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I have a carputer setup with a Nexus 7 tablet and a Carlink wireless carplay adapter connected via OTG splitter cable to the tablet. I have a problem in which the carplay dongle needs constant power to operate properly without resetting itself which often requires the tablet to be restarted to bring the dongle back online and get carplay up.

Needless to say, its a hassle to have to restart the Nexus with every time I start and stop the car ignition.

I need to solution in which I can supply a constant source of power to the tablet and the dongle.

I believe my options are 3. Any suggestions much appreciated for these or any others I may not have considered:

  1. Wire a circuit directly to the battery to avoid any interruption or power drop when the ignition is toggled on/off.
  2. Tap an existing constant 12v circuit such as hazards, power seat, etc. I believe possibly drawback here is that the ignition toggle may still interrupt power for a split second, long enough to cause the dongle to lose power and reset?
    1. Add a Jumper to relay controlling the accessory power socket I've currently got the tablet connected to. The jumper on the relay makes the socket hot continuously rather than on just with accessory. This may also be subject to power drop during ignition toggle?
  3. Get a "pass through" USB portable battery pack and connect to the power socket so that when the car is off, the tablet and the dongle draw power from the USB battery pack and when the car is on, they draw power through the car battery. I can verify that this is subject to voltage drop during ignition toggle, but it may just be that my tiny 3500mah Jackery battery pack is not sophisticated enough to switch from car battery to pack battery and vice versa, without dropping power.
Marcus Müller
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Scott B
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  • Option 3 if it’s a one off or very low volume. – winny Mar 15 '20 at 17:26
  • Most vehicles have constant power fused circuits in the vehicle Fuse panel / Fuse box. There are often spare output terminals available for accessory devices. – Dwayne Reid Mar 15 '20 at 17:37
  • Figure out battery drain and how to make sleep mode then fused non-ign, power – Tony Stewart EE75 Mar 15 '20 at 18:04
  • Option 3 sounds good, as long as you won’t park in the sun for too long. – Kokachi Mar 15 '20 at 19:29
  • I'm already doing option 3, however, the ignition triggers a voltage drop/surge that the battery pack does not immediately handle to switch modes. Therefore the connected OTG device loses power and resets. Trying to keep that OTG fully on at all times. – Scott B Mar 15 '20 at 20:37
  • Update: I tried same dongle and Y splitter OTG+charge cable on my Fire 8 HD tablet and although it does not support charging while OTG is connected, it does not have the restart issues that the Nexus has. I can disconnect the device then plug it back in and it restarts as expected, without requiring a restart. My suspicion is that the Nexus 7 is at fault here. Possibly the ElementalX OTG+Charge programming. – Scott B Mar 18 '20 at 01:51

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