36v motor overvolted to 48v needs what sized controller?

[kmxtornado]

I have a 36v 500w motor that I overvolted to 48v. The existing controller which I'm reusing is rated for 36-48v and 22amps so I'm assuming my motor draws that at the very most. Unfortunately I don't have the specs from this old DIY kit from 2011. I'm trying to add PAS and a display and will need a new controller to make that happen. Should be controller be 500w like the original or 1000w?

Doing the math, 48v x 22amps = 1,056w.

TIA.

 

[E-HP]

Should be controller be 500w like the original or 1000w?

It depends on if you need more power, and if your battery is capable of providing it. Otherwise, go with the 500W.

 

[amberwolf]

What specifically do you need the bike to do for you, under what conditions? That's what determines the amount of power you need, which determines the controller specs.

If you need that power for seconds at a time, infrequently, the motor can be fairly undersized in many cases. If you need that power fairly continuously, the motor probably needs to be bigger, matched to that power requirement.

Then the battery you need is determined by the controller you use, since the battery has to be able to supply all that power, at the right voltage and current.

 

[RTLSHIP]

I had bad experiences overvolting. I had a 36 volt set up and put a 48v pack and controller would short/fail. Problem was solved by getting a more versatile converter. So, I would look at voltage tolerance- not watts

 

[docw009]

If you had a 22A controller, and didn't have any motor issues, why not get another 22A controller?

I would buy a 25A KT controller, and one of their displays. Their better displays like the LCD3 and higher will allow you to set the max current anywhere from 13A to 25A, should you distrust your ability to keep the current at safer levels.

 

[kmxtornado]

What specifically do you need the bike to do for you, under what conditions? That's what determines the amount of power you need, which determines the controller specs.

If you need that power for seconds at a time, infrequently, the motor can be fairly undersized in many cases. If you need that power fairly continuously, the motor probably needs to be bigger, matched to that power requirement.

Then the battery you need is determined by the controller you use, since the battery has to be able to supply all that power, at the right voltage and current.

Yes, it would be more in spurts than running the bike full on all the time. Not trying to turn it into a motocycle. The lack of disk brakes really does scare me as it is already. I'm only looking to be able to go up hills more easily and perhaps better low end torque. Top speed isn't really the focus.

Yes, my battery is a 48v 20mah LiFePo4.

 

[kmxtornado]

Should be controller be 500w like the original or 1000w?

It depends on if you need more power, and if your battery is capable of providing it. Otherwise, go with the 500W.

Thanks, I was leaning in that direction too with the 500w controller.

 

[kmxtornado]

I had bad experiences overvolting. I had a 36 volt set up and put a 48v pack and controller would short/fail. Problem was solved by getting a more versatile converter. So, I would look at voltage tolerance- not watts

My system is doing fine so far. The controller appears to have a 22amp max limit so I'm guessing my motor isn't drawing anywhere near that.

 

[kmxtornado]

If you had a 22A controller, and didn't have any motor issues, why not get another 22A controller?

I would buy a 25A KT controller, and one of their displays. Their better displays like the LCD3 and higher will allow you to set the max current anywhere from 13A to 25A, should you distrust your ability to keep the current at safer levels.

Yes, I am most likely going to replace the controller with another 22A one. No issues to date.
Yes, I'm looking to get a 25A KT controller since it would be compatible with the screen I want. I'm looking at the KT LCD4, the smallest of them. It suits my setup better. I was contemplating on the larger cooler ones, but I'd prefer that it stay stealthy and the small one just looks like a regular bike computer to most people. Also I'd like to keep the handlebar clear of clutter. I hadn't realized that I can set the max current. That would great.

 

[kmxtornado]

I'm watching youtube videos of people replacing their controllers with ones with a higher amp rating and yielding improved speed and torque results. This makes no sense to me in the way I understand how a controller works. Please correct me or explain if I'm wrong.

I understand controllers to act like ESC's on an RC car. The motor is what draws the amps and the Controller/ESC needs to have a high enough amp rating to endure the demands of the motor. If the amp rating on the controller/ESC is too small, then it'll stress out fail. If the amp rating on the controller/ESC is higher, then it just provides more tolerance for any future motor that would draw more amps. It shouldn't actually yield improvement whatsoever. The Controller doesn't natively limit amps that the motor draws does it?

I understand there's a setting that can be changed, but if I don't have a screen/display to begin with, my controller wouldn't have any way of limiting amp draw of the motor. I always thought the motor is free to pull whatever amps is being demanded from it and the controller can either handle it or it can't.

Please correct my thinking if it's wrong. I'm still learning about the ebike electronics. I see similarities with RC cars but can appreciate that there must be differences too.

 

[RTLSHIP]

I have older kit and it runs goes almost 28 mph (then motor stutters) with smaller cheap controller. With another higher amp controller it stutters at 30.5. So controller capacity makes a difference. You want to make sure you don't fry controller due to overvolting.
I didn't see anything about your battery plans. The bigger controller will draw so much that it can trigger a bms shutdown or quickly fatigue the battery.

 

[Blacklite]

I'm watching youtube videos of people replacing their controllers with ones with a higher amp rating and yielding improved speed and torque results. This makes no sense to me in the way I understand how a controller works. Please correct me or explain if I'm wrong.

I understand controllers to act like ESC's on an RC car. The motor is what draws the amps and the Controller/ESC needs to have a high enough amp rating to endure the demands of the motor. If the amp rating on the controller/ESC is too small, then it'll stress out fail. If the amp rating on the controller/ESC is higher, then it just provides more tolerance for any future motor that would draw more amps. It shouldn't actually yield improvement whatsoever. The Controller doesn't natively limit amps that the motor draws does it?

I understand there's a setting that can be changed, but if I don't have a screen/display to begin with, my controller wouldn't have any way of limiting amp draw of the motor. I always thought the motor is free to pull whatever amps is being demanded from it and the controller can either handle it or it can't.

Please correct my thinking if it's wrong. I'm still learning about the ebike electronics. I see similarities with RC cars but can appreciate that there must be differences too.

The controller acts as a current limiter. The “rating” on a motor is more about how much power it can take without overheating. The controller also in a way acts as a buck converter, so the motor phase current can be much higher than the battery current, at a correspondingly lower voltage. If there wasn’t some sort of limit at low speed or stall the motor current would be limited only by the resistance of the wiring, burning out very quickly.

Even if you don’t have a display the controller would have some sort of limit programmed. Modern ebike controllers are microprocessor controlled, even those with no display, and will have some sort of shunt inline to measure current. Hence the so called “shunt mod” to increase power.

 

[slaphappygamer]

I'm watching youtube videos of people replacing their controllers with ones with a higher amp rating and yielding improved speed and torque results. This makes no sense to me in the way I understand how a controller works. Please correct me or explain if I'm wrong.

I understand controllers to act like ESC's on an RC car. The motor is what draws the amps and the Controller/ESC needs to have a high enough amp rating to endure the demands of the motor. If the amp rating on the controller/ESC is too small, then it'll stress out fail. If the amp rating on the controller/ESC is higher, then it just provides more tolerance for any future motor that would draw more amps. It shouldn't actually yield improvement whatsoever. The Controller doesn't natively limit amps that the motor draws does it?

I understand there's a setting that can be changed, but if I don't have a screen/display to begin with, my controller wouldn't have any way of limiting amp draw of the motor. I always thought the motor is free to pull whatever amps is being demanded from it and the controller can either handle it or it can't.

Please correct my thinking if it's wrong. I'm still learning about the ebike electronics. I see similarities with RC cars but can appreciate that there must be differences too.

The stock controller in my bike was a Lishui 22A controller. The ebike company had the amps limited to 18A. No setting could change this. It seems like most ebike companies flash their own firmware to the display annd this locks out the end user from changing most settings.

After realizing that I have 48V22 motor, I wanted to utilize that extra amperage to better help with the hills in my area. I converted to a KT system, while I was at it. I got a 25A KT controller and an LCD8H. It was a perfect fit. The 25A KT controller was a hair bigger than the Lishui controller. It fit in the same cavity that controller resides in the downtube. Recently updated my phase wires and connections too. My bike ride is much nicer now.