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  #1  
Old 08-04-2014, 12:15 PM
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Default LiFePo4 battery on the firewall?

I'm strongly considering using an EarthX EXT36C Lithium battery on the firewall of my 10 instead of in the stock battery box in the tail. A buddy did a structural analysis, and there are no issues structurally, by a good margin. What I'm wondering about is placement. The two places that look like good candidates are on the upper firewall between the brake reservoir and the firewall recess, or centered below the brake reservoir.

The battery I'm considering is very small and light (5.9" x 3.4" x 5.4", 3.5lbs), but still has 680 cranking amps, and importantly in Minnesota, 405 cold cranking amps. I think that this combined with the MUCH shorter wire runs to the starter should give me great starting power.

My original plan was for a PC925 in the tail. This would be a 22.5 lb reduction for me with only the battery, plus the weight of that big #2 cable that will get a lot shorter.

I am also planning a TCW Backup Battery for critical avionics, and a secondary alternator.

Does anyone have any comments about placement or capacity of the battery I'm considering?

http://earthxmotorsports.com/product...ntal-aircraft/







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  #2  
Old 08-04-2014, 12:34 PM
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Operating temps appear to be 60c (140f) on the EarthX batteries. What is the normal temps in that location you are considering?

If you plan to have a 2nd alternator then the higher position picture would interfere I think.
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Old 08-04-2014, 02:07 PM
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I can't speak to the RV-10 specific placement but can speak to the LiFePo-4 in the engine compartment. I've been running two batteries - my main and my backup - on my RV-8 in a location similar to where your reservoir is located for 2+ years now.
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Old 08-04-2014, 02:11 PM
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Default

May I suggest you run a sample W/B with the change in battery location??

There is a reason that the engineers at Vans put the weight of the battery where they did.

You are suggesting not only removing that weight, but adding some on the opposite side of the C/G.
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Last edited by Mike S : 08-04-2014 at 05:48 PM.
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Old 08-04-2014, 02:34 PM
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Quote:
Originally Posted by humptybump View Post
I can't speak to the RV-10 specific placement but can speak to the LiFePo-4 in the engine compartment. I've been running two batteries - my main and my backup - on my RV-8 in a location similar to where your reservoir is located for 2+ years now.
Sorry to derail but got any feedback on the battery? Which ones do you have?
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  #6  
Old 08-04-2014, 02:36 PM
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Quote:
Originally Posted by humptybump View Post
I can't speak to the RV-10 specific placement but can speak to the LiFePo-4 in the engine compartment. I've been running two batteries - my main and my backup - on my RV-8 in a location similar to where your reservoir is located for 2+ years now.
So to clarify....you have been running two LiFePo4 batteries in the engine compartment for 2+ years?
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  #7  
Old 08-04-2014, 03:32 PM
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Quote:
Originally Posted by blahphish View Post
Operating temps appear to be 60c (140f) on the EarthX batteries. What is the normal temps in that location you are considering?
Just a side note here. The PC680 that a lot of use is also recommended only up to 140 degrees.
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  #8  
Old 08-04-2014, 04:50 PM
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Quote:
Originally Posted by J Twilbeck View Post
So to clarify....you have been running two LiFePo4 batteries in the engine compartment for 2+ years?
To be completely accurate, one of the batteries has about 2.5 years on it and one has about 1.5 years. I didn't mean to embellish.

2.5 years ago I did a direct swap of a PC680 for a Shorai 18A. I ran that for about a year when I then wen with an all electric panel. I decided I needed a second battery and went "bigger" with Shorai 36A as my primary and made the 18A my backup.

While I consider these overkill in size for their assigned roles, the EarthX thread suggests the 36A may be right as a main battery if you need the extra CCA.

With my personal results, I would use both 18A batteries in my plane if I were doing it again. I'm not suggesting my decision is right for others; I'm just not seeing the requirement for the larger main battery.
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Old 08-04-2014, 05:30 PM
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All things being equal, keeping electrical items out from under fluids is recommended so the position beside the brake reservoir would be better.
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  #10  
Old 08-04-2014, 06:20 PM
Dorfie Dorfie is offline
 
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Default Was thinking the same about firewall mounted batt

This is very timely posting. I had the same thoughts after Oshkosh. The C of G issues can be overcome by adding smaller weight far back in tail I would think. Huge weight saving. Understanding and trusting LiFePO is another issue I battle with (the article in latest Kitplanes did not instil a lot of trust).
Ed, what is the fire protection on your firewall?
Thanks
Johan
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