MAX speed of 30mph on my DIY E-Bike kit. 3000w, 72v battery, 30amp controller. What am I doing wrong?

[HugeNews27]

I bought a 3000 watt hub motor conversion kit for my 1st gen Pedal Electric e-bike. I purchased the kit on Amazon and it came with a 30amp controller and a S900 display. The controller ended up having the exact fittings that were already wired internally on my bike so I just reused that wire harness for the accessories already installed on the bike: Display( KT-LCD8H), PAS Sensor (which I’m not using but it is plugged in), light, brake sensor, and twist throttle (the kit came with a thumb throttle which I don’t want to use).

Upon testing, I thought the display configurations might be the issue so I changed those (shown in picture) and the bike still won’t go over 30mph???

Any idea as to what I’m doing wrong?

Is there a speed limiter wire I need to cut on the controller? Should I use the display that came with the kit?

 

[bengxe]

30mph sounds about right for a 30 amp controller. You need more amps if you want to go faster. If that's 72v you're barely over 2kw.

 

[DanGT86]

30mph sounds about right for a 30 amp controller. You need more amps if you want to go faster. If that's 72v you're barely over 2kw.

Power is not the issue. I have several bikes that do 35mph on 1500 watts.

Hub motors are available in different windings. The winding is what determines the RPM per volt. You need to know that spec on your motor to know how fast your top speed will be.

Since this kit was sold specifically to be run at 72volts it probably has a slow winding motor.

Does the power feel reasonable? Other than the speed do you think its working correctly?

 

[lnanek]

Some controllers like the Grin Phaserunner can use field weakening to go above the max rpm per voltage determined by the motor winding.

With only 30A to work with, no point in checking if your controller supports that, though. That's like 2kw. My fat bike can't break 25mph if I limit the battery amps that low. There's definitely no overhead to pump more amps into field weakening on top of that.

 

[bengxe]

Power is not the issue. I have several bikes that do 35mph on 1500 watts.

Power is absolutely the issue when he's only making 2/3 of what the motor kit claims. No battery was mentioned, 72v is an assumption, so 2kw is probably a best case. But you're right, OP should check the free speed with no load on it.
And I'd be willing to bet your 35mph 1500w bikes didn't have these little fat tires.

 

[E-HP]

Power is absolutely the issue when he's only making 2/3 of what the motor kit claims. No battery was mentioned, 72v is an assumption, so 2kw is probably a best case. But you're right, OP should check the free speed with no load on it.
And I'd be willing to bet your 35mph 1500w bikes didn't have these little fat tires.

Hard to tell with the info provided, but it looks like this kit: Amazon.com
If so, the controller is rated at 30A, but 60A peak/max, so you might be able to assume it has the necessary power, if the battery is up to snuff. The UPP 72V triangle packs don't provide a lot of current in an 18650 configuration, but if the pack is made with 21700 LG cells, it could provide the 60A peak.
The fat tires are definitely a factor. 1500W can be enough for 35mph with normal tires, but probably not on small fat tires, and a slight grade or headwind could easily require a good deal more. My guess is that the motor is the limiting factor, and the speeds described in the listing are no load.

EDIT: I just went out for a ride and traffic on the path was light, so I decided to do a quick test. My Cycle Analyst is calibrated against my GPS and with the Specialized 24x2.8 plus sized tires I have on now. The tires aren't fat, but fatter, and with more drag, than the 26x2.4 tires I had on before. The additional comfort was a good trade off, since I don't really ride more than 50 miles at a time, or need to go faster.
I only had stretches of 2 to 3 hundred yards at a time to test before I had to deal with cross traffic, so it was really hard to get to a steady 35 and still have enough room to brake. It occurred to me later that I should have set the three speed switch to medium or just used more throttle to get up to speed faster, doh. Anyway, I'm guessing right around 2000W for 35mph for my bike, since I was fluctuating between 1900W and 2150W, while between 33.5 and 36.5mph or so.

 

[lnanek]

Oh, 60A might be doable. In that case, I have seen situations where the display that came with the bike enforced lower maximum values for the advanced settings than the display that came with a kit. In that case both displays were a GD06. One allowed setting max speed to 99, the other capped it at 30. So the firmware on displays with the same model number definitely can vary.

 

[biker3]

Power is absolutely the issue when he's only making 2/3 of what the motor kit claims. No battery was mentioned, 72v is an assumption, so 2kw is probably a best case. But you're right, OP should check the free speed with no load on it.
And I'd be willing to bet your 35mph 1500w bikes didn't have these little fat tires.

My ebike is set for 20 amps and 48 v battery and 30 mph is what it gets, so more likely a KV issue, which means the windings thing , or the controller just is preset max. KV is the rpm per volt. The display was hacked to get the higher speed. Normal is 20 mph.

 

[Diggs]

Does it quickly accelerate to 30 mph and then just stop accelerating or does it get slowly run out of acceleration as the speed climbs and just barely reach 30 mph?

 

[fechter]

Try measuring the max speed with the wheel off the ground.

 

[2old]

It seems incongruous (to me) to combine a 30 amp controller with a "3000w" system, although you should be able to discover whether the system is regulated to Class 3 by measuring the speed off the ground as mentioned above. If it's still possible, I would return the kit.