A mystery rear motor with 36V controller and 48V battery

[MrSkinnyLegs]

Hello!

I am a tad confused and scared now reading that i might catch fire

The person who did a conversion kit for me said the motor was a 500W motor.

Controller reads 36V 22 A +-1. So that adds up to somewhere 750W?

Off road i manage 44km/h without much effort.

Now what got me confused was that the battery is 48V 13A? Is that the reason my controller gets hot to the touch or is it my pouch should have holes for vents or something?

I dont seem to have problems with it besides controller saying 36V and battery being 48V.

 

[vfr400]

What's causing your controller to get hot is the high speed of the motor. It'll stay cool while you're going fast, but when you're travelling at lower speeds with full power, it'll become hot. Basically, the controller is running at 22A more of the time. It's only rated at 11A.

Obviously, the more air it gets, the more it can shed heat.

Show us some photos of what you have.

The battery is fine.

 

[Nealh]

The controller is only rated at 36v so will be running inefficiently at 48v, one would think you must have a 60v capacitor inside, 22a at 48v nominal is a lot. The hot running of the control will be down to running slowly at higher current.

 

[Nealh]

Crossed with vfr's post.
What may or will eventually happen is the controller will start cutting out thermally as the mosfets will go beyond their temp rating, once they & the controller cool it will work again for a while. Controller can easily go beyond 60c once they get very hot.
You shouldn't catch fire but scalding may occur and if crappy bullets are used they or the plastic shrouds will melt on the phase wire connections.

 

[MrSkinnyLegs]

What's causing your controller to get hot is the high speed of the motor. It'll stay cool while you're going fast, but when you're travelling at lower speeds with full power, it'll become hot. Basically, the controller is running at 22A more of the time. It's only rated at 11A.

Obviously, the more air it gets, the more it can shed heat.

Show us some photos of what you have.

The battery is fine.

Okay i assume what you mean is acceleration is harder on controller than staying at high speed.

I red in another thread that having different Voltages between controller and battery/motor will cause damage. I guess i red wrong.

 

[MrSkinnyLegs]

The controller is only rated at 36v so will be running inefficiently at 48v, one would think you must have a 60v capacitor inside, 22a at 48v nominal is a lot. The hot running of the control will be down to running slowly at higher current.

Can you elaborate regarding regarding the 22a at 48V? Since controller is 22 and battery is 48, that means controller voltage is not important?.

I have close to zero knowledge about electronics sorry

 

[Nealh]

There comes a point where to many amps x voltage will be add to much heat for the controller to handle, the mosfets will be heat sensitive with a max temp range.

At 36v/22a the controller will typically give 792w at 48v this jumps to 1056w, the components in the 36v won't be normally configured for 48v use continuously.
48v is making the controller work 33% harder so if it can't do so that extra voltage
in your case will be wasted as heat by the controller, the heat is generated by the mosfets. Heat is due to inefficiency of the mosfets.
The motor won't see all of those watts due to efficacy conversion typically at least 20% of those watts will be lost.

At some point the controller will either cut out thermally or fail altogether.

 

[vfr400]

OK, what you have is generally well matched apart from the motor being too fast for the power you're giving it, so it's running with full power more than the controller is happy with. You'll be OK as long as you're gentle on the power at low rpm.

You probably didn't read anything wrong, but either you didn't understand what you read or what was written was crap.

 

[MrSkinnyLegs]

There comes a point where to many amps x voltage will be add to much heat for the controller to handle, the mosfets will be heat sensitive with a max temp range.

At 36v/22a the controller will typically give 792w at 48v this jumps to 1056w, the components in the 36v won't be normally configured for 48v use continuously.
48v is making the controller work 33% harder so if it can't do so that extra voltage
in your case will be wasted as heat by the controller, the heat is generated by the mosfets. Heat is due to inefficiency of the mosfets.
The motor won't see all of those watts due to efficacy conversion typically at least 20% of those watts will be lost.

At some point the controller will either cut out thermally or fail altogether.

Is there a way to find out motor voltage so i know if i can upgrade to 48V controller?

I dont use the throttle anyways, might as well remove it. Assist is enough for me.

That way the battery would work more efficiently , however the motor might not be able to handle the extra power if it is something like 500W 36V?

 

[MrSkinnyLegs]

OK, what you have is generally well matched apart from the motor being too fast for the power you're giving it, so it's running with full power more than the controller is happy with. You'll be OK as long as you're gentle on the power at low rpm.

You probably didn't read anything wrong, but either you didn't understand what you read or what was written was crap.

How exactly can i be gentle with PA? I only use throttle for start from standing ( while pedaling till i hit the sensor ).

 

[vfr400]

Is there a way to find out motor voltage so i know if i can upgrade to 48V controller?

I dont use the throttle anyways, might as well remove it. Assist is enough for me.

That way the battery would work more efficiently , however the motor might not be able to handle the extra power if it is something like 500W 36V?

Motors don't have a voltage. The two important characteristics are the size and the speed. Lift the wheel off the ground and spin it up to full speed. make a note of the speed, then measure the battery voltage.

Assuming a 26" wheel and that your speed is set correctly:

Motor KV = rpm/volt = [201 x (speed in mph)/15]/battery voltage.

 

[MrSkinnyLegs]

Motors don't have a voltage. The two important characteristics are the size and the speed. Lift the wheel off the ground and spin it up to full speed. make a note of the speed, then measure the battery voltage.

Assuming a 26" wheel and that your speed is set correctly:

Motor KV = rpm/volt = [201 x (speed in mph)/15]/battery voltage.

Makes no sense I bet its funny and irritating at the same time for me to make such silly questions.

 

[vfr400]

Where did you get 402 from?

 

[Nealh]

Your hub is a Direct Drive model although it has a restriction between 250w and we assume 1000w it probably has winding of about 390rpm or so. In a 26" wheel that might equate to around 30mph at 36v/ 22a, at 48v the rpm will increase by some 33% to over 500rpm that in turn would equate to about 39/40 mph.

As vfr has said hubs don't have a voltage but initially they are sold with XXX rpm/winding for X voltage, by adding more voltage then the hub will run faster and at less efficient at low speeds which is where heat comes in to play.

 

[PC2017]

Quick side query, if your using a 36v controller on a 48v battery would this not cause issues with LVC if you ever went a long distance? Assuming the BMS wouldn't cut you out first.

 

[Nealh]

The OP would need to monitor the battery voltage so it doesn't drop below 41.5v, one could try and rely on the bms to cut but unless voltage is monitored one could be stuck miles from home.

 

[harrys]

If the controller is getting hot, it shouldn't be in a bag. Zip tie it to the frame, if you can. The open air will keep it cooler. If you can clamp it to the frame with a bracket, then you'll get the benefit of more heat transfer.

 

[Nealh]

For the UK open air fixing of a controller means the bikes use is limited to dry running use only so would rule out 3/4's of the year. Extra heat sinks might work esp if they were exposed to the air or were in contact with the bike frame to dissipate some of it.
When my KT 6fet turned into a hot potato, I added two 5v mini fans and a heat sink wired the fans into a small 3p1s 18650 battery unit for cooling. Eventually I got tired of faffing so just upgraded to a KT9 fet and all was well, same smooth quite running but with better upgraded mosfets which is where the issue lies and where the heat build up is coming from.
The fact is too slow running at a higher voltage is causing the issue.

 

[PC2017]

I find that in the winter/rain months I can store my black heat absorbing monster (6fet) in a seat post bag although that does have a custom hole for cables but is some-what protected by the seat/bag, in the summer I cable tie it the same spot under the seat and unless it's super high temps I rarely get issues, that said I have added two heatsinks to it, shame there's been no high temp weather to test their functionality.

I was finding aliexpress tricky to search for dual voltage sinewave controllers unless they weren't been made. The only ones I could source where the 22a sine 36/48 or the 14a black 36/48. However, if anyone is interested, I gave the algorithm another chance or ironically they just started making them and found a KT sine 36/48 17a silver - I have just received it and can verify it is daul voltage and sine! Hopefully silver will dissipate heat better if the need arises.