---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 03/05/17: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:37 AM - Re: BATTERY FUSE (Eric Page) 2. 12:54 PM - Eye protection required (Art Zemon) 3. 01:15 PM - Re: BATTERY FUSE (Robert L. Nuckolls, III) 4. 03:16 PM - Re: BATTERY FUSE (user9253) 5. 11:01 PM - Re: BATTERY FUSE (Bill Allen) ________________________________ Message 1 _____________________________________ Time: 08:37:26 AM PST US Subject: AeroElectric-List: Re: BATTERY FUSE From: "Eric Page" One thing that wasn't mentioned in the other responses... I'm sure you're aware -- but your friend clearly is not -- that a "35-amp battery" is in no way limited to a maximum current output of 35 amps. That number is an expression of battery capacity: in this case 35 ampere-hours. A battery's ability to grunt large output currents depends on its internal resistance, which will vary with chemistry, physical construction, temperature, age, and so on. A lead-acid starting battery is typically capable of supplying hundreds of amps. Eric user9253 wrote: > A friend of mine is building a plane with an 8 cylinder automotive engine. I noticed that he had installed a 100 amp ANL fuse in series with the battery cable. The fuse is located 6 inches from the battery and all battery current will go through that fuse including starter current. I asked my friend if that 100 amp ANL will handle the starter current. His response was, "It's a 35 amp battery." [SNIP] > Read this topic online here: http://forums.matronics.com/viewtopic.php?p=466889#466889 ________________________________ Message 2 _____________________________________ Time: 12:54:55 PM PST US From: Art Zemon Subject: AeroElectric-List: Eye protection required This slip of paper came with my transponder antenna. Today I have learned that I need eye protection to read AC43.13-2A =F0=9F=98=8E -- Art Z. Sent from my phone. Please excuse brevity and bizarre typos. ________________________________ Message 3 _____________________________________ Time: 01:15:41 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: BATTERY FUSE At 10:21 AM 3/4/2017, you wrote: > >A friend of mine is building a plane with an 8 cylinder automotive >engine. I noticed that he had installed a 100 amp ANL fuse in >series with the battery cable. The fuse is located 6 inches from >the battery and all battery current will go through that fuse >including starter current. I asked my friend if that 100 amp ANL >will handle the starter current. His response was, "It's a 35 amp >battery." I told him that a 100 amp ANL might not handle starting >current. He said that if it doesn't, he will replace it with a 150 amp. > I think that the fuse will need to be bigger, like 200 amp or > more. Actually I do not think that there should be a fuse in > series with the battery cable at all. It is one more thing to fail > and it adds resistance to the battery cranking circuit. How can I > convince my friend that fuse is not necessary or even desired? If > he will not change his mind, what size ANL fuse should he use? Fuses are cheap, after he pops the first one, he'll discover that upsizing the limiter is indicated. Over a century of experience and product evolution it was rationally deduced that fat wires in light aircraft do not benefit from the addition of over current protection. Consider that hard-fault protection for battery excited fat-wires can exceed 1000 amps. Okay, what's a hard fault? Get out your hammers, chisels and pry-bars. What would you do to create a connection to any 'grounded' feature of the aircraft such that great amounts of current can flow . . . for seconds if not tens of seconds? Experience and experiments tell us that inadvertent and tentative contact of fat wires against anything 'grounded' is orders of magnitude more likely to burn away the conductors . . . with no observable damage to the fat-wire. I share your concerns but perhaps for not the same reasons. Clearly, this gentleman doesn't have a very good grasp of the simple- ideas behind the performance and selection of components. It seem likely that the conversation you had with him about a battery fuse could be repeated many times over concerning other aspects of the build. Perhaps the best thing we can do for him is get him a copy of the 'Connection and see how or if it changes his levels of curiosity/awareness. I'll donate one to the cause. Send me you mailing address. Bob . . . ________________________________ Message 4 _____________________________________ Time: 03:16:03 PM PST US Subject: AeroElectric-List: Re: BATTERY FUSE From: "user9253" Bob and others, thanks for your input. My friend already has a copy of your book. Thanks for the offer. I will quote some of the comments to my friend (and leave out others that he might take offense to). -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=466902#466902 ________________________________ Message 5 _____________________________________ Time: 11:01:26 PM PST US From: Bill Allen Subject: Re: AeroElectric-List: BATTERY FUSE I think that this maybe an example of how what is appropriate standard practice in one industry is not appropriate in another. International safety standards for autos require that, in the event of an impact sufficient to trigger the airbags, certain other items are also activated, amongst which is the automatic battery disconnect. Most vehicles also have separate feeds/fusible links for the starter and consumers, with just the battery feed to the starter becoming disconnected in an impact. Other inappropriate (to aviation) items are fault detection which place the engine management in "limp mode" which will get a car home at low speed, but cause a forced landing in an aircraft. There are many other reasons why auto engines have a much higher risk of failure than aircraft engines, but to successfully transfer an auto engine to an aviation environment requires a much deeper understanding of the environment and operation of both than would at first appear. I hope your friend has done his homework. Bill Allen LongEzDiesel G-LEZE CozyIV G-BYLZ VariEze N2CR On Sun, 5 Mar 2017 at 21:27, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > At 10:21 AM 3/4/2017, you wrote: > > > A friend of mine is building a plane with an 8 cylinder automotive > engine. I noticed that he had installed a 100 amp ANL fuse in series with > the battery cable. The fuse is located 6 inches from the battery and all > battery current will go through that fuse including starter current. I > asked my friend if that 100 amp ANL will handle the starter current. His > response was, "It's a 35 amp battery." I told him that a 100 amp ANL might > not handle starting current. He said that if it doesn't, he will replace > it with a 150 amp. > I think that the fuse will need to be bigger, like 200 amp or more. > Actually I do not think that there should be a fuse in series with the > battery cable at all. It is one more thing to fail and it adds resistance > to the battery cranking circuit. How can I convince my friend that fuse is > not necessary or even desired? If he will not change his mind, what size > ANL fuse should he use? > > > Fuses are cheap, after he pops the first one, > he'll discover that upsizing the limiter is > indicated. > > Over a century of experience and product > evolution it was rationally deduced that > fat wires in light aircraft do not benefit > from the addition of over current protection. > Consider that hard-fault protection for > battery excited fat-wires can exceed 1000 > amps. Okay, what's a hard fault? Get out > your hammers, chisels and pry-bars. What > would you do to create a connection to any > 'grounded' feature of the aircraft such > that great amounts of current can flow . . . > for seconds if not tens of seconds? > > Experience and experiments tell us > that inadvertent and tentative contact > of fat wires against anything 'grounded' > is orders of magnitude more likely to burn > away the conductors . . . with no observable > damage to the fat-wire. > > I share your concerns but perhaps for not > the same reasons. Clearly, this gentleman > doesn't have a very good grasp of the simple- > ideas behind the performance and selection of > components. It seem likely that the conversation > you had with him about a battery fuse could > be repeated many times over concerning other > aspects of the build. > > Perhaps the best thing we can do for him > is get him a copy of the 'Connection and > see how or if it changes his levels of > curiosity/awareness. I'll donate one to > the cause. Send me you mailing address. > > Bob . . . > -- Bill Allen LongEz160 N99BA FD51 CZ4 G-BYLZ EGBJ ------------------------------------------------------------------------------------- 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.