25A KT peaks at 1100W

[Cursor-I-Am]

So I got myself a cafe cruiser.
I realized the controller on my cruiser was restricted to 18A by the display and so I upgraded to a KT 25A controller.
Hard to find exact specs of the battery but Aliexpress replacements of it specify 30A continuous, 50A peak and a google of Samsung 21700 cells says "max continuous 35A and 45A peak"
I should be good to see peaks of up to 1400W.
So I plug it up and go for a ride. I am seeing peaks of 1100W. There is a hill next to my driveway and I am going 15mph up it while only pulling 900W. I'm only 155lbs. I should be pulling more to accelerate me up this hill faster. It's too early in my ride for it to be heat related.
To test if it could actually be heat, I bring my bike home, I let it rest for a while and I plant my feet on the floor and pull the throttle for just a sec (not something I want to really do). Sure enough, peaked at 1100w. So it only peaks at 1100w from standstill and then immediately drops to 800-1000W and fluctuates around that even though I'm going slow uphill.
On my other bike which is a DIY, it has a 36v 750W ebikeling motor , a 48V 22A KT controller and some cheap 20A continuous 48v ebay battery that has 3-4v of sag.
That DIY bike would smoke this one and I don't understand why.
This bike has a 48V 750W G040 motor that after speaking to Ride1up they say it's custom ordered from bafang to be high performance and wound for 750W sustained, not peak. The battery is Samsung cells with only 0.2v of sag and fully charged.

I followed the Bolton ebikes guide to setup my KT controller. C5 is maxed out. I don't know why this is happening.

 

[amberwolf]

First: how is the 1100w being measured? Is it only by the controller's display, or a separate wattmeter? Has the measuring device been calibrated / verified to be correctly measuring current, voltage, power, etc? (comparing to another known-correctly-reading measuring device in the same circuit measuring the same things, etc).

If you've verified / calculated / simulated that the 900w is insufficient to move 155lbs+bike/etc weight at 15mph up whatever that hill slope is, then the measuring device showing 900w must be wrong.

(if the other lower power (measured?) bike can move the same weight up the same hill at the same speed, then doing so doesn't require as much power as your present bike is reporting, so the calibration is off the other way (too high) or the present bike is wasting power in some way).

 

[Cursor-I-Am]

First: how is the 1100w being measured? Is it only by the controller's display, or a separate wattmeter? Has the measuring device been calibrated / verified to be correctly measuring current, voltage, power, etc? (comparing to another known-correctly-reading measuring device in the same circuit measuring the same things, etc).

If you've verified / calculated / simulated that the 900w is insufficient to move 155lbs+bike/etc weight at 15mph up whatever that hill slope is, then the measuring device showing 900w must be wrong.

(if the other lower power (measured?) bike can move the same weight up the same hill at the same speed, then doing so doesn't require as much power as your present bike is reporting, so the calibration is off the other way (too high) or the present bike is wasting power in some way).

Hi, and thanks for responding.

Measured via display but I'm inclined to believe it considering it's performance compared to my DIY bike. Or at the very least, something is wrong as I'm not getting more performance than my DIY even though it's 3A higher. To use a watt meter on this, how do I do it safely? I figured I would need to have it under load whilst using it to see peak wattage readings.

If you've verified / calculated / simulated that the 900w is insufficient to move 155lbs+bike/etc weight at 15mph up whatever that hill slope is, then the measuring device showing 900w must be wrong.

Well, the issue is that my DIY can move me up the same hill at around 20mph. It's very confusing to me. I can also feel my DIY bike pushing me hard even at top speed downhill but this one, while I still feel it pushing, it's very weak. As if it's cutting power to the motor downhill like there is some sort of internal speed limit. It's no-load speed is around 32mph, but it's loaded speed downhill where it becomes very weak is at around 26mph. Which is very odd to me.

I figured it would increase power draw and be constantly trying to reach it's top speed.

(if the other lower power (measured?) bike can move the same weight up the same hill at the same speed, then doing so doesn't require as much power as your present bike is reporting, so the calibration is off the other way (too high) or the present bike is wasting power in some way).

The other bike reaches a peak of 1056w, whereas this bike peaks at around 1140w. My current bike is lighter, probably by around 15lbs as it's aluminum instead of of steel. However, I was expecting that the bike would increase power in order to push me uphill faster than 15mph. Especially if my DIY bike does that whilst being weaker on paper.

or the present bike is wasting power in some way).

I do have an extension cable connecting from the controller to the battery. The controller wires are 14 awg, the ext cable is 14awg and the plug connector wires from the battery plug to the ext cable are 14awg. Is it possible that the cable is too thin and traveling over a distance of around 12in is causing too much resistance? So, extra heat, wasted power, etc?

If so, could I fix this by cutting the battery connectors short and soldering a 10 awg cable?

Here's a diagram

https://imgur.com/dQhllsV

It goes from the controller, under the bike into the hole at the bottom and travels up through the tube to connect to the battery plug.

 

[E-HP]

1. Can you post all of your settings?
2. Can you confirm that both motors are identical (same model and gear ratio, etc.)

Based on the online reviews, it looks like a flat terrain bike. Two review specifically call out the lack of torque in the version of Bafang geared 750W motor the bike uses, compared to other bikes they've tested. They call out the lack of power on hills, and it dies going up a 1/3 mile 12.5% hill on one review, when most 750W bikes they've tested can make it. Given the bike touts assist up to 28mph, it seems they traded off torque for speed, either in the gearing or the motor winding.

Swap your DIY controller over to the cruiser and check the performance then.

 

[From-A-To-B]

Well, the issue is that my DIY can move me up the same hill at around 20mph. It's very confusing to me. I can also feel my DIY bike pushing me hard even at top speed downhill but this one, while I still feel it pushing, it's very weak. As if it's cutting power to the motor downhill like there is some sort of internal speed limit. It's no-load speed is around 32mph, but it's loaded speed downhill where it becomes very weak is at around 26mph. Which is very odd to me.

I figured it would increase power draw and be constantly trying to reach it's top speed.

Just to address this one part- tapering power at 26mph for an bike with an unloaded wheel speed of 32mph sounds about right to me.

Motors cannot make peak power all the way up to their top unloaded speed. I’m not a motor expert, so forgive my layman’s explanation. This can also be visualized with the GRIN motor simulator. Power peaks at around 70-80% or unloaded speed, then tapers from there. As you approach max unloaded speed, you see current REDUCE, not increase.

Additionally, if the controller has a programmed upper speed limit, it will cut power all together once that speed is exceeded.

Lastly, I understand that you’d hoped for more performance from your second bike. IMO, looking for a significant improvement from an extra 90W may just not pan out. That much power could disappear from the drag of different tires and a slightly more upright riding positive.

I agree with E-HP that, if you really want to chase this down, post your controller settings or try swapping controllers.

 

[Cursor-I-Am]

Thank you for the replies

1. Can you post all of your settings?
2. Can you confirm that both motors are identical (same model and gear ratio, etc.)

Based on the online reviews, it looks like a flat terrain bike. Two review specifically call out the lack of torque in the version of Bafang geared 750W motor the bike uses, compared to other bikes they've tested. They call out the lack of power on hills, and it dies going up a 1/3 mile 12.5% hill on one review, when most 750W bikes they've tested can make it. Given the bike touts assist up to 28mph, it seems they traded off torque for speed, either in the gearing or the motor winding.

Swap your DIY controller over to the cruiser and check the performance then.

P1 80
P2 5
P3 1
P4 0
P5 15
C1 02
C2 0
C3 5
C4 0
C5 10
C6 5
C7 0
C8 1
C9 0
C10 n
C11 0
C12 4
C13 0
C14 3

The motor seems weaker than my 36v 750W ebikeling motor. From the specs I looked up and after conversing with Ride1up, they have the same torque and other specs. According to them, they had bafang modify the 500w version of the motor to be wound for 750w sustained.

My only guess is that my 36v 750w ebikeling is overvolted to 48v so maybe rpm and torque is actually higher than my current Ride1up motor and that's the difference I'm seeing. But I swear it feels like there's some sort of internal limit in the motor, the way it rides is hard to explain.

The ebikeling motor will push me hard constantly as if it just loves wasting power. There's a steep hill here that I've went down a few times in the 6 years I've lived here and even down that hill, at 40mph (very steep, I rarely go down it), it'll just keep pushing and you can feel it. On flat it'll push to 28-30mph. And up steep hills it'll do 22mph.

This motor:
- Down the same steep hill = 26mph. Feels like it not really cuts the power off, but, it feels pretty close to it. I'll have to retest but I think it lowered the watts to around 300w meanwhile the other bike was double down that hill. Which I understand that you will see lower wattage as you increase in speed, but it seems way lower.
- uphill 15-17mph.
- flat 24mph

My knowledge of motors is pretty limited. I understand rpm, torque and I've rebuilt/repaired a few motors, but I don't know much about sensors and the small details of windings. I'm not sure if they modified the motor to somehow limit it's performance or if it simply isn't as capable of a motor as my previous

Just to address this one part- tapering power at 26mph for an bike with an unloaded wheel speed of 32mph sounds about right to me.

Motors cannot make peak power all the way up to their top unloaded speed. I’m not a motor expert, so forgive my layman’s explanation. This can also be visualized with the GRIN motor simulator. Power peaks at around 70-80% or unloaded speed, then tapers from there. As you approach max unloaded speed, you see current REDUCE, not increase.

Additionally, if the controller has a programmed upper speed limit, it will cut power all together once that speed is exceeded.

Lastly, I understand that you’d hoped for more performance from your second bike. IMO, looking for a significant improvement from an extra 90W may just not pan out. That much power could disappear from the drag of different tires and a slightly more upright riding positive.

I agree with E-HP that, if you really want to chase this down, post your controller settings or try swapping controllers.

Well, my cruiser has a 25A KT controller. I replaced the original DMHC controller after I bought it. The stock controller is 22A, but it was limited to 18A via the display. It also had a second limit where throttle would only provide 85% power unless you were pedaling with it. So needless to say, I immediately got rid of that.

I told Ride1up about their 18A limit and that they falsely advertised a 22A bike. They told me the display could go above 18A, I showed them a video, they sent me a new upgraded display that they said wouldn't have a limit and it 100% still had a limit. Turns out a year ago they updated the displays to limit them to 18A and they now have changed the sales page to say "18A".

 

[AGS]

Try P1 = 100 and P2 = 6 and set wheel diameter to your actual wheel size and not rim size.

It should go a bit better then.

 

[Cursor-I-Am]

Try P1 = 100 and P2 = 6 and set wheel diameter to your actual wheel size and not rim size.

It should go a bit better then.

With those settings it reads as 5mph.

Something else I noticed is that the walk assist (holding down), with any settings, starts off at normal speed but slowly the motor begins to slow down., Not sure if it's supposed to do that.

 

[AGS]

That’s very strange, a GO40 should have a 5:1 reduction ratio and 20 magnets with 6 magnets for speed sensing.

 

[Cursor-I-Am]

That’s very strange, a GO40 should have a 5:1 reduction ratio and 20 magnets with 6 magnets for speed sensing.

After a lot of digging, apparently the old name of the motor is "CST". I'm still having a hard time finding the magnet number. On another forum, a guy told me that his Ride1up 700, which uses the same motor, was accurate at P1= 80.

Edit: I found a post of a guy that took his apart. It is 16 magnets.

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[Cursor-I-Am]

I took the bike out again today and saw that my once Vsag of 0.2v is now 3-4v from 54.6v even on flat. This is a bike with around 10 miles on it. I'm starting to wonder if my battery is defective. I remember when I bought my battery for my DIY bike, it started off with 1-2v of sag and quickly became 4v of sag. So I'm rather concerned about this one's lifespan.

 

[E-HP]

I took the bike out again today and saw that my once Vsag of 0.2v is now 3-4v from 54.6v even on flat. This is a bike with around 10 miles on it. I'm starting to wonder if my battery is defective. I remember when I bought my battery for my DIY bike, it started off with 1-2v of sag and quickly became 4v of sag. So I'm rather concerned about this one's lifespan.

If the cells are actually Samsung 21700, then based on the battery pack specs, they are likely Samsung 21700 30T cells
(48V15ah Reention Rhino, 39 x 21700 Samsung Cells), so a 13S3P pack. 3P should be good for 105A, so that much sag with the current you are running, troubleshooting the battery is a good idea.

 

[Cursor-I-Am]

I told that to Ride1up (basically copy/pasted your response), they said the 4v of sag is normal.
"Often times issues like this can be caused by excess resistance from an external factor, not the battery itself, since your wattage output does seem to be correct this is very likely. An issue like this can be a sign that there is something causing resistance. The output wattage is the sum of the performance of all the electrical components. If it is hitting the peak of 980 that means that all the parts, battery, controller, motor, and display are all working as intended."

I mentioned it twice but they insist it's something else. That since I'm getting the rated wattage with their stock controller then everything is fine despite my speed issue that no other cruiser's seem to have apparently.

As an update: I hooked the Cruiser to my old bike's motor. I did not swap the wheel, I just put them beside each other, plugged the old wheel to my cruiser and hit the throttle. The power draw on my 36v 750w ebikeling wheel is 30% higher than the cruiser's and it has a no-load speed of 41mph.

Ride1up insists that the Cruiser can reach 28mph on flat, I don't see this even with an upgraded controller. Others in the fb group say they get 28-33mph on flat with PAS. Me over here with 25A, athletic because I do martial arts and bodybuilding for a decade now, and am only 155lbs, am struggling to maintain 26mph with pedaling hard on flat. Uphill is also insanely weak. Much weaker than my other motor which is rated for less torque.

 

[Cursor-I-Am]

Question to everyone here:
Can I just swap the motor on the bike to my old motor? Just slide the cruiser's motor out and slide the old one in? Or would I need to rebuild a wheel?

Ebikeling motor:

Spoiler

Waterproof 36V 750W 26" Rear/Front Geared Hub Motor Wheel

Ebike Conversion Kits - Ebike Batteries - Ebike Accessories - Ebike Cables and Spare Parts

ebikeling.com

Recommended Tire Width	1.75" 1.95" 2.125"
Rim Width	24mm
Rim Diameter (Outer)	572mm
Rim Diameter (Inner)	522mm
Spoke	214mm 12G Carbon Steel Copper Nipples
Rear Dropout	135mm
Rear Axle Length	205mm
Front Dropout	100mm
Front Axle Length	160mm
Motor Torque	50Nm
Motor RPM (Nominal)	260
Motor Hub Diameter	168mm
Motor Magnets	16
Peak Power	0.85kW
Operating Mode	Hall Sensor

Cafe Cruiser:

Spoiler

零部件

Bafang description

bafang-e.com

If not, I called a bike shop and they said they'll build a wheel around a motor for around $80. So I may go that route. Just buy a spare front wheel from Ride1up or a wheel and spokes off amazon and have the shop build it.

Ebikeling wants $200 for a new motor. It's a 36v 750w rated motor but in my experience, it has great performance. That said I may want to opt for a 48v rated one. Any good 48v geared hub motors for under $150?

 

[Cursor-I-Am]

Have you made sure the speed limit is maxed out to 70 on the display?

It is at 72kmh which is the maximum

 

[AGS]

Sorry deleted my post after reading you used the controller on your old motor.