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  #41  
Old 12-28-2019, 09:03 AM
bobnoffs bobnoffs is offline
 
Join Date: Jul 2012
Location: n. wi
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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.
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dakota hawk/jab 3300 built and flying. sold 6/18.getting serious about the 12. in the hangar now as of 10/15/19
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  #42  
Old 12-28-2019, 09:13 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
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Quote:
Originally Posted by Mark33 View Post
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.
Which is, you guessed it, a LiFeO4 battery...
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RV-10
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  #43  
Old 12-28-2019, 09:26 AM
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Mark33 Mark33 is offline
 
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Location: Baton Rouge, La.
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Quote:
Originally Posted by rocketman1988 View Post
Which is, you guessed it, a LiFeO4 battery...
LOL....yes sir, you are correct!! 😊👍
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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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  #44  
Old 12-28-2019, 09:28 AM
rocketman1988 rocketman1988 is offline
 
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Oh, the tangled webs we weave...
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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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  #45  
Old 12-28-2019, 09:46 AM
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rocketbob rocketbob is offline
 
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Location: 8I3
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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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N9187P PA-24-260B Comanche, flying
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  #46  
Old 12-28-2019, 09:55 AM
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Mark33 Mark33 is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
Oh, the tangled webs we weave...
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.
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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)
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  #47  
Old 01-05-2020, 12:36 PM
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rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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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.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 01-05-2020 at 02:06 PM.
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  #48  
Old 01-05-2020, 01:16 PM
McStevens McStevens is offline
 
Join Date: Sep 2019
Location: Edmonds, WA
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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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  #49  
Old 01-05-2020, 02:09 PM
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rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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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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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #50  
Old 01-05-2020, 02:47 PM
McStevens McStevens is offline
 
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Location: Edmonds, WA
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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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