# I'm so lost....KSI relay and potbox connect?



## ClintK (Apr 27, 2008)

vpoppv said:


> I think I finally understand the pre-charge resistor: connect it between the two leads on the contactor. Coil suppression diode soldered on contactor on the side. (I'm looking at page 9, figure 8 of Curtis 1209B/1221B 1221C/1231C manual). But I just don't get the KSI relay. I've read threads talking about it, where it talks about pack voltage. I just don't understand how it physically connects to the potbox. I get the two wires to the controller coming from the potbox, but I don't understand how/why it connects to the KSI relay. Schematics totally confuse me. Anyone know where there are clear pictures of real live KSI relays?


I use 2 contactors in my setup. The first contactor is trigger closed by the key switch. The second contactor has a pre-charge resistor across it. When I press the pedal, the second contactor closes allowing power to flow freely. To do that, I have a 12V line going through the microswitch of my Pot Box then to the Contactor then back to ground.

Basically I turn the key on and wait several seconds to let the controller charge up. Then I can drive normally. The second contactor opens and closes as I drive (extra safety).

My blog post here shows my schematic and a picture of my control plate: http://78electricspitfire.blogspot.com/2009/09/main-cables.html

Seems to work fine, but bare in mind my first test drive was.... TODAY!


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## Dave Koller (Nov 15, 2008)

http://www.diyelectriccar.com/forums/showthread.php/voltmeter-question-36840.html

Above is my post for different question... the drawing is similar to Clintk's .. I also use two contactors -one on plus one on neg - instead of controlling the contactor I just control the smaller relay to the Curtis. Lots not shown there as I latch everything but brake, clutch, key, or Crash will unlatch all... I understand not reading schematics but both our circuits are easy to follow as shown..

Dave


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## vpoppv (Jul 27, 2009)

ClintK said:


> I use 2 contactors in my setup. The first contactor is trigger closed by the key switch. The second contactor has a pre-charge resistor across it. When I press the pedal, the second contactor closes allowing power to flow freely. To do that, I have a 12V line going through the microswitch of my Pot Box then to the Contactor then back to ground.
> 
> Basically I turn the key on and wait several seconds to let the controller charge up. Then I can drive normally. The second contactor opens and closes as I drive (extra safety).
> 
> ...


ClintK,
1) I agree, your wife looks way too happy to use the bat to "help"; I'd be more worried about that than your setup
2) You have a circuit breaker right after the fuse. Is the circuit breaker hooked up to a safety latch you could pull from the inside of the car in case of catastrophic failure?
3) Could you remove the potbox entirely from the system and have the contactors only open on the keyswitch? (that would seem to make one of the contactors redundant)
I think what it boils down to is that I don't understand why you would want to have the contactor open every time you let off the accelerator, even though that's how it's usually done. If the contactor welds shut, the car won't go anywhere if you don't push on the accelerator. If the controller dies full on, you yank on the safety to kill the power.


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## ClintK (Apr 27, 2008)

vpoppv said:


> ClintK,
> 1) I agree, your wife looks way too happy to use the bat to "help"; I'd be more worried about that than your setup
> 2) You have a circuit breaker right after the fuse. Is the circuit breaker hooked up to a safety latch you could pull from the inside of the car in case of catastrophic failure?
> 3) Could you remove the potbox entirely from the system and have the contactors only open on the keyswitch? (that would seem to make one of the contactors redundant)
> I think what it boils down to is that I don't understand why you would want to have the contactor open every time you let off the accelerator, even though that's how it's usually done. If the contactor welds shut, the car won't go anywhere if you don't push on the accelerator. If the controller dies full on, you yank on the safety to kill the power.


Yes, I'll have a safety latch to pull the circuit breaker just in case.

The two contactors aren't completely redundant - they do serve unique purposes. When I turn the key to start, the first contactor closes. That allows my controller to precharge because of the resistor across the second contactor. When I drive the second contactor closes every time I accelerate (and opens every time I let off the accelerator). This gives me an extra layer of safety. If the controller fails full on, my first reaction will be to lift my foot off the pedal (which will open the 2nd contactor and blow the precharge resistor). That will keep the car from speeding away without me even thinking about it. If that 2nd contactor fuses closed, I can either turn the key to off to open the 1st contactor and/or pull the circuit breaker.

Actually the 1st contactor / circuit breaker are probably the most redundant. My 2nd contactor will not close without the key turned to on anyways, so that's sufficient theft protection. If I wanted to flip the circuit breaker on/off every time I left the car I could remove the 1st contactor.

Not everyone does the 2nd contactor / precharge. I just read enough about precharging and thought the extra safety was good justification.


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## Dave Koller (Nov 15, 2008)

ClintK said:


> The two contactors aren't completely redundant - they do serve unique purposes. When I turn the key to start, the first contactor closes. That allows my controller to precharge because of the resistor across the second contactor. When I drive the second contactor closes every time I accelerate (and opens every time I let off the accelerator). This gives me an extra layer of safety. If the controller fails full on, my first reaction will be to lift my foot off the pedal (which will open the 2nd contactor and blow the precharge resistor). That will keep the car from speeding away without me even thinking about it. If that 2nd contactor fuses closed, I can either turn the key to off to open the 1st contactor and/or pull the circuit breaker.
> 
> Not everyone does the 2nd contactor / precharge. I just read enough about precharging and thought the extra safety was good justification.


I agree! Clintk's is probably a safer way to go - I just didn't want the click on the second contactor every time I shift ( I have a clutch) or coast -- but the precharge is the most important to save the contacts on the contactor and take the first inrush of current to the controller.... I started the thread about the voltmeter as I wondered how many people had tried the meter after the precharge.. It would show a slow rise to full pack or that the precharge had sufficiently charged controller.. hence you can safely cut in the second contactor (by whatever means you have devised..). Clintk's release of the gas is what most do on that second contactor. I just have a circuit to latch and release by many other means..

Dave


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## tj4fa (May 25, 2008)

I found this diagram from the website below that might help.










http://evute-nz.blogspot.com/feeds/posts/default


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## Dave Koller (Nov 15, 2008)

tj4fa said:


> I found this diagram from the website below that might help.
> 
> 
> 
> ...


Yep that's the one I changed to this as this one shows A2 being used:


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## O'Zeeke (Mar 9, 2008)

Dave Koller said:


> Yep that's the one I changed to this as this one shows A2 being used:


hey Dave, like your drawing shows i dont presently use the A2 of the controller. Any advantage one way or another if it's connected to A2 on motor?


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## Dave Koller (Nov 15, 2008)

O'Zeeke said:


> hey Dave, like your drawing shows i dont presently use the A2 of the controller. Any advantage one way or another if it's connected to A2 on motor?


Not recommended to use A2 - I hastily copied the small version of what I drew over ... the one below is larger (click on it if not!). I have not figured how some people can post larger pics from the DIY site .. I see how they can refer to another site but I see some over the limit on size.. I know because in the sticks here I am on dial-up 

Do a little checking on A2 (unless you have a forklift lol)

Dave 

The _A2_ connection is merely for dynamic, plugging braking and should _not_ be used in road going EVs.


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