EV help

Thread Starter

scratch

Joined Aug 6, 2010
38
Car runs well, then (wen i think all is well) out of the clear blue sky FET's smoks.
car is a dihatsu charade manual transmision. attacht is the basic circuit, but modified for higher volts & current. Would eventually like to up 72v.
Would like FET's to stop smoking first though.

I dont understand this statment.
Being PWM driven only a few turns of wire between the source and GND of each FET will certainly help balance out the loads.

thank you.
 

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jpanhalt

Joined Jan 18, 2008
11,087
My problem is that i have no current sensing cut back so the FET keeps burning, when ever over current occures.
Are you sure the circuit you just posted is the right one? I see a current sensing and shut down feedback. What have you done in its place?

Really, a lot of people are trying to help you on this, and for some reason, you refuse to post the schematic for your design. Why is that?

John
 

beenthere

Joined Apr 20, 2004
15,819
To be utterly correct, the "schematic" is of of those bogus overunity electrolyzer kludges that we have seen many times before.

To the OP: The circuit is not functional and comes from some strange people. Someone should be able to help you with a better PWM circuit.
 
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Thread Starter

scratch

Joined Aug 6, 2010
38
Here are 2 pic of electric car need help with conrtoller. There are 6 packs each with 10 8amh 12a gel bat.
Motor has the name Nexus on it try to fine online but could not.

pic 1 shows half of battery aray other half in rear.
pic 2 shows motor mounted on transmision.
sorry about pic qaulity phone camera used.
 

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Wendy

Joined Mar 24, 2008
23,415
Let me guess, you are wiring this up without a schematic? This is a very expensive route to go if so. A schematic allows you to anticipate problems before you have them.

Are you using a commercial controller box by chance?
 

Wendy

Joined Mar 24, 2008
23,415
Again, if it is homemade you have to be basing off of something. If you are freewheeling it (designing without drawing) I give this project very low probabilities of success. You need a plan, schematics are only part of it.

My first guess is you are simply pulling too much current. A 350 pound battle bot can draw over 500amps from a dead stop, so you are probably at least a magnitude over that, probably more.

My early question about shoot through is pretty basic stuff. To go in reverse you probably have an H bridge, but this isn't the only way to do it. Goes back to the plans requirement.

Do you have a link to the ezgo controller?

What kind of chassis are you modifying (think weight)?
 

Thread Starter

scratch

Joined Aug 6, 2010
38
car is a dihatsu charade manual gearbox no clutch.
origenal wt about 1700lb.
At 48v without controller igot a speed about 25mph. Speedometer do not work.
posted wose basic circuit , modified for higher volts & current. Would eventually like to up 72v.

will draw schematic.
would be if i could modified ezgo controller work at higher amps / volts.
 

JoeJester

Joined Apr 26, 2005
4,390
Scratch, was it an Cushman EZ-GO EV that you acquired the motor from? Do you remember the model of the cart as EZ-GO manuals are on the internet.

You have to realize that the EZ-GO EV controller feeds a relay H-bridge. Since a schematic is in order, the attached manual from Cushman will give you an idea of how everything was when the EZ-GO is working properly.

At least you'll have some baseline information to build from.
 

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jpanhalt

Joined Jan 18, 2008
11,087
Small point, I don't believe series wound motors can be reversed just by reversing the polarity of the supply to them. They are like starter motors -- at least the older ones -- they turn the same direction regardless of polarity.

You have to access the field and armature separately in order to reverse them. The Cushman controller reference from Joe Jester, page 20, shows how to reverse a series-wound motor. Since the motor being used here came from a forklift, it was possibly used to drive a hydraulic pump. Thus, it may not have the requisite access to make it reversible.

It is a little frustrating to have a schematic presented that is not really the one that was used (see my earlier comment about the current sense loop). I look forward to seeing the actual schematic.

Also, I hope the OP will clarify whether he wants the motor to be reversible and whether the motor allows access to both the field and armature windings.

John
 
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Ron H

Joined Apr 14, 2005
7,063
John, he said the car has a manual gearbox (transmission). Transmissions have reverse built in. There is probably no need to reverse the motor. If I'm wrong, I'm sure I'll be corrected.:eek:
 

jpanhalt

Joined Jan 18, 2008
11,087
Ron, My comment was made with reference to JoeJester's comment immediately before mine and some earlier comments related to using an H-bridge.

This thread has become a bit confusing. It started out as a request for a current limiting circuit. Then it appeared that was built into the "design" that was modified. Now, we know that really was not the design. However, going back to the very early part of the thread, the OP showed a simplified schematic for a typical mosfet controller with two paralleled mosfets and without current sense. He is actually driving 24 paralleled mosfets (as I recall). It is critical to know whatever drive circuitry he is using.

John
 

Thread Starter

scratch

Joined Aug 6, 2010
38
I started This EV conversion about 4yr ago, before that i had never evan herd of PWM controller so i realy need help. I have an audio electronic back ground useto build amplifire, preamp,mixers est. So i know components and can use soldering iron.
Would be real greatful fore help with a better not complex (none smoker) PWM rcircuit.

Thank you every body
 

jpanhalt

Joined Jan 18, 2008
11,087
Scratch, We want to help you. You are going to multiple sites, including this one, and posting the same question over and over again. Yet, you refuse to post a schematic of what you have done.

So far, the only definitive thing you have shown is a picture under the hood that seems to show a pull motor/forklift DC motor attached to something. Then you ask us to design for you a mosfet drive with, presumably, 24 mosfets, for this motor.

PLEASE, post a schematic of what you have done.

John
 

JoeJester

Joined Apr 26, 2005
4,390
John,

The motor I thought the OP had was the drive motor, forward and reverse. That being said, if he only needs forward, because of the transmission, the OP could trace the circuit out to see how that is connected. Electric forktrucks been around a long time. The MTBF with contactors was pretty good as I don't recall the Electricians Mate working on them too often.
 

Thread Starter

scratch

Joined Aug 6, 2010
38
Hello.

Had a little free time so i used it to install Curtis 1205 controller. Not what i expected, but not far off. Controller get's a bit warm will install fan. Climb small hills OK. Need a little more speed, present top speed is about 25mph (spdometer don't work) need 35-40mph. Maybe 72v will be ok.
 

Thread Starter

scratch

Joined Aug 6, 2010
38
Hav a 72v controller built, but shy off smokeing diode so hav not tried full load. Plan to incorporate, Marshallf3's diode & potato pudding's transistor.

potato pudding Don't know how to do this.
Put a tiny amount of equal resistance or a two loop choke under each transistors source. That should balance the loads.

Attasht is circuit. there is 25 fet but only 4 is shown.
1k variable resistor. currant.
10k . speed.
20k .fequency.
 

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