Spreadsheet calculator

[Miles]

Hi all,

I thought the attached power calculator might be useful to you guys..

It wasn't written by me, but I did some minor corrections to it.

Miles

 

[rsscott]

Hi Miles,

welcome aboard and thanks very much for the calculator! One thing i'm working on at the moment is a buyer's guide for the main site which allows the user to specify certain parameters in order to find one or more matching bikes.

Something that was pointed out to me yesterday was manufacturer claims with regard to range would not be accurate as some are more economical with the truth than others. So anything that would help me come up with a Pedelecs method of measuring this is most useful.

cheers
Russ.

 

[Miles]

Hi Russ,

Nice forum.

Without access to a sample bike, it's difficult to verify anything..

What might be useful, is a very simple online calculator, so that visitors could get some idea of what they could reasonably expect from a given size of motor and battery, with realistic efficiencies..... It would give them a reference when comparing specifications. Like the buyers guide, it might be a good draw to your website.

Miles

 

[Miles]

Thought I'd bump this up, in case any of the newcomers are interested.

 

[flecc]

There is a crude range calculator for the eZee bikes on my site, but nothing like good enough for general use. Have a look.

Two problems with the Powercalc approach. First the near impossibility of getting the information on a bike for many of the sections. Second, those of us who don't use Microsoft Office have it in read only mode, if at all. OpenOffice is supposed to handle it, but won't for some advanced features which appear to have been used here.

 

[flecc]

Hi Russ,

Nice forum.

Invisibility achieved!

 

[Miles]

Two problems with the Powercalc approach. First the near impossibility of getting the information on a bike for many of the sections. Second, those of us who don't use Microsoft Office have it in read only mode, if at all. OpenOffice is supposed to handle it, but won't for some advanced features which appear to have been used here..... Invisibility achieved!

Point taken. I'm still on Office '97, myself.

I'm not sure I'd trust anything in a manufacturers spec. anyway. If it's not a distortion of reality, it's a typo....

I still think a simplified calculator, integrated into the website, would be good.

 

[flecc]

I still think a simplified calculator, integrated into the website, would be good.

Yes, definitely.

 

[nigel]

nigel

Quite right
flecc please keep it simple their still are a few dummys out their i inclued my self in this whats the old saying KISS keep it simple stupid.nigel.southampton.

 

[flecc]

I won't be producing it Nigel, I think it's Russ or Miles that's most likely to.

 

[Miles]

Here's the latest version of powercalc. Just tidied it up a bit...

Miles

 

[coops]

Thanks for the update Miles . I'm still thinking how a simplified online calculator should be implemented, from the point of view of a lack of information on motors, and accessibility/usefulness for those likely to use it... but I agree it would be useful if it can be done.

Stuart.

 

[Grandad]

There is a crude range calculator for the eZee bikes on my site, but nothing like good enough for general use. Have a look.

Two problems with the Powercalc approach. First the near impossibility of getting the information on a bike for many of the sections. Second, those of us who don't use Microsoft Office have it in read only mode, if at all. OpenOffice is supposed to handle it, but won't for some advanced features which appear to have been used here.

Ever tried Google Docs & Spreadsheets Tour for online Docs and spreadsheets?
I have used the speadsheet, its good and is useful to pass on info to those without MS Office. At the time I used it there was no graph available but I see that there is now.

I can provide a google mail invite if anyone needs one.

Jeff

 

[Miles]

I just tried Powercalc on Google Spreadsheets. The "Performance by KPH" section works ok but the "Performance by Watts" section doesn't... I'll play around with it some more.

Miles

Edit: It seems to choke on the formula in cell G7.......

 

[Miles]

Version 3 attached.

The expressions used for the formula in cell G7 were revised to enable the spreadsheet to function correctly on Google Spreadsheets.

You can now use this calculator without the need for Microsoft Excel.

Create an account with Google and upload the file to http://docs.google.com/

Please post any bugs/suggestions in this post.

Miles

 

[Miles]

P.S. I'm intending to append a table of "typical values" to the spreadsheet, so that people will be able to enter the value that most closely corresponds to their specific case.

 

[Miles]

Here's another (it's also better..) online spreadsheet site - for those worried about Googles' megalotropism....

Online Spreadsheets - EditGrid

 

[coops]

Thanks Miles

I've been trying it out: its quite good; the really complex calculations (like G7 ) are in place. I realise it wasn't originally written by you, but I have some simple suggestions to extend its usefulness & 1 tiny bug .

The torque value in B17 doesn't seem to be used in any calculation? If it was derived from the motor rpm, gearing & wheelsize, e.g. torque [Nm] = Power [W] / (revs per second*2Pi) [1/s], and/or a speed at maximum torque included in any gradient calculation, could it be used to gauge a "gradient limit" or hill climb ability for for any combination of motor and wheelsize?

A throttle level could also be incorporated?

I tried to guesstimate the effect of pedalling in addition to the motor by reducing motor power output or bike speed, but it would be good if a "pedal power" factor could be included, to see how that reduces the motor power input & reduces wasted battery energy, extending the range?

What do you think?

Just 1 tiny bug I found: in I17 the miles calculation is G17*0.68, while I5,7,11 & 13 use a factor of 0.62 for km-miles .

P.S. The eZee kenda tyres have more rolling resistance than some other tyres, and by increasing the rolling coefficient & frontal area (for me) the range values come quite close to what I get in practice: the calculated range goes down very quickly with gradient though - I'll look at that more once I get the other values more tuned .

Stuart.

 

[Miles]

Hi Stuart,

Thanks for the bug report

Also, the suggestions.

I'll have a think about what I should tackle first.

I'm considering Pedal Input & Headwind Input - they should be relatively straightforward to do....

I was pleased to find EditGrid because it opens the possibility to make an interactive spreadsheet available as a web service.....

Miles

 

[coops]

The pedal and headwind input sound good Miles and they shouldn't be too difficult as you say .

The throttle level may also be useful and not too hard?

I'm having second thoughts about my "peak torque & gradient limit" suggestion: probably too messy & inaccurate to figure out & implement .

Instead, a peak power output & the approximate speed at which it occurs, would be very useful to include (and much easier), similar to the max speed in G & I5, so that people can ensure the peak power/torque of a bike is not unintentionally exceeded in gradient calculations .

With those small additions, I think the spreadsheet, with the relevant "typical values" included (shouldn't be too hard; I'm trying to approximate some as I said) should be a useful guide to ebike ranges on different gradients; their hill climbing limits, and all for different rider weights & power inputs too result! (let's hope).

I've only been using excel so far, but I'll have a look at EditGrid: thats handy if it can be used to make an interactive web spreadsheet, as you say .

I'll keep trying it out & post any more bugs/ideas as they occur.

Stuart.