---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 05/02/09: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:24 AM - Re: Switch (Robert L. Nuckolls, III) 2. 08:20 AM - Grounding Batteries (Dan Ballin) 3. 09:22 AM - Re: Grounding Batteries (ROGER & JEAN CURTIS) 4. 11:57 AM - Re: Grounding Batteries (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:24:19 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Switch At 04:05 PM 5/1/2009, you wrote: >Hi everyone, > >I bought a handful of 1-2 switches for various items i.e., landing >lights, strobes, left & right mag, etc. My question is can I use >the same switch for the master and alternator? Looks like sometimes >people are using the 2-3 and only having one switch - being >multifunctional. Since I now have a small surplus of 1-2 switches, I >thought I might just use them instead. This will be on the Jab 3300 >engine. As you can tell I am ignorant to this area... but I am >trying to learn! Thanks! > The first batteries to go into aircraft were charged by generators. Unlike many if not most alternators, generators would come on line and run by themselves as a useful power source. It was common and practical to control the generator and battery with their own separate switches. When alternators began to replace generators in the 60s . . . we found that product of the day was best operated with a battery on line. This insured that (1) the alternator would have excitation power available to go to work and (2) there was a battery always available to avoid stalling a self-excited alternator when hit with a hi-inrush load (like landing gear motors and/or landing lights). Hence the development of the infamous "split- rocker" master switch for single engine light aircraft. Emacs! This product's rockers were mechanically interlocked to prevent an alternator from being on line without a battery . . . yet allows the battery to be on without the alternator. This functionality is emulated by the use of the progressive transfer 2-10 style switch. Alternatively, some Z-figures show a 2-3 that brings the battery and alternator ON and OFF together. This is okay too as long as you have a means by which the externally excited alternator can be shut OFF for ground maintenance activities. In the case of Z-13/8 I suggest a 2-3 switch when paired with the crowbar ov protection that calls for a pullable circuit breaker co-located with the DC POWER MASTER switch. In the switch panel options drawing at . . . http://www.aeroelectric.com/PPS/Switch_Panels/spanel.pdf . . . all configurations illustrated show a 2-3 DC PWR MASTER and a 5A pullable breaker. In this drawing . . . http://www.aeroelectric.com/PPS/Switch_Panels/Switches.pdf . . . the 2-10 switch is suggested for a DC PWR MASTER. The pullable breaker allows for disabling the alternator for extended ground operations of the electrical system with the engine not running. You can certainly used independent switches to control the battery and alternator. However, it is incumbent upon you to understand the limitations of the equipment items you've installed and to educate yourself (and anyone else who might fly your airplane) as to the proper operation of those switches consistent with those limitations. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 2 _____________________________________ Time: 08:20:26 AM PST US Subject: AeroElectric-List: Grounding Batteries From: Dan Ballin I am working on a Lancair Legacy (ie carbon frame) and basically the Z-14 system 24v with two batteries. The main will have a larger battery and 60A alt, the aux with a smaller B&C battery and an SD20. The batteries will be behind the seats with the power grid contactors. My plan is to run a large ground to the engine/starter for the main (4AWG) and a 10AWG for the aux to a ground stud on the firewall (which then gets connect to the engine case). So here is my question. I want to have a local ground back by the batteries for both main and aux components. Should I have a separate ground bus for each battery? or can I attach both neg terminals to a single ground bus. It seems to me that this does add some redundancy to the ground path, but it also will hide any failure in the ground leads. Thoughts? Thanks Dan Ballin LEG2 #286 ________________________________ Message 3 _____________________________________ Time: 09:22:05 AM PST US From: "ROGER & JEAN CURTIS" Subject: RE: AeroElectric-List: Grounding Batteries I am working on a Lancair Legacy (ie carbon frame) and basically the Z-14 system 24v with two batteries. The main will have a larger battery and 60A alt, the aux with a smaller B&C battery and an SD20. The batteries will be behind the seats with the power grid contactors. My plan is to run a large ground to the engine/starter for the main (4AWG) and a 10AWG for the aux to a ground stud on the firewall (which then gets connect to the engine case). So here is my question. I want to have a local ground back by the batteries for both main and aux components. Should I have a separate ground bus for each battery? or can I attach both neg terminals to a single ground bus. It seems to me that this does add some redundancy to the ground path, but it also will hide any failure in the ground leads. Thoughts? Thanks Dan Ballin LEG2 #286 Dan, You said you are running a 24V system. Are you using 2 - 24V batteries or 2 - 12V batteries? If using 2 - 12V then they will be in series for the 24V system, meaning that the Neg. terminal of one battery will be at ground and the pos terminal of that battery will attach to the neg terminal of the second battery, and the pos of the second battery will be your 24V supply. If you are using 2 - 24V batteries, then the neg terminals of the two batteries can be attached together and to ground, and the pos terminals will give you 2 independent 24V sources. Roger ________________________________ Message 4 _____________________________________ Time: 11:57:48 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Grounding Batteries At 10:17 AM 5/2/2009, you wrote: >I am working on a Lancair Legacy (ie carbon frame) and basically the >Z-14 system 24v with two batteries. The main will have a larger >battery and 60A alt, the aux with a smaller B&C battery and an >SD20. The batteries will be behind the seats with the power grid >contactors. My plan is to run a large ground to the engine/starter >for the main (4AWG) and a 10AWG for the aux to a ground stud on the >firewall (which then gets connect to the engine case). So here is >my question. I want to have a local ground back by the batteries >for both main and aux components. Should I have a separate ground >bus for each battery? or can I attach both neg terminals to a single >ground bus. It seems to me that this does add some redundancy to >the ground path, but it also will hide any failure in the ground >leads. Thoughts? Ground wires can and should be crafted with the robust-as-hell philosophy in mind. I.e., as reliable as prop bolts. This means take some extra care in crafting the conductors, routing for mechanical isolation from risks and bolting things together with metal lock nuts or LockTite on threads. One conductor from crankcase to firewall ground stud. One conductor from firewall ground to a battery ground behind seats (small forest of tabs or perhaps just a stud on which all rear grounds mount). Two conductors from rear ground location to each of the (-) terminals of the batteries. You might want to consider 2AWG welding cable for the fat ground wires . . . MUCH more pleasant to work with than 22759. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ------------------------------------------------------------------------------------- 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.