# sepex without controller



## Superyellow (Dec 8, 2012)

hi there I recently burnt my Sepex controller on my ATV project (Rally 200) and cannot afford another one. 
I have 
36-48 Volt 16Hp sepex motor with Belt Final Drive
4 x 12 volt batteries 
Only one Albright 50v 200 amp continuous contactor that is rewound to 36v on coil ( it has a diode on it)

I would like to run the motor for 2 mile trips for daily commutes without a controller until I can afford replacing my Curtis 1268...
I was thinking of using 3X12= 36v for the motor with a switch wired to the contactor for throttle. and use another 12v battery for the field with an Electrical switch to turn on and off before/after commute.
I have hear from other threads that this is possible with a start up resistor...
what is this thing and where can I find one? I saw some old Golf cart resistors which look like coiled wire hanger(maybe not) . how many watts is this ? 
can I use a capacitor from a washing machine or something like that?

would i be able to run it without it for a week or so?
please enlighten me I am looking forward to move my first big EV project. 
I appreciate in advance


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## major (Apr 4, 2008)

Superyellow said:


> hi there I recently burnt my Sepex controller on my ATV project (Rally 200) and cannot afford another one.
> I have
> 36-48 Volt 16Hp sepex motor with Belt Final Drive
> 4 x 12 volt batteries
> ...


Hey Yellow,

I know you don't want to hear this, but.......bad idea 

Running any EV big enough to carry 3 or 4 batteries and your butt at any speed faster than a crawl without a controller is dangerous. Contactors, switches and/or disconnects have a way of failing welded shut (full on) with inductive loads like motors and motors can produce more torque than the brakes in a lot of cases.

Resistor controllers are a mid evil solution but workable with series motors. I doubt you can find a suitable one for a SepEx motor, possibly if you start it no load and clutch the load in. 

Capacitors don't help you.

Regards,

major


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## Superyellow (Dec 8, 2012)

Major I guess I have 3 options left
A) sit the ATV on the controller like a brick while the rear wheels are floating and run the motor and jump on the ATV (like a Cowboy fleeing the Bar fight) dropping the wheels on the ground with a nice burn out 
B) pick up the rear of the ATV with one hand and run the motor with the other hand and drop the ATV on the hot asphalt and take of with a burn out and a skitch on the back of the ATV and then jump on it like an indian catching a wild horse 
C) stop fantasizing ghetto ways of running my EV and use the wisdom on this forum and maybe a Rheostat on Field to control the speed of the motor. I wonder if a light dimmer would work? I found some 50 Ohm footlong Rheostats would these work? otherwise I might end up toasting the light dimmer 

I found a used Sepex controller hopefully summer won't be over or I be dead before I get my ATV running properly
thank you for the help and letting me have humor


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## DavidDymaxion (Dec 1, 2008)

Like Major said, I would not suggest doing direct drive with no controller -- the starting lurch could pitch you off the machine. If you have a clutch, you could try 12V field and 12V battery, and see how fast the motor spins. That might be enough to do your commute, and be a compromise between too fast and not moving. Be careful you don't stall the motor, like a steep hill, that'll create a huge current surge that might damage the motor. If all goes well there, you could test 12V field and 24V armature, and then 36V if 24V indicates that would be OK.

I drove my Porsche with no controller for a while, just switched 48V directly to a sepex motor. I had to use the clutch to start and had to shift to change speeds.

I just converted a garden tractor. It has a 48V sepex that spins at 3300 rpm and no controller. It works great, but the machine was designed for a constant speed motor, has 4 speeds, and a good clutch. It works incredibly well, I'm very happy. Tall grass that would stall my old lawn tractor doesn't even phase this one. I'm about 1/2 way done with a web page for it, I'll post up once that goes live.


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## Superyellow (Dec 8, 2012)

I learned it the hard way! 48V on Armature and 12v on field welded the contactor on the first attempt! I am glad that the wheels were of the ground. for some reason attempting to start the motor without a controller causes too much sparks! enough to weld and blow up fractures from the copper terminals so there is no way I will attemp to start it again unless I use a circuit breaker. I measured the ohms on the armature and it was too low like 2-3 ohms but some reason I don't understand when there is no load on the motor(only the axle) why in the world does it draw crazy currents and causes sparks? my rear ATV wheels are big like truck tires but not heavy. the wheel and motor spins alright on belt drive.... I used small 12 24 volt motors before and I have not seen this much current before on start up.... I cannot imagine going up the hill with this motor. anyway I assume there is not short on the armature other wise it wouldn't show a few ohms on the armature. Field is easy it draws like 50 watts or something really easy to control and turn on and off. however the armature is is alike a blackhole of current! really dangerous! I have an automic CVT that came with the ATV I would really hate to put it back and swtich to chain drive again.  I appreciate for all your input


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## major (Apr 4, 2008)

Superyellow said:


> I learned it the hard way! 48V on Armature and 12v on field *welded* the contactor on the first attempt!


I told you so 



major said:


> ......bad idea
> ....without a controller is dangerous. Contactors, switches and/or disconnects have a way of failing *welded* shut (full on) with inductive loads like motors....





Superyellow said:


> I am glad that the wheels were of the ground.


At least you weren't sitting on it pointed in the direction of the highway.



Superyellow said:


> for some reason attempting to start the motor without a controller causes too much sparks! enough to weld and blow up fractures from the copper terminals so there is no way I will attemp to start it again unless I use a circuit breaker. I measured the ohms on the armature and it was too low like 2-3 ohms but some reason I don't understand when there is no load on the motor(only the axle) why in the world does it draw crazy currents and causes sparks?


It is quite simple once you understand it. The armature resistance is not 2-3Ω, but more like 0.005Ω. Multimeters will not correctly read such low resistance. So the initial current when a battery is connected to a non rotating motor armature is figured by using Ohm's Law. V = 48V from the battery. R = total circuit resistance which is the armature resistance plus the battery internal resistance plus cables and brushes, so let's call it 0.03Ω. Then the starting current is I = V/R = 48V/0.03Ω = 1600 Amps. 

Depending on the battery and cables, it could have been double that. But suffice it to say, it was more than your contactor could handle. Even the slightest contact bounce will cause enough arc to weld. Then you're screwed.

Live and learn,

major


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## kennybobby (Aug 10, 2012)

Superyellow said:


> I learned it the hard way!


Getting an education is an expensive item whether you go to college or not. Just think how close you were to getting a Darwin Award...


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## Superyellow (Dec 8, 2012)

1600 amps x 48 volts = 76800 = 76.8 kilowatts? is this correct? that explains why shit exploded on my face! 76.8 kilowatss is enough to drain all my batteries in 1 minute if I am alive lol  my concern is what If I get the motor to start spinning some, maybe i'd get the bikini girls to push me or dream of them going down the hill? how much current will I be needing then? I thought a 48v golf cart motor would run on 100-200 amps and occasionally draw 300-500 amps going up the hills? correct me if I am wrong.... will the motor draw less amps at the rated RPMs? i assume it will stop spinning faster around 2500 or so... 

Guys you read Major and me! DO NOT ATTEMPT TO START A BIG GOLF CART MOTOR WITHOUT A CONTROLLER AND NO CLUTCH! SHIT BLOWS ON YOUR FACE! THIS IS NOT A JOKE!

I still wonder how David starts his law tractor with 48 volts and no controller? I see there is no way to even use a contactor since it welds(and literally explodes) on mine. If I cannot spin the free wheels which are off the ground I don't think a clutch would solve my problems though It would be nice. Can you please Enlighten us David? how can you turn on and off the main cirtuit? what happens if you tractor stops for some reason? 76.8 kilowatt kaboom? oh shit I wouldn't wanna be around I have been traumatized once with electric 
thank you all for not letting me kill my self 

@KennyBoddy no comments on College and/or university been there done that unfortunately they don't let me get a Darwin Award in there! I still don't think it's possible to get killed by being electrecuted. seriously I touched the 48 volt and my body doesn't have low resistance like copper I don't think it's possible to die that way unless there is some water and a pace maker involved with it. the serious trouble is the fragmentsflying all over in the form of hot molten metal! I admit i used copper plates that are thicker than the one on 200 amp continous albright contactor. there is no way to turn that thing on an off without a rheostat unless you risk bunch of sparks . I wore prescription safety glasses just like a nerd I think the only danger is the possible lunging of the vehicle or batteries/terminals wires exploding! KABOOM!


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## major (Apr 4, 2008)

Superyellow said:


> 1600 amps x 48 volts = 76800 = 76.8 kilowatts? is this correct?


No  It's just about like these guys that multiply the battery open circuit voltage times short circuit current to get power. Only in the bizzaro universe  The two conditions don't occur simultaneously. So when the 1600A flowed, the battery voltage was likely about 15 or 20 Volts. You might have had 20 to 30kW for a few seconds.


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## Superyellow (Dec 8, 2012)

holy shit Major! You saved my life!  Yellow is a very deadly color I must admit. And this thing needs to move now! 

thank you for the info you are the man!


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## DavidDymaxion (Dec 1, 2008)

On my 11 inch Kostov I would just switch it on and off in neutral at first. I worked my way up, trying at 12V, 24V, 36V, and then 48V. The motor would rev fast for a moment as the field took about 1/2 second to build full strength. It's counterintuitive, but less field = more rpm. 

Then I did the refinement of using 2 switches. I would flip on the field first, and then the armature. The armature switch was after the field switch, to guarantee the field was switched on if the armature was switched on. It worked great.

The tractor has a D&D 6.7 inch sepex motor. On 12V, 24V, and 36V it would switch on just great. On 48V the commutator made a brief flash (likely OK as it'll get turned on only maybe 100 times a year), but I wanted it to be perfect. I have a reed switch with a field wire wrapped around it that turns on a starting resistor. There is a noticeable delay as the field takes a fraction of a second to build, perfect! I then switch on the armature with a manual switch, powered off the reed relay for safety. Eventually I'll put a time delay relay in place of the human switch.

When you hit the brake it also does the clutch, so it should be OK against a high stall current that way. I also have a fuse, so if someone ignorantly tries to pull a big load up a hill in high gear it'll blow the fuse. 

Both cases have a clutch! I would not start engaged in gear! Also I would encourage you to start at 12V, and you might be able to limp along on 12V.

A couple of more points: Switching is done with contactors. The Kostov field was 48V, and the D&D field is 12V.


Superyellow said:


> ... I still wonder how David starts his law tractor with 48 volts and no controller? I see there is no way to even use a contactor since it welds(and literally explodes) on mine. If I cannot spin the free wheels which are off the ground I don't think a clutch would solve my problems though It would be nice. Can you please Enlighten us David? how can you turn on and off the main cirtuit? what happens if you tractor stops for some reason? 76.8 kilowatt kaboom? oh shit I wouldn't wanna be around I have been traumatized once with electric
> thank you all for not letting me kill my self  ...


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