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Discussion Starter · #1 · (Edited)
I propose a new version of this EV calculator.
The problem I noticed in all EV calculators on the WEB, is that they predict, mileage and other stuff at cruising speed.

As you know, you can eat more energy while you are accelerating to reach the desired speed :

- If you accelerate very slowly, your mileage is low for a longer perdiod of time.
- If you floor the pedal, your mileage is high for a shorter period of time.

I try to address this in this new version, so :
- the parameter "Trottle" tell what your cruising speed will be.
- the parameter "Accel" tell how fast you want to reach the cruising speed.

In the yellow cells you know :
- the cruising speed, depending on "Throttle"

First column
- the energy consumed to go to that speed
- the distance to reach that speed
- the mileage (mean) while getting to that speed
- the time to reach the cruising speed

Second column
- the remaining energy, once you are at the desired speed
- the range
- the mileage
- the time remaining if you ride at the cruising speed

Third column
total energy distance and time, global mileage

You can change any parameters in blue text cells
This calculaor run only with OpenOffice (Apache). LibreOffice is buggy and nobody correct bugs when you ask !!!

The "EV" sheet is protected, to avoid messing up things, but has no password.


The graph may have to axis : "Time" or "Speed"
- When "Time" is applied, the Yaec shows only the "best gears"
- When "Speed" is applied, you have the choice to show the "best gears", or the "full gears", you will notice full gears give different times than best gear as you are suppose to start in the designed gear and hence in may be longer.

You can disable a gear, to simulate a start from 2nd or 3rd gear.
You can change the Cell rate, to see the effect on the Torque and Power curve in "Motor" graph.
You can change cell topology, to get best range or max speed.
You can change grade from -30% to +30%.

Enjoy.

Take into account :
- max motor voltage
- max motor amp
- max battery pack voltage
- max battery pack amp
- C rating setting
- max battery power deliverable
- grade
- Gear
- inertia from equivalent mass of rotating parts
- Speed / Time axis
 

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Are you sure the file got updated in your edit?

Excel still tells me:
Cannot open 'Franky EV Calculator.ods': This file has been protected with a password and cannot be opened.

I'll try later with OO, but I downloaded it a machine that doesn't have that installed.
 

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Discussion Starter · #7 · (Edited)
Yes TX DJ

To be sure, I've downloaded it and checked. It has document protection removed, but still has a sheet protection (necessary to avoid messing it all up)

It runs well on OpenOffice (I have version 3.2).

I'm not sure you can run it with Excel, as it makes great use of oooBasic macros.
 

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Discussion Starter · #11 ·
The formula I use to compute acceleration time is too optimistic, as it consider acceleration constant. Does anyone as a good formula ?

It should be an integration of :

dt = m v dv / (Pmax - ½ ρ Ca A v3 -( μ m g + m g sinα ) v)
 

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The formula I use to compute acceleration time is too optimistic, as it consider acceleration constant. Does anyone as a good formula ?

It should be an integration of :

dt = m v dv / (Pmax - ½ ρ Ca A v3 -( μ m g + m g sinα ) v)
Acceleration is definitely not constant. And unless you're only using direct drive you'll need to consider gearing.

I used F=m*(v1-v2)/t or t=m*(v1-v2)/F, the F being what the motor can deliver to the tire patch, less F required at speed (and inclination in your calculations). I used 5mph increments, looks like accuracy should be within 5%.

You really should include what force the tires can deliver to the pavement, since it looks like a friction coefficient of 1 for dry pavement is pretty close to all you'll get. I'm toying with this in my spreadsheet now.

Download the spreadsheet in my signature, you should be able to figure out everything.
 

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maxvtol : I've read the entire thread and downloaded your spreadsheet, but I'm to figure out what are the formulas as I only understand metric.
I haven't done a detail check of the units in your formula, but at first glance it looks ok. It's just for average power over a increment in velocity. You can't use the maximum power of the motor for this, you'll have to use the average power over that increment in velocity, and to find this you'll have to use a motor chart to find the power at your start velocity and end velocity and average that power. You'll need the rpm for this, that's why you'll need the gearing ratios. Then you can just add the times for each velocity increment for an ET.

My formulas are in the cells, mostly under the acceration chart, although I'm using F instead of the P/v in your equation, but same thing. My spreadsheet is more taylored to finding maximum acceleration, but let me know what you're trying to do and I'll help any way I can.
 

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Discussion Starter · #15 · (Edited)
I've done some work to implement gearbox in another sheet (Motors).

All is not perfect, still need some work to do.

But you can choose gear ratio, change gear, or take rid of one or more gear, and see what happens.

Obviously, You'll better have a big powerfull motor and only one reduction gear.
 

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Discussion Starter · #16 · (Edited)
Job finished, and updated V2.

All things in a signle sheet, and more coherency among diffrents formulas.

Take into account, motor torque, gear.

EDIT : BUG correction, graphic has sometime incorrect size
some simplification

EDIT : Added shift time
 

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My EV acceleration calculator...

Determine the power to weight ratio, using estimates for actual voltage and motor efficiency. Find an ICE car with that power to weight ratio and use its numbers. Expect to do a little better in the real world because electric motors have wider power band compared to most ICEs. Follow up with construction and driving to see for yourself how good your calculator is :D

Yes, that means that most golf cart battery powered EVs end up performing like 36hp or 40 hp Beetles.
 

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A few suggestions.

I can only download the zipped file, then open it (only opens as read only), I have to do a "Save As" then use that file to get it to work. If that is the way it's supposed to work, I would put that instruction in post 1 where you download it. Other instructions on how to use in the spreadsheet itself would be useful, either on a separate page or on the flyovers. Somehow marking where the dropdowns are would be nice.

Label the x and y axis on the graphs with the units.

There's no way to adjust motor voltage or amperage which affects performance, this is done with the controller settings on my spreadsheet. To give a realistic performance, that should be included, at least on DC motors. On AC, I'm not to sure how it would be done, but if it requires a certain voltage or amperage battery pack, you could default a battery setting. And I'm curious as to how you're getting your motor charts.

Put the acceleration in G's. In toying with my spreadsheet, if you have close to a 50/50 weight distribution, you'll probably only get roughly 0.5 G's acceleration (more for RWD, less for FWD). If the acceleration shows more than 0.5 G's for a particular motor, it's probably not realistic (at least on a 50/50 weight distribution with similar tires on front as on back).
 
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