Hello, I have a GoldenMotor kit, LIFEPO4 battery, 36VDC with 250W motor (PRO902). I love it, the only problem is that the max speed is about 24-26Km /H.
I can do this much with my road bike.

Would be a problem to buy a 24VDC motor and use it with the 36VDC battery / controller to get more speed. GoldenMotor have two versions of PRO902: 24VDC and 36VDC.
This would be the cheapest option as the battery is veeery expensive. I live on flats, hills not a problem (But very windy).
Any advise would be appreciated.

Thank you.

I believe, this may not be true, that when a motor is available for two voltages like 24 and 36, the lower voltage model will spin faster at 36V but have less torque than the 36V motor on 36V. So you could go faster if the motor is strong enough.

On the other hand, you're saying your current kit is good for 16 mph at 36V. Is there any electronic speed limiter going on? If not, that's pretty weak. My opinion is that your 36V motor and controller hasn't got enough power. Most 36V kits that I've seen will go 18-20 mph with 26" wheels.

You should ask Golden Motor.

You might ask them about the controller since (I think) that it could be the limiting factor. My 36V kit with 15 amp controller goes 20 mph, flat terrain, 180 pound rider, no wind..

When I had a Slot Car, as a child, the hot rodding, was to use a much lower voltage motor than the track's output...

Longevity was never a consideration.

It is a brushless DC motor. The controller is controlling the motor speed, not the voltage. To get more speed, you need to re-program or replace the controller. Changing to the 24V motor will not do anything for the speed, but it will result in the motor and the controller running hotter - and probably burning out.

I believe your problem is not voltage, but the wattage rating of the motor. Most of the specs I could find indicate your speed is about what you can expect from a 250W motor, particularly if you are a big guy and the bike is heavy. I think your best solution would be a 500W 36V motor and a controller adequate to handle that package. 250W is not adequate for serious riding or hilly terrain.

I run a 36V 500W geared motor, 26A controller, 36V/12AH LIFEP04 battery on a 700c hybrid bike. I weight about 220. The system is limited to 20mph (also the Minnesota limit) which it does with ease, and feels like there would be more if not for the limiting. Low PAS mode on level is about 14mph. High PAS mode will max it out. Hills are no problem, and depending on the terrain I have about a 30 - 35 mile range.

I once met a guy on the bike trail with a 2000W motor and massive 48V battery pack on a heavy 24" trail bike. He claimed 40+mph on the flat.

I did it, and it works fine for me (a tiny Cute Q100 motor). I'll tell you what to watch for.

1st, the controller and the battery have to match - not a problem for you as they are both 36v in your case.

2nd - voltage determines the speed of a motor* (current determines the torque).

So, in my case I had a 24v 200rpm motor (no load speed). Like you, that gives me a road speed (with a full sized wheel) of 24km/h. My target road speed was 35kph. Since speed is directly proportional to voltage, 24kph * 36v/24v = 35kph.

That is a big jump in speed. The potential pitfall is that if you can't pedal fast enough to keep the bike in that speed range most of the time, you may overheat something. I do not recommend this for a heavy rider or for climbing hills. But if you put some effort into pedaling, ride somewhere flat, and can keep the bike around 35kph when cruising, you'll be fine.


* motor speed is determined by the number of windings and voltage. Typically when offering a motor in multiple voltages, the manufacturer will change the number of windings so that the motor speed is the same if matched with the appropriate battery voltage.
Also, my "unassisted speed" is 25-30kph, so in my case 35kph with a motor works out well.