Scooter Build Help Please

[Computer Dan]

Hi everyone was hoping for some insight on upgrading my Mongoose FS lowrider scooter. I currently installed a 36V 18ah battery pack which works great. Flat ground I hit 25mph and have logged 31mph down a hill. Sitting on the rear fender and feet on the pegs was a bit scary and wobbly at that speed so I've since installed a seat post. Ok enough rambling, now the issue. The motor gets hot, really hot and starts to smell as you could imagine. I know it is not long for this world as currently setup but I am happy with the results.
Question 1. Is there a way to keep this cooler without replacing the motor?
Question 2. If I do replace the motor, I'd like to go with 12" hub motor(s). I know 1 will not get me the speed I would like but would running 2 increase the speed? Let say 2 350W hub motors with a 1000w controller. Is it possible to tie those both into the same throttle and will it move the scooter along at 25mph? Will my battery be enough to handle?

Any suggestions or comments are greatly appreciated. I have general knowledge about batteries and know my way around a soldering iron and multimeter so any further help would be great.

 

[boytitan]

2 motors won't increase your speed, just acceleration. You have no choice but to get a better speced motor.

 

[Computer Dan]

Can anyone point me to a motor that won't overheat, easy to install without fabricating a new mount? I don't want to lose speed and would like to stay at 36V if possible. I attempted to install a heatsink and fan from a computer which helps a little but not enough. It helps mostly for cooling an already hot motor rather than keeping it from getting hot in the first place. Thanks.

 

[Computer Dan]

Ok so I threw in the towel on the 450W motor. Didn't want to because of the speed and the fact that it had a freewheel but I couldn't ride it 5 miles on a hot day without smelling the motor cooking. That was a problem when my son wants to go on 10+ mile trips.I'm not a big guy, 5'9 and weigh about 155. My son is 11 and weighs about 80 so he is always faster no matter what he rides. Except my Mongoose with the 450W boiling motor I outran him every time. Out it went and I installed a Ezip 900W motor. So much torque I nearly flipped it. I did a wheelie for a good 20ft which scared me initially but I thought man is this going to be fast!! I could even do a wheelie rolling at 3mph and then going full throttle. Top speed 21mph... WTF? 900W VS 450W and 10mph slower?? Sure it takes off like a bat out of hell but my son blows past me after a 100ft or so. Out with the 900W motor and in with a 750W. That should get me faster right?? 2mph faster. Now top speed 23mph. My neck is still hurting from watching my son fly by me. What is going on here? I have lots of scooters and I noticed this is the only one that has a 40A controller. All others have 30A controllers. Would it help to get a 36V volt controller? I hate to lose the 40A controller as it has instant throttle response vs the others that have 30a and have a lag. Is that what is causing all the heat in the motor though, the extra amps? Does anyone know where I can get a different sprocket to run with the ezip 900w motor to gain top speed? I realize I will loose torque but there is plenty to spare. Not riding up too many hills and I don't want to keep ripping up my gravel driveway. Great fun though...

 

[amberwolf]

"Watt ratings" of a motor don't necessarily mean very much, other than *maybe* giving a *very general* comparison of low power vs high power vs really high power types (liek say, a 250w motor vs a 2000w motor vs a 10000w motor)...partly because different systems and different situations use them in different ways. There's a good article about this on ebikes.ca about this issue.

Regarding your speed/etc results, different motors may have different windings that have different speeds for the same voltage, and thus also different torques. So they may be more capable or less capable of a particular speed under a particular load, at a particular voltage and current.


If the mtoors are hubmtors, then the only way to change their gearing is to change the wheelsize. You can up the voltage to increase the speed, if they are capable of enough power to produce that speed against the load, slope, and air resistance.


If the motors are in the frame and chain (or belt, etc) driving the wheel, then you can change the sprocket sizes at each end for different gearing, and thus different torque and speed.


I recommend going to http://ebikes.ca/simulator and reading the entire page to learn what everything is and how it works, and then experiment with different motors/etc under the same situations you're using yours under, so you can see the differences from doing this, and figure out a way to match your needs with specific characteristics that you can then look for in a motor/controller/battery system.

 

[amberwolf]

900W VS 450W and 10mph slower??

Sure--because you traded torque for speed. (that winding thing I mentioned above is one reason for that--if it's a geared motor then the gear ratio makes adifference too).

Out with the 900W motor and in with a 750W. That should get me faster right??

May I ask why you assume a lower wattage motor would get you a faster speed?

I have lots of scooters and I noticed this is the only one that has a 40A controller. All others have 30A controllers. Would it help to get a 36V volt controller?

What does getting a 36v controller have to do with how many amps it has? With being 40A vs 30A?

It sounds like you are either confusing different things, or you're not typing everything you're thinking, so we don't have all the information that you do.

Is that what is causing all the heat in the motor though, the extra amps?

Using a motor at a high load at a low percentage of it's unloaded speed means it draws a lot more current under the same conditions as using it at the same load at a high percentage of it's unloaded speed. (the simulator can help you see how this works).

Changing the gearing of the motor could help with that.

 

[Computer Dan]

May I ask why you assume a lower wattage motor would get you a faster speed?

Well with these Currie motors that has been my experience which I never understood. 450W motor with freewheel, 27mph. 500W motor 25mph, 750W motor 23mph. 900W motor 21mph. These all have have identical batteries, hot off the charger and driven down the same street that has a slight hill. My son adds 3mph to each based on weight. They all are rated at the same rpm's but I guess they are wound that way. The 900w motor is nearly impossible to turn the gear and shaft by hand. Makes pushing the bike really difficult as well. The 500W turns freely by hand and pushes nicely. They have been like that since new.

What does getting a 36v controller have to do with how many amps it has? With being 40A vs 30A?

It sounds like you are either confusing different things, or you're not typing everything you're thinking, so we don't have all the information that you do.

Sorry I was kind of rambling. Trying to find out what is the best controller to run 36V on a 24V motor. I noticed that the 40A controller I have is way more responsive and gets instant power. Wasn't sure if I should go to a 36V controller to run more efficient and if I should keep the amps down in order to keep from overheating if that indeed is a big contributor.

What size sprocket would you recommend to replace the 11T that is currently installed for more speed? I need smaller correct. The simulator was over my head. Thanks again for your help.

 

[Balmorhea]

For more speed, use a larger sprocket on the motor or a smaller sprocket on the wheel.

 

[amberwolf]

Well with these Currie motors that has been my experience which I never understood.

That has to do with the way they're wound, then. Or if they have a gearbox, the gearing it has inside. Or both.

The wattage ratting doesnt' mean much (see previous posts), but in general is about how much heat the motor can handle / get rid of.

Speed doesn't really have much to do with the watt rating, directly, but it does take more watts to go a faster speed, mostly due to air resistance.

The 900w motor is nearly impossible to turn the gear and shaft by hand. Makes pushing the bike really difficult as well.

This probably indicates a problem with that motor. Either something is wrong in the gearbox, or in the motor itself.

It could just indicate that it has a very high gear ratio, and a winding that creates a lot of current (drag) in it when spun at a high speed without power. That might be why it has such a slow speed...but it probably doesn't overheat.

Trying to find out what is the best controller to run 36V on a 24V motor. I noticed that the 40A controller I have is way more responsive and gets instant power. Wasn't sure if I should go to a 36V controller to run more efficient and if I should keep the amps down in order to keep from overheating if that indeed is a big contributor.

Well, you're talking about several completely different things, so you must decide which of those things you want the system to do, then get a controller that does those things.

First, if you have a "900w" motor, and it's at 36v, then the highest curretn you should continuously allow is 900 / 36 = 25A. So to prevent overheating, you should be runnign a 26A controller.

If you have a 450w motor, that would be a 13A controller.

That's assuming the motors are "rated" as the max continuous amount of power they can dissipate as heat, vs teh gearing they are designed for and actually used at, vs teh speed they are designed for and actually used at, vs the load they are designed for and used at.

If they're being used differently than designed, you'd have to experiment with overheating vs power in vs usage (which you're doing now), and if they're getting hot, then you're putting too much power thru them (too high a controlelr current limit) for the gearing and usage you have.


Regarding how quickly teh controller responds, that's just the type of controller throttle response. Some are "soft start" and some are "instant start". Most sellers dont' provide this information, and some have it wrong (or are sending a different thing than the ad says), so i'ts possible to get the wrong kind easily enough.



Regarding the simulator...its the only easy way I know of to show you why you're having the problems you are, because there are a lot of factors to it. It takes a certain amount of power to do a certain amount of work, and it makes certain amount of waste heat to do this dependign on the system you use and how you use it, what speed you're at, your gearing, the load, the wind, the slope, etc. There is at least one thread on the simulator, that helps explain it, if that's useful.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=30108&hilit=simulator
https://endless-sphere.com/forums/viewtopic.php?f=2&t=89877&hilit=simulator
https://endless-sphere.com/forums/viewtopic.php?f=2&t=100461&hilit=simulator
and a number of other threads
https://endless-sphere.com/forums/search.php?keywords=simulator&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search



You can read about all this stuff individually, if it helps; theres' threads here about it, and other websites you can find. But without knowing how this works, you're kinda stuck just using experimentation to find a solution.

 

[Dauntless]

Well with these Currie motors that has been my experience which I never understood.

That has to do with the way they're wound, then. Or if they have a gearbox, the gearing it has inside. Or both.

The wattage ratting doesnt' mean much (see previous posts), but in general is about how much heat the motor can handle / get rid of.

Speed doesn't really have much to do with the watt rating, directly, but it does take more watts to go a faster speed, mostly due to air resistance.

Hey, my big experience is with Currie motors. I don't begin to know the context in which the lower wattage seemed faster. Considering what you MIGHT mean:

Currie seems to target 2,600rpm for the motor at whatever rated voltage. So if you had a 24v 450w and a 36v 900w, if you ran them at the same voltage, the 450w would indeed spin faster. If I remember the Rocket FS was 24v. You're running 36v. This is the winding Amberwolf is talking about. Some of those scooters have the same motor but there's a different setup and one is definitely faster, so even a smaller motor on it would seem fast.

From here I'm guessing, you do not give the information to know, but you can buy the motor with different size sprockets on it, did it come with a sprocket or did you use the original? You use the same 36v battery, the new motor is 36v and then spins lower. If there was a bigger sprocket it would make up for some lower rpm. If it's the same size you should be slower, some improvement in torque but I don't think massive. If it's smaller there's a lot more torque and less speed.

Did you replace the controller? It occurs to me that I learned little about Currie controllers playing with all those scooters because they didn't seem to have problems. But I guess it could limit your current and protect itself from the motor, so you get no speed. Maybe you need a controller.

Figure out the voltage of the old motor and the new motor. If the new motor is higher voltage than the old one, that explains slower at the same voltage and you can increase the voltage you run, right? Maybe you'd like this controller. http://tncscooters.com/index.php?route=product/product&path=41_75&product_id=184 Don't know if you'd need a new throttle.

If the new one is 24v, that site will have a choice of 36v controllers.

But on Amberwolf's calculation for the stock controller, I remember 350w and 450w coming with the same 24v controllers, sometimes 18a and I think a few 22a. I'd say calling the start "Soft" would be an understatement.

The 900w motor is nearly impossible to turn the gear and shaft by hand. Makes pushing the bike really difficult as well.

This probably indicates a problem with that motor. Either something is wrong in the gearbox, or in the motor itself.

Are you sure it's really mounted just right? If it's slightly to one side from where the old motor was, it'll stiffen up. I didn't understand that there was a problem off the scooter. Now a bigger motor can be a bit harder to turn, can't check it myself so I'd be guessing to compare. But if you get a good look at the chain on either sprocket, you might see the problem.

 

[Computer Dan]

Dauntless, thanks for the input. I might not have mentioned but the 450, 750 and 900 are all 24V motors. Here is kind of a recap from what I learned from Amberwolf. I was running a 24v 450W motor with a 24V 40a controller. After switching to a bigger motor the top speed decreased because I traded it for torque. Especially evident with the 900 overvolted to 36V which turned into a torque monster but kind of a dog. I installed the 750w motor hoping to then trade some torque for more speed. It kind of worked but I was used to the 450's top speed and was disappointed. I am happy to say that it does seem to run much cooler then the 450W. Only heated up after climbing a steep hill which is to be expected. I sat down and think I figured out the gears with the calculator. I ordered a 15T motor sprocket to replace my 11T. If my calculations are correct that will increase my speed around 26% with the 900W motor. That would give me a top speed of 26.5MPH. Pretty respectable in my book especially if the motor isn't cooking after a 5 mile ride.

Did you replace the controller? It occurs to me that I learned little about Currie controllers playing with all those scooters because they didn't seem to have problems. But I guess it could limit your current and protect itself from the motor, so you get no speed. Maybe you need a controller.

I did not want to replace the controller as I found out it was an instant start vs a soft start which I am not finding in a 36V for sure. I am ok with the performance was just concerned it was causing the extra heat with it being less efficient.

But on Amberwolf's calculation for the stock controller, I remember 350w and 450w coming with the same 24v controllers, sometimes 18a and I think a few 22a. I'd say calling the start "Soft" would be an understatement.

Stock controller on my Mongoose Rocket FS is 40A.

Are you sure it's really mounted just right? If it's slightly to one side from where the old motor was, it'll stiffen up. I didn't understand that there was a problem off the scooter. Now a bigger motor can be a bit harder to turn, can't check it myself so I'd be guessing to compare. But if you get a good look at the chain on either sprocket, you might see the problem.

Oh yeah 100% sure it is mounted correctly. I have had the "pleasure" of swapping out and installing many of these motors. I now can do them in around 25 minutes if I take my time. The motor is actually nearly impossible to turn the shaft and sprocket by hand not installed in the scooter. This has to be the way it is wound because it has been that way since it was new and hasn't had a problem. Since I started with a 900 I actually thought the pair of 750's I bought had a problem because they rolled so smoothly.

So I am going to wait on the bigger sprocket for the 900W motor, keep the the original controller and see how it runs. If it still overheats then I will replace the controller for one with less amps. Fingers crossed.

Thanks for everyone's input, I appreciate it greatly.

 

[Computer Dan]

First of all thanks to all who took the time to respond to my post and hope this helps someone else as well. I am pleased to say that my 15t motor sprocket finally arrived and I installed it on my 900W 24V motor. Definitely not without its challenges. First of all the pin that came with the new sprocket was too big. I destroyed the original pin trying to get it out. Luckily I had another blown motor and was able to carefully remove the pin with a rivet and a hammer. Installed the new gear and on to the new 100 link chain I ordered. 100ish is more like it. Was definitely a little smaller then the original 100 link chain. I tried to adjust it but the first run resulted in a popped chain and pushing it back home. After refitting the chain to the proper tension, full charge, here are the results..

155lb rider

Slight downhill
11T sprocket 36V 18ah battery 900W motor = 22mph
15T sprocket 36V 18ah battery 900W motor = 29mph

Flat ground
11T 21mph
15T 28mph

Back up the slight hill
11T 20mph
15T 27mph

This surpasses my expectations by far.While the motor gets hot I don't feel like it's getting quite as hot as the 450W despite the increase in speed. Time will tell how it holds up. Haven't had it on a long trip yet. I just enjoyed leaving my son in the dust for now without my motor smelling like it's cooking.