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noelk
Joined: 05 Oct 2007
Posts: 10
Location: Canberra, Australia
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 Posted: Mon Dec 17, 2007 5:06 pm Post subject: Battery Contactors |
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I have just started wiring up a Jabiru 3300 installation, which includes a battery contactor. I wanted to test that the basic power wiring was OK before going too far with the wiring, so I connected a bench power supply to the input side of the contactor, and selected the battery position on the master switch. Everything seemed to be working correctly, except that the contactor became quite hot to touch once it had been on for a while. (There was no load on the main bus at this stage, the only current through the contactor was the coil current.) I removed it and replaced it with a second borrowed contactor, with the same result. I also took the contactors out of the aircraft, and checked them on the bench, and again, they became quite hot. Both contactors drew a coil current of about 750 mA.
Is it normal for battery contactors to run hot, or have I encountered two faulty contactors?
Noel Karppinen
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rjquillin
Joined: 13 May 2007
Posts: 123
Location: KSEE
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| Posted: Mon Dec 17, 2007 5:27 pm Post subject: Battery Contactors |
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At 16:59 12/17/2007, you wrote:
| Quote: | Is it normal for battery contactors to run hot, or have I encountered two faulty contactors?
Noel Karppinen |
Do you perhaps have contactors rated for intermittent (starter) service rather than continuous (battery) service?
Ron Q.
[quote][b]
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schaefer(at)rts-services.
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| Posted: Mon Dec 17, 2007 5:59 pm Post subject: Battery Contactors |
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It’s normal for them to be a little too warm to touch.
The current is about right.
Look at this at a 10W heater. It will get warm!
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Noel Karppinen
Sent: Monday, December 17, 2007 6:59 PM
To: aeroelectric-list(at)matronics.com
Subject: Battery Contactors
I have just started wiring up a Jabiru 3300 installation, which includes a battery contactor. I wanted to test that the basic power wiring was OK before going too far with the wiring, so I connected a bench power supply to the input side of the contactor, and selected the battery position on the master switch. Everything seemed to be working correctly, except that the contactor became quite hot to touch once it had been on for a while. (There was no load on the main bus at this stage, the only current through the contactor was the coil current.) I removed it and replaced it with a second borrowed contactor, with the same result. I also took the contactors out of the aircraft, and checked them on the bench, and again, they became quite hot. Both contactors drew a coil current of about 750 mA.
Is it normal for battery contactors to run hot, or have I encountered two faulty contactors?
Noel Karppinen
[quote][b]
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noelk
Joined: 05 Oct 2007
Posts: 10
Location: Canberra, Australia
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| Posted: Wed Dec 19, 2007 1:24 am Post subject: Battery Contactors |
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| Quote: | At 16:59 12/17/2007, you wrote:
>>Is it normal for battery contactors to run hot, or have I
>>encountered two faulty contactors?
>>
>>Noel Karppinen
>
> Do you perhaps have contactors rated for intermittent (starter)
>service rather than continuous (battery) service?
>
>Ron Q. |
Hi Ron
The original contactor came from Aircraft Spruce, and is one of their master relays, rated for continuous use. The other came fom a local LAME (or A&P, I believe, for all you guys in the US). Since I asked for a battery contactor, I'm pretty sure that would also be for continuous use.
Noel
[quote][b]
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noelk
Joined: 05 Oct 2007
Posts: 10
Location: Canberra, Australia
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| Posted: Wed Dec 19, 2007 1:35 am Post subject: Battery Contactors |
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>It's normal for them to be a little too warm to touch. The current is about right. Look at this at a 10W heater. It will get warm!
| Quote: | _____
>>From: owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)
>>[mailto:owner-aeroelectric-list-server(at)matronics.com] ([email]owner-aeroelectric-list-server(at)matronics.com%5D[/email]) On Behalf Of Noel
>>Karppinen
>>Sent: Monday, December 17, 2007 6:59 PM
>>Subject: Battery Contactors
>>I have just started wiring up a Jabiru 3300 installation, which includes a
>>battery contactor. I wanted to test that the basic power wiring was OK
>>before going too far with the wiring, so I connected a bench power supply to
>>the input side of the contactor, and selected the battery position on the
>>master switch. Everything seemed to be working correctly, except that the
>>contactor became quite hot to touch once it had been on for a while. (There
>>was no load on the main bus at this stage, the only current through the
>>contactor was the coil current.) I removed it and replaced it with a second
>>borrowed contactor, with the same result. I also took the contactors out of
>>the aircraft, and checked them on the bench, and again, they became quite
>>hot. Both contactors drew a coil current of about 750 mA.
|
Thanks, Richard. That makes me feel more confident that there is no real problem.
Noel Karppinen
[quote][b]
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Peter Laurence
Joined: 10 Jan 2006
Posts: 50
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| Posted: Wed Dec 19, 2007 5:12 am Post subject: Battery Contactors |
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Noel
Check the resistance on the coil. A continuous duty contactor will show a resistance of 10 to 18 ohms. An intermittant one will show 3 to 5 ohms
Peter
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nuckolls.bob(at)cox.net
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| Posted: Wed Dec 19, 2007 5:51 am Post subject: Battery Contactors |
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At 08:32 PM 12/19/2007 +1100, you wrote:
| Quote: | "Richard T. Schaefer"
<<mailto:schaefer(at)rts-services.com>schaefer(at)rts-services.com> wrote:
>It's normal for them to be a little too warm to touch. The current is
about right. Look at this at a 10W heater. It will get warm!
|
Dead on target Richard. In times past that this
conversation was conducted, I went to the bench
and held one of our stock battery contactors
in an energized condition until its temperature
stabilized. See:
http://www.aeroelectric.com/Pictures/Contactors/Battery_Contactor_Temps_1.jpg
The effects of temperature rise were obvious
too in terms of the current draw for the
contactor. Room temperature current draw
was on the order of 0.8 amps. But after
two hours of operation . . .
http://www.aeroelectric.com/Pictures/Contactors/Battery_Contactor_Temps_2.jpg
. . . current draw is down to about
0.56 amps. This phenomenon is a function
of the positive temperature coefficient of
copper wire used to wind the coil. As the
device warms up, it's resistance goes up
and the current goes down.
In terms of a gross test of a contactor's
intermittent or continuous duty status, if
it's still functioning after 5 minutes of
continuous operation then it MUST be a
continuous duty device. The intermittent
duty devices tailored for starter motor
control would have spit out all their smoke
after 5 minutes!
It's not often that we are physically able
to "feel" a piece of operating equipment and
find that it's too hot to touch but it can
raise concerns when the device is not
OBVIOUSLY designed to run hot . . . like
engines and exhaust stacks.
The contactors that dissipate about 10
watts don't heat up real fast . . . but in
still air they'll get pretty toasty.
Bob . . .
| Quote: |
>>I have just started wiring up a Jabiru 3300 installation, which
includes a
>>battery contactor. I wanted to test that the basic power wiring
was OK
>>before going too far with the wiring, so I connected a bench
power supply to
>>the input side of the contactor, and selected the battery
position on the
>>master switch. Everything seemed to be working correctly, except
that the
>>contactor became quite hot to touch once it had been on for a
while. (There
>>was no load on the main bus at this stage, the only current
through the
>>contactor was the coil current.) I removed it and replaced it
with a second
>>borrowed contactor, with the same result. I also took the
contactors out of
>>the aircraft, and checked them on the bench, and again, they
became quite
>>hot. Both contactors drew a coil current of about 750 mA.
|
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noelk
Joined: 05 Oct 2007
Posts: 10
Location: Canberra, Australia
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| Posted: Thu Dec 20, 2007 2:52 am Post subject: Battery Contactors |
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Hi Peter
The resistance of mine is 16 Ohms when cold, so it is right in the ball park.
Noel
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noelk
Joined: 05 Oct 2007
Posts: 10
Location: Canberra, Australia
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| Posted: Thu Dec 20, 2007 2:54 am Post subject: Battery Contactors |
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Thanks for that comprehensive reply, Bob. Now I am completely convinced that there is nothing to worry about.
Noel
---
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