Ebike still legal if I run 36V motor at 48V and limit speed to 15mph?

[scott gaza]

"I'm currently using a 250W 36V Bafang G310 rear hub motor and a 25A controller"? just saying what a bike inspection would look at! for changing to a 48v it would bring in the 36v 250w rating of the motor even if it is stamped in to play, im all for playing at the edges of legality but i do have a drivers licence that would cover me if i wanted up to 25kw, but i would need to register the bike and get insurance also exclude me from all off road tracks! PS : just trying to help you out the rpm of you're motor is going to go up at 48v giving less back-emf at 15mph so less efficient and changing over to 48v when you are not working! i dont know what winding's you have on you're hub/size of wheel how fast is you're no load speed?

 

[vulcanears]

Oh, you're right - I haven't clarified this sufficently:

The controller has a 25A peak rating, but is set up in a way that it doesn't peak over 700W. According to Grin Technologies, 700W is the maximum that the G310 can handle (which is more than enough for me).

I have the 13T version, which does 205rpm at 36V, which is 27km/h with load on my 27.5"x60mm wheels.

零部件

Bafang description

www.bafang-e.com

I just saw that the official Bafang website says "Rated Voltage: 36/43"

"at 48v giving less back-emf at 15mph so less efficient and changing over to 48v when you are not working! "

I played around with the motor simulator on the Grin website and the result was the same Wh/mile energy consumption for the motor at 15mph@36V and 15mph@48V - so I assumed that the motor wouldn't be less efficient at 48V. Am I wrong there? Would the ride characteristics (Torque, etc) change?

 

[Woosh]

people get easily confused with torque. It's better to think in term of power which is easier to relate to because you can feel it in your own muscles.
when you increase the voltage from 36V to 48V, you move the RPM of the maximum power point (where the motor shows how grunty it really is) up by 30% (the 48V battery is 13S, 3V battery 10S).
So a code 13 motor is optimised for 27kph on 700C wheels. It will become optimised for 27kph * 1.3 = 30kph or 20mph if you run it on 48V.
Note that at the same time, the RPM where your motor yield drops to 50% will also move up by exactly the same 30%. That is not good. You motor is going to suffer heat exhaustion on hills much earlier than when you run it at 36V. This is why I never ever condone any over voltage.
Choose a code 10 when you go 48V.
Climbing hills is what you pay your money for. Increasing the voltage will shed a lot more heat on steep hills - frying Hall sensors, cooking the insulation on your coils, stripping the teeth of your plastic cogs, wear out the clutch. You turn something designed to last 10,000+ miles into useless metal and plastic after 1,000 miles,

 

[Nealh]

There is no maximum out put in EN15194 for EPAC's. The motor must be rated for 250w continuous without overheating which is different from one running at a higher output.

 

[vfr400]

Pumping up to 900w through a 250w motor is not strictly legal and even less so at 1200w. As the inclusion of a motor of no more than 250 Watts (maximum continuous rated power) are to be considered as bicycles and known as EAPCs. Also you may be asked as the builder of said bike with 7a x 36v = 250w why you are using 25a x 48v = 1200w. 4.8 times the rated power?

There is no law limiting how much current or how many volts you use on an EAPC, neither is there any law on how much power your motor makes or consumes.

No OEM electric bike has been limited to 7 amps x 36V. The lowest 36v I've ever seen was 12 amps. 15 amps used to be the modal max current, but now around 18A is more common.

 

[scott gaza]

https://www.ebikes.ca/tools/simulator.html?motor=MG310_STD&cont=C25&hp=100&grade=10&wheel=27.5i&cont_b=C25&motor_b=MG310_STD&wheel_b=27.5i&grade_b=10&bopen=true&batt_b=B4823_AC&axis=mph&kv=6.33&kv_b=6.33&black=load as close as i could get on a 10% incline with a (5 or 7 minute overheat)

 

[vfr400]

"I'm currently using a 250W 36V Bafang G310 rear hub motor and a 25A controller"? just saying what a bike inspection would look at! for changing to a 48v it would bring in the 36v 250w rating of the motor even if it is stamped in to play, im all for playing at the edges of legality but i do have a drivers licence that would cover me if i wanted up to 25kw, but i would need to register the bike and get insurance also exclude me from all off road tracks! PS : just trying to help you out the rpm of you're motor is going to go up at 48v giving less back-emf at 15mph so less efficient and changing over to 48v when you are not working! i dont know what winding's you have on you're hub/size of wheel how fast is you're no load speed?

The inspection looks at the 250w stamped on the motor. Changing the voltage doesn't change the power rating for the motor.

 

[flecc]

Hello everyone.

I'm currently using a 250W 36V Bafang G310 rear hub motor and a 25A controller that can do 36V and 48V.

I'd like a bit more speed when going off-road and considering building a 48V battery but limiting it to 15.5mph when ON the road.

Would the bike still be road-legal in the 48V 15.5mph configuration?

OFF ROAD SWITCH - the position in UK law

I hadn't seen this thread earlier or I'd have joined in.

There is no UK law which specifically states that an off road switch incorporated in a pedelec is illegal.

There is no UK law specifically stating a pedelec rider cannot use an off road switch.

Nowhere in UK pedelec law is the term Off Road Switch ever used.

The terms "Off Road Switch/Button" were created by the Department of Transport (DfT) to describe any means for a pedelec rider to alter the legal operating conditions of a pedelec.

The first instance of them using these terms that I know of was in a joint meeting of the DfT, the Police and pedelec trade and interested parties on 13th April 2013 to clarify the position of pedelec legal maximum power. That meeting agreed that the police would not prosecute 250 watts, despite the UK law stating 200 watts, pending the DfT's intention to alter the UK law to 250 watts.

However, to prevent this being a signal that a "free for all" was being given, the DfT incorporated the following in their statement of intentions:

"The DfT and Police are aware that electric bikes currently sold and used in the UK are fitted with 250W motors, they do not intend to become involved in prosecuting those that sell or ride them. The use of an "Off Road Button" however is strictly forbidden now and is specifically mentioned in documents appertaining to new and existing guidelines."

Note the word "use", not fitment.

You can see that is only their legal opinion, not supported in any parliamentary law. Since such a use will undoubtedly breach the law on the use of a pedelec, the courts will of course support their view should a prosecution arise and duly convict, but it is not the law until so ruled in a test case in a senior court, meaning the High Court or its Appeal Court, or the Supreme Court.

So Vulcanears, your bike is not illegal as a pedelec at present, nor at risk of confiscation and destruction, so long as you don't get caught using the ability to defeat the usage law on assist speed and power.
.

 

[Gavin]

The inspection looks at the 250w stamped on the motor

Sorry chaps, I'm back again!

Forgive my ignorance of the whole industry, but does that mean that a manufacturer could take a 1kw motor, find some sort of testing house to "rate" it at 250w then sell it to me as legal?

 

[Woosh]

how do you define a 1KW motor? most e-bike motors can take in 1kw but some will last longer than others.
The test concerns with running the motor at 250W for 30 minutes at 25 degrees C. The motor needs to be stable temperature wise.

 

[flecc]

Sorry chaps, I'm back again!

Forgive my ignorance of the whole industry, but does that mean that a manufacturer could take a 1kw motor, find some sort of testing house to "rate" it at 250w then sell it to me as legal?

Yes.

Some pedelecs sold as legal have had gross powers (consumption) of 1000 watts and nett powers far above half that.

One popular pedelec like that in the previous decade was owned by 38% of our members declaring their bike model!
.

 

[vulcanears]

https://www.ebikes.ca/tools/simulator.html?motor=MG310_STD&cont=C25&hp=100&grade=10&wheel=27.5i&cont_b=C25&motor_b=MG310_STD&wheel_b=27.5i&grade_b=10&bopen=true&batt_b=B4823_AC&axis=mph&kv=6.33&kv_b=6.33&black=load as close as i could get on a 10% incline with a (5 or 7 minute overheat)

Thank you. When I adjust the 48V throttle to 76% so that both systems move at the same speed, both systems overheat after 7 minutes and both have the same Wh/mile consumption.
So is one more efficient than the other at the same speed?

 

[Woosh]

When I adjust the 48V throttle to 76% so that both systems move at the same speed

that means you have to pedal very hard with the 48V system to make it match the 36V. Not what you want to do normally.

 

[Woosh]

So is one more efficient than the other at the same speed?

No. The 36V is more efficient at low speed, the 48V is more efficient at high speed.
The crossover point in this example is 18mph where both systems are equally good.

 

[vulcanears]

that means you have to pedal very hard with the 48V system to make it match the 36V. Not what you want to do normally.

The human power input is set to 100W in both systems. And both systems (the 36V at 100% and the 48% at 76%) produce the same power output of 725W.
I still don't get why I would have to pedal harder with the 48V system.

 

[vulcanears]

I switched to a custom battery and made both batteries the exact same capacity of 825 Wh at 36V and 48V. Same human power input, same overheat-time, same range, same Wh/mile consumption, same speed.
Where is the flaw in my thinking?

 

[scott gaza]

The Inrush current is high because the motor is not producing any back EMF, so the input supply "sees" the motor winding resistance. As the motor spins up, the back EMF increases, opposing the input source, reducing the voltage across the winding resistance and reducing the current. Having the throttle at 75% in the simulation both motors would be the same 48v - 25% = 36v

 

[vfr400]

Sorry chaps, I'm back again!

Forgive my ignorance of the whole industry, but does that mean that a manufacturer could take a 1kw motor, find some sort of testing house to "rate" it at 250w then sell it to me as legal?

They already do that. It's been going on for 10 years or more. The same motors can be stamped 180w, 250w or 350w depending on where they're sold. There have been many identical motors, but with different software in for different motors.

Just consider this. When Bosch started, they stated that their motor gave around 40NM and had a max speed of 25km/h. Their latest Gen 4 CX gives 75NM and has a max speed of 25km/h.

Power = torque times rotation speed. If they're both 250W, how can 40 x 25 = 75 x 25? Go figure! That's why they only ever mention torque in their list of performance characteristics. If they listed the actual maximum power output of around 600W, people might start asking questions.

 

[vfr400]

Thank you. When I adjust the 48V throttle to 76% so that both systems move at the same speed, both systems overheat after 7 minutes and both have the same Wh/mile consumption.
So is one more efficient than the other at the same speed?

It's very complicated, but can be explained in simple terms. When you use 75% throttle, the controller reduces the power with its PWM, which effectively reduces the voltage supplied to the motor, so at 75% throttle, the effective voltage might be reduced from 48v to 36v, so the motor behaves exactly the same as it would at full throttle and 36v.

 

[vfr400]

I switched to a custom battery and made both batteries the exact same capacity of 825 Wh at 36V and 48V. Same human power input, same overheat-time, same range, same Wh/mile consumption, same speed.
Where is the flaw in my thinking?

There's no flaw in your thinking. The 48v allows a higher speed and allows you to run with less current for the same power output. If you supply the same current to each motor, the 48v one will make more torque and power. If you select settings that make voltage x current the same, then they behave the same. That's a generalisation. At low speed, you have to consider efficiencies, and at high speed, the 48v will always have the advantage.