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Thread: EarthX battery inside the firewall?

  1. #11
    Senior Member Delta Whisky's Avatar
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    Default Re: EarthX battery inside the firewall?

    Thanks John - I then do have the heavy duty starter.

  2. #12
    Birdseyeview's Avatar
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    Default Re: EarthX battery inside the firewall?

    To close my reason for starting this thread - it turns out the price tag on the Odyssey PC680 battery was attractive enough to buy one and try it. I bought the "Extreme" version at AutoZone for $163 and they said I could bring it back for a refund if it didn't crank my engine over good enough. The "Extreme" version has a metal sleeve around it and comes with a larger terminal bolt adapter (which I didn't use). Although I don't need the metal sleeve since I've mounted the battery on the inside of the firewall, I thought it may come in handy someday if I ever wanted to move the battery forward of the firewall. At 50F ambient temp outside it worked great, even though I don't have the heavy duty starter or the "soft start" feature. The same battery without the metal sleeve and terminal bolt adapter is $126 at my local Autozone. I hope it cranks over this good this coming winter.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  3. #13
    Senior Member PapuaPilot's Avatar
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    Default Re: EarthX battery inside the firewall?

    The Odyssey 680 is a good battery. You should be okay as long as it isn't a big distance from the battery to the starter.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  4. #14
    Birdseyeview's Avatar
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    Default Re: EarthX battery inside the firewall?

    Phil,

    Thanks for your comment. I assume you mention the length of the positive cable from the start solenoid to the starter because of a potential voltage drop impact. My battery is mounted just inside of the firewall and so is the start solenoid (see the picture below). I've got 6 gage multi-strand cable, per the build manual schematic from the solenoid to the starter, and all the ground cable from the battery to the engine ground lug. This arrangement isn't as bad a voltage drop as a battery mounted way back in the tail but it's not quite as ideal as a config with the battery and start solenoid mounted on the front of the firewall. However, I'm believing that the difference between my install compared to the ideal should be insignificant due to the fact that my cable length is only a few inches longer (4-5" max) than the ideal. However, I could easily change out the cables from the 6 gage to something larger if the general consensus of the more experienced builders thinks this is the way to go.

    IMG_8260.jpg

    Note how close the battery is to the firewall. The master solenoid is the one most visible in the photo with the start solenoid just below it.
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  5. #15
    Senior Member PapuaPilot's Avatar
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    Default Re: EarthX battery inside the firewall?

    You have a short run and it shouldn't be a problem. I had an Odyssey battery in the tail originally and there was a pretty big voltage drop. Now I have an EarthX in the same position as you do and it works great.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  6. #16
    Senior Member jrevens's Avatar
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    Default Re: EarthX battery inside the firewall?

    If your connections are good it should be just fine there with #6 wire.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  7. #17
    Birdseyeview's Avatar
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    Default Re: EarthX battery inside the firewall?

    Phil,

    Which EarthX model battery did you install?

    I'm curious about the impact on your CG when you made the switch from the heavy Odyssey to the light weight EarthX. That must have been a drastic CG impact. How did you compensate for that big a change?
    Larry Olson
    Kitfox Series 6 - 1st Flight Oct 2021
    Tri-gear, smooth cowl
    912 ULS

  8. #18
    Senior Member Delta Whisky's Avatar
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    Default Re: EarthX battery inside the firewall?

    Recommended Length and Amperage for Battery Cable while maintaining a 2% or less voltage drop at 12 volts
    Battery Cable Size 50 Amps 100 Amps 150 Amps 200 Amps 300 Amps
    6 Gauge (AWG) 11.8 ft 5.9 ft 4.4 ft 2.9 ft 2.2 ft
    Larry - you'll be fine with 6 gauge cable and a PC680. Note the above table is for a 2% or less voltage drop (0.24V). Unless my eyes failed me during research, the PC680 battery is rated at 170A for 30 seconds at 0F and 280A at 32F. (Those values aren't too meaningful because the test routine allows the battery voltage to drop to 7.2 volts but they do give a good indication of available power. Most starter motors work fine until the battery voltage drops to about 10V.) Your starter motor is rated at 0.6kW (about 50A) but the limit is 10 seconds of starter time followed by 2 minutes of cool off time. An extreme PC680 will is spec'd at 520 Amps for 5 seconds. Bottom line, neither the battery nor the cabling should be an issue.

  9. #19
    Senior Member PapuaPilot's Avatar
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    Default Re: EarthX battery inside the firewall?

    Quote Originally Posted by Birdseyeview View Post
    Phil,

    Which EarthX model battery did you install?

    I'm curious about the impact on your CG when you made the switch from the heavy Odyssey to the light weight EarthX. That must have been a drastic CG impact. How did you compensate for that big a change?
    I got the ETX680C. Yes, it would have made a big change in my CG, but I left the Odyssey battery in the tail. I have been working on getting more stuff in the tail to move the EWCG farther aft. So far I have added autopilot servos and the T3 shock strut, which helped a little. I hope to put a tool kit where the original battery was someday, but I need about 10 lbs. to make the CG work.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

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