# What is a KSI relay?



## booksix (Aug 26, 2008)

Ok, so this is probably another dumb one on my behalf, but I can't find the answer ANYWHERE! Seems like some setups use one, some don't. Either way, I don't know... what is it?!?


----------



## KiwiEV (Jul 26, 2007)

Hi There!

A KSI relay is basically an on-off switch for your controller. Mine looks like this:








When I turn on the ignition the contactor closes and the circuit becomes live. At the same time the above relay turns on and lets the + voltage of the main pack go to the KSI pin on the controller. 
On a Curtis controller, the KSI pin is the top one (of the three pins).

Hope that helps!


----------



## booksix (Aug 26, 2008)

Perfect! Funny you responded first. I was actually just going to PM you but I figured other ppl might need the answer as well. Great vids btw 

edit, another question: where did you pick those up? For some reason I can't find relays through any EV parts suppliers online.


----------



## Tom W (Jun 9, 2008)

So KSI means Key Switch Input, what is a KLK fuse?


----------



## KiwiEV (Jul 26, 2007)

booksix said:


> Perfect! Funny you responded first. I was actually just going to PM you but I figured other ppl might need the answer as well. Great vids btw
> 
> edit, another question: where did you pick those up? For some reason I can't find relays through any EV parts suppliers online.


Hey you're very welcome mate! I picked up a couple (one for the heater too) from RS Components. They have a full cattledog (slang for catalogue) on their website with prices. They're not expensive if you live in the USA, otherwise the freight costs more than the relay.


----------



## booksix (Aug 26, 2008)

thanks for the info! I'll check them out. bummer about the shipping cost!


----------



## CPLTECH (Sep 14, 2007)

In the USA, try Newark dot com or Digikey dot com for electronic parts. Newark (part # 04M7461 for the Omron G3NA-D210B) has some that are in the $50 range + S&H. Those places also sell the good old standard “ice cube” types a lot cheaper.
Should you decide to purchase the “solid state” variety, be aware that you *MUST* specify (1) the control voltage and (2) is the control voltage *AC* or *DC*, and finally (3) can it switch AC & DC and at what max voltage & amperage.
When it comes to the less expensive mechanical relays with contacts, merely specify load amperage and 12V *DC *coil voltage
PS. Usually when solid state relays fail, they fail shorted. Yes, contacts in the mechanical relays can short (weld together) but not as frequently.


----------



## Hondacrzy (Mar 15, 2008)

Does anyone have any none SS relay recomendations?

Chris


----------



## booksix (Aug 26, 2008)

More questions:

1. What 12v source should be tapped into for the side of the relay that actually feeds the controller (not the 'signal' side)?

2. If the relay is triggered by the ign switch, why can't the relay be skipped in favor of a direct connection to the same ign switch 12v (maybe the same circuit that previously powered the engine computer?


----------



## TelnetManta (Jun 5, 2008)

The KSI is looking for PACK VOLTAGE, you are simply using the 12V source as a trigger. It was explained to me that a 12V relay was okay to use because there's only milliamps going through the relay.


----------



## booksix (Aug 26, 2008)

oh, really? I didn't realize that. So to be clear the KSI relay is sending full pack voltage to the controller....? Is this the actually power supply for the controller? I was under the impression this was merely a trigger circuit to tell the controller to turn on (similar to a car audio amp).


----------



## kittydog42 (Sep 18, 2007)

As Ben explained, you need to use the relay since you are switching voltage from one source (the pack voltage) with voltage from another source (the accessory voltage). The power to the coil of the KSI relay usually goes through your throttle pot and any safety limits you have added, so that all of those conditions have to be satisfied before the relay closes. When it closes, it applies +144V (or whatever voltage you are using) through the normally open contact to the KSI terminal, which is internally referenced to the B- terminal. Some controllers also allow you to tap into a lower voltage and still work, as long as it is referenced to the B- terminal, which your accessory battery is not. The accessory battery is frame grounded and the traction pack should not be. This is for safety, so that you do not have high voltage potential to ground, making it safer to work on the batteries when proper safety procedures are followed.


----------



## Hondacrzy (Mar 15, 2008)

Are most people using a normal 12v automotive relay for the KSI relay? If anyone else could list what they used, that would be helpfull.


----------



## kittydog42 (Sep 18, 2007)

You can use a standard automotive relay without a problem. The pack voltage is higher than the relay contact's ratings are supposed to handle, but there is such a small current that it does not cause any problems.


----------



## PerfectAsThis (Aug 3, 2010)

hey did you ever use an automotive relay? i'm stuck in the same shoe you were in i think B-)


----------

