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Old 07-02-2019, 08:28 PM
scorn001 scorn001 is offline
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Default First run results (48V 1800W on a large kart)

So to any who are interested, I got everything put together enough to make a test run this afternoon.

Pretty much as I though, it's significantly under-powered. It does go plenty fast when it's able to reach a reasonable speed (level ground, not turning). However when going uphill, it runs out of steam very quickly, if you try to make a turn when going uphill - it just can't do that. Motor will come to a complete stop. I think having the live axle makes those turns very hard on the motor, and even more hard when you are already slowing due to having to make a climb.

The controller would become very hot to the touch, not so hot that you couldn't touch it, but hot enough that you couldn't touch it very long, same with the motor. When first starting, when trying to carry my 200lbs in a turn with no momentum, just trying to slowly get myself pointed the right direction before trying to take off, the chain would clatter and it would all just stop, and the motor would stop responding, I'm guessing this is due to an overcurrent/temperature issue or something with the controller. If I would wait a few minutes, it would work again. Once up to speed, it would do just fine - again, until you hit a hill or started trying to turn again.

My plan is to purchase a 2nd motor and controller and run it on the opposite side of the axle with the same sprocket that I have running on the normal drive side. Not sure how hard it will be - ordinarily there would be no drive on that side so there is no mount point where the motor will need to be.

Anyway, that's what I've got so far. It's fun to see it running, and I can't wait to see what it'll do with 3600W pushing it.
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Old 07-03-2019, 02:29 PM
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Kool, glad you got 'er going
I too have noticed that heavy karts + live axles + big wheels = don't mix too well
...then, we go & add a bunch of batteries (~40 extra lbs.)

Does your controller have a (3) speed option/plug?
...if so, do you have a switch connected?

If not, you may be only running at "medium speed"
...this is the default speed, if a switch is not connected to this plug.
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Old 07-03-2019, 05:56 PM
scorn001 scorn001 is offline
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I do have the speed selector connector. All of the very rough documentation I was able to find indicated that leaving the circuit(s) on this connector open was the fastest option (yellow to ground == slow, blue to ground == medium, open == fast).

I remember you posting a video about this, I'll go back and have a look.

Thank you.

Edit: I just went out and tested, on my controller, connecting either the yellow or the blue wire to ground yields a lower top speed.

Last edited by scorn001; 07-03-2019 at 06:27 PM. Reason: Additional information
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Old 10-28-2019, 07:58 PM
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Hey Scorn... how heavy is your cart? I am building a two seater Campground cruiser and i am thinking about adding a second motor. (48v 1800w). My total weight is going to be around 500lbs with two people on it. 35ah batteries dont help with reducing weight.
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Old 11-04-2019, 08:24 AM
scorn001 scorn001 is offline
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I honestly don't know. I don't have a way to weight it. I'm out of town right now but should be home on Wednesday. I'll dig out the manual (before my mods) and see if I can find a weight listed.
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Old 11-09-2019, 09:15 AM
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Sorry I'm just now getting back to this. I got out and looked at the manual and receipt for the original kart and saw no reference to weight at all. I suppose I'd guess without and one in it maybe 150? I know I can lift the back to spin it around or out it on jack stands, but it is heavy. I know that doesn't help much.
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Old 11-09-2019, 09:27 AM
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Ok, thank you. I am probably going with a 60V setup instead of 2 motors.

Thanks again.
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Old 11-15-2019, 05:06 PM
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A single 48v 1800w motor can get 300lbs (including rider) moving at 30mph and this setup has the ability to climb hills. If you modify the controller to send 50 amps max it accelerates even better.

The same motor with a 24v 400w controller can make 300lbs go about 12mph with no hill climbing power.

I haven't gotten around to using my 60v motors and controllers yet.
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Old 11-16-2019, 06:11 PM
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How do you make this modification to the controller?
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Old 11-16-2019, 09:32 PM
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Add solder to the shunts to reduce their resistance. Here's a picture of the shunts before I added my solder. The glob that's already there came from the factory. I extended that glob about halfway up that pair of the shunts. The improvement in acceleration is very noticeable and I pull just over 50 amps according to my shunt meter.
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Old Today, 09:54 AM
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yeah it's called placebo effect!

I don't need no circuit diagram to see that that black wire has about TWICE the resistance and HALF the current rating of that shunt in stock form it is attached to.

so in the end you did nothing to alter the powerlevel of the MosFets.
those are the only things inside a controller limiting the motor power
(batterywire-busbar-MosFet-phasewire-motor ... nothing else really)
and your's will at least be rated 60Amps.. 200Amps is more likely these days really.
throttle position will determine at which rate they're fired.. but once on they're ON at full power.

WITH the circuit diagram I could tell you what you actually did instead..
I'm guessing that shunt you soldered isn't even really part of the power bars for the mosfets.

Soldering without checking is the equivalent of replacing a blow fuse with a bullet shell..
sure, the lights are now brighter (*cough*) but you might burn your house down


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Old Today, 02:48 PM
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Quote:
Originally Posted by itsid View Post
yeah it's called placebo effect!

I don't need no circuit diagram to see that that black wire has about TWICE the resistance and HALF the current rating of that shunt in stock form it is attached to.

so in the end you did nothing to alter the powerlevel of the MosFets.
those are the only things inside a controller limiting the motor power
(batterywire-busbar-MosFet-phasewire-motor ... nothing else really)
and your's will at least be rated 60Amps.. 200Amps is more likely these days really.
throttle position will determine at which rate they're fired.. but once on they're ON at full power.

WITH the circuit diagram I could tell you what you actually did instead..
I'm guessing that shunt you soldered isn't even really part of the power bars for the mosfets.

Soldering without checking is the equivalent of replacing a blow fuse with a bullet shell..
sure, the lights are now brighter (*cough*) but you might burn your house down


'sid



sid sid sid, you never fail to amuse. This modification is nothing new. Read up.

Quote:
The controller monitors its current draw with a shunt. A low resistance piece of wire, it reads the voltage on the wire and from that extrapolates the current draw. Ohm's law and all that.

If we solder the shunt, we lower it's resistance, allowing it to pass more current for a given voltage drop. In effect tricking the controller into thinking it's still drawing it's normal current limit, but it's really drawing more current.
Here's a shunt mod thread from 2008

For over a decade the shunt mod has been proven to increase the current capacity on these chinese controllers. I have a fuse inline with my battery and I also didn't care if I blew this $40 controller. I now pull over 50 amps from this controller which is rated for half that and it gets considerably warmer with improved acceleration (no placebo effect).

I did the same mod with a smaller $20 24v 350w controller for my daughters pink gokart. Before the mod, the cart could not push me if I stood in front of it, tires wouldn't even spin. Did the mod, stuck it back in and now it can push me backwards with ease.

The proper way to do this mod is to measure the existing resistance and add the correct amount of wire to reduce the resistance to get the desired current output. I've also read that solding halfway up is usually safe and that solder alone can work as long as it doesn't get hot enough to melt.
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Old Today, 09:22 PM
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and nowhere a diagram to be seen...
that's what I meant

That shunt is more than likey just as I expected part of a protection circuit.
And sure a 40 dollar controller lost isn't the end of the world, it's just the end of 40 dollars

Quote:
Originally Posted by Bmr4Karts View Post
The proper way to do this mod is to measure the existing resistance and add the correct amount of wire to reduce the resistance to get the desired current output.
increasing all of the wiring and tracing (bus bars and such)
can up the controllers capability sure..
and tricking the controller into misreading the currents to stall overcurrent protection then does make sense..
But you haven't said a word about wires needing to be upgraded before did you?
and without that all you do is put stress on the traces mostly..
and turn electricity into heat really
(just disabling the protection)

And HOW is that upgrade of the tracing dialed in.. eyeballing?
not too scientific is it?
calculated? what term has been used?
thermal correction terms in place?
Questions amongst questions.

And yes I know that many people around the internet do the most curious experiments with electric devices...
doesn't mean it's generally safe or to be considered a good idea.

You risk your 40 dollar controller.. feel free, I surely do not stop you.
You can also tell someone that if they are aware that they risk their's that this might be a valid way to do so.
(in case they do follow all steps, not just the bad one)

But I haven't read such "be aware.." statement neither here:
Quote:
Originally Posted by Bmr4Karts View Post
A single 48v 1800w motor can get 300lbs (including rider) moving at 30mph and this setup has the ability to climb hills. If you modify the controller to send 50 amps max it accelerates even better. ....
nor here:
Quote:
Originally Posted by Bmr4Karts View Post
Add solder to the shunts to reduce their resistance. Here's a picture of the shunts before I added my solder. .... I pull just over 50 amps according to my shunt meter.
No, all you mentioned was "solder the shunt"
and that by itself is in fact bad advice
And if the chinese haven't started overbuilding controllers lately... it's also not really much of an improvement until the worst case rears it's ugly head.

So.. what about the "stick with safe advice" mantra?

Yes I drive my motorcycle w/o a helmet if I so desire..
I would never suggest it's a good idea to anyone!
(yes exaggerated example..)

And THAT is what I meant by mentioning the
bulletshell in a fuse holder..
might work.. but as likely to fail catastrophically.
and most of all.. very bad advice!


'sid

PS NOW.. if you have a pcb schematic,
I can tell you what you want to modify and how
to turn your 50 amp controller into a 100a controller..
and in a mostly safe way... but be aware: it's cheaper and safer to just buy a bigger controller
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  #14  
Old Today, 09:31 PM
Bmr4Karts Bmr4Karts is offline
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Like I said before, it's not a placebo.

As for getting a bigger controller it would safer but not cheaper. The controller and motor combo cost almost the same as the motor by itself so it's almost a free controller.

To anyone reading this I suggest trying the shunt mod. Just go to YouTube and search for "motor controller shunt modification." If the controller fails, then you buy a bigger one. The big controller I bought was $500 but I've got a bigger motor and bigger battery to go along with it.

As with all internet advice provided by me, sid, or any other complete stranger that you've never met, you are on your own if it kills you. Now go out and have some fun.
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