How long can a relay be on?

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stanward

Copper - Posts: 57

Joined: April 09, 2003

Location: Hawaii, United States

Posted: April 09, 2003 at 4:55 AM / IP Logged

Hello all,

How long can the coil of a standard automotive relay be energized? I understand that the relay coil will produce heat that determines the lifetime of the relay.

Anyone have an insight to my question?

Thanks,

Stan

greenbroncoguy

Copper - Posts: 299

Joined: March 27, 2003

Location: Florida, United States

Posted: April 09, 2003 at 5:54 AM / IP Logged

i wouldn't tink that a relay would "go bad" just from being left on. the running lights on your automoblie are turned on using a relay when your head lights are on, and some lights are left on a long time wich means that relays are left on a long time also.

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sufferrar

Copper - Posts: 190

Joined: July 17, 2002

Location: Trinidad and Tobago

Posted: April 09, 2003 at 9:11 AM / IP Logged

This has my interest too.

"I'm So Loud It Hertz"

ggrizzle

Member - Posts: 19

Joined: February 19, 2003

Location: United States

Posted: April 09, 2003 at 12:56 PM / IP Logged

I have done a lacthing relay on some neons and i leave them on alot while my car is parked. I have had it installed for about two years now and i have never had no problems. i would think a relay that is on for long periods of time will burn out quicker than one the is just pulsed momentary from time to time. Just my thoughts on the subject. I know that the headlights and parking on vehicles have relays that control them and they last for years and yearsWhat is it exactly you are trying to do, if we know maybe I or someone can better assist you?

g.g.

stanward

Copper - Posts: 57

Joined: April 09, 2003

Location: Hawaii, United States

Posted: April 09, 2003 at 1:49 PM / IP Logged

I'm using a DEI relay, with a 90ohm coil resistance.

I plan to use it to control my aftermarket power windows. The ignition power will switch the relay "on" and I will fuse the supply of the relay before it goes to the window motors.

Thanks for the replies, keep them coming!

Stan

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Joined: March 07, 2002

Location: Louisiana, United States

Posted: April 09, 2003 at 2:18 PM / IP Logged

I've had Bosch and Potter & Brumfield relays connected behind displays that have literally stayed on for years with the exception of a few power outages, but if you want a more accurate figure, check the manufacturer's specifications on the relays you are using. They will provide you with expected mechanical and electrical life ratings (usually at minimum) and typically will be far beyond what you will require. I've yet to have one go bad simply because it was left on too long.

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Haku

Copper - Posts: 204

Joined: November 22, 2002

Location: United States

Posted: April 09, 2003 at 10:06 PM / IP Logged

Think of it this way.... most electic fuel pumps run off a relay.. a standard 30A relay, so whenever the car is running, the relays is "on". Of course, amp draw on the output of the relay, if excessively high, can shorten the life of the relay. These fuel pumps usually draw 8-15A max. So, for most aftermarket applications, a relay will last a very long time.

Hak

Siemens Autostart

ViperATC5

Copper - Posts: 202

Joined: January 17, 2003

Posted: April 09, 2003 at 10:16 PM / IP Logged

when a relay is "on" - that only refers to the relative position of two contacts. When the relay is energized, it "clicks" and the contacts move - technically the relay is at rest untill that energy is gone, then the relay will click again and be back in the rest position. The only time the relay is actually doing anything, is while it is actually switching

cpgoose

Gold - Posts: 1,098

Joined: July 08, 2002

Location: United States

Posted: April 10, 2003 at 8:29 AM / IP Logged

This is interesting....

This is why I'm a little reluctant to implement one of the fuel cutoff methods I saw, which would switch a relay on while the car was running, and stay on while the car was running. I'm a little afraid the relay will die while I'm driving, and the car would shut off.

chuckles

Member - Posts: 39

Joined: February 11, 2003

Location: United States

Posted: April 10, 2003 at 5:34 PM / IP Logged

A relay will last for almost ever, as long as the voltage to the coil, electromagnet, is not exceeded. I've put automatic transfer switches in hospitals and gone back 25 years later and they still have the same relays. The relays control the emergency generator and are latched constantly by the power company so when they loose power the relays drop out and start the generators.

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