Wh/mile on the fly

Hi
I know that the Cycle Analist has a Wh/Mi in it that after about half a mile it gives the average Wh/Mi since the last reset, what I am looking for is a formula for working it out on the fly so to speak.
The measurements I have avalible to me is M/h, W ,A, V , distance in miles and W/h. I have an idea of a formula but am not sure, of the things I can measure I discount V and A as combined they give I am leaning towards Watts and speed, to do an example calculation I will consider the values to be constant speed =20M/hr power 1000W, from that we can derive that in 1 hour 1000 W/h will be used and 20 miles will be traveled, so in 1 mile 1000/20 W/h will be used which is 50W/h per mile or 50 W/m. This example is not very efficient but it is only an example.
From that calculation it can be derived that the W/m being traveled at any one moment is the Watts drawn decided by the speed.
Constantly working this out on the fly would be dangerous so I would work out common values to for example speed 10mph you just decide the Watts by 10.

Are my calculations correct or have I messed up some how?
Geoff

The one setting I would love to have on the CA, is real time wh/mi. In addition to wh/mi average.

A real time wh/mi display would really help a rider adjust his pedaling output and wattage on the fly, to maximize range.

I would love to see a table with pre calculated values for speed, and watts including any pedaling watts, using air resistance values typical for an mtb and rider weight between 175 pounds and 200.

On the flat of course,, and perhaps additional tables for 3%, 5%, 8%.

What this would do is give you some basic speeds and wattages to hit, to achieve specific range goals. What would be the best speed on 3% grade for example, full speed, or 15 mph? By 5% I can guess, full throttle, full pedal, get up it in shortest time at the highest hub motor rpm.

I'm assuming hub motor. Mid drive just change gears and slow down all you want, without rpm inefficiency penalty.

Real time watthour display would be great.
On my 780km summer tour i managed 9,9wh/km with a DD.

http://e-cruiser.blogspot.fi/2017/07/grand-tour-2017.html

geoff57 said:

I know that the Cycle Analist has a Wh/Mi in it that after about half a mile it gives the average Wh/Mi since the last reset, what I am looking for is a formula for working it out on the fly so to speak.

Click to expand...

dogman dan said:

The one setting I would love to have on the CA, is real time wh/mi.

Click to expand...

The CA 3.1 beta has had realtime instantaneous Wh/mi display since the b14 release in Feb. The following custom fields can be selected to appear on the main display:


However, it sounds like you might be looking to derive this value from the continuous log data stream captured from the CA with your phone or Analogger (?).

In any case, if we follow the dimensional analysis, an easy means to compute this using the data on hand is simply:

V * A / Speed = V * A / (mi/hr) = W/ (mi/hr) = Wh/mi

dogman dan said:

I would love to see a table with pre calculated values for speed, and watts including any pedaling watts, using air resistance values typical for an mtb and rider weight between 175 pounds and 200.

Click to expand...

The ebikes simulator provides this information quite simply.
Here we just use the 'bike calculator' portion of the program and disable the motor simulator to get a nice plot of the power required to propel any bike at any speed, on any incline. This is the basic rubber-to-the-road power requirement to move the bike for any drive system - human, electric, or otherwise.

Here's a graphic 'HowTo' for our well-known data point of requiring 1000W to propel a bike at 30mph...


Any Human Watts pedaling contribution is simply subtracted from the result. If you want a table, move the cursor in steps of 5mph and jot down the corresponding power values. Done.

Like you've already figured out, the calculation is very simple. At any moment in time, the wh/m is the watts divided by your speed in mph, so if you're using 500w and going 20 mph, your consumption is 500/20 = 25wh/m

Duh,, I was thinking you'd need to compensate for terrain, weather. Of course, the motor will do that, pulling more when it needs it.

Even simple math on the fly is a challenge for me though. There is a reason I have no engineering degree.

Figuring it out on the fly, in round numbers anyway, gives me something to do while waiting to get there. It's always further/longer then I'd imagine, and I have yet to be stuck somewhere out of juice.

Thanks for the input.
My latest conversion is an electric moped into something with a bit of punch to it, there was not enough room for a cycle analist so I fitted it with a meter that provides volts, amps, watts and watt/hours luckily the Wh do not reset, a simple cycle computer rounds off all I needed i will be using the cycle analysts i have on other projects.
Geoff

Hi
Ive found the battery meter I got is crap should have known not to trust something that cost only £10 from china, I thought it would be ok as I used it first to Finnish charging the battery pack for that the volts and amps were accurate looks as if it is not so accurate at high amperage I'll keep it as a charging meter.
I have found a silver lining in this though I had a spare cycle analyst lying around not waiting to go on a bike, I thought it had been stolen but it had just been misplaced, there is a few problems, it is ver 2.23 so no on the fly W/m that's ok I can live with that as this thread has shown, it is a stand alone version with separate speed sensor the cable for both are too short for the job I have some 9 core cable that should be fine with the extra wires ide like to encorperate the speed sensor in with the rest and use the hall sensor output from the controller I'll have to up the poles from 1 to the number in the motor but the separate speed controller will help me work that out I'll still use the stand alone shunt as that means I don't have to recalibrate the cycle analyst.
Hope this works.
Geoff

When using the hall signal for speed sensing, the CA uses the yellow Sp wire in the normal CA-DP cable. This is disconnected from the CA PCB in the wheel pickup model. So - you won't need to run any extra wires for the pickup - you will have 3 extra wires in that 9-conductor cable...

See "Appendix B. Add/Remove Wheel Speed Pickup Sensor" in the CA3 Guide which is generally applicable to the CA2 as well, although the PCB pads are in slightly different locations.

Also as shown in the Guide "Appendix D. Adding a CA-DP Connector to a Generic Controller", you can just tie the yellow wire from the CA standalone shunt breakout cable to any motor hall connection as a source for the speed signal.

d8veh said:

Like you've already figured out, the calculation is very simple. At any moment in time, the wh/m is the watts divided by your speed in mph, so if you're using 500w and going 20 mph, your consumption is 500/20 = 25wh/m

Click to expand...

Exactly. It's even easier in metric units since most of the time you are hovering around 10 wh/km so the math becomes doable at a glance. See 450 watts at 30 kph? I know immediately that's 15 wh/km. 500 watts at 40 kph? that's 12.5 wh/km. Going downhill using 250 watts at 45 kph? I'd say ~6 wh/km. That's part of why it took so long to make displaying this value in realtime a priority, I got so habituated to doing it in my head. But as Teklektik pointed out we've finally got it implemented in the V3.1 firmware.

On my own ebike I tend to have it only show the average wh/km on the rotating display, since the instantaneous value isn't quite as useful as you may think. It really fluctuates a lot as you go uphill/downhill or accelerate and slow down, and what you see at any given instant isn't very indicative of your trip average.