Author Topic: Thoughts on using a relay for power  (Read 6027 times)

Offline Pukwudji

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Thoughts on using a relay for power
« on: March 21, 2011, 02:29:55 PM »
All of the articles I've read on mounting a radio mobile say to connect the power directly to the battery.  I can see a downside here of potentially draining the battery if you neglect to turn off the radio.

What I'm muddling over is using a single-pole single-throw normally open relay in the power line connected to an accessory location in the fuse panel.  This way the radio is off unless the key is on or turned to ACC.  The relay gets power and closes the circuit to provide power to the radio direct from the battery.

Has anyone done something like this?

Brian

Offline phlat

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Re: Thoughts on using a relay for power
« Reply #1 on: March 25, 2011, 06:56:05 PM »
As long as it's a 12VDC coil to run off the car's acc power, and the power side is rated to 30A@12VDC as well, it could be done.  But if your talking about a normal mobile rig, these things only suck 1A or so on standby. Even less if you have a powersave feature to turn on.
 Unless you aren't in your car for days at a time, it won't drain the battery if you leave it on.

Offline JerseyVince

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Re: Thoughts on using a relay for power
« Reply #2 on: March 25, 2011, 10:13:38 PM »
Check your accessory power fuse location and see if it has power all the time or key/ACC on only? Most vehicles today have an power outlet not lighter plug that powers up only when the key is on or in accessory and some have the fuse for it able to be moved over to change it to either on all the time or key on only. check your owners manual for specs on the power outlet fuse. You could just wire it to the outlets wiring depending on what your radio draws transmitting

Offline Carl

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Re: Thoughts on using a relay for power
« Reply #3 on: February 22, 2015, 12:08:53 PM »
Most radios have a menu for AUTO POWER OFF usually with 1 hour incremental settings...read your manual.

What radio do you have?

Offline Pukwudji

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Re: Thoughts on using a relay for power
« Reply #4 on: March 02, 2015, 11:40:13 AM »
Yaesu FT-7900 and FT-857d.  I'll look into that as an option as I'd rather have the ability to have it wired direct to the battery instead of based on ignition state for those times I want to operate without the extra drain related to having the key on.

Offline Carl

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Re: Thoughts on using a relay for power
« Reply #5 on: March 02, 2015, 12:04:58 PM »
Yaesu FT-7900 and FT-857d.  I'll look into that as an option as I'd rather have the ability to have it wired direct to the battery instead of based on ignition state for those times I want to operate without the extra drain related to having the key on.

FT 7900 ,has auto power off on Page 60 of the manual ( it is MENU ITEM #1 and has setting from 1/2 hour to 12 hours)

The FT 857 has auto power off also (MENU #007  APO TIME  1 hour to 6 hours)

Looks like you will 'get 'er done'

Offline armymars

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Re: Thoughts on using a relay for power
« Reply #6 on: March 02, 2015, 05:45:43 PM »
I have a FT2900 that would pull power all the time. I would have to replace my car battery every 2 1/2 years because of it. I finely put in a double pole , double throw switch to stop it from happening.

Offline Carl

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Re: Thoughts on using a relay for power
« Reply #7 on: March 03, 2015, 06:00:26 AM »
I have a FT2900 that would pull power all the time. I would have to replace my car battery every 2 1/2 years because of it. I finely put in a double pole , double throw switch to stop it from happening.

Page 63 of the manual tells you how to set Automatic Power Off (SET MENU item ONE)feature
from 1/2 hour to 8 hours...but a dead auto battery every 2 to 3 years is about normal unless
you purchase premium batteries as the receiver only draws .3 squelched to max of .7 amps at full audio out..
You can't kill a 50 amp/hour battery with 10 amp hour draw or so overnight unless it is already compromised.

Offline armymars

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Re: Thoughts on using a relay for power
« Reply #8 on: March 03, 2015, 11:31:12 AM »
  Thank Carl,
  The radio is too big to put in my present car so I bought a JT 270M that will fit in my consul. 73

Offline Pukwudji

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Re: Thoughts on using a relay for power
« Reply #9 on: March 03, 2015, 11:42:48 AM »
Could you run two parallel circuits?  One on a switch and another on a relay?  That way when the car is on the radio could always be on, but if the car is off you have the option of the switch to turn the radio on. 

If one were really industrious I could see running a relay on the line with the switch that is connected to a battery monitor that could turn off the radio if the battery got below a certain charge level (bypassable in the even of an emergency).  Or if you had remote start capabilities in your auto you could possibly have the battery monitor trip the circuit to start the car automatically when the battery got low... 

Okay, those last couple of ideas are just rambling thought streams, but I thought I'd throw them out to inspire more thoughts.

Offline Carl

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Re: Thoughts on using a relay for power
« Reply #10 on: March 03, 2015, 11:46:58 AM »
  Thank Carl,
  The radio is too big to put in my present car so I bought a JT 270M that will fit in my consul. 73

That radio is cute as a bug and 10 watts is great for most repeaters and such,actually will work as good as higher powered radios in most all the worst of conditions(I rarely use more than 5 watts for repeaters anyway)

Offline Carl

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Re: Thoughts on using a relay for power
« Reply #11 on: March 03, 2015, 11:55:41 AM »
Could you run two parallel circuits?  One on a switch and another on a relay?  That way when the car is on the radio could always be on, but if the car is off you have the option of the switch to turn the radio on. 

If one were really industrious I could see running a relay on the line with the switch that is connected to a battery monitor that could turn off the radio if the battery got below a certain charge level (bypassable in the even of an emergency).  Or if you had remote start capabilities in your auto you could possibly have the battery monitor trip the circuit to start the car automatically when the battery got low... 

Okay, those last couple of ideas are just rambling thought streams, but I thought I'd throw them out to inspire more thoughts.

Why add all that extra when the RADIO HAS AUTO POWER OFF AND YOU TIE IT TO THE BATTERY? It just needs to be set to power down after 1 hour of non-use and as it runs direct from the battery ,it will run with the car running ,or not...

Why add relays ,switches and wires (and FIRE HAZARDS) that do NOTHING to improve the operation of the radio?
The radio on receive simply will not run a battery down with the average,under half amp current,needed in a 24 hour period and the auto power off will shut it down just fine.