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Thread: Battery Backup on Race car

  1. #1

    Default Battery Backup on Race car

    When running a race car with a battery disconnect, the ECU loses date & time when the battery is disconnected. I like having the datalogs date & time stamped and it's not always possible to grab the computer to resync the time after the power is turned on in the car. Not to mention the numerous times one of the crew turns off the power or it gets accidentally bumped.

    I'd like to wire up a 9V battery with a diode (to prevent it getting cooked from car power) to retain the memory. Would this work? I'd also put a diode on the main power line to the ECU to prevent the 9V from trying to power anything else in the car. Would this work or is there a better alternative?

  2. #2


    Wire the ECU's main power DIRECTLY to the battery (around the cutoff switch). That is legal and your issue will be solved. NEVER insert a diode in the ECU's main +V. You cannot tolerate the voltage drop across the diode.

    Also. First time you forget to close the switch and turn on the ignition you'd kill the 9V battery and potentially lose the tune. I would NOT DO IT.

    I have two COPOs, seven Super stockers, one pro-stock, and 50+ bracket guys with the main power wired to the battery around the switch. Never had an issue. NHRA tech just wants to make sure the engine will die if you kill the disconnect.
    Last edited by fastmanefi; 09-14-2020 at 05:11 PM.

  3. #3


    Thank you!

  4. #4


    You're welcome. It'll be fine.

  5. #5


    Got that wiring switched around yesterday (also on a COPO). I wish I would've asked a few years ago. Took less than 15 minutes. Duh!

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