Can you software limit a bafang motor to 250w to make it road legal?

[seosamh1977]

HI all, I was just wondering. looking at the bafang kits, I see you can get a program wire to change the motor section.

Can you reprogram a higher rated motor down to 250W?

I was just wondering, as the 250w 36v, with 15amp controller bafang is legal. But obviously the 750w 48v with 25 amp controller isn't. Could you just reprogram the 750w controller down to make it legal, if so, technically what are the numbers you'd need to change? (Even if it wouldn't make it legal, i'm curious as to how you would technically do it anyway?)

Having a complete guess.

36 x 15 = 540peak power.
48 x 25 = 1200w peak power.

Would limiting the controller via software 750w machine from 25amps to 11.25amp, just make it run/perform equivalent to the 250w machine? ie 48 x 11.25 = 540w too?

I'm new here, so please go ahead, tear this logic apart and educate me! Will be dipping my toes into the ebike market soon enough, just want to understand if it's possible to limit a higher rated motor!

 

[anotherkiwi]

No you can't the power of the motor is the one that is engraved on it.

 

[seosamh1977]

Are you saying it's impossible to software limit it? I don't believe that.

 

[cyclebuddy]

The trick is to buy the Bafang motor you'd like, but labelled as being 250 watt.

My own e-bike uses a 350-watt Max-drive, but it was labelled as 250w/14A at the factory by Bafang at the request of the e-bike importer: At the LCD display, you can limit speed to 15.5mph/25kmh - or not limit it, if that's what you choose to do. With the programming cable, you can make the drive do pretty much whatever you want it to do (within the limits of the motor itself).

A number of resellers of "higher-powered" kit BBS motors seem to do this too - import higher-powered motors labelled at the factory as 250w. In other cases it seems that individual owners have their own rating plates made to (falsely) show the rating of a higher-powered motor as 250w.

But as I understand the law, any motor above a nominal rating of 250w is illegal even if the actual power has been software/firmware limited.

 

[anotherkiwi]

Are you saying it's impossible to software limit it? I don't believe that.

No I am not saying that I am saying that limiting power to 250 W does not make the motor legal.

Read this: http://www.pedelecs.co.uk/forum/pages/electric-bike-law-uk/

 

[peter.c]

To stay legal on public roads as the nice met police traffic officer {he showed a good interest and knowledge} explained it to me it has to be 36 volts only and labeled 250 watt and have a ce sticker and set to 15.5 mph and not have a twist throttle. The bafang 36v 500 watt can be turned down but this still will not make it legal .
The 48 volt even at 250 watt does not comply and no sticker or serial number will make it legal

 

[Woosh]

To stay legal on public roads as the nice met police traffic officer {he showed a good interest and knowledge} explained it to me it has to be 36 volts only and labeled 250 watt and have a ce sticker and set to 15.5 mph and not have a twist throttle.

he's made it easy although not strictly enforceable beside the 25km/h.
If you have a certificate of conformity, he's unlikely going to book you if it does not say 36V (eg 24V or 48V or anything in between), or the missing CE logo or you have a twist or a thumb throttle.

 

[peter.c]

I have to agree he was just interested as it was the first diy conversion he had seen. And as he was parked on the cycle path after a stop on a hgv I had slowed to a walking pace he made the comment is that an e bike and a conversation followed he refused the offer of a test ride The only thing he did not realise is you can pedal to a higher speed after the assist stops .

 

[Woosh]

he is going to see an awful lot more conversions by this time next year when the huge anti-dumping duty on Chinese e-bikes kicks in by this time next month.
Kits are still not hit by anti-dumping.

 

[seosamh1977]

Cool, part 1 of the question answered, not legal, cheers, so lets move on from that.

On to part 2. How do you actually go about limiting a 750w bafang to act the same as a 250w 36v bafang. What are the numbers you need to change with the programming cable? Is my logic above sound, or are there other things I need to change? I've had a look at the program I know there's a few changable parameters.

 

[Woosh]

On to part 2. How do you actually go about limiting a 750w bafang to act the same as a 250w 36v bafang. What are the numbers you need to change with the programming cable? Is my logic above sound, or are there other things I need to change? I've had a look at the program I know there's a few changable parameters.

there is nothing to change.
When you ride on a flat road at 15mph, you use about 200W less your own pedaling effort, you will never break the law on electric bikes.
When you climb a steep hill, as long as you do not exceed 15mph, you are temporarily allowed to use more than 250W.

 

[GLJoe]

The only thing he did not realise is you can pedal to a higher speed after the assist stops .

For a copper following an ebiker along a road and checking his speedo, wondering whether to pull him over to prosecute .... that's a pretty fundamental lack of knowledge!!

 

[flecc]

The 48 volt even at 250 watt does not comply and no sticker or serial number will make it legal

He was wrong, that isn't true, 48 volts is perfectly legal and there are entirely legal models with that voltage.

But if one puts a 48 volt battery onto a 36 volt bike or kit, that makes it go a third faster and so it becomes illegal. That's probably what he has misinterpreted.
.

 

[GLJoe]

But if one puts a 48 volt battery onto a 36 volt bike, that makes it go a third faster and so it becomes illegal.
.

???

 

[flecc]

???

Yes, motor speed is directly related to voltage. Double the voltage and the motor will double it's rotation speed. Of course the controller components must be adequately rated, but most 36 volt ones wil take 48 volts.

The speed gain can be limited by power, so the gain isn't always pro rata.
.

 

[GLJoe]

Yes, motor speed is directly related to voltage. Double the voltage and the motor will double it's rotation speed. Of course the controller components must be adequately rated, but most 36 volt ones wil take 48 volts.

The speed gain can be limited by power, so the gain isn't always pro rata.
.

Yes, but if you have a (legal) pedelec with a 15mph cutoff, then surely it doesn't matter. Both a 36 and a 48v bike are still going to go at a max of 15mph ?

 

[flecc]

Yes, but if you have a (legal) pedelec with a 15mph cutoff, then surely it doesn't matter. Both a 36 and a 48v bike are still going to go at a max of 15mph ?

Yes of course, if limited, but many hub motor bikes are not like that. My legal one at 36 volts nominal is only limited by voltage. When first charged it runs to 17 mph but by end of charge it's around 14 mph. It has a very high current controller so will easily run to a third faster with 48 volts.

That will be what that police officer was thinking of, but misinterpreting as a ban on 48 volts.
.

 

[seosamh1977]

So is everyone dodging the answer to my question because you don't know or don't want to tell me?

 

[tommie]

he is going to see an awful lot more conversions by this time next year when the huge anti-dumping duty on Chinese e-bikes kicks in by this time next month.
Kits are still not hit by anti-dumping.

Haven`t been following this anti-dumping thing but isn`t this specific only to countries within the EU, ie not UK after 29th March - or is it worldwide?

 

[tommie]

So is everyone dodging the answer to my question because you don't know or don't want to tell me?

Just buy this,
https://eggbikes.com/eggrider/eggrider-v2-display-android-iphone-bluetooth-mobile-app-e-bike-bafang-sondors-kunteng-lishui

has a `Road` setting (ie legal 250W/15.5mph etc)

and an `Off Road` setting (whatever power/speed you like!)
they tell me this will be accessed via a PIN code.

shoot them an email for more details.