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Is a battery contactor really needed?

 
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nuckolls.bob(at)aeroelect
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PostPosted: Wed Apr 26, 2017 2:20 pm    Post subject: Is a battery contactor really needed? Reply with quote

At 09:39 AM 4/26/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: "eschlanser" <eschlanser(at)yahoo.com>

It's been a couple of years since I designed my plane's electrical system with no battery contactor.

What brand or style battery contactor is preferred/acceptable for a OBAM airplane with a Z - (x) wiring system? I installed the barrel style starter contactor but replaced it with the flat style when Bob recommended that change. Now I'm wondering if there's a new style of battery contactor that has superseded the barrel style.

The 'whisky barrel' style contactors have
a track record that goes back nearly 100
years. Process and materials improvements
have been applied throughout that time . . .
they are of excellent value.

The recommended change for starter contactors
was based on the fact that even low duty-cycle
whisky-barrel devices featured large area, low
pressure contact surfaces compared to the
more modern devices designed specifically for
starter control. But assuming you've got a
Plan-B in place for managing a battery contactor
failure (or its wiring, switch, terminals, etc)
then the style is of little significance.

If it were my airplane, the battery contactor
would be one of these . . .

http://tinyurl.com/koq788n

. . . or its several cousins.

Contactor failure in the whisky-barrel styles
is rare and it usually announces an impending failure
with finicky starter performance. So the first time
you get an intermittent starter behavior accompanied
by a black panel or 'chattering' starter contactor,
then it's time to replace the critter (assuming your
battery satisfactorily passes cap and load tests).


Quote:
One advantage to eliminating the battery contactor is keeping the voltage available for starting that would be lost to the battery contactor.

energy demands of a battery contactor
are trivial compared with that required
to energize the starter . . . hence
no energy conservation benefits there . . .



Bob . . .


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