---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 05/03/20: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:22 AM - DC clamp meter (blues750) 2. 06:12 PM - Re: Re: Z-12 Architecture, Back-Up Alternator Wiring (Robert L. Nuckolls, III) 3. 06:12 PM - Charging two EarthX batteries (Hariharan Gopalan) 4. 07:27 PM - Re: DC clamp meter (Robert L. Nuckolls, III) 5. 07:43 PM - Re: Charging two EarthX batteries (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 08:22:26 AM PST US Subject: AeroElectric-List: DC clamp meter From: "blues750" Looking for recommendations on a suitable DC clamp meter to do capacity checks on my EarthX batteries. Prices seem to be all over the place. Am curious what kind others might be having good experience with. Thanks all! Dave Read this topic online here: http://forums.matronics.com/viewtopic.php?p=496171#496171 ________________________________ Message 2 _____________________________________ Time: 06:12:16 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Z-12 Architecture, Back-Up Alternator Wiring At 05:12 PM 5/1/2020, you wrote: > >So I took your advice and crafted a Z-12 version. >-------- >Michael Fleming Michael, Did about 200 miles of 'asphalt engineering' yesterday on this thread. Picked up some parts for a friend's welder/generator in Enid. His Chute is electro-hydraulic and he had some cattle to work today I've incorporated some of your input along with musings from the List and my own starry-eyed stare down the highway. https://tinyurl.com/y9n57vlw This drawing needs some notes to explain on some new ideas: Z12 lite could be pretty simple. No optional busses. Dual alternator dependability combined with a dutifully maintained battery would take you far and in confidence. This drawing illustrates and preserves the aux alternator installation as offered by B&C. Depending on proposed accessories and operating modes one might wish to add battery or clearance delivery/endurance busses. Purely optional . . . if you gotta use for one, add it. Question: your drawing shows a fused feeder off the battery to the p-mag. What is the rational for utilizing this source as opposed to simply tying it to the main bus? What is the current draw of this feature on the p-mag? Bob . . . ________________________________ Message 3 _____________________________________ Time: 06:12:49 PM PST US From: Hariharan Gopalan Subject: AeroElectric-List: Charging two EarthX batteries I have two earthX batteries and use an external port to connect an optimate TM-291, 5 AMP charger to charge these two batteries. Current setup is to manually connect / disconnect the cable from the port to either battery. The only problem with this approach is that when one battery is charged, I have to manually connect the second battery. Some kind of a voltage sensing relay to switch out the first battery and and connect the charger output to the second battery would be an ideal solution. Wonder if anyone has any tips? I looked at some dual battery chargers, but not sure how these would work with the optimate charger and earthX batteries. Thanks Hari ________________________________ Message 4 _____________________________________ Time: 07:27:04 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: DC clamp meter At 10:20 AM 5/3/2020, you wrote: > >Looking for recommendations on a suitable DC clamp meter to do capacity >checks on my EarthX batteries. Prices seem to be all over the place. >Am curious what kind others might be having good experience with. Thanks all! > >Dave Help us out with your mission. A 'capacity test' is a measured depletion and recharge of a battery to deduce its contained energy. This could be accomplished at a prescribed discharge rate commensurate with your anticipated 'endurance loads' (useful capacity of a battery varies with load). In the attached chart you can see how a battery rated at 18Ah under a 20Hr discharge rate delivers only 12Ah if discharge over 1Hr rate. 2/3rds of its capacity is tossed off as internal heating of the battery. To accomplish a capacity test, you need a means for establishing a constant current load at some selected rate while recording the battery's output voltage until it falls below some artfully selected cut-off voltage. Alternatively, consider a device like this: https://tinyurl.com/moaoaus I have used these on numerous projects over the years. I'm thinking of upgrading my 20+ year old device. The newer ones have some really nice software features. I'm wondering if you're interested in the battery's cranking (load bearing) characteristics. This is a different test that quantifies the battery's internal resistance -and- state of the chemistry under heavy load. For this you need a critter like this https://tinyurl.com/yag4529y I have a couple of these HF testers . . . got a $high$ AutoMeter tester too but the el-cheeso works just fine for our purposes. You hook this to your battery under test. Just before you crank up the load such that battery voltage falls to 9V, push the 15 second timer button. Adjust load during the 15 second interval to maintain 9V reading. Take note of the CURRENT delivered by the battery at the end of 15 seconds. Acquire this benchmark value for a new battery. Note the value with a sharpie on the battery case along with date. At any later time, should the battery perform to less than 80% (*) of new, consider replacing the battery. Same thing goes with capacity checks 80% is the 'retirement' value for batteries in TC, flight-for-hire aircraft. (*) Of course, you CAN establish your own benchmarks if some other numbers make more sense for how you operate your airplane. But pick other numbers based on understanding, not because your trying to squeeze more service out of the battery. EARTHX batteries (and all other LIFePO4 batteries) are special cases. Your load test value will probably be more than 9V . . . internal resistance of these batteries is very low and you probably can't load it down to 9v without tripping internal current limits. If you want to capcheck your EARTHX, fire up your airplane's anticipated endurance mode accessories and measure the time before auto-disconnect. Make note of that time for the new battery. Think about replacing the battery when those minutes fall by 25% or so. As for DC clamp-on ammeters, they've been around for some time. I have a Fluke meter I bought about 20 years ago . . . hall-effect device . . . works mostly okay for large measurements (10+ amps) but flakiness typical of contemporary technology at low current levels. I have one like this https://tinyurl.com/y9gb4cgs . . . but haven't had much occasion to exercise it's capability. It has a ZERO read function on DC amps that wipes out most of the variability in the hall-sensor at low current readings. Seems to work well. Will follow up when I've learned more . . . but the price/performance numbers are certainly attractive. Bob . . . ________________________________ Message 5 _____________________________________ Time: 07:43:53 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Charging two EarthX batteries At 08:09 PM 5/3/2020, you wrote: >I have two earthX batteries and use an external >port to connect an optimate TM-291, 5 AMP >charger to charge these two batteries. Current >setup is to manually connect / disconnect the >cable from the port to either battery.=C2 The >only problem with this approach is that when one >battery is charged, I have to manually connect >the second battery. Some kind of a voltage >sensing relay to switch out the first battery >and and connect the charger output=C2 to the >second battery would be an ideal solution. > >Wonder if anyone has any tips? I looked at some >dual battery chargers, but not sure how these >would work with the optimate charger and earthX batteries. > >Thanks >Hari Why do you need to 'charge' these batteries? How often do you fly. How long is your longest storage interval? There is 'tribal knowledge' that suggests a benefit for hooking 'shore power' to the battery(ies) in a parked airplane. But unlike the flooded battery in your grandpa's '54, 6v Pontiac, modern SVLA and LiFePo batteries have very low self-discharge rates. Unless you're storing the airplane for a long period of time, shore power connection isn't really useful . . . and if the charger is poorly designed for such service . . . it may be detrimental to the service life of the battery. What does EarthX recommend for battery maintenance during various intervals of inactivity? Here's a data-dump on the topic of self-discharge in batteries . . . along with a wealth of other battery info. https://tinyurl.com/yczco6vp If you're going to store for a long time and especially if ambient temps are high, consider removing the battery(ies) for storage under your bed . . . or some other environmentally friendly space. Otherwise, your batteries should live and perform well with no external attention. You do need a charger in case of inadvertent depletion of the battery(ies) . . . in which case, I would charge them independently before flight. 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