# Brake light relay for Curtis 1238



## Caps18 (Jun 8, 2008)

I am installing an HPEVS AC-75 and a Curtis 1238 controller. It is option #1, brake wiring type #2 in their manual.

I haven't heard back from HPEVS yet, so I will see if anyone here knows which relay to buy or what the specs are? I know the brake light side is 12V, but what about the signal side? 5V or 12V? Maybe it doesn't matter. I would still think that there would be some more details.


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## frodus (Apr 12, 2008)

All the io on the Curtis is 12v. But it's not isolated.... Hence the relay.


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## Caps18 (Jun 8, 2008)

http://www.newark.com/crydom/dc60s3/solid-state-panel-mount-relay/dp/93K7532?MER=BN-PG-93K7532

So it is this relay then. I have used these before, but to make this process easier, I think some of this should be built into the controller or pre-build a module with a bunch of these components already put together... Or at least recommend one in the documentation and label what it is.


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## evmetro (Apr 9, 2012)

It has been awhile but I wired one of those into my first conversion. I may be wrong, but I thought the relay was using 24 volts like the contactor, and I had gotten a 28v coil on the relay. Like I said though, it has been awhile and I am not looking at my diagrams. Frodus walked me through much of my first conversion, and I would put his info above mine on this.


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## frodus (Apr 12, 2008)

Just use 12v automotive relay from the auto parts store.


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## Moltenmetal (Mar 20, 2014)

Just asked this same question of HPEVS- their drawings do not show the coil voltage.

The coil drivers such as the one used to drive the brake light relay are PWM outputs which use high voltage B+ (the KSI input, pin 1) as their source, and can be programmed (if you have the programmer).

My main contactor (supplied with the motor/controller package) has a 48VDC coil.

I suppose I could just put a resistor between the brake light coil driver output and the coil return and measure the (average) voltage, but I will report back what HPEVS says. I presume they do what would make sense and program this coil driver for 12VDC so you can use a normal automotive relay, but won't be putting one on there before I hear back from either HPEVS or someone who has measured that voltage.

They don't show a fuse on the coil side of that circuit, but I'll be putting one in there.


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## Caps18 (Jun 8, 2008)

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=182054514&uq=635808478379409244

I just bought this relay (Crydom ED06F5) on Monday to do this. It is a 48V one, but I would be interested in hearing what HPEVS has to say. I figure that this will turn on the brake lights when the regen is active, but I'm not sure about coasting with no regen. I'm also afraid that it would be the reverse, where it is closed when the accelerator pedal is pushed, but maybe there is an internal circuit in the 1238 that flips it.

The relay is pretty small and the spade terminals are 3/16" wide ones. A fuse probably isn't a bad idea, but I would have no idea what size to get.

I did run the blue and orange (with white stripe) 48V wires directly to the high voltage battery contactor on the signal side, and will have another wire from the blue/white terminal on the contactor go to the brake relay. The brake lights might have a fuse in-line with that circuit.


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## Moltenmetal (Mar 20, 2014)

HPEVS sent me an e-mail reply right away- excellent service!

HPEVS says that they set the coil driver output up to drive a normal 12VDC automotive cube relay coil. That's for the brake light relay- the main contactor coil driver is set up based on what they sell you when they sell you the motor and controller.

Set up that way, it probably won't pull in a 48 V coil.


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## Caps18 (Jun 8, 2008)

Here are the specs for the relay I am planning to use:

Load Current 5A 
Voltage - Input 35 ~ 72VDC 
Voltage - Load 1 ~ 48 V

I would think the load is the 12V brake light system, but the input would be the 48V from the coil return line.


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## Moltenmetal (Mar 20, 2014)

Caps18- throw it away and use an automotive cube relay. $3, 12V coil driven by the controller, 12V contacts rated for about 30A DC. Available from any car parts place. I installed mine today with contacts in parallel with the pedal switch on the mechanical brakes, and it works great. 

I assume that Crydom relay (which comes up as "page not found" so I can't check the specs on that Digikey link) is a sold state relay, which the controller's coil driver circuit is likely to fry.


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## Caps18 (Jun 8, 2008)

http://www.digikey.com/product-detail/en/ED06F5/CC2232-ND/2665146

Maybe this link would work better.

I'm still not sure what is the right way to hook this up. Maybe there isn't a difference between these two ways to wire it up, but I thought that the relay would be seeing 48V. Maybe I'm wrong, it wouldn't be the first time when it comes to voltage in circuits.

The manual doesn't say much, except to not put the coil return with the KSI, and I'm not using those two together on the KSI relay... 



> KSI input provides power for all low power control circuits, power capacitor precharge (before main contactor turn on), power supply outputs, and high power output drivers. Battery voltage is sensed on the input for the VCL bat- tery discharge function.
> 
> 
> 
> ...



It can operate at (MaxV + 10 V), is coil return like a Ground in the circuit then? I guess I'm not too familiar with sharing a ground when there are two different voltage levels on the circuit.


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## Moltenmetal (Mar 20, 2014)

Drawings 1 and 2 are exactly the same, electrically. They show two relay coils- your main contactor and a new brake light relay, each connected to a coil driver output from the controller, and returning current to the coil return on the controller.

Power comes from the KSI input, which is main pack B+. It is pulse width modulated (turned on and off on a fast duty cycle, rather like what a DC motor controller does) by coil driver pins 3 and 8. The duty cycle is set by programming in the Curtis controller, at a level which is not accessible to adjust via the Spyglass- it is in their "VSL code".

The DC current flows from KSI, through the coil driver circuit inside the controller, through the coil driver pin, through your relay or contactor coil, and returns to coil return pin 13 (which is ultimately connected inside the controller to main pack B-, through some protective circuitry no doubt).

Pin 8 (the one that drives the main contactor) is set up to generate an average of 48 VDC to drive your main contactor relay coil- exactly the same as on mine.

Pin 3 is programmed to generate a PWM signal equal to roughly 12VDC to drive a normal automotive relay.

I can't guarantee that this coil driver circuit will not burn out the input LED of a solid state relay. But I can tell you that a 12VDC automotive cube relay coil connected between pins 3 and 13 works just fine, and does not burn out.


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