peak power vs graph power

[OmCheeto]

Hate to be a pest, but......

In my constant promotion of your project, I randomly pick trip data to
display to the uninformed masses of how the world actually works.

Today I discovered that the peak power(90.49kw) displayed in the
textual section of Scott's trip:
http://chargecar.org/data/253
does not match his graphs peak power(~27kw in trip segment 3)

Unless of course you are using the absolute value of peak power(~
-91kw in trip segment 1).

In which case I would recommend posting both positive and negative
values of peak power, as I am easily confused.

:)

[Leland Thorpe]

Yeah, this sign issue is tricky business, and we ourselves sometime get tripped up by it. What's plotted is power flowing into the battery pack, so negative numbers are power leaving the battery pack. This is more or less the time derivative of the amount of energy stored in the batteries. So +27kW means that the car could be recovering 27 kW through regeneration; -91kW means that the car is using 91 kW to move (probably accelerate and/or change altitude). So when the text says "peak power usage" we're looking at the largest magnitude negative peak in the plot. This is a key data point when we study the impact that driving has on batteries, and how a capacitor can mitigate these effects.

Now, all that said, it may be a good idea to show both peak draw and peak return (the largest magnitude negative and positive numbers, respectively).

Thanks for exercising the website!

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[pdille]

Yes, that value is the largest absolute power value from the entire
tip (it could either be a charge or discharge point). I agree that
it's confusing and we can easily modify the site to show peak charge
and discharge values. In fact, that is extremely informative and
should have already been displayed.

Thanks for mentioning this. The site should be updated in a few days.