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12-28-2019, 09:03 AM
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Join Date: Jul 2012
Location: n. wi
Posts: 778
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just an observation.........the 10 deg c. and doubling rate is a law of chemistry/physics. same law that makes keeping an engine always warm in the winter questionable....it rusts faster.
my observation about all this is that i would think fwf applications should not see a drop in performance. someone needs to put a probe on their battery and go fly in the cold. i'd be glad to do it if i had something flying.
__________________
Bob Noffs
n. wi.
dakota hawk/jab 3300 built and flying. sold 6/18.getting serious about the 12. in the hangar now as of 10/15/19
RV-12 kit as of 9/13
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12-28-2019, 09:13 AM
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Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,189
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Quote:
Originally Posted by Mark33
Thanks Ross,
My electrical architecture is such that the only thing in the airplane that?ll be dependent on the backup battery will be the electronic ignition and electronic fuel injection which is powered via the ?essential bus?. Everything else is on the main bus, with its own IBBS backup battery.
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Which is, you guessed it, a LiFeO4 battery... 
__________________
Bob
Aerospace Engineer '88
RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...
Dues+ Paid 2019,...Thanks DR+
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12-28-2019, 09:26 AM
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Join Date: May 2010
Location: Baton Rouge, La.
Posts: 753
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Quote:
Originally Posted by rocketman1988
Which is, you guessed it, a LiFeO4 battery... 
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LOL....yes sir, you are correct!! 😊👍
__________________
Mark H.
RV-7- IO-360, EFII, Whirl Wind C/S, (Built and sold)
RV-4- O-320, Catto three blade, P-Mags (Sold)
RV-8- IO-360, Hartzell C/S (Flying)
RV-7- (Building)
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12-28-2019, 09:28 AM
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Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,189
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webs
Oh, the tangled webs we weave...
__________________
Bob
Aerospace Engineer '88
RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...
Dues+ Paid 2019,...Thanks DR+
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12-28-2019, 09:46 AM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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A few years ago I tested a Shorai LFX18 battery with a CBA IV load tester. I found with a 7A essential bus load I had 50 minutes until voltage fell to 11V. At that point the discharge curve fell off rapidly. Battery-only endurance is not much of a concern to me as I have a dual battery/alternator architecture. But if one wants to use a LiFePo4 battery in a single battery setup then you need to upsize it as the amp-hour ratings can be deceiving.
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Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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12-28-2019, 09:55 AM
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Join Date: May 2010
Location: Baton Rouge, La.
Posts: 753
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Quote:
Originally Posted by rocketman1988
Oh, the tangled webs we weave...
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All I know is that when the ?you know what? hits the fan and the only thing that matters is getting the airplane on the ground safely, the most critical thing is to keep that big fan blade turning out front....?EVERYTHING? else is secondary. That?s why I have my electrically dependent ignition and injection on its own separate ?essential bus? and completely separated from everything else in the airplane and I?ll have that big 900 series vented EarthX battery as backup to power this ?essential bus?.
However, in saying that and understanding the importance of everything else in the airplane, including IFR navigational equipment, the ?main bus? has its own separate IBBS backup battery to keep all of the pretty screens lit up and functioning properly.
__________________
Mark H.
RV-7- IO-360, EFII, Whirl Wind C/S, (Built and sold)
RV-4- O-320, Catto three blade, P-Mags (Sold)
RV-8- IO-360, Hartzell C/S (Flying)
RV-7- (Building)
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01-05-2020, 12:36 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Video
Here is the video I put together on the test: https://www.youtube.com/watch?v=FPBaAil4dNg
This kind of thing is like watching paint dry so I really shortened it up just showing the essentials.
Last edited by rv6ejguy : 01-05-2020 at 02:06 PM.
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01-05-2020, 01:16 PM
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Join Date: Sep 2019
Location: Edmonds, WA
Posts: 105
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This is great, thanks for testing like this. Correct me if I'm wrong but so far it sounds like the Shorai batteries get less than half of their rated capacity. But this test was also a little harder on the Li batteries because of the cold, but also maybe something to do with the load that was used?
2 36Ah batteries are around 9lbs and $700, hmm.
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01-05-2020, 02:09 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Yes, if you look through this thread, you'll see that these so called 18AH Shorais are closer to 6AH in terms of this sort of current draw over 20ish minutes. Great for starting the engine but limited in endurance for this purpose.
You can go bigger of course for more money and weight.
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01-05-2020, 02:47 PM
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Join Date: Sep 2019
Location: Edmonds, WA
Posts: 105
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Looking at the Shorai website I found in the FAQ where they say they use 6Ah cells, but it's not clear they mean this is all they use. In their LFX18 example does this mean they could be using 3 12V 6Ah cells in parallel?
Are we attributing the apparent reduction in capacity to the correct thing?
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