Brushless Scooter Motor vs Hobby RC Motors?

Hello Guys,
Im Jan from Germany and Im pretty happy to final have passed that registration question. It was hard, no kidding!
I am currently searching for a motor for some small EV projects (Kart, Bike, Board) and was wondering about the power output of certain motors.
The first product I was watching is a brushless scooter motor made by Boma (I think) it is rated 48v 1600w 4600rpm 34-42amps and weights 3,8kg with 107mm in diameter.

I've compared it to many low kv brushless outrunners which only weight less than a kilo, diameter and lenghts is around 59mm and they have a rated output of 2,5-3kw and I just dont get it. Okay they can draw double the amps but is it right that they have more "power"?
I would appreciate every help and explanation according this case, the information on the german side of the Internet is limited
Of course I have searched this forum for the motor but just found out little... I've read things like "I dont know who would chose this Motor, anyway" and someone said he's put it in a kids quad after the my1020 burned and he is pretty happy with it.
Whats so bad about this motor and why is the output so weak for a motor of its size and weight (if it is)?
Thanks already for reading this mess till the end, please enlighten me

Hi Jan,

The size and weight of a motor relates more directly to its torque capability, rather than its power capability. So, if a motor is designed for a very high speed it can be quite small and light. Also, the RC motor ratings are for an open motor with a strong throughput of air from a propeller.....

Thanks Miles,
thats what Ive thought because of the diameter and the longer "leverage" of the motor.
When I do the math to calculate torque for the Boma Motor and a Turnigy SK3 149kv, the Turnigy still has got a slightly higher value. Mainly because of the higher max current. I assume that the Motor can put out a higher torque but only at a pretty high speed where it has to take its time to get there when its used in an EV and not in a RC plane where the only resistance is the prop in the air. Kind of right?

The data you need to compare the basic potential of different motors is:

Phase to phase resistance.

Velocity constant (Kv)

At least two values for no load amps at different speeds.

That's why we developed this spreadsheet: https://endless-sphere.com/forums/viewtopic.php?f=30&t=65757

The torque constant of the scooter motor is 0.1 Newton metres per amp

The torque constant of that Turnigy SK3 is 0.064 Newton metres per amp

So, the scooter motor will output 1.6 times more torque, per amp of current, than the SK3.

For most motors, the torque limit is set by the heat generated and the ability to dissipate it. This is why you need to know the phase to phase resistances.

Miles said:

The torque constant of the scooter motor is 0.1 Newton metres per amp

The torque constant of that Turnigy SK3 is 0.064 Newton metres per amp

So, the scooter motor will output 1.6 times more torque, per amp of current, than the SK3.

For most motors, the torque limit is set by the heat generated and the ability to dissipate it. This is why you need to know the phase to phase resistances.

Click to expand...

I'm not trying to hijack your thread, but rather give you some information about these motors. The short version is with a couple of minor changes, I really like these motors. Read on for the details.

My 1500 watt motor has given me zero troubles on a cheap Chinese controller or on a KBS72221E Kelly controller. It just works. I ran it for a full year at 48 volts and it pulled my 240 pounds and 85 pounds of scooter around at a top speed of 32mph with no problem. Acceleration was a little weak for the amount of weight and pulling hills would cause me to slow down a little, but if your total weight is less than mine, well you will do just fine. This last fall I upgraded to the 2000 watt version of the same motor and also went to 72 volts. The 2000 watt motor runs hot much quicker than the 1500 watt motor (See below about that). It has way more torque even at 48 volts than its 1500 watt cousin. I was tempted to not upgrade to 72 volts and just run it at 48 volts, but I wanted lots more speed and knew I could get it with more voltage. These motors typically come with a T8F 9 tooth sprocket on them. They have a "DD" motor mount. See the sprocket picture. Sprockets can be easily found on ebay for it. Same for chain and wheel sprockets. I have 9 tooth to 15 tooth sprockets. The motor has a 10mm shaft and the flats for the sprocket are at 8.5mm. There are several things I like about these motors. They are cheap...about $120 to $150. They are inrunners so dirt and grime don't get into the motor easily. Mine sits right next to the back wheel and gets sprayed with water and dirt all the time coming off the tire. It has never gotten into the motor. They work pretty well. Are there better motors out there? I sure hope so considering what these things cost! Parts for them are readily available out of China. They are a low Kv inrunner. If a 3000 watt version of this motor existed, I would buy one right now. Regarding weaknesses of these motors...they are inrunners so this is true for any inrunner, but some kind of forced air cooling would be good. The hall sensors are a little strange. They don't output clean square waves so some motor controllers will act weird with the motor. In one of my 1500 watt motors I replaced the hall sensors with better ones to fix the problem. I use Kelly motor controllers and have two of them. One controller (KLS7230S) would spin up the motor, but then the motor would studder and jerk a lot. This was a completely unusable combination. I also have a KBS72221E and all of my BOMA motors work great with it. The difference is how the controllers detect the hall signal. I don't know about other sensored motor controllers. Replacing the hall sensors in the motor is pretty easy since they are very easy to get at and replace once you have the motor apart. The bullet connectors on the motor fields are crap, I recommend replacing them immediately with 5mm or larger R/C bullet connectors.



I have 2 1500 watt and 1 2000 watt version of this motor. The 2000 watt motor is rated at 60 volts and the other 2 at 48 volts. The 1500 watt motors say 5600 rpm on them so if I divide 5600 by 48 doesn't that give me the Kv of the motor? So that's 116.66 Kv. On field to field resistance, that's about .35 ohms on my DMM for either the 1500 or 2000 watt versions. I have run the 1500 watt motor at 48 volts for 20 miles straight and the motor gets hot after a while, but it never has failed to work after a full year of daily commuting 10 miles. I few heat sink strips wrapped around it would have taken care of the heat issue. These motors come with super light weight bullet connectors on them. In one of the below pictures I show that I cut the motor cable off at about 8" and then added new connectors. The black connector is a weather proof connector I found on ebay for $4. They are about the size of your fore finger fully assembled. I used 8mm bullet connectors for the field wires. The original bullet connectors are super cheap and over heated.



This is my 2000 watt BOMA motor. I'm running it on 20S or 72 volts nominal and it gets warm after about a mile so I have added heat sink strips for passive cooling and am currently working on a blower and manifold to force air through the motor. I can't ride more than a couple of miles before the motor is way too hot without some kind of cooling. Those are brass fittings I got at the local hardware store. I drilled them out a little for better air flow and tapped the holes in the motor end plate so the fittings would thread in. There will be short sections of nylon tube pushed over the ends of the brass fittings and then over to a manifold that attaches to a small blower. The 2000W motor says 5400 RPM so at 60 volts that's 90Kv and at 72 volts that's 6480 RPMs...assuming my math is right. Feel free to correct a total noob in the world of motors. The 2000 watt motor ran slightly warmer than air temperature on 48 volts when run hard for 10 minutes. I never tried it at 60 volts since I knew I was going to 72 volts.

ElectricGod said:

The 1500 watt motors say 5600 rpm on them so if I divide 5600 by 48 doesn't that give me the Kv of the motor? So that's 116.66 Kv. On field to field resistance, that's about .35 ohms on my DMM for either the 1500 or 2000 watt versions.

Click to expand...

Thanks for all the information E.G.

Yes, that should give you the approximate Kv. Always better to test yourself, though.

DMMs are just not designed for measuring the very low resistances in electric motors directly. You can get an accurate measurement via Ohms law, though. See: http://www.rcgroups.com/forums/showthread.php?t=2611857
I bought one of these: http://www.ebay.com/itm/OLED-Four-wire-digital-micro-ohm-resistance-meter-micro-ohm-meter-milliohm-/111378757065?hash=item19eeb0f5c9

Useful reference: http://www.bavaria-direct.co.za/constants/

Miles said:

ElectricGod said:

The 1500 watt motors say 5600 rpm on them so if I divide 5600 by 48 doesn't that give me the Kv of the motor? So that's 116.66 Kv. On field to field resistance, that's about .35 ohms on my DMM for either the 1500 or 2000 watt versions.

Click to expand...

Thanks for all the information E.G.

Yes, that should give you the approximate Kv. Always better to test yourself, though.

DMMs are just not designed for measuring the very low resistances in electric motors directly. You can get an accurate measurement via Ohms law, though. See: http://www.rcgroups.com/forums/showthread.php?t=2611857
I bought one of these: http://www.ebay.com/itm/OLED-Four-wire-digital-micro-ohm-resistance-meter-micro-ohm-meter-milliohm-/111378757065?hash=item19eeb0f5c9

Useful reference: http://www.bavaria-direct.co.za/constants/

Click to expand...

Yes..good point about testing rather than just believing specs. I bought a tachometer and did just that and my 2000 watt motor at 72 volts runs at 6450 RPM so the estimate was pretty close.

Janred...
I had my 2000 watt motor all torn apart anyway since I am adding forced air cooling to it. I decided I wanted to replace the factory wires and halls. It took several hours to complete, but was pretty easy to do. Removing the old hall sensors was the easy part. They slide down into a small channel in the motor. All you need is a small screw driver to force under the bottom edge of each one and then they lift out easily. I rewired the new halls with silicon wire and once they were all wired together, slid the new ones back into the same channels. A little super glue on each hall keeps it in place. The hard part was unsoldering the old field wires and replacing them. The field wires are 12 awg on the 2000 watt motor. The wires are teflon coated and the wire strands are 28 awg each. It makes for a stiff wire and then multiply by 3. I wish I had some 10 awg silicon wire in blue, yellow and green, but all I had was some 12 awg in those colors so that's what I used. The new field wires are super flexible and the hall wires are 18 awg silicon wires. There is a hole in the motor end plate that all the wires exit. It was kind of rough edged so I rounded off the rough spots and then used a piece of heat shrink tubing around the wires where they exited the motor. The actual fields in the motor are made up of many 20 awg transformer wires. I stripped the silicon insulation off of about 1.5" of the new field cable and then completely coated it in solder. I then wrapped 3 or 4 strands at a time of the feild strands around it until I had all of then wrapped as tightly as I could get. I unsoldered the motor field strands from the old field cable with a small butane torch. I have a Hakko solder station and it tops out at 1000F so I cranked it up and needed every bit of that heat to get the new field cable and motor strands to solder together well. Once the solder cooled, I used 2 layers of heat shrink tubing to completely cover the feild wire solder connections. You label everything in advance so you never confuse one hall sensor with another and replace one feild wire at a time for the same reason. That way when you are all done it should all work at least as well as it did before you started. Once all the new wires were soldered together and wrapped in heat shrink, I used zip ties to hold everything down so it couldn't get in the way of the armature or the screws that hold the motor together. The motor worked exactly like it did before I changed everything out. I'll try it on my other Kelly controller soon to see if the new halls fix that issue or not.

Also, since I had the 2000 watt motor apart, I grabbed a 1500 watt motor too. The outside can is identical, but when you open them up and look at the armatures and fields you see the difference. The 1500 watt motor has shorter magnets on its armature than the 2000 watt version. The same for the field coils. They are about 1/2" shorter.

Anyway, that ought to get you going with these motors. They are easy to work on, generally work well and are cheap. What more could you want?

Wow, and I was afraid to not get an answer!
Thanks Miles for the calculating, it helped a lot to understand the differences of these motors.
The drillpress method is kind of funny but easy and makes sense. I wont check the KV of the motor (or maybe when Im bored )
when its powerful enough I dont really care about the specs anymore.

Huge thanks also to you ElectricGod, thats like the first experience report in the whole web!
Hopefully it will help some other guys also - makes the push on the purchase button super simple for me
I will run it with the chinese controller the shop suggest to use with the motor, seems super simple and I dont even know if I would find kellycontrollers somewhere here in Germany.
Weight of the bike would be around less than 55lbs and I am 160lbs, that should work just fine.
I have read through your scooter build thread, so many words

I am searching for a fitting lipo pack to build a small 12S. The bike will do 6-8 Miles max, for more I would take the motorcycle or car. Will two 6S 20C 8Ah packs be enough or is there a risk of destroying the batteries..?
For changing I would like to go with the IMAX B6, so basically just unplug the batteries and charge one at a time.
And what is the best way to care for/save the batteries? Can get pretty expensive to kill them.
I dont want you to write so much, a link to a thread or website would be nice! Maybe via PN, because this is not really thread related, dont want to let this drift apart to much. Im hyped and get carried away easy.
Thanks again!

Janred said:

Wow, and I was afraid to not get an answer!
Thanks Miles for the calculating, it helped a lot to understand the differences of these motors.
The drillpress method is kind of funny but easy and makes sense. I wont check the KV of the motor (or maybe when Im bored )
when its powerful enough I dont really care about the specs anymore.

Huge thanks also to you ElectricGod, thats like the first experience report in the whole web!
Hopefully it will help some other guys also - makes the push on the purchase button super simple for me
I will run it with the chinese controller the shop suggest to use with the motor, seems super simple and I dont even know if I would find kellycontrollers somewhere here in Germany.
Weight of the bike would be around less than 55lbs and I am 160lbs, that should work just fine.
I have read through your scooter build thread, so many words

I am searching for a fitting lipo pack to build a small 12S. The bike will do 6-8 Miles max, for more I would take the motorcycle or car. Will two 6S 20C 8Ah packs be enough or is there a risk of destroying the batteries..?
For changing I would like to go with the IMAX B6, so basically just unplug the batteries and charge one at a time.
And what is the best way to care for/save the batteries? Can get pretty expensive to kill them.
I dont want you to write so much, a link to a thread or website would be nice! Maybe via PN, because this is not really thread related, dont want to let this drift apart to much. Im hyped and get carried away easy.
Thanks again!

Click to expand...

Don't bother with the 1600 watt version. Go straight to the 2000 watt version. As time passes you will want more out of your bike. TRust me on this!!! Every EV builder eventually wants more. The 2000 watt motor will take you lots further than the 1600 watt motor. For the same amount of current draw I was surprised how much more torque I got out of the 2000 watt motor over the 1500 watt version. After that it is all about gearing and the correct sprockets.

I don't use R/C LIPO packs, but the turnigy and zippy packs work pretty well if that's the way you go. I buy individual cells like you saw on my scooter and battery threads and build my own packs. 8000mah packs will depending on terrain and acceleration and current draw get you around 8-10 miles for a small kick scooter. For you I suggest going with 20,000mah packs. Yes they cost more, but you will be able to go several days between charging. With any battery, charge cycles defines the life of the battery. People don't think about it, but plugging in your phone all the time means the phone battery is using up its total number of charge cycles faster. Let's assume that your phone battery can take 200 charges before it reaches 50% capacity. If you can charge every other day, then your 200 charges lasts 400 days rather than charging every day and getting 200 days of use out of the phone battery. Your EV batteries work the exact same way. Typical decent quality R/C LIPO packs get around 200 charges before they reach 50% of their original capacity. I know that the marketing and specs often times say things like 500 charge cycle life. That's absolute BS. So get batteries with way more capacity than you will typically use so you stretch out the charge cycles for as long as possible. The weight difference between an 8000mah pack and a 20000mah pack wont matter to you on your bike and the size difference isn't a big deal either. At 48 volts I ran 4 12S, 8000mah LIPO packs or 32,000mah. I could go 24 miles on a charge. My typical round trip from home to work to home was 10 miles. That meant charging every other day and having a little surplus just in case.

Drill press method...I used a chordless drill...but same idea. Honestly...hook up the motor and controller to the voltage you are going to use and then use a laser tachometer to measure RPM at full throttle. From there it is easy to calculate Kv. BTW...Kv is not realistic in my opinion. A free wheel RPM is not remotely like reality. Who cares if the motor can do 8000 RPM at 48 volts free spinning. What can it do hauling my 240 pounds and 100 pounds of scooter? That is what really matters. My scooter up on blocks with no load on the back wheel can do 70 MPH, but on the ground it can do 40 MPH. That's a huge difference!

If you read towards the bottom of my thread you saw where I had my gearing ratios way too close to 1:1. The motor pulled a ridiculous amount of current and I didn't go any faster. I had to widen the ratio to get the best speed and best current draw. You will have to figure that out for your EV to find the best gearing ratio for you.

R/C chargers...let me be simplistic about this...very time consuming and the slowest possible way to balance charge without charging each cell individually. People think that balance charging is something you must do every time you charge. LOL! Do it when you need to and the rest of the time, don't bother. I have 3 20S LIPO packs and 7 20S LION packs running my scooter now. I have yet to balance charge more than once a month. If you are running at 20S and you are running LION cells (18650's), well you know that fully charged is 4.1 volts per cell times 20 or 82 volts. Just use a power supply option that gets you 82 volts and you can use it for balance charging or not. I use 2 1200 watt DC-DC converters in parallel connected to a 24 volt power supply to get 82 volts. My BMS hasn't been used yet for balance charging. It will get used soon as my cells drift away from balance more and more. I will post up the charger build soon on my thread.

If you want a 2000 watt motor you can get them here. They are hard to find. The 1500 watt is easy to find.
http://ykphoenix.en.alibaba.com

I'm currently talking to them and shipped to my door will be $205. I'm buying a second one. I've damaged the magnets on my existing motor with too much heat and they have lost some strength as a result. I'm running it at 72 volts nominal and it got waaay too hot once. Now I'm using a blower and heat sinks to keep it cool, but the damage was already done. This was totally not the motors fault. I was stress testing things and just enjoying all the new speed and power i had and forgot to see if the motor was cooking or not. LOL...it was cooking.

Thanks Buddy,
I am purchasing mine in Austria at http://www.elektromoped.at/index.php?cat=c193_Motoren---Controller-Tuning-Teile.html
they are pretty cheap and offer me another 10% off everything.
I won't have to pay import fees and taxes this way while having a limited warranty.
I'll stick to the 1600w 48v Motor because it's just a fun hobby project and not my daily driver so I am on a budget.
I just want to make something that drives, for now

Hi Jan

I use this 1600Watt Motor for a couple of weeks in my D.I.Y Project the Motor work great....the Controller to .
And i´m the guy who want to use it for Children Quad but for this project i will tune it down to less power :wink:

I also order it from "elektromoped" they are trusty and the delivery is very fast .

Im interesting in the 2000Watt BLDC(60v) Controller .
Can you post some Picture here if you change your mind and order the 2000Watt version .
Im interesting in it, because i want to know ......do they use the 1600watt 48volt controller also for the 2000Watt 60Volt BLDC "is it the same Controller".

verbally in advance...Thank you


MfG
Martin

thanks for all the info on the bona motor! picked one up but my controller spins it up then cuts off 2/3 thirds into throttle

here is my solution for cooling 1020 or boma sized motors

3s edf should through motor

Any suggestions on where to pick up a bracket like yours for the 2000w motor?

ElectricGod said:

Miles said:

The torque constant of the scooter motor is 0.1 Newton metres per amp

The torque constant of that Turnigy SK3 is 0.064 Newton metres per amp

So, the scooter motor will output 1.6 times more torque, per amp of current, than the SK3.

For most motors, the torque limit is set by the heat generated and the ability to dissipate it. This is why you need to know the phase to phase resistances.

Click to expand...

I'm not trying to hijack your thread, but rather give you some information about these motors. The short version is with a couple of minor changes, I really like these motors. Read on for the details.

My 1500 watt motor has given me zero troubles on a cheap Chinese controller or on a KBS72221E Kelly controller. It just works. I ran it for a full year at 48 volts and it pulled my 240 pounds and 85 pounds of scooter around at a top speed of 32mph with no problem. Acceleration was a little weak for the amount of weight and pulling hills would cause me to slow down a little, but if your total weight is less than mine, well you will do just fine. This last fall I upgraded to the 2000 watt version of the same motor and also went to 72 volts. The 2000 watt motor runs hot much quicker than the 1500 watt motor (See below about that). It has way more torque even at 48 volts than its 1500 watt cousin. I was tempted to not upgrade to 72 volts and just run it at 48 volts, but I wanted lots more speed and knew I could get it with more voltage. These motors typically come with a T8F 9 tooth sprocket on them. They have a "DD" motor mount. See the sprocket picture. Sprockets can be easily found on ebay for it. Same for chain and wheel sprockets. I have 9 tooth to 15 tooth sprockets. The motor has a 10mm shaft and the flats for the sprocket are at 8.5mm. There are several things I like about these motors. They are cheap...about $120 to $150. They are inrunners so dirt and grime don't get into the motor easily. Mine sits right next to the back wheel and gets sprayed with water and dirt all the time coming off the tire. It has never gotten into the motor. They work pretty well. Are there better motors out there? I sure hope so considering what these things cost! Parts for them are readily available out of China. They are a low Kv inrunner. If a 3000 watt version of this motor existed, I would buy one right now. Regarding weaknesses of these motors...they are inrunners so this is true for any inrunner, but some kind of forced air cooling would be good. The hall sensors are a little strange. They don't output clean square waves so some motor controllers will act weird with the motor. In one of my 1500 watt motors I replaced the hall sensors with better ones to fix the problem. I use Kelly motor controllers and have two of them. One controller (KLS7230S) would spin up the motor, but then the motor would studder and jerk a lot. This was a completely unusable combination. I also have a KBS72221E and all of my BOMA motors work great with it. The difference is how the controllers detect the hall signal. I don't know about other sensored motor controllers. Replacing the hall sensors in the motor is pretty easy since they are very easy to get at and replace once you have the motor apart. The bullet connectors on the motor fields are crap, I recommend replacing them immediately with 5mm or larger R/C bullet connectors.

I have 2 1500 watt and 1 2000 watt version of this motor. The 2000 watt motor is rated at 60 volts and the other 2 at 48 volts. The 1500 watt motors say 5600 rpm on them so if I divide 5600 by 48 doesn't that give me the Kv of the motor? So that's 116.66 Kv. On field to field resistance, that's about .35 ohms on my DMM for either the 1500 or 2000 watt versions. I have run the 1500 watt motor at 48 volts for 20 miles straight and the motor gets hot after a while, but it never has failed to work after a full year of daily commuting 10 miles. I few heat sink strips wrapped around it would have taken care of the heat issue. These motors come with super light weight bullet connectors on them. In one of the below pictures I show that I cut the motor cable off at about 8" and then added new connectors. The black connector is a weather proof connector I found on ebay for $4. They are about the size of your fore finger fully assembled. I used 8mm bullet connectors for the field wires. The original bullet connectors are super cheap and over heated.

This is my 2000 watt BOMA motor. I'm running it on 20S or 72 volts nominal and it gets warm after about a mile so I have added heat sink strips for passive cooling and am currently working on a blower and manifold to force air through the motor. I can't ride more than a couple of miles before the motor is way too hot without some kind of cooling. Those are brass fittings I got at the local hardware store. I drilled them out a little for better air flow and tapped the holes in the motor end plate so the fittings would thread in. There will be short sections of nylon tube pushed over the ends of the brass fittings and then over to a manifold that attaches to a small blower. The 2000W motor says 5400 RPM so at 60 volts that's 90Kv and at 72 volts that's 6480 RPMs...assuming my math is right. Feel free to correct a total noob in the world of motors. The 2000 watt motor ran slightly warmer than air temperature on 48 volts when run hard for 10 minutes. I never tried it at 60 volts since I knew I was going to 72 volts.

Click to expand...

I've come across four different wind versions of this motor across the net but only have experience of the 1600w I've noticed motors with stickers on top of stickers so there's a bit of a question on the 42a 48v.
The 48v 1500w has a KV of 117, 31 amp rated
The 48v 1600w has a KV of 100, 33 amp rated
The 48v 2000w has a KV of 94, 42amp rated
The 60v 2000w has a KV of 90, 33amp rated
The 60v is the best option for higher voltage 20s + users that want the most power/ torque for tall gearing and push to high rpm.
The 48v 2000w will be at its best around 16s with a higher kV than the 60v, but being 2000w at 48v means it has the highest rated current handling of 42amp so it should handle acceleration boosts of 80amp or so no problem.
And the 48v 1600w is the motor I can vouch for this one as i have used the shit out of it, it has the simular kV as the 48v 2000w but is rated at nearly 25% less, I've managed to to push 3.7kw through this and its had enough torque to push me to 45mph + and do it for 30 minutes or so close attachment to this motor it revs well and its the fairly efficient one of the bunch when treated nicely.
48v 1500w is the runt of the litter it need to be geared high and runs hot struggling away I have not used one but just by specs alone its on the back foot but maybe useful for smaller lighter folk.
As for construction I'm not sure if there are any sizes difference between them other than the copper layout being altered but ultimately I'd like to have the 48v 2000w motor run on a 20s system should be good for 50mph + bursts on the right ride.

I'm considering buying the boma motor. I am running 48 volts currently and looking for maximum torque. Is it correct to expect more torque from the 60 volt 2000 w motor running on 48 volts than the 1600 watt 48 volt on 48 volts. I am hearing good things about these boma brushless motors for the money. Looks like it will drop right in my sons razor mx650 which we are currently over volting to 48 volts. Looking for tons of torque as he is riding it in dirt/sandy conditions . Clarification as to the boma to order for maximum torque running on 48 volts would be greatly appreciated .Thanks

I would say get the 60v 2000w and you can upgrade in the future it will take 84v 60amp bursts easy with a youngens weight that's a mighty fast toy, and at 48v it will still be a hoot.
I've found that my two 48v1600w are slightly different one is 125cm long the other is 135cm looking through the end caps the internals are longer two so how many variants are there.

Thanks for the reply.Is there a cheap fairly reliable 48v controller you would recommend for the boma brushless motor ideally through Amazon or eBay. Thanks again!

48v-72v 1500w sunwin I've been using its a trapizodial controller so no regen but its self learning and gets the motor really going when its on the high speed setting my scooter revs to 30mph with 2kw'ish then switches to sensorless and shoots off to 45mph with 3.7kw on 16s lipo, So it could be set for 20mph 30mph or 45mph+ with my gearing and just upgrade the battery as you go 12s to 20s compatible.

This is what I am looking to do. Razor MX 650 running 48 volts using 4x 12 volt 15ah SLA batteries. 60 volt 2000w boma motor.Would this set up work well with the 48v-72v 1500w sunwin that you mentioned to create maximum torque. I am not an electrical guru so I greatly appreciate sound advice from others. I am skilled at fabrication and design just not so much on the electrical side of things .We are more interested in torque than speed due to the riding conditions the bike will be exposed to. Also looking to do it on a budget if possible hence the SLA batteies. We have just been over volting for a while but looking to take it to another level. Thanks again for the input.

If you plug in the extra battery to your MX650 now, you'll feel the difference. I've considered 72v and a new controller with the same motor, but where do all the batteries go? I have three of those, I'd say the format itself peaks well before you get that 2000w motor in there. I just suggest you find a bigger, more stable platform.

4 batteries is an easy mod.we have been overvolting for a couple of years now.However the motor will run very hot on challenging terrain.To run four batteries we discarded the plastic engine shroud.Theres plenty of room in there for 4 SLA batteries.We are going to try the boma brushless 60v run at 48v to push more amps to get maximum torque then we will play with the gearing to tweak it.These little bikes are very adaptable and will take a beating and parts are cheap.A lot of bang for your buck if you can find a used one even better if it's not running and you are creative and mechanically inclined.My son has hammered his almost daily for 3plus years now.

What you will find is the 60v will have a lower no load current so it will use less amps but spin slower for the same voltage, The 48v will use more amps at no load but spin faster.
The advantage of the 60v is when the 48v 1600w is all out of puff around 16s lipo or 68v 60amp, The 60v will be able to be pushed further more power = points and prize's.
So for the stock setup 48v you will find the 48v 1600w faster and plenty of torque but will use more power ploding around, The 60v will be slower it will have more torque like you want and use less power bimbling around, Then in a years time shove 20s /84v up it arse and a slightly steeper gearing watch it fly.
(Check the length of your brushed motor the bomas are all different length, shorter you can deal with but longer will not drop in your swing arm)

If you're after more torque why not go for lower gearing? A front sprocket with 1 or 2 teeth less or a rear sprocket with 8 to 12 teeth more (and a longer chain) would do it.