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Thread: Replacement Li Ion Backup Battery

  1. #1

    Replacement Li Ion Backup Battery

    I have an AF3500EE (non S) EFIS that I installed in my RV-8 back in 2009.
    Been flying since 2010 and this year the small coin battery that keeps the date/time finally died. I bought a new CR1225 to replace the old BR1225 Rayovac Lithium battery.
    Seems to work great, any idea whats the difference between CR and BR ?

    I'm wondering if I should replace the "Backup Battery" at the same time while I have the EFIS removed from the panel
    I'm talking about the 7.4V 2.2Ah Li-Ion battery from VARTA Microbattery
    How much does a new one cost ?
    What do you use to glue it to the back of the cover ?

    I disconnected it and put a voltmeter on it and it shows 8.3 volts so I'm wondering your thoughts on if it's still ok or if I should get a new one.
    How long should it keep the EFIS functioning and what voltage is indicated when powering the EFIS ?

    Thanks for taking the time to repsond to my query's.
    Dave Rogers
    Last edited by Wicked Stick; 11-06-2014 at 07:05 PM.

  2. #2
    Advanced Flight Systems Shawn McGinnis's Avatar
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    whats the difference between CR and BR ?
    CR Battery Chemistry
    CR denotes Lithium Manganese Dioxide (LiMn02). These kinds of batteries are often used in cameras because of their high energy density and ability to perform in low-temperature environments. CR batteries are also used in smoke alarms and security applications. Anything that requires a small high-powered battery probably uses Lithium Manganese Dioxide chemistry.

    CR Batteries:

    1. Provide a high density charge in a small package
    2. Work well in digital cameras and computer peripherals
    3. Can handle low temperatures relatively well
    4. Discharge quickly and evenly (for a camera flash)
    5. Have a great shelf life

    BR Battery Chemistry
    BR denotes Lithium/Carbon Monofluoride Li-(CF)x. Batteries with this kind of chemistry are well known for their superior shelf life. BR batteries often last 7 years on the shelf. They have one of the slowest self-discharge rates of any battery on the market. That’s why they are commonly used in clocks, pacemakers, and not surprisingly, long range missiles.

    BR Batteries:

    1. Last up to 7 years on the shelf
    2. Have been used in space applications since 1976
    3. Can be found in pacemakers
    4. Function up to 85 degrees Celsius
    5. Usually discharge less than 0.5% each year

    from: http://www.cr2032.co/chemistry-article.html

    How much does a new one cost?
    The 71,700 Backup Battery goes for $120, and can be order by calling 503-263-0037

    What do you use to glue it to the back of the cover?
    We use silicone to adhere the battery but this comes attached to the battery.

    How long should it keep the EFIS functioning?
    The internal backup battery should be able to power your EFIS for over half an hour. The easiest test is to enter calibration, SELECT into Airspeed, and change your Airspeed Adjust to 50 kts. This will keep the EFIS from powering down. SAVE and RETURN to EFIS mode. At this point turn off your master and start a timer to see if the EFIS can remain for over 30 minutes. Be sure to return the Airspeed Adjust back to its original settings after this test.

    I would recommend about every 5 years replacing both backup batteries.

    and what voltage is indicated when powering the EFIS?
    There is a small battery in the lower left of the EFIS. That has 4 bars showing charge.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  3. #3
    Shawn, thank you for your informative and educational reply with regards to the CR/BR question.
    I really appreciate your taking the time to explain it to me.

    Quote Originally Posted by Shawn McGinnis View Post
    The 71,700 Backup Battery goes for $120, and can be order by calling 503-263-0037
    With regards to the 7.4V backup battery, that price seems awfully high.
    I did some searching for other 7.4V 2.2Ah Li-Ion battery packs and they were selling for $30 to $45 and included the protection circuitry.
    Is there something special about the ones from Advanced that I'm overlooking?
    Last edited by Wicked Stick; 11-10-2014 at 06:44 PM.

  4. #4
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Quote Originally Posted by Wicked Stick View Post
    Is there something special about the ones from Advanced that I'm overlooking?
    We provide a finished product that is guaranteed to work with the EFIS and it's charge controller. Other batteries may work.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

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