Discussion. "Legal" power

Positive discussion on ebikes and pedal assist bicycles

Discussion. "Legal" power

Postby OldNick » Fri Nov 02, 2012 9:56 am

To me this seems a curly question. "Maximum power _output_ capability" is now 250W in Australia. But is that power out at the wheel or power drawn from the battery? I will assume that it's with batteries fully charged. If I have an input of 300W and a system efficiency of 80%, then my power to the tyre is 240W and falls within the power range.

I have the Magic Pie III. The programming software allows you to work with 24,36,48V and also to limit the current from any of these voltages: therefore I can set the power. But the _potential_ is there at 48V for around 1000W, and perhaps 1200W. So the motor is capable of more than the power allowed BUT...If I set the system up to have 48V/5A (which at full charge can be just over 50V at 5A), so I am under the power limit. But back to part 1 :) Maybe I should go to 6A max and have 80% drop me down again?

I do have to say that unless I was found doing a ridiculous speed on the bike, there would be little reason except curiosity or vindictiveness to stop me, and how on earth is the average patrol office going to test all of this?

This seems to me to be a thing that will either be ruthlessly pursued, or simply rely on catching speeders, then doing a "yellow sticker" on the bike. I know there a quite a few people out there screaming around on 1000-5000W bikes, who just do not care, and I am more than a little angry about them. But I hope that people like me, who just want the dependability of the bigger motor, working with ease, will not get caught up.
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by BNA » Fri Nov 02, 2012 5:16 pm

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Re: Discussion. "Legal" power

Postby Joeblake » Fri Nov 02, 2012 5:16 pm

My understanding is there are two ways of measuring e-power, continuous and peak power. Continuous power (as I understand it the generally accepted measure) is the amount of power generated by the motor which will not cause the motor to overheat so it can run continuously, whilst peak power is the maximum amount of power a motor can generate, but will cause overheating.

The 250w motor might be rated as 250/400 ie 250 w continuous power but 400 w peak power. This is why an e-motor should have a built in thermistor (thermal resistor) which will cut the motor off if it overheats. My Heinzmann has excellent thermal protection, and cuts the motor if I'm climbing Welshpool Road at full throttle on a day when it was 38 degrees C.

I think it's difficult to measure power at the battery since there are other losses between the battery and motor, eg a loose connection can generate a lot of heat and lose power without the power being transferred to the road. You'd have to measure the power at the motor itself, but I'm much more concerned about how much power goes into my battery from my PV cells. BUt there are on my understanding meters of various types which will measure the power going into the battery and out of it, so you can calculate how much range you have, though I've never bothered with those.

Joe
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Re: Discussion. "Legal" power

Postby Joeblake » Fri Nov 02, 2012 5:21 pm

Although this is (again) about the Heinzmann it contains some interesting bits about pedal sensors and the way the motor "ramps up" its power (2 seconds) to prevent unwanted acceleration.

http://www.kinetics.org.uk/html/the_control_board.shtml

Joe
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Re: Discussion. "Legal" power

Postby OldNick » Fri Nov 02, 2012 7:23 pm

hmmm...well if it's the power from the motor, _that it can sustain without overheating_, then I would possibly be in trouble no matter how I had programmed the motor controller. The motor can sustain 1000W at least. However I would argue that in my system, it can't. It can only do 200W. That is because I have only 24V and I can limit its power....so it can sustain 200W without overheating :) I know I am straining at gnats, but I really wanted a motor that just loafed, with me, the dog, trailer and sundry gear.

However, while you are correct about power measurement of a motor, I was more talking about "the LAW". It just says that it's not to be capable of more than 200W or 250W depending on the age and type of bike. At most a roadside check would be Volts * Amps, probably not even allowing for system efficiency, which is to our disadvantage
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Re: Discussion. "Legal" power

Postby Joeblake » Fri Nov 02, 2012 8:16 pm

I've heard whispers, mostly unfounded, that the motor may be assessed on entry to Oz, and any one which doesn't fall within the range will either not be allowed in or hit with a huge import tariff of some sort. Probably they'll ask the manufacturers to fit a compliance plate, and any maker who fails may be prohibited from importing to Oz. But as I say, that's not something I'll swear on. But it seems the bureaucratic way of doing it. It's worked with cars, so why not motors?

Joe
To acquire immunity to eloquence is of the utmost importance to the citizens of a democracy
Bertrand Russell
Many people feel their lifestyle has a high price, but they're quite cool with that .. as long as somebody ELSE pays the price.
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Re: Discussion. "Legal" power

Postby John Lewis » Fri Nov 02, 2012 8:36 pm

The Avanti Electra had a 200W front hub motor running at 12V.
That motor with the right controller andf more battery is quite capable of 1000W from what I've read.
I have one here that I acquired in a dismantled state. It sure looks capable of that even if it was pretty hopeless on the Electra.

Almost all electric hub motors would be capable of higher output. It might not do them a lot of good though. If it is set up on the bike via batteries, controller etc to only output the lgal power and that can't be easy altered as you ride I can't see a problem. If you are pulled over and it is determined you have set it to higher power then that would be a different matter.

I doubt the average Rozzer could tell anyway. Whatever is on the label/plate will be all they are interested in.


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Re: Discussion. "Legal" power

Postby OldNick » Fri Nov 02, 2012 8:45 pm

AH! Except you are dealing with companies that _voluntarily_, by default, falsify the price, make things a "gift" or "sample", for quite serious items like cameras, RC models...just about everything.

BUT...If the vendors are happy to fit compliance plates (so sue them) and bureaucracy is happy to accept them, then I will not argue. HOWEVER, it would annoy me if I was forced to get my existing ciccle complied. Just hope the Grandpa clause does not cut both ways.\
\
Nick
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Re: Discussion. "Legal" power

Postby OldNick » Fri Nov 02, 2012 8:53 pm

My big concern here is that kits will become either a thing of the past, or so complex and expensive (because the law itself is that way) that they are non-viable. DOA DIY. Bike makers rubbing hands in the name of "safety". I mean we are talking battery specs, frame specs....brake specs. People have been riding at far greater levels than 250W for years, and far faster than 25_K_ph. Even I have done 40Kph and I am the archetypal chicken. Wait...what...I forgot to whom I talk! :D

This business of allowing an extra 50 W, but at the expense of meeting to EU guides, just really makes that an expensive 50W.

however I am going to see about setting everything to 200W nominal, 25KPH limit, and hope that does what I want. A sustained 200W will certainly boost MY ride, I have to say.

Nick
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Re: Discussion. "Legal" power

Postby Joeblake » Fri Nov 02, 2012 9:56 pm

From memory the 250 watts figure was around in Europe (and other places) for quite some time. I think it was found to be easier to allow 250 w motors to be legalised than to try to get makers to cater to a smaller (ie Australian) market.

I suspect that in the long run, the deciding factor will actually be battery technology. The problem (other than legality) with bigger motors is the restricted range. If you fit a "big" motor but don't use it to its full capacity for fear of not being able to get back home because of a flat battery then you may as well not have fitted the motor in the first place. More efficient and less expensive batteries may overcome that "range rage" but it has to happen first. Because I've got a "smaller" motor and on-board recharging, I don't really have that problem and if I could find them I'd probably fit even smaller batteries (sealed Lead Acid) because I've never flattened the batteries, although I have come close on one occasion. It's probably swings and roundabouts. Over a long enough distance I suspect my average speed would be the same as a bike with a bigger motor because although I'm not as speedy, my PV panels are like a "little blue pill" ... I can keep it up for longer. :lol: Or maybe it's more like the hare and the tortoise. So better batteries and/or photovoltaic panels will probably make it all worthwhile.

But I can't see any benefit for me in fitting a bigger motor. But that's tortoises for courses. :lol:

Joe
To acquire immunity to eloquence is of the utmost importance to the citizens of a democracy
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Re: Discussion. "Legal" power

Postby OldNick » Sat Nov 03, 2012 10:32 am

While what you say makes sense, I am not lowering the power because of range. Unless you insist on pushing the heck out your 1000W motor at 48V, you would get quite a good range out of 20AH I would imagine. Given that a 200W motor can get you around quite well, an d help up hills, I would imagine that the bigger motor will do the same for maybe an average current consumption of 4-5 A @48V for normal cruising. So that's a careful 1.5 hours with a 10AH battery: maybe 30-40Km. Those are the sort of claims. I chose the bigger motor for its torque (I have not seen figures but to me it seems that a bigger diameter means more magnetism and more torque) and the fact that it will be nowhere near its capacity, if I use it at a lower power, to pull a quite heavy load. Because I am limiting it, it may run out of power and need pedal help (which is fine by me) but the motor itself is not anywhere near its mechanical capacity. With a trailer, a dog, camera gear, water, possibly food etc if we go for a longer ride, I need help, and I need a motor that is never near straining, or getting hot etc.

Until I get the motor on the bike, all this is supposition on my part, but it gels with my experience in the past.

Nick
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