250 w e bike with a 50–60v battery

[yuval120360]

Hi, i live in Israel and legal ebikes are limited to 250w here.
I want to buy a conversion kit online but im limited to 250w.
I wanted to ask if i buy 250w kit with a 50 or 60v battery i can reach 40-50 km/h?
I know the range will get a lot shorter but its fun by me cause i only need to go 5–8 km each time

 

[wheelbender6]

The most voltage I have seen applied to a 250w motor without damage is 36 volts. Rather than applying high voltage to one 250w motor, why not install a pair of 24v/250w kits on your bike, along with a pair of 12v batteries for each kit.You could get more performance without damaging the kits. Maybe you could hide or "stealth mount" one of the kits to avoid a ticket. Good luck.

 

[ddk]

depends on your controller is all.
As in: can it work at 60V successfully.
I run 58V to a small geared-hub motor mounted in a 16" wheel for almost 20 mph (or 32kph). The same motor mounted in a 24" wheel does 50kph (or 31mph) with 58V.

 

[arkmundi]

Your controller, if its well matched to the motor, will not deliver more amps than the motor can handle, nor will the motor draw more than its coils require. Hence, you've oversized the battery, and are paying for it, without the effect you're looking for. No point in it.

 

[ddk]

Your controller, if its well matched to the motor, will not deliver more amps than the motor can handle, nor will the motor draw more than its coils require. Hence, you've oversized the battery, and are paying for it, without the effect you're looking for. No point in it.

tell that to my trikes please, because they apparently disregardful your statement as in: sometimes true, sometimes false..
Controllers usually only limit the system amps (I), not the system watts (IxE) Adding more voltage always increases the motor's RPMs -unless the controller limits the speed of the motor via a speed sensor of some sort (some do)(most don't).

 

[fechter]

Just get some of these: http://endless-sphere.com/forums/viewtopic.php?f=31&t=35048 :wink:

Then you can run a 'little' over the limit without getting in trouble. Most cops don't carry a Fluke meter.

 

[wheelbender6]

Fetcher's idea is probably the best. We preformed similar acts of deception with gas assist engines.

 

[dogman dan]

Too much variation in 250w kits to really answer your question. But 50 kph is optimistic, since that takes 800-1000w. Enough to quite possibly damage a very small motor. So, try to find one with a highish rpm motor, like 300 rpm at 36v. That should provide 30-35 kph with a 36v battery.

Then either modify the controller you get, or replace it with a higher amps one. 36v 15 amps (500w) should be tolerable by even small motors.

 

[arkmundi]

tell that to my trikes please, because they apparently disregardful your statement as in: sometimes true, sometimes false.. Controllers usually only limit the system amps (I), not the system watts (IxE) Adding more voltage always increases the motor's RPMs -unless the controller limits the speed of the motor via a speed sensor of some sort (some do)(most don't).

Yes, up to a finite limit. Amps are in the Watts & so are volts. Over volting ups the potential. The entire circuit from battery, wires, controller, more wires, and motor is resistance. The weakest point can melt and its the melting that does damage. You don't want to do that. Its why I recommend volting to design. A 36 volt motor should have a 36 volt battery and a controller to match. I don't over-volt, but understand that a lot ES'ers will to press the limit of their motors. The question is what is that finite limit? My opinion is with the setup described, that he'll be OK, not that I recommend it. The penalty I suggest avoiding, however, is the cost, of paying for battery capacity he'll never use.

 

[ddk]

I just realized I'm comparing oranges to apricots. sorry
No, I wouldn't recommend a 250W-rated hub motor for speeds above 40kph. It should overheat rather quickly beyond 25mph. On a bicycle probably sooner.
I ride a recumbent trike which in no way resembles the aerodynamic characteristics of a bicycle.

That said, I used about 12A-13A @58V (750W from the battery) for my lil' ride @ 30mph, and when I say lil', I mean I didn't stay at that speed for long. It was only a short test ride.
I ride @ or below 20mph (32kph)... generally between 10-15mph (16-24kph) because I like to see stuff.

You'd a thunk I would just have used a simulator to guestimate my top speed with a 58V battery... but there's so many variables where I just had to see for myself, hence, the test ride.