Would double battery = double mileage?

[Frank Lee]

I think VW 1L is pretty much unmatched efficiency for a street legal vehicle. If they'll build it.

[ShadeTreeMech]

There is the above option, or simply bassjoos out a honda civic and get close to 70 mpg going 60 mph.

[bwilson4web]

Originally Posted by dcb

. . .
from seconds 335 to 355 you are indicating an increase in speed from maybe 43 mph to 49 mph. At the same time you are indicating the ICE wattage going from a peak of ~13.5kw down to ~10kw. The battery isn't doing anything terribly interesting either at that time, . . .

Correct as this is field data. I don't have the exact altitude data but the profile is consistent with driving north from a stoplight at:

• latitude longitude :: altitude
• 34.665634 -86.572073 :: 186m(*)
• 34.674184 -86.574830 :: 180m
• 34.678893 -86.576275 :: 180m

The 6m drop in altitude is enough to contribute the slight speed increase while the engine power is going lower.

The data shows:

• 298-304 - traction battery supported launch from dead stopped
• 304-318 - normal operation where MG1 is the generator and MG2 is the motor
• 318-320 - transition from normal to energy recirculate mode
• 320-end - MG2 is generating the power that flows to MG1 to provide counter torque for the ICE

Originally Posted by dcb

. . . conditioning efficiency of 70% prior to mechanical conversion? . . .

This reads like professor Raf Catthoor's efficiency number, 70%, which he states without showing how it was calculated or measured. Perhaps you can show how the 70% was calculated?

For efficiency, I prefer to use lab measured, ORNL/TM-2006/423, Appendix B, which gives a range of values from 55.5-92.7%. Given the fairly low power range, the efficiencies should be relatively high.

Bob Wilson

* - there are multiple stop lights along this route and any one of them could have been the starting point. It would be easier to re-run the test with a GPS track IF there were a serious question about the data.

[dcb]

Originally Posted by bwilson4web

...
This reads like professor Raf Catthoor's efficiency number, 70%, which he states without showing how it was calculated or measured. Perhaps you can show how the 70% was calculated?

Sigh, for being about the most cryptic guy on here, how could you miss such an elaborate sentence as:

Originally Posted by dcb

...at 355 you are taking something over 10hp from the driveline to generate about 10hp with mg2 to pump ~7hp (conditioning efficiency of 70% prior to mechanical conversion?) into mg1.

the thin blue line vs the thin green line @ 355... You have an actual measurement of efficiency of some sort right there, if you are tapping the output from mg2 and the input to mg1 then just the electrical path lost 30% somewhere and it isnt going into the battery...

Originally Posted by bwilson4web

For efficiency, I prefer to use lab measured, ORNL/TM-2006/423, Appendix B, which gives a range of values from 55.5-92.7%. Given the fairly low power range, the efficiencies should be relatively high.

Well, you measured one part of one step and it was a fairly low 70%

some other strong verticals near zero battery wattage, positive number over abs(negative number)
305: 10.5kw/12kw = %87.5
315: 4.5kw/6.5kw = %69

so I'm not sure what you consider "relatively high efficiency", but this is efficiency for an electric only path, without even accounting for actually doing or using mechanical work as far as I know. I only bother to point this out because this path is very similiar to one link in the "series hybrid" path and nobody has been willing to actually measure the losses on one of those, preferring instead to cherry pick random high efficency numbers from the web to make laughable claims.

But it generally looks like the thing acting as generator has to make notably more kw than the thing acting as motor uses, and I am suggesting conditioning losses (i.e. boost/buck) because I don't know any better and I have chosen spots where battery kw is low to eliminate that as a variable.

[bwilson4web]

Ah, I see what you're doing.

When I get home tonight, I'll find the original data which includes the traction battery load. Then I'll see if I can post a table here with the data. That will be a lot more accurate than trying to read points off the graph. If not, I'll just put the data in a small spreadsheet and attach it to the message.

I'll also include some of the raw data recorded from the Graham miniscanner. One of the beauties of the NHW11 is the ability to record up to six, data metrics but they are snapshot over ~1 second interval. Some of the calculated values are subject to sampling errors but we'll go over that in the follow-up.

Bob Wilson

[jamesqf]

Originally Posted by ShadeTreeMech

The reason to have an electric vehicle is to make use of electricity from the power grid...

Only secondarily. The main reason is to make use of the energy I'd collect from my solar PV and/or wind generation, which I'd install if I had an electric/PHEV vehicle to use the surplus instead of giving it back to the power company. (The drawbacks of a $40/month power bill :-))

On a different point, what I've heard from the EV builders I've spoken with (other than Tesla owners) is that typical EVs just don't climb hills all that well, if at all. It's a matter of current draw and how much sustained current the batteries can provide. Typical flatland operation would be a few seconds of high current to accelerate to cruising speed, then modest draw to maintain speed on the flat. But around here, it's not uncommon to climb 4000 vertical feet or more at 6-7% grade, which requires acceleration power levels to be maintained for 20-30 minutes instead of 10-20 seconds.

[bwilson4web]

I have good news and bad news. First the bad news:

Originally Posted by bwilson4web

Ah, I see what you're doing.

When I get home tonight, I'll find the original data . . .

This data comes from March 2007 but it also corresponded to when my computer was running out of disk space. It looks like I probably deleted that data when in the spring and summer I ran a series of gasoline tests.

The good news is I have two more graphs from the same set of data from high-speed hill climb and a descent of the same hill in "B".

HILL CLIMB AT 80 MPH


Now there are two points where the traction battery load briefly goes to zero. These are the interesting points when all power is just the engine with power split between the mechanical and electrical paths. To improve accuracy, I've used PowerPoint to expand and read out the values:

Reading out the values:

• Seconds 1034.5, 12250 / (-1 * -12500) ~=98%
• Seconds 1037.3, 12750 / (-1 * -13000) ~= 98%

Notice we can see a distinct rise in transaxle temperature from the mechanical and resistive losses of MG1 and MG2. So we're looking at:

• 2% * 12,500 W ~= 250 watts to heat up the transaxle

This is just the electrical losses of power flowing between MG1 and MG2. Losses in the inverter take a coolant loop that passes through the transaxle case. This loss does not include the mechanical path losses.

DESCENDING HILL IN "B"

Here is the descent:

The problem here is the engine is being driven by the energy captured from MG2 and we do not have a way to measure how much was sent to MG1 for the counter torque needed to drive the engine. However, we know it is fairly small since MG1 is about 300W and the transaxle temperature did not increase. It is also dealing with only 10,000 W of power, 1/5th the amount on the hill climb.

CONCLUSIONS

The only thing is 98% seems too good to be true but it is only the electrical path, the part that is independent of the mechanical path. The subsequent mechanical losses through the power-split-device, chain drive, reduction gear and differential are not measured. The earlier Knoxville reports included these mechanical losses. But there is additional room for error due in part to the limits of the Graham miniscanner.

The Graham miniscanner uses a fixed rate to read the data with a little over one second per cycle. This means calculated values were not sampled at exactly the same time. To address this problem I used a linear approximation between points proportional to the data element time-stamps. Better than nothing, it is not exact. Also, we are assuming the metrics returned from the Prius ECUs are close enough without going through a calibration cycle.

Bob Wilson

[dcb]

spot checking that first picture, it looks like the kw totals for battery plus mg1 + mg2 are all very near 100%, which is very different from the previous picture, something isn't right here.

[bwilson4web]

Originally Posted by dcb

spot checking that first picture, it looks like the kw totals for battery plus mg1 + mg2 are all very near 100%, which is very different from the previous picture, something isn't right here. . . .

It is the data. If you have an NHW11, 2001-03 Prius, I'd be happy to loan a Graham miniscanner and perhaps you can get something else out.

Since I have both an NHW11 Prius and Graham miniscanner, if you'd like to propose any set of six metrics and I'll record a fresh set:
ECROS Technology - Z8 Encore! Products

I can also share spreadsheets with formulas to convert these raw metrics to whatever you are interested in.

Bob Wilson

[bwilson4web]

I'm planning to meet with Good Prius Friend Hobbit at the Lookout Mountain hang gliding center about 90 miles away. This gives me a chance to re-record the data across multiple driving conditions:

Nuvi GPS:

o velocity - true
o altitude

Graham Miniscanner

o MG1 rpm
o MG2 rpm
o ICE mass airflow
o MG1 torque
o MG2 torque
o traction battery amps

From these metrics, we can calculate:

indicated_mph = k * MG2_rpm
ICE_rpm = F(MG1_rpm, MG2_rpm)
ICE_hp = F(MG1_torque, MG1_rpm, MG2_rpm)
plot operating BSFC
plot true mph vs MPG
plot power split device efficiency
plot power split device power levels
hill climb efficiency vs mph

For grins, I may change the ICE oil at the flight center and measure the effect on the way back.

Bob Wilson