Power Gauge

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David in TN

David in TN

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The Clarity has a power gauge which appears very similar to a tachometer. It even has marks like a tach would.

When I'm running around town, for the most part, I don't pay a lot of attention to this gauge. However, when I am driving 30+ miles of interstate, I do. I attempt to keep it at the 2nd tick mark, or lower, if at all possible. Doing so seems to result in range greater that the EV indicates. Of course YMMV.

I'm thinking that there has to be someone with enough of an engineering background in our group who can figure out what the individual tick marks represent. I'm sure it relates to power delivery. Have no idea if it is linear, logarithmic, or what.

So, given the coefficient of drag, frontal area, weight, speed, etc. It should be possible to calculate power (hp or KW) required to move this vehicle at a certain speed.

Thoughts?
 
When we had the two Prius cars I paid a lot of attention to trying to get 50mpg as often as possible. I used driving techniques I'd learned from the internet. But with the Clarity I just tend to drive it and not pay attention to my driving efficiency other than I am a soft pedal driver in general. Both my wife and I like the idea of driving in EV 100% of the time so that's the only thing we really pay attention to.

I tend to spend more time playing with the ACC in town to see how well the programmers dealt with controlling the car given the radar and camera data.
 
Enginerd here.
We don't know the actual Cd for this car. Calculating steady state speeds is already pretty sensitive, so figuring out power using approximated drag coefficients would result in some dirty data. Good for a Fermi approximation, but not much more.

Luckily, this is a pretty fun Newtonian physics problem, and we have lots of tools for that.

Method 1:
P=W/t=½mv²/t
where...
P = Power [watts], the amount of power delivered at the wheels. This is what we want to calculate. We can convert to horsepower later.
m = Mass [kg], the mass of the vehicle. Measure this at a weigh station.
v = Instantaneous velocity [m/s]. Measure this by your speedometer when you stop the stopwatch.
t = Time [seconds]. Measure this with a stopwatch.
To find power at a particular "tach mark," accelerate your car from a standstill, holding the needle on that mark. Use a stopwatch to time your run. After you hit a particular speed (say, 30mph to keep wind resistance minimum), stop the stopwatch and record your speed. Plug it into the ½mv²/t formula and you have the average power for that run!

Method 2:
P=W/t=Fv=(ma)v
where...
a = Instantaneous acceleration [m/s²]. Measure this with your cell phone's accelerometer.
v = Instantaneous velocity [m/s]. Measure this by your phone's GPS.
Perhaps you suspect that the car is delivering a different amount of power later in the curve?
For Method 2, you'd need to perform your 0-30ish mph runs at steady tach mark, but this time set your phone to record its accelerometer readings and GPS speed vs time. There are a number of apps that can do this. Spit the data out to a spreadsheet and plug each data point into the (ma)v formula to calculate instantaneous power.

Method 3:
P=whatever Torque Pro says it is
So I realized while writing Method 2 that you could just use Torque Pro and let the app do the grunt work for you. I use a BAFX OBD2 bluetooth dongle I got off Amazon, and the wiki tells you all the rest.
https://torque-bhp.com/wiki/horsepower/
 
David in TN said:
The Clarity has a power gauge which appears very similar to a tachometer. It even has marks like a tach would.

When I'm running around town, for the most part, I don't pay a lot of attention to this gauge. However, when I am driving 30+ miles of interstate, I do. I attempt to keep it at the 2nd tick mark, or lower, if at all possible. Doing so seems to result in range greater that the EV indicates. Of course YMMV.
Click to expand...

You're using the gauge just as it was intended. I do the same thing. After experiencing the instrument-panel feedback on my gen-1 and gen-2 Insights, I find the design of the Clarity's POWER/CHARGE Gauge to be brilliant. My gut feeling is that it's as linear as Honda could make it because logarithmic gauges are not very intuitive. I don't know what unit of measurement would work with the tick marks, however. Watts? Ergs? It's the relative position that matters, not the units.
 
insightman said:
You're using the gauge just as it was intended. I do the same thing. After experiencing the instrument-panel feedback on my gen-1 and gen-2 Insights, I find the design of the Clarity's POWER/CHARGE Gauge to be brilliant. My gut feeling is that it's as linear as Honda could make it because logarithmic gauges are not very intuitive. I don't know what unit of measurement would work with the tick marks, however. Watts? Ergs? It's the relative position that matters, not the units.
Click to expand...

Someone on this forum reported that the tick marks represented 15, 30, 60, 90, 120, 150 amps.
 
I’ve tried paying attention to the power meter, but don’t find it actually gives me any useful information.
 
Fast Eddie B said:
I’ve tried paying attention to the power meter, but don’t find it actually gives me any useful information.
Click to expand...
Perhaps not any useful data, but certainly useful information. People who want to maximize their EV range can use the POWER/CHARGE Gauge to understand how their driving style can be modified to achieve that goal. If you're an experienced hypermiler, however, you already know how to avoid over-exuberance and the POWER/CHARGE Gauge won't provide any information that can help you do any better.
 
insightman said:
Perhaps not any useful data, but certainly useful information.
Click to expand...

Maybe a better way to say it is, "useful feedback".

I certainly don't consider myself a hypermiler but do know how and can use many of their techniques. For example in a forum challenge, I think I'm still the C-Max hybrid forum gas economy champ at 65mpg (unaided) for an entire tank (EPA 40mpg combined). Using the similar type of power bar in that car was pivotal for throttle control.
 
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Yes its more complicated than hypermiling in a standard ICE car, where I believe the best results are obtained by holding the throttle steady as possible (IE slow uphill, fast downhill unless coasting).
 
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