---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 11/08/18: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:20 PM - Re: Re: Dual Battery Dual Alternator Power Distribution System (Bill Watson) 2. 05:15 PM - Re: Dual Battery Dual Alternator Power Distribution System (lwesterlund) ________________________________ Message 1 _____________________________________ Time: 02:20:24 PM PST US Subject: Re: AeroElectric-List: Re: Dual Battery Dual Alternator Power Distribution System From: Bill Watson I do actually use the redundant feeds on my GRT screens but each unit is redundantly connected to 1 bus. One feed goes through a power stabilizer and the other directly to the bus. One of the things I wanted to be able to do was to run parts of avionics bus with engine off, without endangering a start by running down my battery. I knew from my previous IFR flying experience that being able to run the panel without killing the starter battery was useful in fllight planning and waitiing out local weather. I have (3) GRT HX MFDs. They do not have integral on/off switches and I chose not to add any. They are all on 1 bus along with the the G430. When that bus is switched on, one battery starts to drain pretty quickly. When I first installed them I connected them to only 1 bus and things worked as desired. During some upgrades and load rebalancing I decided to connect them to both buses without really thinking it through. I mean, belts and suspenders must be better, right? That was a mistake because now I could not control where the load from the (3) MFDs went unless I turned off 1 bus (and during flight planning and clearance receptions I ideally want the whole panel with dual comms up and running). But I did add a power stabilizer to avoid brownouts during tough starts. With that added, I did use the redundant feeds to connect to the power stabilizer and the bus directly, with both connections fed from the same bus. That now works as desired. As as been discussed elsewhere here, the proliferation of backup batteries can be a problem. Each of those batteries should be maintained as carefully as the main battery in a single battery system. What's the use of the backup if it doesn't perform in a predictable way when needed? So I will soon be running with zero backup batteries and depending entirely on the robustness of the Z-14. Even my backup EFIS will depend entirely on the Z-14 for power. It seems that one key thing I had to understand about the bus architectures and the Z-14 in particular is that they are designed and built in a manner as robust as say the control system. There are a few fat wire connections at a few points with only a few very reliable components that could possibly fail. The failure of an alternator or controller is signaled and bypassed while the battery keeps everything running, etc. With dual buses, batts and alts, having redundant power feeds on individual components is redundant. One relies on the redundant bus architecture to handle power failures. On 11/5/2018 2:03 PM, lwesterlund wrote: > > Mauledriver, > > Thanks for the quick and detailed response. > > I completely agree that Z-14 is an amazingly robust architecture. The one limitation, as I see it, is that it doesnt take advantage of the dual power feeds for capable equipment. You wrote: > > But I initially had my dual input gear (the 3 GRTs and the G430) connected to > both buses but over time came to understand that it was unnecessary > redundancy with the cross feed capability and sometimes it was a > liability. Maybe we can discuss the experiences that led me there later. > > Please help me to understand why using the redundant feeds might be a bad idea. Thanks. > > Lance > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=484447#484447 > > --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 2 _____________________________________ Time: 05:15:25 PM PST US Subject: AeroElectric-List: Re: Dual Battery Dual Alternator Power Distribution System From: "lwesterlund" Again, thanks for the detailed reply. Your approach certainly makes sense when using a conventional power bus. Afterall, what could possibly go wrong with a solid brass bus bar? Its darn near bullet-proof. As I asked in my reply to Bobs response, what if you are using the VPX system? As robust as it is, its still not as failure proof as a solid hunk of metal. Even with dual power feeds, it becomes a single point of failure. Hence my proposed design. If theres a better way that leverages that technology, Im all ears. But I dont think you can just plop the VPX into the Z-14 architecture without modifying it to resolve the new SPOF. I appreciate that the more conservative approach from a power system risk management perspective is to simply use Z-14 as published. Im interested in the VPX because, IMO, it helps to reduce other elements of risk. For instance, it prevents deploying the flaps above Vfe, will detect and alert an open circuit (like the pitot heater), and will control wig-wag lights. Any thoughts or suggestions or insights on how to include a VPX in a dual bat dual alt system would be much appreciated. Lance Read this topic online here: http://forums.matronics.com/viewtopic.php?p=484638#484638 ------------------------------------------------------------------------------------- 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.