Confused about power ratings...

[milesinfront]

I'm currently in the process of converting my scooter from brush to r/c brushless.

The original motor was a Unite 36v 800w. A big chunky brute which did a great job, until I upgraded the controller and did a test run at 50v. Was never the same since and eventually burned...

I did want to go to an 80/100 Turnigy, but they never seem to be in stock. So with the advice of a regular poster here I opted for a 63/74 from Leaderhobby, which is rated at 3,250w.

When I received the 63/74 I was rather deflated by the small size and weight. Can this thing really hold a candle to the big old Unite motor?

Can I directly compare the BDC's 0.8kw against the BLDC's 3.2kw?

How do they come up with the kw rating? Upon launch, the old BDC was drawing 155amps at 37v. That's nearly 6kw right?

I guess my ultimate question is will I go faster with the little 63/74?

[milesinfront]

....adding to my confusion:- http://www.thesuperkids.com/20wabmcbrpoe.html That thing is HUGE yet is only rated at 2000w...

[gwhy!]

hiya mileinfront,
What will be the ready to ride weight of your scooter ? just the scooter.

this will be a factor to how well the motor will perform also what is the top speed that you are aiming for, is it a single speed scoot ?.

[milesinfront]

With the Unite motor the weight is a hefty 32kgs. Previous max speed was about 42km/h on flat ground.

Performance from the Unite motor was great! Acceleration was brutal, and had to be managed to keep the front wheel down.

The burnt motor is an opportunity to improve. I could simply replace it for around $100, or even upgrade to 48v Unite for a little more coin!

So if I spend $300+ for a BLDC R/C setup and go backwards in performance then it would be a failed mission...

So back to my original question, can I compare the BDC 800w to the BLDC 3000w?

[Thud]

When I received the 63/74 I was rather deflated by the small size and weight. Can this thing really hold a candle to the big old Unite motor?

that tiny motor will destroy the unite in overall performance....I was stupified the 1st itme i rode a a bike with only a 50mm motor powering it.

now for the reality...the rc stuff is truley over rated when it comes to our application....they read the watts the motor draws under ideal conditoins for 5 minutes (prolly spining a prop blasting it with cool air)

you need to be certain you gear your motor to spin freely. you can over load it for a very short time but you will be safe by keeping the average input in the 1000 watt range with very short peaks in the 4kw range

select a gearing senario that keeps it at a reasonable speed...

EDIT: cross post LOL.
answer to your question: No, you can not compair the the high reving outrunner to the brushed unite...after the fact that they are both powered by ellectricity.....its apple & oranges.

[milesinfront]

that tiny motor will destroy the unite in overall performance....I was stupified the 1st itme i rode a a bike with only a 50mm motor powering it.

Okay that provides a lot of reassurance...

I'm running 8mm chain with an 11t drive sprocket. I forget the tooth count on the rear sprocket. (56 I think) I'll go to a larger rear sprocket to keep the revs up.

As I intend to mount the 63/74 inside the old unite motor, I was considering adding a fan for cooling. Will hurt top end a little, but might help longevity...

[parabellum]

Controller is usually limiting factor on BLDC low speed, high power end (short duty cycle high current) but after you get faster they are great. Starting torque is easier to archive on BDC setup (looking from controllers point of view again). What controller will you use?

[milesinfront]

I'm thinking this:- http://kellycontroller.com/keb7245024v- ... p-275.html

[gwhy!]

Ok this might be a little more reassurance this pitbike in this clip weighs around 36kg its geared for around 28mph ( around 45kmph ) the current limit is set for only 3.2kw max, it can be ridden continually as in this clip ( offroad ) and the motor only gets barely warm. I have pushed upto 6kw through these motors but once you get above the 4kw mark it starts to get very hot very quickly ( without any active cooling ) fitting a fan will help loads. The gearing will have to be thought about carefully and this is one of the drawbacks of using these motors the reduction needs to be alot compared to a brushed motor I dont know what size wheels your scoot has but as a example the pitbike has a wheel circumference of around 1500mm and the total gearing is about 14:1 so you may have to have additional reduction in you system.



edit: and this is using a moddified 6 fet tiny controller .

[parabellum]

I'm thinking this:- http://kellycontroller.com/keb7245024v- ... p-275.html

Be careful to chose right erpm version. Will you install hall sensors internally?

[milesinfront]

Kelly claim 40,000 rpm! Will run external halls...

Thanks for the vid! I'm looking forward to being VERY impressed...

I was blown away by the upgrade from SLA to LiPo, so hopefully the BDC to BLDC will be just as great!

I seriously want to get my hands on an 80/100 now...

[Thud]

Kelly's 40k is E-rpm....you will need to divide that by the pole pairs in your motor (7) for a maximum rpm of 5715 (30% short of your motors potential)

If you go with a kelly & want to run 12cells,I suggest upgrading to the the chip that will give the motor full speed potentials.

You want to get this motor into the 8krpm range at full speed. if power delivery is your ultimate goal.

[milesinfront]

Kelly's 40k is E-rpm....you will need to divide that by the pole pairs in your motor (7) for a maximum rpm of 5715 (30% short of your motors potential)

Thanks for the heads up! There is a high speed option 70,000 ERPM for an extra $50.

So this motor will go to 8krpm? Wow, I'll definitely have to play with my gearing...

[Bluefang]

Kelly controllers are ok for the motors but have you looked at the controllers Lyen is selling in the for sale section, one of his modified 6fet controllers would be good. Also talk to Gwhy as i think he has been building some hall sensor mounts for adapting RC motors to halls. Where abouts in Australia are you? If your on the Gold coast i am happy to help you out.

[parabellum]

Right, if you need to spend extra 50 or 90 U$ to get in 70-100ERPM, then better look at Lyens controller, you can get 10KW capable programable controller for under 300U$.

[gogo]

Kelly's 40k is E-rpm....you will need to divide that by the pole pairs in your motor (7) for a maximum rpm of 5715 (30% short of your motors potential)

Thanks for the heads up! There is a high speed option 70,000 ERPM for an extra $50.

So this motor will go to 8krpm? Wow, I'll definitely have to play with my gearing...

Yep. As far as comparison goes, if you ran the brushless motor at the same RPM and watts as the brushed, it would burn up too. The brushless advantage is the ability to run at higher RPMs, but that means an investment in the gear-down apparatus.

[oops edit] I meant to say brushed instead of brushless.

[milesinfront]

@Bluefang I'm in Brisbane. Not meaning to offend anyone, I've looked into the Lyen controller... Are they appealing because they're better, or appealing because they're cheaper? I didn't find a spec on ERPM for the Lyen either... Keep in mind that I ultimately see myself with an 80/100 (or bigger) in the future, so I want a controller with plenty of 'balls' in reserve...

Are the Lyen controllers hard to program? The Kelly's a have a nice and simple menu system.

@gogo The scooter runs 10in tyres, so I should be able to get desirable gearing with a single stage reduction...

[milesinfront]

Also talk to Gwhy as i think he has been building some hall sensor mounts for adapting RC motors to halls.

Yeah, he's already helping me out there!

[gwhy!]

@Bluefang I'm in Brisbane. Not meaning to offend anyone, I've looked into the Lyen controller... Are they appealing because they're better, or appealing because they're cheaper? I didn't find a spec on ERPM for the Lyen either... Keep in mind that I ultimately see myself with an 80/100 (or bigger) in the future, so I want a controller with plenty of 'balls' in reserve...

Are the Lyen controllers hard to program? The Kelly's a have a nice and simple menu system.

@gogo The scooter runs 10in tyres, so I should be able to get desirable gearing with a single stage reduction...

The Keywin/e-crazyman ( Lyen controllers ) are very good value for the money they will run a RC outrunner motor upto at least 10k rpm ( maybe more ) , they are programmable with simple menu driven software. The main thing about the Lyen controllers are they are very well documented as regards upgrades and mods and repairs. If you want a controller with enough to spare i.e drive a 80/100 then get at least the 12fet controller, or you could put 2 or 3 of the smaller motors together and just use 2 or 3 of the 6fet controllers to drive them .

[Bluefang]

The Keywin/e-crazyman ( Lyen controllers ) seem to be able to do everything that the kellys can for less and in a smaller package. As gwhy says they also are pretty well documented on the site with a few members offering upgrades or addons to make them even better, timing adjuster, better fets.


How much power do you want in your scooter? As i might have a 130kv 80-100 for sale, its second hand and it has some silicon over the windings to hold them in so it will only be good to <5kw, it was running my first attempt at a Nuvinci bike for a week or so untill i decided to change plans. I think i migh also have a modded 6fet somewhere too thats brand new which should be able to handle that power level

[milesinfront]

Okay I'm sold on the Lyens... I sent him a PM on Saturday which he hasn't responded to yet. I hear he's pretty busy...

How much power do you want in your scooter?

The answer is always 'more power, fcuk the question!'

I'm sure a limited 80-100 will get my 'fix' for a while. PM sent!

How many volts should I run the 80-100 at?

[Bluefang]

With the volts it depends on the speed you want to run your scooter at with in reason. ~9000rpm seems to be about the limit these motors want to run at which is ~70 volts, so anything below that gearing dependent is going to be about right. Higher volts means the controller will survive better specially if you gear the motor to run at a top speed of like 50km/h. From a quick calculation you will probably need 12-1 ratio or better to use that sort of Voltage. 18s lipo in a tiny scooter would be insane tho

[milesinfront]

It's pretty big, as far as stand up scooters go... I did 52km/h down a slight decline with the old 36v brush motor, so I'm hoping for more like 60, but any improvement will be welcome!

[Bluefang]

well then it just makes it easier for you to gear it, plus i think my calculation is probably abit off so it might be around 60km/h already as i was not sure how big your tire was on the 10" rim.

The C80-100 was enough to push my bike along at 60+km/h with out breaking a sweat through 2 reductions and a nuvinci which lowers efficiency to <80% lol, it got warm but nothing i could not hold my hand on so your little scooter been 1 reduction should be going pretty fast

[milesinfront]

10in is the OD of the tyre... Current gearing is about 5:1 (11t/56t) I can get a 72t sprocket off the shelf. (large dia sprocket does increase risk of ground contact however) From memory 5krpm at the motor was ~60km/h. I may still need to invent a 2 stage reduction...