Post your no load, wheel up amps @ various volts

M

Matt Gruber

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Feb 8, 2007
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Purpose is to compare stock with higher volts to measure heat loss.
Example, my mbike
36v 2.8a
48v 2.8a
60v 3.6a
my motor starts to waste amps by 60v
how about yours?
 
thanks guys!
let's expand this to include ALL, even if u never intend to raise the voltage. Then we can try to cross-reference the data.

my E300(psev), 250w 5:1 #25 chain driven scooter is 1.25a at 24v.
 
I've just got a stock Unite 750 Watt 36 Volt motor and they list the rating as 1.5-2.5 for the no-load amps and I'll just take their word for it. Doing the math that makes from 54 Watts to 90 Watts.
 
Interesting thread. Seems a good technique for indirectly measuring heat. I need to build some kind of bike stand. I don't fully trust my lithium packing job; some subpacks sit side-by-side so I prefer not to lay the bike on it's side.
 
no chain MY1016 250w 24v
0.87a 12v
1.01a 24v
1.14a 36v

anybody else?
 
How do you account for aero losses at higher voltages? No load speed on my wheel will blow papers around and sounds like a ceiling fan set on kill.
 
.
 
Lowell said:
How do you account for aero losses at higher voltages? No load speed on my wheel will blow papers around and sounds like a ceiling fan set on kill.
Click to expand...

and the amps are?
 
Matt Gruber said:
Lowell said:
How do you account for aero losses at higher voltages? No load speed on my wheel will blow papers around and sounds like a ceiling fan set on kill.
Click to expand...

and the amps are?
Click to expand...

1.7 amps at 100v, 99km/h. The DrainBrain speed limiter kicks in at 99.

Edit: changed to mph and it no loads at 77mph around 3.5 amps.
 
I just whipped up a quick simulation for a 5304 at 100 volts. If your aerodynamics are of the "mountain bike" variety you will need to run 60 amps through your controller to actually use the full powerband. 40 amps at the controller and you never get to your top speed. Above 60 amps and you just get more hill climbing ability but no more speed. (the point at which the bike stops going faster is limited by the voltage and the corresponding wind resistance)

:arrow: The bottom line is that bike should go 50 mph if you can get a 60 amp controller on it. Otherwise it will be more like 45 mph. (or you get into a tight tuck :wink: )
 

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Ypedal said:
holey crap... you not afraid the tire will fly off the rim at those speeds ? lol... i bet it ballooons out quite nicely. :p
Click to expand...

Doesn't noticeably deform. I never really thought to compare the normal rolling circumference at rest compared to top speed. Maybe I'm actually going faster than the DrainBrain shows?
 
This is a dumb question but where do i place my meter to get my no load wheel amps :?:
 
i took out the fuse and put 1 lead on each terminal.
.
anywhere in series with the battery pack will do.
 
48V 406 0.7A 61.5kmh

Is that good or bad :?:
 
29a said:
48V 406 0.7A 61.5kmh

Is that good or bad :?:
Click to expand...

If you like going 50 km/h it's not bad.

Do you have a DB on your bike ? if you don't . i highly recomend one. !

It's a real eye opener to see the max amp draw almost all the way up to your no-load speed !!!! Those nicads are really not happy above 1.5C so 16ah ( 2 x 8 ! ) is good for 30 amps.. a 20 amp controller is ok. but a 40 amp controller makes them work too hard.. You can draw 3C for a few seconds but not for an extended period of time without causing alot of HEAT..
 
So are the 3c Nicd wrongly rated :?:
My 406 @48V will not go over 34kmh
slower than my 408
still trying to figure out why :!:
Tried diff batts = no diference
Tried diff controller = no difference
 
It seems the 40*'s draw the same power,
At whatever speeds you want to compare.

It seems 15 mph is going to cost the same (more or less) whatever combination of motor size and volts you choose to use.

I'd bet that 406 isn't seeing enough volts to show it's true colors at 48 volts.
Bump up the voltage and I think the 406 would become as efficient as the 408. Or on second thought, might be not enough amps.
Big difference between 20 and 35 amps on the low end.

I'm still trying to get a handle on the differences of the 408/4011 combination.

Kyle
 
hmm...to find out how much air resistance is accountable for power usage at higher rpms, try running a motor with no rim/tyre/spokes at high speed (if anyone has one handy)? Surely a significant amount of power goes to drag at higher speeds?
 
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