Making a 1000W, 48V conversion kit Road Legal (temporarily!)

[Arby]

Hi, DIY ebike builders!
I have a fantastic home-built (Chinese) rear hub 1000W ebike conversion which I love, however I do fear at some point I'll get stopped by the Feds and my beloved ebike will be seized and crushed into a cube! I'd like to make it properly road legal when I'm commuting on the road but don't know how to limit the power. Reducing the top speed is easy on the KT-LCD3 display but not power. Can I just fit a lower rated controller or will this simply blow up, could I run the 48v, 1000W motor with a 36V battery to reduce the power output when I'm on the road? Or is there a better way?
Any advice gratefully received!

 

[the_killjoy]

Feds?

The only way to make it legal is to change the motor.

 

[rich_r]

As above - the law states that the motor must be rated for 250W (continuous) or less. Obviously most motors sold as 250W will happily run at more than that, but it's what the manufacturer declares it as that matters. You could try putting a '250W' sticker on it I guess

 

[skinny_arbuckle]

Thanks, sorry I mean the Police!
I really want to change as little as possible so I can access the full power for use on private land.
If I change the motor my 48V, 26A controller will probably mean a 250W motor will still deliver more than 250W power.
So would changing the controller for a 15A max (6A continuous) version result in gutless, legally compliant, performance?
(I'd be happy to add my own 250W motor sticker IF the power is truly limited).

 

[Fordulike]

So would changing the controller for a 15A max (6A continuous) version result in gutless, legally compliant, performance?

You'll notice the biggest performance loss, in acceleration from a standstill and hillclimbing. I'm guessing it's a direct drive motor, so torque will be pitiful at 15A. It will be important to keep the speed up on steep hills by pedalling more, otherwise you may overheat the motor, due to it being wildly out of its efficiency zone.

Remember, If it is one of these generic direct drive motors capable of 30mph, then they are designed to be at their most efficient moving along at the 20mph+ mark. Anything less and heat will build up in the controller and motor, meaning a potential for damage.

 

[Nealh]

Looks like your doing a Kirstin with post 1 & 4 , your alter ego taking over from one post to another .

A point less task as the hub will still be illegal, use it as it is and just be sensible. Running it at less speed and amps will take it out of its efficient operating zone and will prove to be gutless. Those 1kw D/D hubs usually have a speed of > 390rpm so to get the power and speed they need more amps and volts not less. Reducing the amps will make it struggle even over speed humps and then when you get to a proper hill it will stall and get very hot, ending up with you pushing.

 

[danielrlee]

If I change the motor my 48V, 26A controller will probably mean a 250W motor will still deliver more than 250W power.
So would changing the controller for a 15A max (6A continuous) version result in gutless, legally compliant, performance?

It doesn't matter how much power you are running a motor on, it's the motor rating that matters when it comes to its legal classification. As has already been pointed out, a 1000W rated motor can never be legal under UK law. However, a 250W rated motor running on 1000W is legal.

 

[Deleted member 4366]

You can't make it legal other than change the motor, but if you remove any labels on the motor and fix the speed to 25 km/h, you'll probably be OK.

 

[anotherkiwi]

Or find Fsck Trump! and I'm protecting the planet! stickers and no one will dare bother you

 

[mxer]

Use it! Just pedal....Evetwhere!!.

it's up to them to determine who was powering the bike at the time?. Sounds like a load of wasted police time to me?