---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 07/18/14: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:17 PM - Are 'serial' contactors really needed? (Charlie England) 2. 02:26 PM - Re: battery choice (GLEN MATEJCEK) ________________________________ Message 1 _____________________________________ Time: 12:17:04 PM PST US Subject: AeroElectric-List: Are 'serial' contactors really needed? From: Charlie England 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 _____________________________________ Time: 02:26:21 PM PST US Subject: AeroElectric-List: Re: battery choice From: GLEN MATEJCEK >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 ... > >...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.... ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.