---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 05/04/14: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:42 AM - Dual trim indicator buffer (Robert L. Nuckolls, III) 2. 09:20 AM - Alternative battery technologies . . . (Robert L. Nuckolls, III) 3. 10:09 PM - Re: Re: How do I prevent starter engaged LED from failing? (Bob Verwey) ________________________________ Message 1 _____________________________________ Time: 06:42:06 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Dual trim indicator buffer Here's the drawing I alluded to last night . . . http://tinyurl.com/pdacqjp Had a power failure yesterday afternoon which led to a discovery that my AutoCAD backup feature had not been set up on this machine . . . lost 90% of the work and had to put it back together this morning. Well considered critical review from kindred herders of electrons is solicited and welcome. This project could be laid up on a board that would fit into a 15 pin d-sub housing. The pots will allow adjustment of gain over a 1 to 2x range. Offset is good for about 30% of range. This will allow a builder to make the trim indicator display full, as-installed stroke of the actuator. Bob . . . ________________________________ Message 2 _____________________________________ Time: 09:20:43 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Alternative battery technologies . . . The battery-buzz these days is focused on lithium . . . and for good reason. They ARE lighter yet retain many of the desirable qualities of a lead=acid battery for engine cranking. Another rising-star wannabe is a product by FireFly Energy . . . an svrla battery that features a carbon foam plate material with a advertised gee-whiz feature of offering a lower weight replacement for the legacy lead grids. This is not a 'new' idea . . . I think the patents have already been renewed once . . . but only recently have potential consumers of this technology been able to put their hands on real product. http://tinyurl.com/kfzsj5p This is a group 31 battery (read BIG) that weighed in at 73.6 pounds and presented and open circuit voltage of 13.09V at ~20C right out of the box. A 600A load drops voltage to 9.30V. Therefor (13.1 - 9.30)/600 = 0.00633 Ohms internal resistance. Okay, how about available capacity under various loads? Emacs! When discharged at 5A, it took 20+ hours to take it down to 10.0V. So one could say that the capacity of this battery at 20-hour rate is over 100aH. Not bad for a 75# battery. At higher rates, we see that the capacity drops off pretty much like all other batteries . . . the 50A discharge delivered only 80Ah . . . one might extrapolate from this data that the battery's one-hour rate (as an aircraft battery would clock in at about 65Ah. Again, not bad for a 12V, 75# battery. From the data taken, we can estimate that a 24V cousin of the same active materials would be slightly more than the 75# due to addition of extra cell walls. The internal resistance would go up by a factor of 4. Twice as many half-sized cells in series. A 4x increase in internal resistance would have a profound effect on delivered capacity at the higher rates. In other words, when sliced up and reassembled as a 24V battery, this device would not be able to deliver 1/2 the one-hour rate deduced above . . . it's more likely to be down to something like 20Ah or so. I'm going to see if I can model the 24v version and do some predicted plots. From the aircraft perspective, the 24v version would be unable to start a turbine engine. While the capacity is there at moderate discharge rates . . . internal resistance kills its cranking abilities. The plots above include some charging performance data on a Schumacher XC75W picked up new at a Walmart store a few weeks ago. http://tinyurl.com/k7fatrm On the outside of the box it says 3A charger/maintainer, 5A charger, 20A charger and 75A engine cranking output. Okay, the first recharge cycle of the 100Ah "AGM" battery under test produced the recharge curve in black. It topped off at about 15.7 volts and had the battery 'wheezing' from the vent valves. The second recharge in the "GEL" mode produced the curve in blue which topped off at 14.8 volts. MUCH better. The third recharge in the "STD" mode produced the curve in red which again topped off at 15.7 volts and squeezed a few more molecules of disassociated hydrogen and oxygen from the cell vents. Clearly, this charger is not programmed for the advertised service. Either I have a bad charger or Schumacher has stubbed their toe. This is like finding a Fluke voltmeter that's only good to 2% or so . . . I am told that Schumacher's engineering staff is willing to talk. I'll be looking for a contact in that venue to discuss my findings on this particular Schumahcer product. In the mean time, know that the 20A rate appears to be a modulated 'peak' rate. Time to stuff 100Ah plus back into this battery at the 20A setting on the charger took 8+ hours. Not a big deal. It was reasonably expeditious and didn't abuse the battery in the GEL mode . . . other modes are yet to be explained/understood. So what about these 'new' technologies? Mixed bag. Clearly the carbon foam battery plate is not ready for prime-time in aviation. Service in anything but moderate rate discharge in RV's, boats, etc would be disappointing at anything over .3C rates. Pretty sure I'm not ready to poke out $375 for one of these things. Tho I AM glad my client was willing . . . The charger was disappointing on two fronts. It's clearly NOT a 20A fast charger. It's also unsuited to the tasks advertised for maintenance of AGM/Flooded batteries. MUCH too abusive. A learned professor once opined "Numbers not accompanied by degrees of uncertainty are meaningless" (Walter Lewin). Another pretty sharp cookie was known to have said, " . . . when you cannot measure [a thing], when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind . . ."(Lord Kelvin). This is a good illustration of the difficulties encountered by the CONSUMING community when factions of the SUPPLIER community get into rock-throwing contests (Recall the tiff that Odyssey got into with one of the battery maintainer guys? I forget which). It would have been good and responsible for both parties to publish the numbers instead of throwing rocks with consumers caught in the middle. Now that I have the numbers . . . I can go back to the folks who have claimed certain kinds of performance based on those numbers for clarification . . . Watch this space. Bob . . . ________________________________ Message 3 _____________________________________ Time: 10:09:19 PM PST US From: Bob Verwey Subject: Re: AeroElectric-List: Re: How do I prevent starter engaged LED from failing? I have had an LED indicate "Gear in transit" for 10 years with no protection.... Best... Bob Verwey On 3 May 2014 23:02, user9253 wrote: > > Eric, > I am not knowledgeable enough about the characteristics of a starter motor > to answer. In my circuit, any diode, zener or not, will short out a > negative voltage. A 16 volt zener will short out any positive voltage > above 16. Attach your latest circuit idea for others to comment on. > It would be interesting to learn more about starters, any induced > voltages during normal operations and also the voltage output and current > capabilities of a starter that remains engaged with the engine after > starting. > Joe > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=422759#422759 > > ------------------------------------------------------------------------------------- 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.