Today's Message Index:
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1. 12:17 PM - Are 'serial' contactors really needed? (Charlie England)
2. 02:26 PM - Re: battery choice (GLEN MATEJCEK)
Message 1
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Subject: | Are 'serial' contactors really needed? |
Someone's recent question/comment about master & starter contactors caused
my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto
engine conversion in an RV-7.
Given the typical automotive starter with self-contained contactor/bendix,
and a starter contactor, could a case be made for switching the cockpit
loads with smaller (lower coil current draw) contactors or even heavy duty
switches, and using only the heavy starter contactor between the battery &
starter?
I'm envisioning the starter button activating both the contactor and the
starter's built-in contactor. This way, if either sticks, current would
still be removed from the starter when the button is released. There would
be no voltage available on the starter's heavy wire except during starting,
as is current practice (pardon the pun). The only failed-on single point
should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more
importantly, saving the 2+amps of draw by the normal master contactor. If I
elect to go with a single alternator (weight, simplicity), the 2 amp draw
of the main contactor is a significant percentage of load in a failed
alternator situation. Note that similar engine installs have flown for 45
minutes or more (typically plenty of time to find a runway) while operating
'battery only' using common 18-20 AH SLA battery installations.
Thoughts?
Charlie
Message 2
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Subject: | Re: battery choice |
>Finally got the plane back together yesterday from the panel upgrade,
>and am reporting back to the list with the results. I installed one of
>these as the main battery:
>
http://www.amazon.com/gp/product/B001G8FY38/ref=oh_aui_>>detailpage_o07_s00?.ie=UTF8&psc=1
<http://www.amazon.com/gp/product/B001G8FY38/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1>
...
>
>...I was only able to do taxi testing yesterday due to weather, however,
>the UB12220 battery turned the engine over just as fast as the previous
>B&C battery, so no issues with cranking power (in summer at least).
>I'll let you know more as I test further.
FWIW, I installed a pair of those in my as yet unfinished -8. It seems my
battery tender jr smoked them....
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