new to this

[itsid]

hmm...

as I said, might be just enough for a small pedal kart,
but don't forget that you only have ~80% efficiency on the motor and you need mechanical power, not electrical in order to move around.

IDK really, tough to estimate not having a small pedal kart to weigh,
but you read the essence thread, do the math and see what you come up with.
You're likely a bit on the low side, but maybe just enough for some cruisin (not much fun though especially for the older one)
a two seater is out of the question for sure.

go for the mower instead,
cover the rear in nylon mesh though, in order to keep as much debris out as possible without blocking too much of the airflow for cooling.

I know the controller is six to seven times as expensive as for the weed eater, but
it's well worth it, especially since you have enough power to keep both of your kids entertained with it for the next 6 to 8 years (not just one or two)
if you gradually speed the kart up

'sid

 

[alim]

Hypothetically if I went with the 18v, what battery and controller would I use?

 

[itsid]

well cheapest would be to overvolt slightly (24V) and get one of those 10 buck controllers off ebay;
and yes, that also means you need to run it off 24V not 18V batteries.

or if the weed eater had speed control, reuse that (even cheaper... just not as reliable)

'sid

 

[alim]

No speed controller on the weedeater, just a switch.

Will take apart the mower and see if it's got a controller.

 

[Functional Artist]

I put the Kelly controller on El Moto my electric motorcycle

It's Bad Azz

http://www.diygokarts.com/vb/showthread.php?t=37062&page=4


Yup, I'd recommend them

So far, I have NOT had any problems with mine

*keep in mind when you get into the bigger motors (for safety)

...you'll need a contactor

...& an applicable fuse

like in this kit

http://kellycontroller.com/small-kds-assembly-p-334.html

 

[alim]

No speed controller on the mower, just a simple switch (that looks like a hand grenade).

The interesting thing is the switch says "25A" on it, but from my tests the motor actually can pull 125A.

 

[itsid]

that's indeed nothing but a switch, one NC one NO side.. nothing special really..
yours made by ZHEJIANG JIABEN (the JB logo is saying so)
but it's indeed no controller.. you sure there is no other small box between the batteries and the motor?
nothing?

it can be as tiny as a matchbox (in fact it'd fit nicely inside the trigger switch, but no.. if they haven't opened it up, it's just a trigger switch )

IDK to be honest I'm baffled to say the least...
does the blades run at a single speed only really?
I thought they're somewhat adjustable in speed *shrugs*

if not, maybe that's correct then, no controller and a current limiter somewhere inside the battery to would make the 25A switch work. (or maybe just a solenoid somewhere)

frankly, this doesn't make any sense IMHO...
I again googled the motor number you posted earlier,
I came across some mowers, some craftsman mowers and I can only suspect there's a controller in that chunky box on the handle..
but frankly, there is no breakdown of that part anywhere so might indeed just be that switch there *shrugs*
and the rest is not telling.. the battery breakdown is nice (two SLAs in a box with an indicator pcb and some wires)
bu nothing that'd led to believe there's a controller you can identify as such

(frankly.. HF sells LiIon 18V cordless drills with a pwm motor controller... for ~20 bucks... I mean.. there's no reason I can think of a mower would lack such "comfort")

IDK, I really don't, I never seen a mower with a fixed speed blade
(it'd rev to the moon and back w/o load aka grass ...sooo!?)
So all I could tell you is to follow each and every wire on in and around the mower to see where it goes and inspect each and every plastic piece that's somewhere in between;
but it's not impossible this mower indeed has no controller and simply relies on the beefiness of this undersized switch.. (900W rated switch for a ~1800W motor)


'sid

 

[alim]

So all I could tell you is to follow each and every wire on in and around the mower to see where it goes and inspect each and every plastic piece that's somewhere in between;
but it's not impossible this mower indeed has no controller and simply relies on the beefiness of this undersized switch.. (900W rated switch for a ~1800W motor)

'sid

Ok, I'll do that.

By the way, I combed kijiji for people dumping their 24v cordless mowers (usually due to bad batteries). Ended up buying two: a Duramax and a Homelite, they are pretty much identical, got them for $20 each, the motors look exactly like the one I pulled out of the craftsman. Haven't tested them yet but will get around to it this week. Will post the results here.

While I was at it I also picked up a non-working pocket bike ($80) so I'm gonna tear out the gas works and put in electric... eventually...

Alim.

 

[alim]

Great news, those motors I combed off kijiji from cordless 24v lawn mowers, one of them is around 2250w and one of them is around 2750w! Score!

 

[alim]

Ok all, I have followed every wire on the mower, actually all three mowers are basically identical. They all have the same switch hidden inside the handle, like the one I showed in an earlier pic. The only other electric part is the battery indicator, I am attaching a pic - could this also be serving the purpose of a controller? I doubt it because there are only thin wires (three of them) coming out of it, no thick wires. Have a look and tell me what you think.

 

[itsid]

tough from the backside..
I suspect the three solderjoints on the right in the second pic to be a MOSFET or some type of transistor at least...
Then again, that could also be either a switching transistor for the charger circuit or just a TO220 package of rectifying diodes

The top side would be giving more away let's say..
but no, from first glance, I agree that does NOT look like a motor controller,
more like a charging controller, maybe with an included current limiter (which would explain not only the thin wires, but also the switch being rated at only 25A )

The last pic shows a good sign of discoloration which was surely heat induced
Now coincidentally (NOT!) that's more or less the region where said transistor sits
likely where the black wire is connected to internally.. no matter if it's limiting, amplifying or just rectifying that's what failed first on that PCB.

Is that soft putty or hard resin? or more directly: can you remove the PCB from the case without destroying it to show the business end of things?

'sid

 

[alim]

It's soft, feels like silicone, looks like it would be easy to open up. Stay tuned.

 

[alim]

Voila!

 

[itsid]

Yeah just a voltage regulator (the fairchild TO 220 in pic one) [12V 2Amps]
and a voltage comparator (the texas instruments LM239 Dip pack in pic two)
apart from the LEDs it controls nothing I'm afraid

Funny enough it has a motor pin and two battery pins (B+, B-for battery M+ for the motor)
but it's likely just to shut down the motor in case the battery is about to die
(undervoltage protection)

Anyways, no controller... odd but alright,
Now you'd need to find a controller matching your motor.

Sorry, I'm amazed...
thinking that even the cheapest cordless drills have a controller inside for speed control,
I was basically sure a mower needs to at least govern the blade speed
and thus have to have a controller of sorts *shrugs*
I stand corrected

'sid

 

[alim]

Ok, so time to grab the Kelly controller then?

 

[Functional Artist]

Ok, so time to grab the Kelly controller then?

Have you made any progress on the kart?

Just an idea

Maybe start off with a cheap alternative like

http://www.ebay.com/itm/36V-48V-100...06&rk=1&rkt=1&&_trksid=p2045573.c100506.m3226

It will NOT be as powerful

but, you don't need a contactor like you will with the Kelley

That will get you going for under $20.00 delivered

Then, move up to the more powerful Kelly

...& you can still use the smaller controller on one of your other motors

 

[alim]

I thought I couldn't use a cheapy controller from eBay because the motor was too powerful? That controller is rated for 1000W max, the motor is 3000W max. It would fry the controller, no?

Haven't done any physical/fabrication work on the kart yet! That's next, maybe while I'm waiting for delivery of the controller

 

[itsid]

Ok, so time to grab the Kelly controller then?

Frankly ... I'm unsure yet.
Yes.. 1900 Watts roughly require a decent controller and kelly provide the cheapest reliable solution for that (especially since it's only 24V)

BUT there is no current limiting anywhere on that PCB that switch is only rated at one fifths of what the motor should be able to draw.

I am not sure there isn't any mistake in that initial reading or the assumptions about the motor itself.

And frankly I'd be really upset if you'd buy a 100 dollar controller because of a mistake I made,
when all you'd need is indeed one of the cheaper chinese controllers off ebay.

So forgive me when I'm a bit hesitant to tell you what to do

I'd get one of these (10 bucks delivered.. just 500W instead of the possible 600W for an assumed 25A system current)
make sure to pick 24V/500W
http://www.ebay.com/itm/Aluminium-A...tor-Brushed-Speed-Controller-LJ-/112553845867

or find one that's allowing a higher power on 24V (not 36V or more!)
it'll be 'wasted' eventually, so buy as cheap as possible,

Frankly I'd even go so far and say get an appliance controller instead of an EV one:
http://www.ebay.com/itm/2000W-40A-1...d-Control-PWM-HHO-RC-Controller-/221842925195

it handles up to 40Amps and is even cheaper
that thing should blow... (I said it'll be wasted, right )
and once it does and you can be reasonably sure the motor is indeed drawing more than those 40 Amps.

THEN it'd be time to get the more expensive Kelly controller.
if not you can either work with that until it fries on the kart
or get a proper EV controller that's closest to your need.

But again, that is NOT advice, it's a SUGGESTION!
(it's what I personally would do to be honest)

Something about that mower setup is fishy (everything but the motor indicates lower currents)
and if the motor is not throttled (some current limiting controller)
it should burn out everything else including the switch with it's 125Amps

That's why I'd get a second 'opinion' in form of a cheap controller that'd blow if the high amps are actually drawn.

'sid

 

[alim]

Wise words 'sid.

Isn't there some sort of power measurement device I could use to get a reading? Can't a multimeter be used for that purpose?!?

 

[itsid]

frankly.. I don't know any.. a voltage divider is the most accurate I could come up with I'm afraid.
At least when it comes to 'stationary no load testing'

You could test the motor whilst running of course (proper amp draw reading)
BUT that too comes at a heavy price.. an amp meter that's able to withstand the assumed 125Amps will be not only hard to find but also expensive.
And worse to properly test the motor doesn't only need to run it needs to run at a load (close to stall speeds)
the torque and worse inertia involved as soon as it breaks free (or starts turning) is not something you want to physically be involved in (no joke, it'll hurt you really badly!)

Maybe those AVR Transistortester can read sub 1Ohm impedances..
at least theoretically they should... (and yes you can buy chinese readymades on ebay for cheap LCR-T4 or LCR-T5)
BUT I'm not exactly sure it'll change the outcome.
and in the end it remains to be a static test wich might be flawed to begin with.

the motor specsheet would help a lot, any chance one of the other motors has a better label (some number that'd yield a search result on google)?

The best multimeters I know (FLUKE) are not accurately reading sub 2 Ohm impedances
So no.. a mulitmeter might not really help here without a voltage divider.

Talking of which, maybe we can cheat...
could you run the motor for a while
battery the switch and motor.. all connected (motor properly tied to an immovable object )
and run it for a few minutes (until it gets warm to the touch but not hot... "operating temperature" let's say, what you feel comfortable with.
THEN without allowing it to cool down, retest it with the voltage divider as before and see if there's a difference.
(hot coils should have a higher impedance than cold ones... not by much to be honest, but at least it's closer to what you end up with running it on a kart.)

for now that's the only "cheap" way I can think of to verify the previous results.
everything else is quickly getting more expensive than even buying the kelly controller

Wait.. hang on.. FA??
You got that cheap'ish Voltage/Amp meter off ebay, right?
you happen to have a link for us?
Maybe that's a good way to test the motor w/o controller under some load (from a safe distance perhaps ) to get an idea of it's thirst...

'sid