Power used per mile

[Psycosis]

I know this has been discussed previously but i can't seem to find the discussion on the forum.
I am trying to find out what the typical usage is for a bike under full throttle per mile in watts.

Obviously this depends on the motor, whether there are hills , rider weight etc.., but an average figure is ok.
I saw somewhere that going flat out a bike would draw something like 95w per mile. Other sites seems to think 40w is more reasonable.

What do we think?
I was looking at picking up a watts up type device to check the battery capacity, ideally i want to know what power the motor is drawing so i may need to buy something a bit more specialist like a cycle analyst.

Additionally is it possible to limit the power the motor can draw, therefore limiting the speed, so you can go full throttle but know there is a limit to how much power the motor will draw.

 

[Fecn]

The most often quoted figure for average power usage in real-world conditions is around 10watt-hours per mile. From my own long distance rides, that seems about right (30 miles from a 260Watt-hour battery).

I've done some big big hill climbs on a 'derestricted' bike (~450W average motor power) and found that it used around 17.5 Watt-hours per mile.

For full-throttle use... well.. totally depends on the motor, top speed etc.... If your motor was using 250W of power and to attain a top speed of 20mph, then you'd be using 250Watt-hours per 20 miles, which would give you 12.5watt-hours per mile.


40watt-hours per mile sounds like far too much.... unless you had a 1KW motor or something like that.

 

[flecc]

The most powerful motors on the legal eZee bikes can consume as much as 25 watt-hours per mile in a hilly area when run flat out with minimal pedalling (15 miles from 37 volt 10 Ah), but most use much less.

I've even heard of the odd eZee Forza in the USA down to 10 miles on that battery (37 watt-hours per mile), but that's with the 350 watt rated US version motor.
.

 

[piotrmacheta]

I run an eZee hub on my mountain bike and travel to work and back each day (about 15miles) on relatively flat ground and with a bit of pedalling (to 20mph)I use about 20Wh/mile (eZee 37V LiPo battery) but when I go for a long ride I am more gentle (not in a rush and don't want to run out) and have managed less than 10Wh/mile. My worst journey was 30Wh/mile (how lazy) and best was 8.7Wh/mile.

 

[Geebee]

This is the same as a Watts up and a lot cheaper HobbyKing Online R/C Hobby Store : Turnigy Watt Meter and power Analyzer $23.95
I have one and its great, it will tell you how much power you are using, how much you have used from your battery, your voltage etc.
The Cycle analyst will allow you to limit your current so that no matter how much throttle you use it wont exceed the preset, I would love one but at 8X the price of the above I find it hard to justify.

I use about 3.5 w/h per km when being heavy handed and with lots of climbing, more generaly I use 2.5 w/h per km again with a lot of climbing.
I use the power to assist only as I ride for fittness but some days the steeper hills are more than I want, thus the e-assist.

 

[tangent]

The Turnigy is brilliant, I would thoroughly recommend it. Seems very accurate as well - I tested it with a multimeter. Got mine on ebay for about £20 including delivery. I cannot remember who the supplier is though as I cannot get to ebay from my work computer!

According to the Turnigy, my journey to work this morning used 81.5Wh. This was on my rickety old Giant Twist, 7.5 miles, negligible hills, but a noticeable headwind. I was profligate with the assist though as I am running in a new battery. Unfortuneately I do not have the luxury of a throttle on this bike.

 

[Psycosis]

Excellent thats good then, i stuck in another post that i bought my 20ah 48v battery which should give me 48v*20ah=960w accoring to some website i read.
Providing thats correct i should be able to do my 20 miles on full throttle which has always been my aim. 40w per mile seems like the top end so i may actually be ok on this front i thought it was going to be terrible.
Especially since during my testing with 4*7ah SLA's i got about 2 miles range when they were fully charged.

I bookmarked one of those on ebay, not too sure about connecting it up, from reading another post it doesn't sound too complicated, and i need some sort of fuse. I used a fust previously but it would blow constantly when the throttle was opened. I removed the fuse and everything runs fine.
I was told there is a surge of over 20amps sometimes and it will kill any car fuse as they aren't big enough.

 

[tangent]

You can get 30A spade fuses. These are used in my 24V giant Lafree battery and I have ever blown one. The Turnigy has reported occasional spikes up to 22A.

The Turnigy comes with 4 fairly short 12 AWG wires - 2 for power in, 2 for power out. I just soldered on a couple of Deans connectors so I could connect it up easily. Male for power in, female for power out would be the normal convention as this avoids accidental shorts.

 

[alex_h]

yes 12.5Wh/mile sounds about right on the average power consumption, if you get more than that you must live either in a very hilly area (option 1) or you are bloody lazy fat bastard (option 2)

 

[Psycosis]

Lazy but not fat
its purely by choice, the bike weighs a ton now so even pedaling it when there is no power is very hard. It started off life at about 6KG, with all the other junk it must be over 20KG, thats 1/4 of my weight again and for all the claims of no drag there is some.

I'll do some tests and maybe pop some pictures up

on the same notw, Daniel posted about the Wilog, does this do the same thing?

 

[wurly]

What do we think?
I was looking at picking up a watts up type device to check the battery capacity, ideally i want to know what power the motor is drawing so i may need to buy something a bit more specialist like a cycle analyst.

Additionally is it possible to limit the power the motor can draw, therefore limiting the speed, so you can go full throttle but know there is a limit to how much power the motor will draw.

You don't have to go to the expense of a CA. I built my own limiter using a shunt and a small circuit to 'clamp' throttle voltage. You ride at full throttle and adjust the power level you require. I made four, two for me, JohnP had one and so did Frank. JohnP reports that it works very well (but i knew that ), it stops you drawing too much current. Hall effect throttles are not very good at controlling power really, mine tend to be off or on even at a 'sweet point'.

I did think about making some more (possibly without the display) and making them smaller. Not sure if there would be much demand though......
Mel