---------------------------------------------------------- RV8-List Digest Archive --- Total Messages Posted Sat 01/28/12: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:55 AM - battery selection (Larry Bowen) 2. 10:40 AM - Battery choice par deaux (Stan Loer) ________________________________ Message 1 _____________________________________ Time: 05:55:00 AM PST US Subject: RV8-List: battery selection From: Larry Bowen Thanks for the input Carl. You've got me thinking. I was mostly focused on endurance, I have to admit. I'm also using a VP-X which accommodates management of a second battery. So I may decide to take advantage of that. Klaus is the one that prompted me to consider one alt, one bat. His website talks about the endurance of your main battery being enough to get you home. There are many single points of failure. Some of them are best addressed by ongoing inspection and maintenance. Belt and suspenders vs simplicity.. .. I changed my LSI mount to allow for some more ventilation. Thanks for the input. -- Larry Bowen Larry@BowenAero.com http://BowenAero.com On Fri, Jan 27, 2012 at 5:15 PM, Carl Froehlich wrote: > > In a single alternator, single battery install the battery is primary and the alternator charges the battery, it is not a backup to the battery. I few thoughts: > > 1. Look at where your alternator connects to your battery. I offer that there are at least two points in the system where a single post failing (loose, melted, shorted) takes down your entire electrical system. Not long ago a twin engine plane (two alternators and two batteries) had a total loss of electrical power when the common post on the master relay failed. > > 2. Look at the single post for ground on your battery. Again a single failure will lead to total loss of power. > > 3. Many alternator installs do not run well without a battery floating on them for reference (source) voltage. Some do, some don=92t. > > 4. For a simple example your master relay fails open. Unless you have dedicated auxiliary feeds from the battery you have lost all power. > > > I suspect many dual battery installs have only increase capacity to offer, not added redundancy. Again the objective is to not have a single failure bring down all your power. It is the system that counts, not the individual components. > > > The most reliable electrical component in your plane is the battery. This is why I have two batteries feeding independent master relays and dedicated smaller relays for the panel, and a single alternator. The odds of an alternator failing (I had two go south in my 8A over the last 9 years) is way higher than a battery failing in flight. Now if you crank a battery(s) into the dirt and then take off hoping the alternator will charge it (before the alternator craps out), you are just asking for trouble. > > > For a dual Lightspeed install some sort of battery backup for the ignition is mandatory. The simple Panasonic battery with the diode isolation as illustrated in Klaus=92 manual is the bare minimum. It will a t least let you land at the closest runway instead of an engine out landing in a field. For an all electric panel, redundant power is mandatory as well. > > > BTW ' I took a look at your website link. So you know, the Lightspeed ignition box generates some heat. As you have them mounted back to back you might want to give Klaus a call to see if this reduction in heat transfer surface is a problem or not. In my 8A I had them mounted aft of the fire wall on spacers to allow air to get at the back of the box. I also had insulation on the cabin side of the firewall to isolate engine heat. > > Carl > > > From: owner-rv8-list-server@matronics.com [mailto: owner-rv8-list-server@matronics.com] On Behalf Of Larry Bowen > Sent: Friday, January 27, 2012 3:57 PM > > To: rv8-list@matronics.com > Subject: Re: RV8-List: battery selection > > > I'm already committed to the dual LSI. PMags were still wet behind the ears when I made the decision. > > > Alternator is primary, main battery is backup. How is that not practical? Educate me. > > -- > Larry Bowen > Larry@BowenAero.com > http://BowenAero.com > > > On Fri, Jan 27, 2012 at 3:33 PM, Carl Froehlich < carl.froehlich@verizon.net> wrote: > > No backup battery on a LightSpeed ignition install is not practical. > > For no a backup battery system (or one with a back up battery) a dual P-Mags install is a better approach. If you want, I can tell you the name of the person I gave my dual Lightspeeds to when I yanked them off my 8A (replaced with P-Mags). You can get them real cheap. > > Carl > > > From: owner-rv8-list-server@matronics.com [mailto: owner-rv8-list-server@matronics.com] On Behalf Of Larry Bowen > Sent: Friday, January 27, 2012 3:03 PM > To: rv8-list@matronics.com > Subject: Re: RV8-List: battery selection > > > Can't help you on the battery, I've only used the 680. > > > I'll have all glass and dual LSI in the RV-7, and I'm actually considering one alt and one battery. Crazy, or just practical? TBD... > > > In the RV-8, I put my Pointer ELT under the VS. No added structure needed and helped a little with fwd CG. > > > Cheers, > > -- > Larry Bowen > Larry@BowenAero.com > http://BowenAero.com > > On Fri, Jan 27, 2012 at 2:26 PM, Stan Loer wrote: > > Has anyone installed the Odyssey PC625 battery? I know that the PC680 is more common, but I'm looking at a dual installation with one battery forward and the other aft. The 625 is slightly smaller and lighter than the 680. My 8 will be all electric, no steam gauges, and set up for day/night VFR, so a dual battery installation makes more sense to me than a back-up alternator. Seems to me that dual paralleled PC625 batteries should provide plenty of get-home power in case of an alternator failure, even at night, but my electrical expertise is limited and I'll take all the help I can get. > > > While I'm at it, a question re ELT mount locations. I've seen several mounted on the "hat shelf". This is tempting as it's very > > convenient, but the shelf is kinda flimsy. Beef it up? I'm also looking at possibly mounting it on brackets off the side of the aft battery box. More complex, but maybe a better choice. > > > et="_blank">http://www.matronics.com/Navigator?RV8-List > > tp://forums.matronics.com > > _blank">http://www.matronics.com/contribution > > > http://www.matronics.com/Navigator?RV8-List > > http://forums.matronics.com > > http://www.matronics.com/contribution > > > et="_blank">http://www.matronics.com/Navigator?RV8-List > > tp://forums.matronics.com > > _blank">http://www.matronics.com/contribution > > > http://www.matronics.com/Navigator?RV8-List > > http://forums.matronics.com > > http://www.matronics.com/contribution > > =========== =========== =========== =========== > -- -- Larry Bowen Larry@BowenAero.com http://BowenAero.com ________________________________ Message 2 _____________________________________ Time: 10:40:53 AM PST US From: "Stan Loer" Subject: RV8-List: Battery choice par deaux Thanks much for the feedback. It's great to have a pool of expertise to tap into for us novice builders. Not to belabor the point, but just to add some specifics not included in my last post: I'll be installing at least one P-Mag and one E-Mag. Maybe dual P-Mags. Circuit protection will be through a VPX-Sport. Each battery will feed its own "always hot" battery bus which will supply the mags and at least the radio. The Dynon Skyview installation will include the back-up battery option. I want to be able to turn off both battery master switches and still have get home power in the unlikely event of a contactor failure. May not however, be night legal depending on how much complexity I'm willing to add with back-up circuits. Stan Loer RV-8 very slow QB ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv8-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV8-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/rv8-list Browse Digests http://www.matronics.com/digest/rv8-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.