Trying to understand how many amps/watts a motor can actually take.

[Edward312]

Hi ES,

First of all, I’m new to ebikes and motor technology please pardon me for my stupidity.

I have been searching, reading for the past months trying to figure out how much amps a motor can actually take.

So far, what I have learned is amps/torque is what heats up the motor.
1. So I can pump as much amps as I can, as long as the motor stay cool? ( cooling mod, ventilation..)
2. My controller is pulling 80amps from battery during acceleration, and ~30 near top speed ( within 90%). So if I swap to a 150amps controller, same condition same load, the controller will pull 150amps during acceleration then ~30amps within 90%?

If these are true, then does it mean that if my motor will do fine with any bigger controllers, as long as condition and load stays the same ( to pull 30amps near rpm).
So what do I look for? I want a bigger, beefier controller.

I’m running 72v, the rating of motor is unknown.
80amps controller, after a long ride with heavy load, motor stays warm.

Thank you

Edward

Edit: it is a hub motor

 

[john61ct]

What motor?

Amps don't get pushed.

The weight of the load, the slope of the hill, the motor rpm / voltage determine how many amps get pulled.

Besides the heat issue there is a point where the maximum torque is reached, is determined really by the mass of the magnets, the iron & copper.

The other issue is, you get much greater reliability & longevity by not pushing anywhere near the maximum limit, true for all the components involved.l

 

[spinningmagnets]

take the motor apart and log all the details on the inside. What thickness of laminations, the number of magnets in the rotor, the number of stator-teeth, etc. Install a temp sensor (or two), and re-install. If its possible to enlarge the motor phase wires inside the motor as they exit the motor case, now would be the best time to do that. If the passageway has room for fatter wires, it's probably only $20 or so to upgrade them.

Learn to program the controller, and start at a reasonable level of amps, Make some runs and record the temps inside the motor. Never let the motor reach 200F / 93C, and I would recommend 140F as a good daily running temp (with occasional higher temporary peaks). Slowly raise the amps and repeat the baseline run, recording the increased temps. If you reach a point where the heat dramatically rises for the same small increase in amps, you have likely reached the point of saturation. Any amps above that will only provide a small performance boost, and it will cause significant heat. Take the amps to 5A-10A below the saturation point as your max.

The possibility may exist that you could add 10ml of ferro-fluid, which is also called Statorade. This a very cheap way to dramatically increase the heat-shedding ability of the motor, which would allow you to use higher temporary peak amps.

 

[Edward312]

take the motor apart and log all the details on the inside. What thickness of laminations, the number of magnets in the rotor, the number of stator-teeth, etc. Install a temp sensor (or two), and re-install. If its possible to enlarge the motor phase wires inside the motor as they exit the motor case, now would be the best time to do that. If the passageway has room for fatter wires, it's probably only $20 or so to upgrade them.

Learn to program the controller, and start at a reasonable level of amps, Make some runs and record the temps inside the motor. Never let the motor reach 200F / 93C, and I would recommend 140F as a good daily running temp (with occasional higher peaks). Slowly raise the amps and repeat the baseline run, recording the increased temps. If you reach a point where the heat dramatically rises for the same small increase in amps, you have likely reached the point of saturation. Any amps above that will only provide a small performance boost, and it will cause significant heat. Take the amps to 5A-10A below the saturation point as your max.

The possibility may exist that you could add 10ml of ferro-fluid, which is also called Statorade. This a very cheap way to dramatically increase the heat-shedding ability of the motor, which would allow you to use higher temporary peak amps.

I re-read numerous time on electricbike on this topic. I’m glad that I can hear from you.
That is my plan for this summer, getting a 150amps sabvoton. Open the motor up and install temp sensor+ add some fluid.
If I log the details inside the motor, is there anyway that I can predict how far can I push it for?

Also, phase wires coming out of the motor are 10awg. Are they good enough?

Thank you

What motor?

Amps don't get pushed.

The weight of the load, the slope of the hill, the motor rpm / voltage determine how many amps get pulled.

Besides the heat issue there is a point where the maximum torque is reached, is determined really by the mass of the magnets, the iron & copper.

The other issue is, you get much greater reliability & longevity by not pushing anywhere near the maximum limit, true for all the components involved.l

It is a qsmotor, no specs stamped on the cover, comes with the bike. No there is a limit to it. Guess I’ll spend time figuring it out. I assume it is rated for 1500-2000watts at 48v, bc when I got it it came with a 48v50amps controller.

Thank you

 

[amberwolf]

2. My controller is pulling 80amps from battery during acceleration, and ~30 near top speed ( within 90%). So if I swap to a 150amps controller, same condition same load, the controller will pull 150amps during acceleration then ~30amps within 90%?

If these are true, then does it mean that if my motor will do fine with any bigger controllers, as long as condition and load stays the same ( to pull 30amps near rpm).
So what do I look for? I want a bigger, beefier controller.

before getting into any of that:

*why* do you want a bigger, beefier controller?

what, specifically and exactly, do you want that controller to do for you?

because if you only use the same power when at cruising speed, you get nothing extra out of the controller during that time; it'll be the same as what you already have---so no point in changing it if that's where you need a change.


you *would* get quicker accleration, though how much quicker depends on the specific motor and the phase amps the controller feeds it, and the weight, slope, rolling resistance, etc.

you may want to go to http://ebikes.ca/simulator and read the *entire page* so you can see what everything is for and how it works, and then play with different controllers but the same battery and motor and conditions and bike setup, so you can see what changes and how.



you would also get better hill climbing, but the motor will also be getting hotter becuase the current will be higher....


justin_le has a thread titled something like "definitive testing of heating and cooling of hubmotors" that has a lot of information you may want to read.

 

[Edward312]

2. My controller is pulling 80amps from battery during acceleration, and ~30 near top speed ( within 90%). So if I swap to a 150amps controller, same condition same load, the controller will pull 150amps during acceleration then ~30amps within 90%?

If these are true, then does it mean that if my motor will do fine with any bigger controllers, as long as condition and load stays the same ( to pull 30amps near rpm).
So what do I look for? I want a bigger, beefier controller.

before getting into any of that:

*why* do you want a bigger, beefier controller?

what, specifically and exactly, do you want that controller to do for you?

because if you only use the same power when at cruising speed, you get nothing extra out of the controller during that time; it'll be the same as what you already have---so no point in changing it if that's where you need a change.


you *would* get quicker accleration, though how much quicker depends on the specific motor and the phase amps the controller feeds it, and the weight, slope, rolling resistance, etc.

you may want to go to http://ebikes.ca/simulator and read the *entire page* so you can see what everything is for and how it works, and then play with different controllers but the same battery and motor and conditions and bike setup, so you can see what changes and how.



you would also get better hill climbing, but the motor will also be getting hotter becuase the current will be higher....


justin_le has a thread titled something like "definitive testing of heating and cooling of hubmotors" that has a lot of information you may want to read.

I want power, and more power, fast and faster take off. And see how much abuse can the motor take, and learn from that.
I have tried the stimulator, but I have zero information of the motor, how should I set it up?
Definitely check the post out, sometime I get lost at the search since there are too much information.

Thank you for your response

 

[amberwolf]

there is certainly a lot of info in threads like that. sometiems to even use the info you have to read a lot to learn what the terminology all means. this thread
https://endless-sphere.com/forums/viewtopic.php?f=1&t=82507
has links to indexes of useful threads you might find handy.

power for power's sake can be fun...but expensive.

when you add that higher current controller, it's a fair bet you'll end up having to add a bigger better battery to support it. the one you already have may not be able to supply the current it needs. the battery is the heart of the system;

if it can't supply the current the system needs, it'll sag in voltage a lot and you wont' get as many watts, so the system won't do the things you ask of it as well (or at all). it'll also heat up more. if it has a bms that's setup to protect against overcurrent, it may just shut off power to teh whole system whenever you throttle up hard, if the batteyr can't handle it.


for the simulator, to learn how the systems work in general, you can use any of the motors. just use the same one, but with different controller current limits. theres the mxus 450x series that may behave similarly to what you have. 4503, 4504, 4505, 4506, in the motor list if you choose "show all" at the bottom of the list.


if you want to use a motor similar to yours, you'd need to know more about what yours actually is.

qsmotor cant' tell you what it's properties are (they don't know how and/or refuse to do this for any of their motors), so you can't put in custom numbers unless you figure out how to determine those numbers for your motor on your own, with the right test equipment and some math. but some of this is already known for some motors, if we can figure out which one yours is, so we can guess one tha'ts close enough for estimation purposes.

all the qsmotors i've seen myself have a number engraved or etched into the cover somewhere. usually looks like a long serial number or something. like this:

at a guess, yours is a qs20x (where x = a number we don't know).

if you take good clear pictures of the motor from both sides and one from an angle that shows the whole motor relative to the bike, we can at least make guesses as to which one it is, if not which winding. then attach them to your posts using the attachments tab below the box you type your post's text into.


if the motor came with a 50a controller, for a 2kw system, it's a good chance it's a big and heavy one similar to but possibly not as thick as this (but yours probably still has axles :lol: ) :
https://www.endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1526261#p1526261

if so, it's likely it will take short (few seconds to even minutes at a time) bursts of much higher power. the one above experienced nearly ten times the power it was rated for on occasion, before it's axles sheared off. the motor itself, other than that, is undamaged. (though that's severe damage, it's fixable by replacing the axle or a few other things--much easier than dealing with overheating damage).

it will probably take a few minutes of twice the rated power, but if you're doing that a lot, at that point i'd want to wire up the temperature sensor it probably has installed (usually a white wire, and you use the hall sensor ground for the other wire) to something you can monitor temperature with on the handlebars, or use a controller that can monitor that particular temperature sensor.

if you get your controller from qsmotor, you can have them make sure the controller is already setup for your particular motor if you can get them the information that is on or in the motor to tell them which one it is, and also make sure that if your motor does already have a temperature sensor that the controller is compatible with it and setup for it.

 

[Edward312]

there is certainly a lot of info in threads like that. sometiems to even use the info you have to read a lot to learn what the terminology all means. this thread
https://endless-sphere.com/forums/viewtopic.php?f=1&t=82507
has links to indexes of useful threads you might find handy.

power for power's sake can be fun...but expensive.

when you add that higher current controller, it's a fair bet you'll end up having to add a bigger better battery to support it. the one you already have may not be able to supply the current it needs. the battery is the heart of the system;

if it can't supply the current the system needs, it'll sag in voltage a lot and you wont' get as many watts, so the system won't do the things you ask of it as well (or at all). it'll also heat up more. if it has a bms that's setup to protect against overcurrent, it may just shut off power to teh whole system whenever you throttle up hard, if the batteyr can't handle it.


for the simulator, to learn how the systems work in general, you can use any of the motors. just use the same one, but with different controller current limits. theres the mxus 450x series that may behave similarly to what you have. 4503, 4504, 4505, 4506, in the motor list if you choose "show all" at the bottom of the list.


if you want to use a motor similar to yours, you'd need to know more about what yours actually is.

qsmotor cant' tell you what it's properties are (they don't know how and/or refuse to do this for any of their motors), so you can't put in custom numbers unless you figure out how to determine those numbers for your motor on your own, with the right test equipment and some math. but some of this is already known for some motors, if we can figure out which one yours is, so we can guess one tha'ts close enough for estimation purposes.

all the qsmotors i've seen myself have a number engraved or etched into the cover somewhere. usually looks like a long serial number or something. like this:

at a guess, yours is a qs20x (where x = a number we don't know).

if you take good clear pictures of the motor from both sides and one from an angle that shows the whole motor relative to the bike, we can at least make guesses as to which one it is, if not which winding. then attach them to your posts using the attachments tab below the box you type your post's text into.


if the motor came with a 50a controller, for a 2kw system, it's a good chance it's a big and heavy one similar to but possibly not as thick as this (but yours probably still has axles :lol: ) :
https://www.endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1526261#p1526261

if so, it's likely it will take short (few seconds to even minutes at a time) bursts of much higher power. the one above experienced nearly ten times the power it was rated for on occasion, before it's axles sheared off. the motor itself, other than that, is undamaged. (though that's severe damage, it's fixable by replacing the axle or a few other things--much easier than dealing with overheating damage).

it will probably take a few minutes of twice the rated power, but if you're doing that a lot, at that point i'd want to wire up the temperature sensor it probably has installed (usually a white wire, and you use the hall sensor ground for the other wire) to something you can monitor temperature with on the handlebars, or use a controller that can monitor that particular temperature sensor.

if you get your controller from qsmotor, you can have them make sure the controller is already setup for your particular motor if you can get them the information that is on or in the motor to tell them which one it is, and also make sure that if your motor does already have a temperature sensor that the controller is compatible with it and setup for it.

The qsmotor that I have unfortunately, no information on it, I believe for ‘legal’ reason. Also no wire for temp sensor, just same old 5 halls. My battery can take hell of loads, 30ah, 6C discharge rate. Bms is not a problem, I can ditch it, run with the pack’s main pos and neg.
So I’ll be playing with the stimulator before parts I need come in. I’m planning to use this temp sensor, and somehow mount it inside when I have a chance to open the hub out.
https://a.aliexpress.com/_d8FYEUX
So my last bet is to dissemble the motor, measure, log as much as I can, hoping to get this hub identity :lol:

Thank you so much for all the links, I have been hungry for knowledge.

 

[markz]

If you are concerned about not having enough motor power, then its wise to buy more motor then you need. This is not considering the controller at the moment. You can play around with these tools. Motor simulator is good if the motor is listed, if not then to get an idea is to go ahead and use the Trip Simulator to see the terrain you are riding, slopes, distances, power, Ah, Wh etc.
https://www.ebikes.ca/tools.html

You can use the motor to its full potential, and perhaps beyond for magic pixie smoke, then you maybe left stranded. Thats why you go more motor then you think you need.

So instead of studying all aspects of some random 1000W motor to see the tipping point of power, then go ahead and buy yourself a Leaf 1500W or MXUS 3000W. The Leaf has been well studied for max power potential, as well as the MXUS.

 

[flat tire]

How much current a motor can take depends on how much voltage you have to push and the specs of the motor. Ultimately motors will "saturate" or reach a point where more current makes no more torque.

You can play with different combinations at the grin motor simulator:

https://www.ebikes.ca/tools/simulator.html

 

[DogDipstick]

take the motor apart and log all the details on the inside.

Never let the motor reach 200F / 93C, and I would recommend 140F as a good daily running temp (with occasional higher temporary peaks). ~ a point where the heat dramatically rises for the same small increase in amps, you have likely reached the point of satu~

T

Spinning Magnets. Ron.
I know you a have been saying this for some time, I have read for two years now you saying "140*F".... You do have experience.. but.. I have been running with a 180*C (356* F) ( far away from your "140* F") cutoff without many problems for about 700 miles now. I get hot. This is on a KTY83.

Amps for my motor are listed as "20A, 40A for a short time"... and you know I push 100A on the shunt..... Still making higher power numbers with the more voltage.. ?

I would love to know the hard limit of my motor. Or when it gonna burn. I am consider in less amps but much more power from the same motor... a 33% increase in voltage, with the similar amperage..( 60A contin, higher "peak") just to see what happens.

I mean what if you take a hub and run 400v and 10A? (4Kw) Will it live? What will fry? The insulation? How about 400v and 50A? will she put out 20Kw? Lol. Where is the voltage capped ( insulation grade in winding?) and what caps the amps (saturations)..?

Markz: you say :

So instead of studying all aspects of some random 1000W motor to see the tipping point of power, then go ahead and buy yourself a Leaf 1500W or MXUS 3000W. The Leaf has been well studied for max power potential, as well as the MXUS.

Where can I find the "Leaf 1500w" data? I think my motor is a clone of that.... and I would like to see the data, or someone difinitivly saw " It can take THIS many amps and THIS much power"... Link? Ty, .


Limited to 140*, 20A and I wouldnt have ANY fun. Hell my motor is still under warranty. Gotta make sure its a good one, right?

 

[markz]

Neptronix has a whole thread on it.
63 pages - https://endless-sphere.com/forums/viewtopic.php?f=30&t=66489
Happy reading!

 

[John in CR]

Current handling is determined by the phase-to-phase resistance. Measure that (and make sure it's essentially the same for all 3 combos while you're at it to make sure there aren't any winding problems) and post it here. Motors of the same model wound to different Kv's will have drastically different current handling capabilities.

 

[DogDipstick]

Make some runs and record the temps inside the motor. Never let the motor reach 200F / 93C, and I would recommend 140F as a good daily running temp (with occasional higher temporary peaks).

Well, you were right Mr. Magnets.

My hall sensors died in 746 miles of abuse in the 150-180*C range.... over like 25-45 miles I got the stutters and finally every ride was a reset, to get home.


Turning down the Ca now and trying again. Amps and temp limit. I'll have to live with it. The windings were not even browned a bit.. but the sensors gt replaced and Im back running.

 

[serious_sam]

My hall sensors died in 746 miles of abuse in the 150-180*C range

For future reference, Honeywell SS41 hall sensors are rated to 150C.

 

[DogDipstick]

My hall sensors died in 746 miles of abuse in the 150-180*C range

For future reference, Honeywell SS41 hall sensors are rated to 150C.

IDK if thats the problem but thankyou, seems I jumped the gun... Sensors were triggering. I have no idea as to whats the problem theres another thread. Just wanted to comment that yes, this temp running broke something in 700 mile. I havnt figured it out yet: new sensors did nothing.