---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 06/27/20: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:04 AM - Re: RV10 Single Batt + Dual Alternator (bobmeyers) 2. 03:42 PM - Re: RV10 Single Batt + Dual Alternator (supik) 3. 06:53 PM - Re: Measuring battery internal resistance (Robert L. Nuckolls, III) 4. 08:37 PM - Re: Re: Measuring battery internal resistance (Dick Tasker) ________________________________ Message 1 _____________________________________ Time: 08:04:19 AM PST US Subject: AeroElectric-List: Re: RV10 Single Batt + Dual Alternator From: "bobmeyers" I would rethink what you are trying to accomplish. With all the monkey motion going on, it would seem you would be better served going with a Z-14 rather than a gummed up Z-101. Why an avionic bus at all let alone two? I would kill them both and their relays. A utility bus seems way over the top. If you wish to control a utility device just have a power switch for that device co-located with it. I would kill the utility bus If the motivation for the avionics buses is to avoid brown out of all the avionic devices not on the GAD 27, a Z-14 system will solve that for you. Most of the Garmin devices have a second power input you can connect to a second bus. You can use a bridge rectifier to enable dual power feeds to any device that only has one power input. When I wired my RV14 I first drew up something similar to the ideas behind Z-101. If the current Z-101 had been around I may have been more confident in using that kind of layout. I went with a Z-14 layout instead. When I get in my plane, I turn on batt 2 and all the avionics come up and stay up. I turn on batt 1 as part of my startup checklist and during engine start, no brown outs to the avionics occur. This is the only reason I didn't go with my sorta Z-101 back then. I can think of no other reason to choose between a straight Z-101 or a Z-14. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=497058#497058 ________________________________ Message 2 _____________________________________ Time: 03:42:33 PM PST US Subject: AeroElectric-List: Re: RV10 Single Batt + Dual Alternator From: "supik" Version 35 -UTIL BUS eliminated / rebranded to MAIN BUS fuse block (non essential stuff) -AutoPilot head unit + servos moved to ESS BUS https://i.ibb.co/VwNhKK5/Diagram-OM-ELA-Igor-v-035.jpg -------- Igor RV10 in progress Read this topic online here: http://forums.matronics.com/viewtopic.php?p=497060#497060 Attachments: http://forums.matronics.com//files/diagram_om_ela_igor_v035_322.jpg ________________________________ Message 3 _____________________________________ Time: 06:53:31 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Measuring battery internal resistance At 07:27 PM 6/26/2020, you wrote: >Hi Bob, >Thanks for the plot information...Maintainers and their profiles. >Your details brought up a question. >Would you have a suggestion for a simple setup >for measuring internal cell/battery resistance, IR, of lithium based cells. >Modelers use a lot of Lipo based >batteries.=C2 And there is a strong need to keep >track of their condition and it seems like >tracking IR could be the best option. A >practical way to run the tests is sorely needed. >Your suggestions are always appreciated. Hmmmm . . . internal resistance can be measured 'instantly' as opposed to doing a total-discharge cap-check. The results of a 'severe load' test considers a combination of chemical potential (capacity) -AND- internal resistance (ohmic losses). An internal resistance test can be conducted at lower energy levels than the load-test. Of course, all three tests require some instrumentation and process. The hammer-n-tongs way to measure cell impedance is to load with some handy value resistor, measure the voltage then increase the load by say, double or tripling it and read the voltage again. Example: Suppose your battery under test puts out 12.35 volts with a 10 ohm load. Your base current is 12.35/10 = 1.235 amps Temporarily add a second load resistor . . . any practical value, let's say another 10 ohms. Let's assume the new reading is 12.220 volts. Okay, total R across the battery is now 5 ohms. 12.22/5 = 2.444 amps. So, for a delta current of 2.444A we read a delta-volts of 0.015V .015/2.444 = 6 milliohms One could craft a test box containing the necessary resistors, push-button and meter connections to simplify the setup but you'd still have to get out the calculator and do the math. I designed a direct reading battery resistance meter about 20 years ago. It featured a constant current load system that was switched with a multi-vibrator at about 10 cycles per second. It toggled between 1 and 11 amps. A pk-to-pk reading voltmeter would show the ripple voltage created at the battery terminals as the electronic load oscillated between the two current values. Internal resistance was nearly direct reading where 10 mv pk-pk equated to 1 milliohm of resistance. I've probably got those drawings around here somewhere. In my recent studies of on the garden tractor battery . . . http://www.aeroelectric.com/Pictures/Battery_Tender_Jr_Performance/03_BTJr+C CCY_Energy.jpg I was able to command the CBA IV battery analyzer to deviate between two accurately known load values while accurately reporting the battery voltage. That delta-E/Delta-A deduced a rather high internal resistance of about 60 milliohms. So there's three ways to go about it ranging from the hammer-n-tongs to poke-n-read. Bob . . . ________________________________ Message 4 _____________________________________ Time: 08:37:22 PM PST US Subject: Re: AeroElectric-List: Re: Measuring battery internal resistance From: Dick Tasker Oops. For your example, the delta current is actually 2.444-1.235=1.209A. So the R=0.015/1.209=12.4 milliohms. You forgot to subtract the first reading. Other than the simple math error (something I do all the time...) the rest of the explanation is spot on. Dick Tasker Robert L. Nuckolls, III wrote: > At 07:27 PM 6/26/2020, you wrote: >> Hi Bob, >> Thanks for the plot information...Maintainers and their profiles. >> Your details brought up a question. >> Would you have a suggestion for a simple setup for measuring internal cell/battery resistance, IR, of lithium based cells. >> Modelers use a lot of Lipo based batteries. And there is a strong need to keep track of their condition and it seems like tracking IR could be the best option. A practical way to run the tests is >> sorely needed. >> Your suggestions are always appreciated. > > Hmmmm . . . internal resistance can be > measured 'instantly' as opposed to doing > a total-discharge cap-check. The results > of a 'severe load' test considers > a combination of chemical potential > (capacity) -AND- internal resistance > (ohmic losses). An internal resistance > test can be conducted at lower energy > levels than the load-test. Of course, > all three tests require some instrumentation > and process. > > The hammer-n-tongs way to measure cell > impedance is to load with some handy value > resistor, measure the voltage then increase > the load by say, double or tripling it > and read the voltage again. > > Example: Suppose your battery under test > puts out 12.35 volts with a 10 ohm load. > Your base current is 12.35/10 = 1.235 amps > > Temporarily add a second load resistor . . . > any practical value, let's say another > 10 ohms. Let's assume the new reading is > 12.220 volts. Okay, total R across the > battery is now 5 ohms. 12.22/5 = 2.444 > amps. > > So, for a delta current of 2.444A > we read a delta-volts of 0.015V > > .015/2.444 = 6 milliohms > > One could craft a test box containing > the necessary resistors, push-button > and meter connections to simplify the > setup but you'd still have to get out > the calculator and do the math. > > I designed a direct reading battery > resistance meter about 20 years ago. > It featured a constant current load > system that was switched with a > multi-vibrator at about 10 cycles > per second. > > It toggled between 1 and 11 amps. > A pk-to-pk reading voltmeter would show > the ripple voltage created at the battery > terminals as the electronic load oscillated > between the two current values. > > Internal resistance was nearly direct > reading where 10 mv pk-pk equated to > 1 milliohm of resistance. I've probably > got those drawings around here somewhere. > > In my recent studies of on the garden > tractor battery . . . > > http://www.aeroelectric.com/Pictures/Battery_Tender_Jr_Performance/03_BTJr+CCCY_Energy.jpg > > I was able to command the CBA IV battery > analyzer to deviate between two accurately > known load values while accurately reporting > the battery voltage. That delta-E/Delta-A > deduced a rather high internal resistance of > about 60 milliohms. > > So there's three ways to go about it ranging > from the hammer-n-tongs to poke-n-read. > > > Bob . . . > ------------------------------------------------------------------------------------- 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.