Exactly! By happy accident, the sampling interval gives me Joules and though I'd been calculating watts, the ~1 second sampling interval also gives me ~Joules. Fortunately, that won't matter soon as I'll be redoing all of my energy studies.

I had good success last night combining GPS NEMA with Graham scanner data, which means I'll be able to add altitude and calculate total vehicle energy:

• Potential Energy (PE) change - using GPS altitude and mass
• Kinetic Energy (KE) change - velocity and mass
• ICE Energy - torque and rpm
• Battery Energy - volts and current
• MG2 Energy - regenerative, assist and recycle
• MG1 Energy - start, stop and recycle
• fuel - grams per interval

The data is noisy but there is enough to support some analysis and insights as long as I treat it as noisy. It will take a little more time to work on the filters and optimize data collection for future studies. Then I'll be ready to repeat benchmarks and this data will be my road map to understanding and optimizing NHW11 2001-2003 Prius performance.

Bob Wilson

Operation Iraqi Oil Freedom:

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bwilson4web — Okay, I think we've cleared up most of the confusion regarding your graphs — all your quantities 'W' are approximately in joules, and your graphs show the changes in energy (in joules) on the vertical axis. Now, I know that you're a fussy guy, like me. So, you won't mind if I make a couple more related comments:

1. In your post #31, the four quantities you call "ICE Energy", "Battery Energy", "MG2 Energy", and "MG1 Energy" presumably meant to use the word "Power" and not "Energy" in each case.
2. What you're trying to do is quite remarkable! But, I see no allowance being made for energy losses caused by air resistance and by tire rolling resistance, which also have to be made up for by the ICE and/or NiMH battery. What you seem to be calculating is just the work required to be done to accelerate/decelerate the mass of the car, and you're even planning to include the work done to change the car's potential energy as well, by taking elevation changes into account. Am I missing something, because these losses are very significant, and can't be ignored?

Stan

Thanks Stan,

It is refreshing to meet folks who understand the differences between energy and power and the utility of this information. In spite of lacking altitude, there was information to be gleamed from this data. For example, documenting short periods when the cruise control was using the engine as a brake, sinking energy instead of putting it into the battery. To the best of my knowledge, this detail had not been previously discussed.

I'm not ignoring "air and tire" drag but have to deal with the data available. Fortunately, air and rolling drag (the "N" combines both) had been addressed in this chart:

I've added data points from actual experiments to see how well theory and practice match up.

As I'd mentioned, I've been working on combining GPS altitude data and Graham mini-scanner data. Now I'm still checking the data to make sure I haven't made a mistake (NOTE: I found and corrected an error, 09/02/2007) however, this chart gives some insights:


In USA units:


Large hills were not such a bad thing:

The potential energy gained climbing one side was used on the downgrade. I suspect at highway speeds, the drag is enough that engine 'braking' is not needed to moderate the speed. I have the data and can find out.

Regenerative braking effects were also recorded:

Acceleration to resume speed appears to put a dent in the MPG that takes awhile to average out after cruise speed is achieved. Even after coming to a stop with the associated regeneration, the braking energy seems missing or to not make a significant impact on the subsequent acceleration. What this suggests is the rate of acceleration needs to be investigated to find out if there are optimum acceleration rates that significantly improvement performance.

I have no idea where these insights will lead but the data traces back to the major Prius power assemblies. But looking at the regenerative braking curve, I'm beginning to think about the advantages of a hydraulic hybrid.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

wow i am so lost in those grids. i will have to show DH hes a mechanic for ferrari and maserati. All i know about the warranty is that in california its 150k or 96 months hence why i got my prius because we were weary of the batteries. and i think its a california law for all hybrids correct me if i am wrong anyone in california but that is how it was explained to me by the toyota dealer. I added the platinum protection for the rest of the car so it lasts a while and i pay nothing if it breaks because the parts are probably expensive and my dh being a fabulous mechanic said " those cars scare me because i dont know enough about it so we need an extra warranty" he never admits that unless he means it. hes one of the perfectionist type mechanics that you are grateful they worked on your car because you never have to bring it back so if the car he fixes still needs other stuff he wont let it go til its perfect

Hi,
Warranty is the right answer when faced with a new technology and you've got a good handle on it. Universally in the USA, we get an 8 year / 100,000 mile warranty on the hybrid parts right off the bat. I understand California has a long warranty and of course there are extended warranties.

GOOD LUCK!
Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Yes, definately. But ya gotta go with your strengths!

I am not sure if you are suggesting that you are going to do this experiment on a bench with your spares, or in your Prius with your existing batteries. If on a bench, you don't have the vibration factor that you would have in a car. I don't know if that is significant or not for NiMh batteries. Thoughts?

I'm looking through the literature to see what 'kills' NiMH batteries and so far:

1) over charging above 100% SOC - death by so many ways
2) excessive rate charging - death by (I**2)R heating at high temperatures
3) below freezing operation - death by chemistry vs. electrons

Of these three risk factors, I don't see any point in testing #1 since the battery and hybrid ECUs limit charging to 80%. However, #2 seems plausible and #3 too for colder climates.

For excessive rate charging, I plan to test the H2 vents for KOH using a pH tester. If it shows evidence of KOH venting, then this becomes a likely protocol for age testing. It is also something consistent with warmer climate Prius that often face large hills where substantial charging and regeneration currents might occur.

We know our battery assemblies are rated at 6.5 Ah giving the standard testing charge rate. Yet I've seen peak current rates in excess of 100 A with my Graham miniscanner, more than 10C. Also, I've noticed that the battery temperature floats above ambient but don't have good data on this, yet. Of all of the failure test scenarios, this is the one I'm most interested in.

For #3, the only alternative is to get a freezer and see what happens with the test cells. I would need to read up on what happens to NiMH batteries beyond the limited information provided by the vendor data sheets. The vendor sheets suggest the Ah capacity decreases at cell temperatures below freezing but there are no charts. This is testable and could give more insights about traction battery aging.

Done right, we should be able to measure the loss of cell capacity in #2 and #3. With luck, I may be able to do it with ordinary, commercial AAA or AA batteries for the initial surveys. Then comes the challenge of how to measure current Prius cell pack capacity to determine where my test cells are on the aging curve.

This really is an interesting problem because we'll use COTS NiMH cells to establish what happens. Then we can ramp up the test to some of my test cell assemblies. Then at last, we'll have another data point while waiting on Toyota to release the lab report (don't hold your breath!)

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.