large road legal electric go kart build. need help!

[galderdi]

I thought about suggesting some sort of extra gear between the motor and CVT to up the gearing. But you would still have the noise issue. Direct drive might work but check your final ratio first.

The motor cutting out sounds like a controller issue to me. Either a configuration not right or a fault of some kind.

Maybe give us some video to work with?

 

[falshami]

so that is what we are doing, instead of a 10 tooth we are moving up to a 21 tooth and seeing how much thay helps, the noise is still going to be super loud, i would like to have a full on toothed belt drive for noise but im having trouble sourcing them. so the machine would sometimes stutter while in motion , i was thinking it was the motor, its actually the belt drive slipping oddly enough. the motor does occasionally cut out all together so that is a controller issue. i will get a video for you guys very soon as soon as i get it all hooked up again ! my gear box ration is almost 1:1 its a 1 3/8:1 drive ratio, what ratio do you recommend for this?

 

[galderdi]

Well done for progressing this far so quickly. Can't wait to see how it turns out once you iron the bugs out

 

[falshami]

thank you, the project is like 90 percent done, its at a stand still untill we receive that new sprocket, it should ship tomorrow, theres a few small things i need to finish up like blinkers, fog light wiring, wiring the subwoofer. and installing the underbody panels for aerodynamics! i will get more progress stuff for you guys soon!

 

[falshami]

most recent update! the drive train has been totally reworked to a direct drive, its lovely so far, much quieter, but it is a bit finicky and jerky, if i let off the throttle the motor isnt as happy as it could be, its jerky overall. we managed to get the buggy up to 27mph top speed using a 10 tooth sprocket onto a 32 tooth axle gear. with 26 inch tires. we will be trying an 18 tooth next then at 21 tooth, we are close to our goal. our goal is 60 mph which means we are almost half way there, this was using low power settings as well, only 125 phase amps and 100 battery amps. which is pretty spectacular. thats less than 5kw that got us here on poor gearing and a vehicle that weighs 800lbs! im thinking at these power settings and better gearing we will get it up to maybe 35 or 40 mph. which is really good. only concern was a warmer than id like controller. motor ran really nice and cool. im thinking on 27 inch tires , and a 28 tooth sprocket we should reach our speed goal. any thoughts?

 

[falshami]

So further update. Most things are installed on the buggy now. Speakers subwoofer. Lights . all that's left is wire management. But the issue of the drive train is now larger than ever. I need a new controller for my motor. It was claimed at 20kw max but things seemed off since it got crazy hot at just 4kw. And when we went slightly over it just gave out all together. Any reccomendations for a new controller? I need to finish up this project ASAP! The gearing the vehicle is set at is also as follows in case this helps. 18 tooth sprocket to a 32 tooth pinion with 27 inch tires. Also when I release the throttle it still jerks a bit any suggestions on dampening that? I was also thinking a controller with soft start might be helpful. I just need one that does 10kw or more with regen and reverse

 

[falshami]

i do need opinions guys as i am reworking and re thinking my setup, do you guys think a high amperage 48v setup will ever get my 800lb buggy to 60 mph realistically or am i forced to look into a much higher voltage setup to get to these speeds?

 

[falshami]

so is this or is this not a 10kw controller? witha peak output of 20kw?

http://kellycontroller.com/kbl48501e24v-48v500abldc-controllerwith-regen-p-1206.html

 

[galderdi]

I am not sure where you got those figures but yes they would be ball park for the controller.

 

[falshami]

thank you, i spoke to kelly and they said no its a 5kw controller which had me lost, since from my understanding if i put 48v in, 48v comes out and what is varied is the amperage correct?

 

[galderdi]

I am not sure if it is true for all controllers but generally they control both amps and volts out to the motor. At low revs when torque is needed the controller provides lower volts and higher amps. As the revs increase the controller reduces the amps and increases the volts. You will never see the maximum volts and maximum amps at the same point in time.

 

[falshami]

that makes perfect sense, since as the volts go up so do RPMs, so ive settled on an altrax 500 amp peak controller , this puppy should send me scooting along just fine and i can upgrade my motor size if i need to, is there a consensus that the 5kw motor should be just fine for me?

 

[galderdi]

consensus? I don't even think there is consensus that consensus is a word. This is a forum after all. Its like herding cats. But in this case it is probably justified. It is really hard to predict what the results will be like. There are so many factors. And even if the performance can be quantified, how does that equate into you're perception? The result is totally subjective. Will a 5KW motor work? Yes. Will it give drag race performance? No. The answer is somewhere in between these. Really, you've already come this far, I suggest sticking with your plan and seeing if you are happy with the outcome.

 

[falshami]

fair enough, im hoping with proper cooling that 5kw motor should handle just fine, i dont need a dragster, just a fun and economic ride for around town and some mild offroading, i just dont want anemic performance is all .im having a heck of a hard time buying that alltrax controller though!!

 

[falshami]

So after a few weeks of dealing with it, I finally got a new Motor and controller. a golden motor 10kw BLDC 48v setup with a 10-20kw of TRUE power. so after a test we got her up to 31 mph with current gearing of 19 teeth to 32 and 32 inch tires. however i noticed that this set up is rated for a continuous 200 amps and it only got up to 5700... it never exceeded a draw of 130 amps. so im guessing i have more power to give from this setup but i couldnt acheive it, why could this be? a 10kw motor should have no issue whatsoever moving this machine to at least 54 or 50, so what gives? the acceleration wasnt snail pace like is used too be with the old crap controller.but its not blowing doors off either. its adequate. but at 31 it stops speeding up. im guessing more amps would fix this? maybe if i drop the pinion gear size it will help its acceleration a bit and potentially let the motor open up a bit more as well? im at a loss. i will try to reporgram the controller and see if perhaps thats the issue? is 48v just not enough? i mean the motor should spin at 6000rpm no load at 48v... and around 4500 with load? ideas?

 

[galderdi]

I don't know what would be limiting your current. But I know it would not be your batteries, so that only leaves your controller or motor.
Increasing current increases torque not revs. So you would improve your accelleration but not the 31mph.
If you increase the current and increase your gearing you could improve both accelleration and speed.
Alternatively you could increase your voltage but if you are already seeing 5700 I wouldn't recommend trying to increase the revs.

Try a test: if you have a handbrake try driving with it on. Or maybe skull drag some dead weight (like a pallet with some concrete etc on it). Check the currect while doing this.
What I am trying to consider is whether there is not enough load for the motor to draw more amps. If that is the case then increasing the gearing alone might be the solution.

 

[Hillhater]

?...... after a test we got her up to 31 mph with current gearing of 19 teeth to 32 and 32 inch tires. .....however i noticed that this set up is rated for a continuous 200 amps and it only got up to 5700... ?

???...only got up to 5700 what ??...rpm ?
Are you still running direct drive 19 teeth on the motor to 32 teeth on the axle ? ( thats a 1.7:1 ratio !)
None of those numbers make sense, 5700 rpm on the motor wold mean 3,300 axle rpm ...which is crazy fast !

 

[falshami]

My mistake folks, 5700 rpm should have been about 1200 rpm. if i got 3300 rpm id be faster than a bugatti veyron and dead... I am going to see if i can try a hand accelerator, maybe that is the issue? gearing is part of the issue however.

we dropped down the gearing from 10:32 and now it is much zippier, as far as top speed i dont know what we got up to. maybe we need more volts? i didnt get a read on rpm or anything else, just the faster acceleration. also a few details, the machine weighs about 900lbs 35 inch tires. 10kw GM BLDC and a VEC500 heat on both motor and controller was next to nill.

should we try a more powerful controller? can a 48v BLDC get pushed up in volts like a brushed motor can?

here are update photos

http://i.imgur.com/6ehZT3X.jpg

http://i.imgur.com/jELj9Hc.jpg

http://i.imgur.com/BgkIb3f.jpg

http://i.imgur.com/QzRd8Hf.jpg


these photos are with the 5kw motor which has been yanked and replaced with a 10kw motor. also the 5kw motor is now up for sale

 

[litespeed]

I'd just push the limits on the gearing....keep going higher gearing till you get to 200 amps and the top speed you want. If the motor/controller start to heat up then you went to high. Just a balancing act and you have center stage.

Or you can go higher voltage for a higher speed. Not sure what max voltage is on your controller?

Cool build.

Tom

 

[falshami]

thata a good rule of thumb, gear up till its warm, i sm trying to see what the max voltage is, can BLDCs be over volted? we are doing a jack shaft set up this week to help get the gearing where we want it

 

[Hillhater]

Do you know what the gearing is in that hidden differential unit ?
Check how many turns of the motor to one turn of the wheels.
Also, are you sure those are 35" tyres ?..they do not look that big.
EDIT..:
If those are the 215/70/14 tyres you mentioned earlier, then they are definitely not 35" dia....they will be 26" dia
I suggest you get some more instruments, for rpm, mph, to help sort these issues.

 

[falshami]

i was clearly in a disillusional state while replying to a few of these messages! hahaha. yes 26inch tires seems about right. so what kind of instruments can i use to measure RPM and general motor stats? i will be checking the differential gearing soon! do you guys think there is any hope with this setup to get her past 60 mph ?

 

[galderdi]

Cycle analyst does have an RPM input sensor. The only catch is that you need to find somewhere to mount a magnet on a spinning part of the motor and somewhere to mount the sensor close enough to pick up the magnet as it passes. All while making sure not to put your setup out of balance. But you seem quite capable so I am sure you would work that out.

 

[nuxland]

I had in my kart 10kw 48V GM motor and VEC500 48V their controller.
I could get like 300A max from the battery and max kw i saw was 13kw, because of the voltage sag.
Motor was very ok with that power but controller overheated after 6 laps of racing.

with 150kg kart + driver I could do 100km/h in 12 seconds with that setup

Afterwards I upgraded my battery to 60V, because VEC500 has 75V fets inside. And I could see rpm rise with it.

 

[falshami]

are you saying that with the VEC500 48v model, we can actually run as high as 60v safely and run the 10kw motor also at 60v? what kind of power did you squeeze out of that?