Buwizz power limit

[CharlesD]

Hi,

I have designed a series of tracked vehicle using either 4 or 6 L or XL motors with two buwizz. And the problem i keep having is that after about 30 seconds to a minute the power to one side is shut off.

If i then leave it to rest for a minute it will go again, but it will cut out sooner after that. The components to not heat up noticeably.

I have experimented with different sizes and weights, and the problem is more noticable at higher speeds and weight. but weirdly enough it runs fine before the "limit" kicks in.

I have cross connected the motors so it is not one buwizz that is at fault.

Is there some sort of power limit i am reaching?

 

Thanks in advance.

[Zerobricks]

I think your motors are overheating, simple ast that. if youa re not sure, just attach a PF LED on the same port as the motor and you will see.

[CharlesD]

You mean that the led should stay on if the motor is not working anymore?

[Zerobricks]

7 minutes ago, CharlesD said:

You mean that the led should stay on if the motor is not working anymore?

Exactly

[CharlesD]

allright, thanks, will try that.

[CharlesD]

After some testing with a laster thermometer i saw that the L motor cuts power at around 28 C on the casing.

So i figured i need some cooling and i soldered two molex connector to a Power functions connector, and low and behold this monstrosity;

I

It works a bit longer but still gets to hot after about two minutes.

 

Is this a problem that other people have seen? there is suprisingly little information to be found about overheating motors.

 

[Zerobricks]

Motor use Polyfuses for protection. These are triggered by too high currents and/or temperature. You are drawing too much power from the motors, your gear ratios are too low for the motors.

[CharlesD]

Right, i thought that having 6 L motors on a 1.5 kg vehicle would be enough, would it work better if i add another buwizz?

[amorti]

More motors will cause a voltage drop.

After that I would guess it goes by Ohm's law...

Fewer volts for the same watts means more amps (right?) So it'll all get hotter.

6 motors on one buwizz is kinda pushing your luck anyway. I bet it'll work better if you remove two if them. 4 motors on 1.5kg is enough for some serious speed (that's about what Koncept Mantis has over there in my shelf).

Or add another buwizz.

Edited November 10, 2020 by amorti

[Mechbuilds]

While talkign about buwizz and not wanting to make another thread, buwizz can be run with a powerbank attached to extend playtime? 
Any suggestion what powerbank should i get? 
This powerbank would be only used with the buwizz exclusively and i would glue lego beams on the powerbank so it could be connected to mocs via studs. 

It also needs to be a budget powerbank so probably chinese would suffice. 
Has anyone ran buwizz with a powerbank? 

[CharlesD]

I have two buwizz, and i tried the same setup with 4 motors, but with the same result.

I have a feeling that the tracks create a lot more resistance, it makes a hell of a noise.

The chassis is pretty much fully enclosed so there is little cooling from airflow.

[amorti]

Your pic is poor Res, but I did think the tracks looked pretty taut.

[CharlesD]

18 hours ago, amorti said:

Your pic is poor Res, but I did think the tracks looked pretty taut.

I shrunk it so i could post it here. I created a link to onedrive;

https://1drv.ms/u/s!AsdRVifG8uuDhKogFIVDJUe3A8ZiQw?e=gIq5Gv

 

 

18 hours ago, Mechbuilds said:

While talkign about buwizz and not wanting to make another thread, buwizz can be run with a powerbank attached to extend playtime? 
Any suggestion what powerbank should i get? 
This powerbank would be only used with the buwizz exclusively and i would glue lego beams on the powerbank so it could be connected to mocs via studs. 

It also needs to be a budget powerbank so probably chinese would suffice. 
Has anyone ran buwizz with a powerbank? 

I tried that but there was no performance gain, also the weight is a concern. If you want to extend your time than it is obviously a good idea, however mine never charge faster than .70 amps/hour.

Considering the slow charging rate any powerbank would suffice.

Edited November 11, 2020 by CharlesD

[amorti]

Hard to tell what's right in Lego chains, but I don't think I'd run a motorcycle chain that tight. Maybe try softer springs on the tensioners?

I think the real problem is running too many motors on one buwizz. It's not the motors heating up that's causing your power to cut, it's the circuit inside the buwizz which has a thermal fuse.

I have didumos's greyhound on the shelf with 4 Chinese higher power L-motors.

It works with one buwizz, properly on low and mostly okay in normal, but on high or ludicrous it'll trip the protection immediately when you try to pull away.

With two buwizz it'll be fine in normal, but trip out the protection on high as the battery gets low with a very harsh stop/start, and on ludicrous with anything other than a very gentle start.

TL;DR: adding a second buwizz makes a real difference to how much current can be delivered without tripping the thermal protection circuit breaker.

EDIT:

In one of the pictures you have two buwizz attached.

What is the point of this thread? You've already tried with two, you must know it solves your problem.

I also see stacked extension leads, although I can't quite make sense of what's going on with them. I would suggest not putting more than 2 motors on the same output.

Edited November 11, 2020 by amorti

[CharlesD]

34 minutes ago, amorti said:

Hard to tell what's right in Lego chains, but I don't think I'd run a motorcycle chain that tight. Maybe try softer springs on the tensioners?

I think the real problem is running too many motors on one buwizz. It's not the motors heating up that's causing your power to cut, it's the circuit inside the buwizz which has a thermal fuse.

I have didumos's greyhound on the shelf with 4 Chinese higher power L-motors.

Are those the Cada L-motors that run at 1200 rpm?

34 minutes ago, amorti said:

It works with one buwizz, properly on low and mostly okay in normal, but on high or ludicrous it'll trip the protection immediately when you try to pull away.

With two buwizz it'll be fine in normal, but trip out the protection on high as the battery gets low with a very harsh stop/start, and on ludicrous with anything other than a very gentle start.

TL;DR: adding a second buwizz makes a real difference to how much current can be delivered without tripping the thermal protection circuit breaker.

That is pretty much my experience too

34 minutes ago, amorti said:

EDIT:

In one of the pictures you have two buwizz attached.

What is the point of this thread? You've already tried with two, you must know it solves your problem.

Yes, sorry, i stated that at the beginning, and i guess i am demanding more from the buwizz then it can deliver.

34 minutes ago, amorti said:

I also see stacked extension leads, although I can't quite make sense of what's going on with them. I would suggest not putting more than 2 motors on the same output.

That was for organizing and extension purposes.

[amorti]

They're MouldKing Black Furious motors. They claim +30% speed and torque, and while I can't measure that scientifically I can believe it.

Greyhound could get up stuff with those in fast that it couldn't get up in ludicrous with original Lego motors. It's also at least as fast in fast, as normal motors in ludicrous. Lego motors didn't give two buwizz any problems at all, but these Chinese motors certainly do in ludicrous, so that extra power they have isn't for free.

I also have a couple of MouldKing Black Hyperspeed motors, they claim something like 1200rpm. They have very low torque but even so it's very nippy on a 400 piece buggy.

I also have 2* of the new CaDA higher speed higher power L motors. Two of those can propel the 3200 pieces of Bruno's red supercar across the living room at a decent lick, I don't believe for a second that normal L motors could do as much.

All those motors are in my various models. I also have some original Lego motors that just sit spare. So slow in relative terms, I don't want to put them in anything!

[wguarnere]

On 11/10/2020 at 3:54 PM, amorti said:

More motors will cause a voltage drop.

After that I would guess it goes by Ohm's law...

Fewer volts for the same watts means more amps (right?) So it'll all get hotter.

6 motors on one buwizz is kinda pushing your luck anyway. I bet it'll work better if you remove two if them. 4 motors on 1.5kg is enough for some serious speed (that's about what Koncept Mantis has over there in my shelf).

Or add another buwizz.

Is there a chart that recommends an X number motors, with a Buwizz. How to determine the number or the size of the motors according to the weight and the gear ratio?

[marshmallow]

Hi @CharlesD,

 

Those tanks/ripsaws look awesome!

So I had this same problem with a tracked vehicle with subtractor and did a lot of troubleshooting. Same issue of power cutoff after 30s. Initially, I thought it was an issue with one of the BuWizz units or motors. It wasn't, the transmission was just not geared down enough.

The easiest solution is to gear down further, I'd suggest 3:1 with the 24 and 8-teeth gears. I did that close to the axles that drive the sprocket wheels, it was a simple fix and solved the problem for me.

[CharlesD]

On 11/15/2020 at 1:26 AM, marshmallow said:

Hi @CharlesD,

 

Those tanks/ripsaws look awesome!

So I had this same problem with a tracked vehicle with subtractor and did a lot of troubleshooting. Same issue of power cutoff after 30s. Initially, I thought it was an issue with one of the BuWizz units or motors. It wasn't, the transmission was just not geared down enough.

The easiest solution is to gear down further, I'd suggest 3:1 with the 24 and 8-teeth gears. I did that close to the axles that drive the sprocket wheels, it was a simple fix and solved the problem for me.

Hi,

Yes that would work, however i wanted to build something that was just stupid fast. I saw a video of a buwizz powered 42065 that did some drifting and that was what got my whole interest in technic tingling again early this year.

And right now i am finally able to drift, albeit for a couple of minutes :)

[FoxOne]

22 minutes ago, CharlesD said:

Hi,

Yes that would work, however i wanted to build something that was just stupid fast. I saw a video of a buwizz powered 42065 that did some drifting and that was what got my whole interest in technic tingling again early this year.

And right now i am finally able to drift, albeit for a couple of minutes :)

Oh, that ridiculously overpowered 42065 had triggered me, too)). Bet it was RacingBrick's version, right?

I was able to pull it off with one BuWizz and 2 XL's. Very lightweight vehicle, basically bare chasis without any bodywork.

In this configuration she's able to drift a little on a hardwood floor, in high gear. (I have also integrated some simple 2-speed gearbox, to negotiate some 50 degrees slopes as well).

 

Edited November 16, 2020 by FoxOne

[Ullum Zurt]

Apologies for digging up an old thread.

I'm looking to build a small buggy, powered by Buwizz 2.0, with 2 L motors, and hoping to run in ludicrous mode.

I will need to procure the motors though.
Would it have to be PF motors so that the power cut-off is not hit, or can I go with cheaper MouldKing or Cada high-speed versions?

Thanks!

[amorti]

9 hours ago, Ullum Zurt said:

Apologies for digging up an old thread.

I'm looking to build a small buggy, powered by Buwizz 2.0, with 2 L motors, and hoping to run in ludicrous mode.

I will need to procure the motors though.
Would it have to be PF motors so that the power cut-off is not hit, or can I go with cheaper MouldKing or Cada high-speed versions?

Thanks!

Mouldking hyperspeed motors will definitely hit the limit in ludicrous mode and maybe in Fast mode too depending how heavy the model is. But, you won't need ludicrous mode anyway since they're already so stupidly fast.

Mouldking black furious motors may trip the limit in ludicrous, but again they'll be faster in Fast than Lego motors are in Ludicrous.

CaDA Pro motors will probably be the best mix of speed and torque. They're almost twice as fast as Lego motors but with comparable torque. They'll probably trip the buwizz in Ludicrous, but again you won't need ludicrous mode with these motors.

Still the problem is servos, buwizz glitches with cheap ones, and Lego servos are now stupid money.

[Ullum Zurt]

1 hour ago, amorti said:

Still the problem is servos, buwizz glitches with cheap ones, and Lego servos are now stupid money. 

While really OT for this thread, what about Cada Pro servos?

1 hour ago, amorti said:

CaDA Pro motors will probably be the best mix of speed and torque. They're almost twice as fast as Lego motors but with comparable torque. They'll probably trip the buwizz in Ludicrous, but again you won't need ludicrous mode with these motors.

Do the Cada Pro L.motors trip on ludicrous mode with minimum/no load or only under moderate/heavy load?

[amorti]

29 minutes ago, Ullum Zurt said:

While really OT for this thread, what about Cada Pro servos?

Do the Cada Pro L.motors trip on ludicrous mode with minimum/no load or only under moderate/heavy load?

CaDA Pro servos are still 1-0-1 and will glitch the same as an other.

Two of those work fine in ludicrous on Madocca's PF buggy. Keep the model light and you'll be fine.

[Ullum Zurt]

Thank you!