FAQ KC's Power System Spreadsheet - Version 5.0

[K.C.]

You've got a couple of options:

1) You can load a configuration data file, like the "Example" one that I've made available in the first post of this thread. The example data file contains sample configurations for the Logo 10, Eolo, Raptor 50, and Zoom. I removed all of the default configurations from the base spreadsheet to make it smaller, since a lot of people have their own configs from previous versions.

2) You can use the "Create New Configuration" function on the main page if you'd like to start from scratch.

Hope that helps - sorry for the confusion!

KC

[JoeR]

Thanks KC,

I guess my question is even more basic than that. How do I load the configuration data files?

If I am at the openning page in your spread sheet, what do I enter to get to the next screen? Your sample configurations are just what I am looking to start with.

Thanks again, Joe

[RC Man]

I was never able to get the latest version of the optimization page to work with my old version of Excel (Excel 97). The first versions with the optimization feature works but the latest ones get several errors.

Any ideas on how to make the optimization compatible with Excel 97? I don’t want to spend the money to upgrade Excel because I seldom use it.

[K.C.]

New Component Data available, and minor fix of spreadsheet.

The new data file includes the TP G2 730mAh cells and a couple of "Chili Pepper" motors from BMI. I also fixed the kV for the AXI2808-20.

KC

[K.C.]

Joe - Enter the path & file name of the configuration file in the "Load Configuration File" section and hit the "Load" button. If you downloaded my example file, the file name would be "Default_Configurations". If you don't enter a path, it will look in Excel's default file location.

RCMan - what errors do you get? The more recent optimization routines are more complex and VB intensive than the early ones, and I'm guessing that some of the VB syntax isn't compatible. If I can figure out what commands are causing the problem, I may be able to find a way to get it to work for you. I doubt you're the only one out there that's using Excel 97...

KC

[JoeR]

K.C. I got in, Thanks! It seems I did not need the file type ending on the file name (I just did a copy/paste from properties.

One question...
I am looking at an Eolo. My setup Mega 22/20/2, Phoenix 45, 8x 3300 GP NiMH pack, and 19 tooth pinion. Your spead sheet indicates a max head speed of 15XX rpm. I am however getting an rpm of 1850. Any idea why it is so far off? This is on the ground with the blades having just a slight neg pitch to kept it on the ground at full throttle.

I am trying to figure out if I can realize any performance gains with a 20T pinion with everything else remaining the same.

Thanks! Joe

[K.C.]

Sometimes the spreadsheet's estimates are dead-on (ask Gary...), and other times they're off by as much as 20% (ask Gary again... ). As usual - I'm not sure of exactly why its wrong in your case.

But my primary suspicion is nearly always battery parameters. The spreadsheet assumes a very simple electrical model for batteries, and it doesn't account for the dependence of resistance on load current or state of charge. So the the nominal cell voltage I provided for the GP3300 in the component data may be too low, so you could try bumping it up a bit. You might also try reducing the wiring resistance, but that probably won't have much impact at the power levels you'd see in an Eolo. Lemme know if you make any discoveries...

KC

PS - Based on your experience with loading a file I've added a note to the first post here regarding the use of extensions in the file names.

[GGoodrum]

Ben and I did some further tests, using the FDR, and I think I now now what most of our problem has been with high readings. We were checking the headspeed right at the beginning of a flight. Looking at the voltage plots, it looks like it takes about 30-45 seconds for the pack to settle into its "nominal" voltage. Readings taken during this period are going to be higher, usually by about 10%. If you wait for about a minute before checking, it seems to be a lot more accurate.

I still think the numbers are off a bit, but now it's only about 50-100 rpm at 2000. I don't think the cell voltage is the culprit either, because the voltage in the charts is close to the per cell value in the SS. I think it is probably a combination of things. Part of it could be errors in the kV values, and part of it could be that the losses generated by the SS are on the high side.

-- Gary

[Tazcat]

I've noticed the same higher-than-predicted rpms on my converted Hirobo GPH. At just under 10 lbs (it's a pig) it hovers @ 25 Amps, 23 Volts, 1520 rpm (actual in-flight values 3 minutes into the flight). I'm running 600 mm blades with an Aveox 36/38/2, P-60 ESC, 20 - GP3300s, and a 17.1 overall ratio. The spreadsheet predicts an rpm around 1375 at the equivalent electrical wattage (575 Watts). That's about 10% lower than actual, but still respectable considering all the variables, and conservative at that!

I think it's a good tool for assessing absolute performance, and a great tool for comparing relative performance.

KC -Keep up the good work!

Dave

[wildstallion]

Is there a step by step guide on how to use this tool properly for the absolute novice?

[K.C.]

I wish. I'm working on creating one, since the spreadsheet has gotten so darn complex. I've had trouble finding time lately, but I plan to post one at some point.

In the meantime, you might be able to get along if you check out the previous two spreadsheet threads.

First, I'd recommend downloading the example configurations and loading them into the spreadsheet. That'll give you some configurations to play with. You can then edit those to your liking, or create new ones using the appropriate function on the main sheet. Just tinker with the drop down boxes and any cells highlighted in green. If you'd like to play with the optimization engine, you can find some decent directions for that in the first post of this thread.

If you've got any specific questions, feel free to post them, or you can even PM or email me if you'd like.

KC

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[rroback]

doh. I can't use it becuase its protected. any way I can crack the password? Not that I really have any idea how to use this, but I'm trying to find a new setup for my logo 20
thanks,
Rhett

[K.C.]

What is it that you're trying to do? What message(s) are you getting?

You don't need the password to use the spreadsheet.

KC

[rroback]

I try to click in the space to select anything ( such as a motor) and it says I first have to unlock the spreadsheet. my mac also had to do some sort of updating the macros, so i'm not sure if that tweaked everything.

Rhett