# dc electric bike questions

Discussion in 'General Electronics Discussion' started by Gillesfizzog, Apr 2, 2020.

1. ### Gillesfizzog

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Jan 14, 2014
Hi, i have a stationary bike connected to a dc permanant magnet alternator. With no load connected, i metered 10 amps and 26 volts dc at 20km/h. when i connected a 2000 watt electric heater to the pma, i generated 17 amps and 24 volts dc at 20 km/h. It seems unlikely to me that im generating over 400 watts, am i missing something? My second inquiry is ; when i was metering 24V connected to the heater at 20km/h i felt the drag of the resistance in the alternator, but when i measured (amperage) 17A in series with the heater i did not feel the drag of the resistance. Why is that? -Thanks

2. ### Bluejets

4,750
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Oct 5, 2014
How did you measure any current flow with zero load..? Not possible.
What is this 2000w electric heater..? 220v...??
How did you measure the 17A load..??

Fairly well known that a fit adult human can produce (for a limited time) approx. 1/7 hp or 746/7 = 100W approx.
So @ 24v this is approx. 4 Amp.

3. ### Gillesfizzog

18
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Jan 14, 2014
thanks for the reply. im aware that commonly u cant get current without a load. but, with a magnet motor, does the magnets passing the coils induce a current that can be metered? When i start pedaling with only the meter as a load( on dc amperage), it raises from 0 to 10 at 20km/h. is that reading not of the motor but of the meter i wonder.. im as confused as you.
the electric heater is designed for 240/208V, but considering its a simple resistive load, i think it serves well for my dc experiment. as i pedal faster and raise the voltage, the current raises as well because they're directly proportional.

to measure the 17A load, i connected the motor to the heater than opened the circuit at 1 point to add my meter in series. it was set to dc amperage. it raised from 0 to 17 at 20km/h... maybe i should change the batteries in my meter haha -Thank You

4. ### Hunter64

49
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Nov 20, 2018
With no load connected you can't measure 10amps. You're doing something wrong, with no load there is no current. Please explain how things are connected.

5. ### Bluejets

4,750
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Oct 5, 2014
Double post....confusing

6. ### Gillesfizzog

18
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Jan 14, 2014
when i was turning my meter to dc amps it was showing 7 amps at a stand still so i would hold the zero button and it would turn to zero, thats how i was going from 0 to 10 and 17. i just tried to start pedaling when it start at 7 amps and it dropped by its swlf to 0 but increased to 2.5A at 20 km/h . maybe thats the right reading

7. ### Gillesfizzog

18
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Jan 14, 2014
thats with the heater connected

8. ### Gillesfizzog

18
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Jan 14, 2014
accually now i just tried that method on the motor with no load and it was also 2.5A. darn

9. ### Bluejets

4,750
999
Oct 5, 2014
Again, you cannot measure open circuit current, not possible.

What meter are you using and what range do you have it set to.

Post photos as that is easier than some way out explanation.

As a side note, expect a visit from the moderators as double posting is a no-no.

2000w heater/220v = 9 amp.
220v/9amp = approx 24 ohm.
24v /24 ohm = 1 amp.

Last edited: Apr 3, 2020
10. ### Gillesfizzog

18
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Jan 14, 2014
that sounds right to me. just wish my meter agreed its cl900 klein, didnt realize i posted twice whoops - Thanks

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Nov 17, 2011

12. ### Harald KappModeratorModerator

11,424
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Nov 17, 2011
Ah ah, same post under two different thread headers spaced a few minutes apart and you didn't notice? We're not dumb, maybe sometimes a bit slow...

13. ### Gillesfizzog

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Jan 14, 2014
those few minutes was me searching for my first post with no success. i realized after that i may have posted twice, not as i was posting. but i guess if u think im a liar none of this matters -pce

14. ### Harald KappModeratorModerator

11,424
2,621
Nov 17, 2011
Find any post of yours (or any other member):
- go to "members" (menu bar on top of the forum page)
- find your name, klick on it
- on your profile page click on "posting" or "recent activity"

15. ### Gillesfizzog

18
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Jan 14, 2014
Didnt know i could use the clamp to measure dc amps, its showing around 1A on the clamp and i can feel the drag of the load in the pedals. so all seems well. - Thanks

16. ### Bluejets

4,750
999
Oct 5, 2014
Appears just where these mystery reading came from are lost into oblivion forever.

I've no doubt some resemblance will pop up some time in the future though.