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BTS3 draining my battery

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  • BTS3 draining my battery

    Installed my BTS3 per instructions on my 2007 BMW Z4. Works great.
    When I don't use the Z4 for 5-7 days the battery goes dead.
    Without putting the key in the ignition can connect my iPhone 11 to the BTS3 cable and it starts charging.
    Is this correct or could I have wired the power wire incorrectly.

    Harold L

  • #2
    In BMW the car "wakes up" when it senses the key, and the BT3 wakes up with the car. This is the reason you are able to connect the iPhone, and it will start charging. In general the BT3 does not drain the battery, however if the battery itself is already weak, as it happens often in older vehicles, adding BT3 can affect it.