---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 07/07/12: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:48 AM - battery boil/overheat (Owen Baker) 2. 08:05 PM - Re: Boiling batteries (Robert L. Nuckolls, III) 3. 08:16 PM - Re: battery boil/overheat (Robert L. Nuckolls, III) 4. 09:27 PM - Re: Z12 Alternator Amps (RV7ASask) ________________________________ Message 1 _____________________________________ Time: 09:48:37 AM PST US From: "Owen Baker " Subject: AeroElectric-List: battery boil/overheat 7/7/2012 Hello Ed, This posting from the aeroelectric-list archives may be of interest: Match: #10 Message: #48521 Date: Feb 19, 2010 From: "Robert L. Nuckolls, III" Subject: Re: B&C Regulators and water-falls =98OC=99 Baker Time: 07:45:33 AM PST US From: "Ed Anderson" Subject: Re: Battery only time -AeroElectric-List: Z-19RB clarification I certainly agree, Bob. A clear case of a where my design focused on a very low probability occurrence (boiling battery) ending up almost assuring that at some point that switch would get in the incorrect position and cause a problem. In fact, has anybody on the list EVER experienced or have first hand knowledge of someone who had a battery boil/overheat due to run away (over voltage) alternator?? Ed ________________________________ Message 2 _____________________________________ Time: 08:05:33 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Boiling batteries At 09:44 AM 7/6/2012, you wrote: I certainly agree, Bob. A clear case of a where my design focused on a very low probability occurrence (boiling battery) ending up almost assuring that at some point that switch would get in the incorrect position and cause a problem. In fact, has anybody on the list EVER experienced or have first hand knowledge of someone who had a battery boil/overheat due to run away (over voltage) alternator?? There are many such cases over the 100 year history of aircraft . . . or the hundreds of millions of other vehicles with DC power systems. Spectacular events in aviation, like spectacular events elsewhere, get lots of attention mostly because they are rare . . . and spectacular to boot. The ship's alternator is a significant source of energy often rated at 60 amps or more and virtually boundless for voltage during a runaway condition unless (1) shut down in a timely manner or (2) held in a state of current limit by ship's loads + plus what ever the battery is able to accept. RG/SE/SVLA/AGM style batteries offer the most benign responses to OV abuse of any technology. They contain so little liquid that steam-driven events are non-existent. There have been some explosions of liberated H2-O2 mixtures when batteries were boxed up in an airtight container along with an ignition source. But for the most part, the most severely abused batteries will produce failures such as these . . . http://tinyurl.com/cgjoheo http://tinyurl.com/blt9x3l http://tinyurl.com/ckbes36 http://tinyurl.com/bn2wd67 http://tinyurl.com/82azaht http://tinyurl.com/88lhd4n The OV event is an immediate hazard to electro-whizzies with damage taking place in tens to hundreds of milliseconds. Batteries take much longer. In fact, during the first few milliseconds of an OV condition, the battery will "throw itself into the line-of-fire" to forestall rate of rise in bus voltage until the ov protection system (automatic or manual) has time to react. Battery failures due to over-charge are very slow events taking tens of minutes to hours to manifest. An airplane fitted with a capable OV protection system will never suffer such an event. Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:16:45 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: battery boil/overheat At 11:44 AM 7/7/2012, you wrote: 7/7/2012 Hello Ed, This posting from the aeroelectric-list archives may be of interest: Match: #10 Message: #48521 From: "Robert L. Nuckolls, III" Subject: Re: B&C Regulators and water-falls OC Baker I'd forgotten about that one. I searched without success for a discussion on a Glasair battery box explosion. An RG battery suffered an extended OV condition within a tight battery box and apparently out-gassed to an ignition source within the box. The box blew up and scattered pieces into the tail cone but the engine was magneto sparked and continued to fly. The pilot got it back on the ground and was able to tell the tale. The modern alternator in an airplane, like a big gun in a battle, can be an essential component of survival. But unleashed in unintended circumstances it can be a substantial hazard too. FAST ov protection is a requirement in TC aircraft . . . for rare but compelling reasons. -------------------- FAR23.1351(c) Generating System. There must be at least one generator/alternator if the electrical system supplies power to load circuits essential for safe operation. In addition-- (1) Each generator/alternator must be able to deliver its continuous rated power, or such power as is limited by its regulation system. (2) Generator/alternator voltage control equipment must be able to dependably regulate the generator/alternator output within rated limits. (3) Automatic means must be provided to prevent damage to any generator/ alternator and adverse effects on the airplane electrical system due to reverse current. A means must also be provided to disconnect each generator/ alternator from the battery and other generators/alternators. (4) There must be a means to give immediate warning to the flight crew of a failure of any generator/alternator. (5) Each generator/alternator must have an overvoltage control designed and installed to prevent damage to the electrical system, or to equipment supplied by the electrical system that could result if that generator/ alternator were to develop an overvoltage condition. Bob . . . ________________________________ Message 4 _____________________________________ Time: 09:27:15 PM PST US Subject: AeroElectric-List: Re: Z12 Alternator Amps From: "RV7ASask" I went flying today and did an Aux alternator check as you suggested Bob. After turning most of the electrical load off, once again I was left with 8 amps and 14.4 volts on the Main Alternator. Cruising at 2400 RPM I selected the Main Alternator Off. Voltage dropped to 12.9 and the Aux Alternator came on line with a steady 12.9 volts. The amps then slowly climbed up to and settled down at 20 amps, more than double the reading of the Main? To the best of my knowledge everything is wired correctly. Any suggestions? Regards David Lamb Read this topic online here: http://forums.matronics.com/viewtopic.php?p=377590#377590 ------------------------------------------------------------------------------------- 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.