[Oeva-list] Should I use an intermittent contactor ....

jray3 at aol.com jray3 at aol.com
Mon Sep 25 12:25:54 PDT 2006


I have a slightly different plan that I've already run past a few of you, so here goes for general feedback.
Since I'll be using a pre-hairball Zilla 1400 with no keyswitch input, I had to come up with my own.  The idea is to use an EV 200 as my main contactor, which will pull in as low as 9V, and hold down to 6V.  Bench tests have worked with the following:  Use a small regulated dc-dc to provide 7.5 volts to the contactor at all times the keyswitch is "ON".  This will not be enough voltage to pull the contactor in, but will keep the main contactor energized until turned off by the keyswitch, inertia switch, or 'big red button'.  To start the car, the keyswitch will be used as with the original ICE starter solenoid to provide momentary 12V to the contactor, bringing it in with a nice-crisp 14.5V.  The keyswitch 'on' will also provide juice for controller precharge.  I've yet to figure out a time delay or voltage sensor to automatically delay the "START" feature until precharge is complete, but a countdown timer or voltage readout should be simple enough for 'manual' start delay.  
 
Cheers, 
Jay Donnaway



----------------------------------------------------------------------

Adan:

I think you should use a continuous duty cycle rated coil. It will be energized 
the whole time you are driving your car, right? An intermittant duty cycle rated 
coil may get too hot.

Here is a description I found:
"Duty Cycle ? The duty cycle of your application is the ratio of the "on-time" 
divided by the total time for one complete cycle (on + off).  Duty cycle is 
usually expressed as a percentage or a fraction (50%, 100%).  A more simplistic 
representation of duty cycle is to call < 100% duty solenoids "Intermittent" and 
100% duty cycle solenoids "Continuous".  All intermittent duty solenoids (< 100% 
duty cycle) also must have a maximum "on-time" allowed to avoid overheating that 
can eventually lead to a burned out coil.  The "on-time" must not exceed the 
power dissipation limits of the coil.  Proper heat sinking and/or additional 
cooling improves heat dissipation which allows a broader duty cycle range.  Very 
close attention must be paid to the maximum "on-time" data provided in 
conjunction with the duty cycle calculation to avoid damaging your solenoids.  
For example, although an application with a one hour cycle time and a 3 hour 
off-time might calculate to a 25% duty cycle, thi!
s is not realistic in practice. A more realistic solenoid application might be 
an on-time of one second and an off-time of 3 seconds for the same 25% duty 
cycle."

Rick Barnes
Aloha, OR

=====================
From: Adan Vielma <vielma at lclark.edu>
Date: 2006/09/22 Fri AM 10:40:58 CDT
To: oeva-list at oeva.org
Subject: [Oeva-list] Should I use an intermittent contactor or a continous  for 
the starter?

Hi!I recently was doing some research into the component design for an ev and 
have a question on contactors.?For the starter contactor, basically the one that 
when you turn the key it is activated so that the battery pack power is now 
connected to the motor controller, would you use an intermittent coil-type 
contactor or a continuous coil-type one??The item I'm looking at is the SW-200 
Single Pole Single Throw, Normally Open contactor from:http://www.tecknowledgey.com/catalog/product_info.php?cPath=57_61&products_id=530?They 
said they only have the continuous coil-type in stock and not the intermittent. 
I was a bit confused as to which coil-type is used in normal EV conversions for 
the starter or other contactors.?If you can answer this question, I'd be more 
than happy.Thanks so much!Sincerely,Adan Vielma

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