FarDriver controller ratings question

[Wheelsandall]

I’ve got this scooter that had 60v sla batteries in it and didn’t run. I made a 72v lithium pack for it and used a FarDriver nd72280 controller. Works great and has a ton of power. I believe the original 10” hub motor is 1.5k-2k watts. Today I found someone selling a motor and other components from a similar electric motorcycle including the hub motor. My original plan was to put the new hub motor in the front and hav a two wheel drive electric scooter because, why not.

Anyway turns out the motor is a 12” qs 3k watt motor. Now the new plan is to just put the new motor in the back and see what it does. According the FarDriver the nd72280 is good for 1-5k-2k watts. However it’s rated for about 60 line amps. The would give me (72*60) 4.3k watts which even at peak should still be well within the controllers limits. Is far driver just being overly cautious here or am I missing something and should I upgrade my controller to get the most out of the new motor? I’m going for top speed at this point. I’d rather not spend the money if I don’t have too.

 

[E-HP]

I’ve got this scooter that had 60v sla batteries in it and didn’t run. I made a 72v lithium pack for it and used a FarDriver nd72280 controller. Works great and has a ton of power. I believe the original 10” hub motor is 1.5k-2k watts. Today I found someone selling a motor and other components from a similar electric motorcycle including the hub motor. My original plan was to put the new hub motor in the front and hav a two wheel drive electric scooter because, why not.

Anyway turns out the motor is a 12” qs 3k watt motor. Now the new plan is to just put the new motor in the back and see what it does. According the FarDriver the nd72280 is good for 1-5k-2k watts. However it’s rated for about 60 line amps. The would give me (72*60) 4.3k watts which even at peak should still be well within the controllers limits. Is far driver just being overly cautious here or am I missing something and should I upgrade my controller to get the most out of the new motor? I’m going for top speed at this point. I’d rather not spend the money if I don’t have too.

Is this the controller? 80A @ 72v (5760w) seems like a decent power for the motor.

 

[Wheelsandall]

Yes that’s it. See how it says 80 line amps at 72 volts but then says 2kw motor.

 

[E-HP]

Yes that’s it. See how it says 80 line amps at 72 volts but then says 2kw motor.

Seems conservative. I believe the rating is peak, so continuous might be more like 50A, which should be fine for a 3kW motor. You could test it, and upgrade if it doesn’t perform.

 

[j bjork]

It is just a rekomendation what size motor it is suitable for. It will work with a bigger motor of course, it just means that you wont get anywhere near the performance the motor is capable of.

 

[dominik h]

The fardriver values are not peak for a few seconds, they are values that can be used until the controller gets to hot and then it will reduce power step by step until it does not get hotter anymore or it cools down.
It will shure run with a 3kW motor, but with a bigger controller you could get more tourque and power if the battery, the wiring and the BMS can keep up.

 

[E-HP]

It will shure run with a 3kW motor, but with a bigger controller you could get more tourque and power if the battery, the wiring and the BMS can keep up.

Do you use some personal guidelines around the controllers rating vs the battery current capabilities? Meaning if the battery is rated 300A continuous, do you use a 300A controller, or something less to account for some degradation in battery capability as it ages, etc. (e.g. in your signature build, are the Li-NMC batteries rated higher than 400A fardriver)?

 

[Wheelsandall]

my BMS is rated at 125a and I doubt the battery pack I built would be capable of even that. So the battery will be the weak point as of now. I guess I just want to make sure it will survive the initial testing until I see how performance is.

 

[dominik h]

Do you use some personal guidelines around the controllers rating vs the battery current capabilities? Meaning if the battery is rated 300A continuous, do you use a 300A controller, or something less to account for some degradation in battery capability as it ages, etc. (e.g. in your signature build, are the Li-NMC batteries rated higher than 400A fardriver)?

If the battery can handle much more current as the controller can draw, you will have less voltage sag and longer battery life.
And I still want to crank up the battery current, whenever Fardriver lets me do this again.

 

[E-HP]

If the battery can handle much more current as the controller can draw, you will have less voltage sag and longer battery life.
And I still want to crank up the battery current, whenever Fardriver lets me do this again.

I’m allergic to voltage sag

 

[Wheelsandall]

the motor is on and works fine. I did notice the phase wires get warm to the touch but nothing major. It is hungry. It’s killing the battery almost around the block. It doesn’t help that my homemade battery is so out of balance that I won’t charge past 81v

 

[E-HP]

the motor is on and works fine. I did notice the phase wires get warm to the touch but nothing major. It is hungry. It’s killing the battery almost around the block. It doesn’t help that my homemade battery is so out of balance that I won’t charge past 81v View attachment 389474

Looks beefy . Are you using field weakening on your test ride?

 

[Wheelsandall]

I didn’t see a field weakening option in the FarDriver app. I have used it on a flipsky before but I don’t see the option in the FarDriver. It’s probably there just named something else the translation in the app isn’t the best.

 

[dominik h]

Weak response is the paramater you are looking for
0-6 and 7-disabled or 7-none
0 is strongest field weakening


and you have to raise the values in the ratios of speed at higher rpms, if they are to low then you will see no field weakening

 

[Jason73]

I agree with your observation and confirms my belief of Weak response, but unfortunately people on Facebook groups don't understand the the scale is inverted meaning after auto learn your default settings for Weak response is 0, meaning 100% FW is being supplied and they feel it's normal and a at the same time there motor is running hot,I'm done ranting about uninformed, and misguided people,thanks for the post so I could confirm

 

[dominik h]

When I bought the first Fardriver (ND96850) there was not much to find in the Internet.
So I had to test every thing by myself.
If I had directly installed the ND96850 I bought first, then maybe I had no need to tweak every parameter.
But a few weeks later the ND72680 was so cheap delivered from China, that I decided to test everything with this one. Paid 1/4 the price from the 96850. But after a few months I found it a bit to weak (not enough phase amps) for my heavy scooter.
In the meantime I found an unused 721800 for cheap (1/2 the price I paid for the 96850) and a few weeks later also a QS273 10kW hub motor. Now I have plenty of power and speed and no need for field weakening at all and an unused ND96850 sitting downstairs.

I never answered what my battery can handle.
The single cell is rated 8c continous and 9c peak. 4c (400A) produce 6V sag at 25 degrees Celsius.
I have already tested 450A and it still accelerates noticable faster. I want to raise to 500-600A for acceleration and I use 200A for longer periods like 10-15minutes.

 

[Wheelsandall]

so more field weakening equals more rpms correct?

 

[dominik h]

Yes more field weakening equals more rpm and more losses in the motor which produces more heat.
If I had bought a motor with lower kV, I would get better acceleration with the same phase amps and would loose top speed or had to use field weakening to get to higher speeds.
So for my intended goals, fastest acceleration and over 100kph, I bought the wrong motor as it does over 125kph without weakening field.
But the world exists of compromises, as the motor sitting here in Germany was half the price like one delivered from China and my old one was permanently overheating, I did not think long about speed or windings and upgraded to the QS273 10kW motor.
If I had bought a new one from China, I probably also could have bought the wrong winding because I had no clue which one to choose.

 

[Wheelsandall]

so now I’m wondering if I set the max rpm too high, to a point where the motor can’t reach, would the field weakening never kick in?

 

[dominik h]

Only if you set 7-none
With the other settings the controller would try to raise rpm with field weakening .

Only if you set the max rpm lower as the motor would naturally reach, the field weakening would never kick in