to be to do this properly. I'm also calculating my KWh usage by measure SOC before and after via the SGIIx and assuming the pack capacity is as spec'd at 1310Wh. There is LOTs of room for error in that step to be sure since I don't think the SOC reported is all that linear. But with that said, here are the numbers.
_seg_|_start soc_|_end soc_|_gal gas used_|_miles driven_|_Wh guestimate_|_Notes_
A|71.0|50.5|0.05|6.7|268.6|This was highway, so very small delta W
B|71.0|49.0|0.00|2.4|288.2|All sub division, low speed, ICE never lights
C|71.0|54.5|0.00|1.9|216.2|All sub division, low speed, ICE never lights
D|71.5|47.5|0.00|1.0|314.4|Battery went thermal on this leg so I cranked up AC :(My findings.
Miles Driven = 12.0
Gas Used = 0.05 gal
MPG_gme = 240 (MPG_gme is Miles per Gallon of GM equivalent Gas *wink*).
Without GM hackery:
Miles Driven Mixed = 12.0
Wh Used Mixed = 1087.3
MPG Mixed = 240
Wh/mi Mixed = 90.6
MPGe = 102.1 (based off my MPGe calculator (http://www.cleanmpg.com/forums/downloads.php?do=file&id=28) and Texas GHG emission per KWh (http://www.google.org/recharge/dashboard/calculator))
Breakouts:Segment A: A few miles of suburbs followed by 4 miles of highway.
Mixed mode Driving: 134 MPGg + 40.1 Wh/mi = 100.5 MPGe
Segments B-D: All subdivision driving.
EV only Driving: 154.49 Wh/mi = 104.1 MPGeSince my battery went thermal, I cut the test short, but at 154 Wh/mi and a 3.5 miles left in commute, my projected utilization for the whole trip would have been 0.05 gal and 1551Wh over 15.5 miles. That would have yielded 290 MPGg + 98.26 Wh/mi = 104.7 MPGe. My consumption rate was 36.85 Wh/min and the Enginer Kit produces 48Wh/min (2880 W / 60 min). So my Fantasy Football PHEV seems like it would work just fine.
That felt about right. 80 mpg would have been my best possible on that route with the highway. That's 25% less CO2 by hypermiling a PHEV compared to hypermiling a HEV. It requires a TOTALLY different approach though, but very VERY interesting
...but what really got my attention was how the battery acts. I for the first time found the EV deny thermal threshold *buc = 45 C*. I also noted that the Current Charge Limit moved around a lot more than I thought it would. It's important to leave some room in the battery for regen. At the end of my run my Battery was refusing EV at 47C, so looks like AC is a requirement for PHEV operation (or at least I STRONGLY suggest it).So on the last segment my battery went thermal. It latched me out of EV. It didn't light the engine but it wouldn't let me engage pure EV mode for deeper accelerations. At this point I pulled up the buc gauge and cranked up the AC. The battery was at 47C but I got it back down to 45. After that I opened the trunk and ran with it opened. This helped if I was moving air around but accelerating and decelerating, since this mixes cabin air pretty good. But when I was stationary, very little air seemed to be making it to the battery.
I think thermal surfing will be very important for real good numbers from a PHEV kit.
11011011
As I mention below I'm interested in an Enginer.us PHEV kit. To test how I would do, I choose a completely unscientific method.... I drove it ;). There is a way (*wink*) to top off a Prius battery to any level you choose. So I did the following.
Top off Battery for segment A
Reset Gauge for segment A
Record start SOC for segment A
Drive segment A (until charge is depleted)
Record end SOC for segment A
Record how much fuel was burned since reset (exclude top off exercise) for segment A.
Top off Battery for segment A
Reset Gauge for segment A
Record start SOC for segment A
Drive segment A (until charge is depleted)
Record end SOC for segment A
Record how much fuel was burned since reset (exclude top off exercise) for segment A.
etc...My thoughts were to get a feel for what the MPG delta would be (which I did)Now for the numbers. Keep in mind this was COMPLETELY unscientific (kinda like the VOLT figures). I ignored LOTs. The top-offs heated the engine allowing it to operate more efficiently. The gauges also only read to 1/10th of a mile and 1/100th of a gallon, which is not nearly as discrete as it needs to be to do this properly. I'm also calculating my KWh usage by measure SOC before and after via the SGIIx and assuming the pack capacity is as spec'd at 1310Wh. There is LOTs of room for error in that step to be sure since I don't think the SOC reported is all that linear. But with that said, here are the numbers.
_seg_|_start soc_|_end soc_|_gal gas used_|_miles driven_|_Wh guestimate_|_Notes_
A|71.0|50.5|0.05|6.7|268.6|This was highway, so very small delta W
B|71.0|49.0|0.00|2.4|288.2|All sub division, low speed, ICE never lights
C|71.0|54.5|0.00|1.9|216.2|All sub division, low speed, ICE never lights
D|71.5|47.5|0.00|1.0|314.4|Battery went thermal on this leg so I cranked up AC :(My findings.
Miles Driven = 12.0
Gas Used = 0.05 gal
MPG_gme = 240 (MPG_gme is Miles per Gallon of GM equivalent Gas *wink*).
Without GM hackery:
Miles Driven Mixed = 12.0
Wh Used Mixed = 1087.3
MPG Mixed = 240
Wh/mi Mixed = 90.6
MPGe = 102.1 (based off my MPGe calculator (http://www.cleanmpg.com/forums/downloads.php?do=file&id=28) and Texas GHG emission per KWh (http://www.google.org/recharge/dashboard/calculator))
Breakouts:Segment A: A few miles of suburbs followed by 4 miles of highway.
Mixed mode Driving: 134 MPGg + 40.1 Wh/mi = 100.5 MPGe
Segments B-D: All subdivision driving.
EV only Driving: 154.49 Wh/mi = 104.1 MPGeSince my battery went thermal, I cut the test short, but at 154 Wh/mi and a 3.5 miles left in commute, my projected utilization for the whole trip would have been 0.05 gal and 1551Wh over 15.5 miles. That would have yielded 290 MPGg + 98.26 Wh/mi = 104.7 MPGe. My consumption rate was 36.85 Wh/min and the Enginer Kit produces 48Wh/min (2880 W / 60 min). So my Fantasy Football PHEV seems like it would work just fine.
That felt about right. 80 mpg would have been my best possible on that route with the highway. That's 25% less CO2 by hypermiling a PHEV compared to hypermiling a HEV. It requires a TOTALLY different approach though, but very VERY interesting
...but what really got my attention was how the battery acts. I for the first time found the EV deny thermal threshold *buc = 45 C*. I also noted that the Current Charge Limit moved around a lot more than I thought it would. It's important to leave some room in the battery for regen. At the end of my run my Battery was refusing EV at 47C, so looks like AC is a requirement for PHEV operation (or at least I STRONGLY suggest it).So on the last segment my battery went thermal. It latched me out of EV. It didn't light the engine but it wouldn't let me engage pure EV mode for deeper accelerations. At this point I pulled up the buc gauge and cranked up the AC. The battery was at 47C but I got it back down to 45. After that I opened the trunk and ran with it opened. This helped if I was moving air around but accelerating and decelerating, since this mixes cabin air pretty good. But when I was stationary, very little air seemed to be making it to the battery.
I think thermal surfing will be very important for real good numbers from a PHEV kit.
11011011