[Nexus 7 (2013) Q&A] antc101:
Hi there everyone,

I have been trying to get my Nexus 7 2013 installed into my car seamlessly without problems since December 2015. I have Timur's Kernel v4 (6.0.1) running on it, and it was working flawlessly.

However, I decided that the no battery mod needed to be done as I just could not leave that battery inside a hot car - way too risky.

So, I did the Kevdav no battery mod - with success.

However, once the battery connection was receiving 5v via a usb car charger the OTG cable connected to the tablet's mini usb port would not wake/suspend the tablet properly. It would wake it up, but once it was awake the little battery icon at the top would forever show that it was 'charging' and once power was cut to the otg y cable / mini usb, it would not suspend (would still show as charging).

I did research, and bought a Drok DC-DC step down converter. I lowered the voltage to the battery mod connection to 3.7v (and tested up to 4.7v) and this alleviated the problem of suspend/wake. I think since the original battery gave out less voltage then the otg/charging connection, this needed to be replicated in order for the otg to work.

However, I now have a new problem that I cannot seem to fix. This problem only seems to happen in the car and does not occur when testing it in the house using normal wall chargers.

For clarity, this is how everything is wired up in the car.

Nexus 7 battery mod side of things:

Nexus 7 battery terminals > 22awg usb cable > drok dc dc step down power supply (this board has a female usb port for output) set at 3.7v (tested up to 4.7v) > input is connected to car's constant 12v connected directly to battery on a fused wire.

Nexus 7 mini usb port side of things:

Nexus 7 mini usb port > usb otg y cable > mini usb cable > 2.4a usb car cig adapter hardwired to car's switched 12v accessory wire.

The link to the drok dc dc step down is this - https://www.amazon.co.uk/dp/B01FDBY66Y/ref=twister_B01GO268W6?_encoding=UTF8&psc=1

I turn on acc ignition to send power to the otg connection. It'll power up. However, if left in standby overnight the tablet won't power up. If I physically press the tablet's power button it'll wake up, show the wake up animation, and react as normal (including any subsequent power downs). However, if I don't press the power button and I turn off the ign again, an icon on my car's instrument cluster will be faintly illuminated - this is odd behaviour and should be completely out. When this is the case, if I get out and try to lock the car the remote central locking doesn't work.

This light will go out if I physically disconnect the otg y cable from the tablet, and low and behold the remote central locking works.

I'm no expert on electronics and such, but it seems to me that power may be flooding back into the OTG connection from the no battery mod power?

Does this make sense? Sorry for the long question, but I was wondering if anyone had any experience with troubleshooting or any advice? I've this one problem and then I'm set but I just can't seem to figure anything out and need someone's advice who is in the know rather than take wild stabs in the dark using my own logic because if I do the latter, not only will I waste money on needless components but I'll more than likely break something. I've read stuff about diodes or something in order to regulate power flow but I'm not even sure I'm using the correct terminology here so if anyone can tell me I'm onto something here or I'm talking complete nonsense then anything is appreciated!

I did search these forums and google but I really cannot find anything that is similar to my problem.

Thanks for any input guys, whether it be any tips on what I'm missing or what I need to change (software or hardware, electrical, etc) - it's all very much appreciated.

Antony﻿

Edit: so sorry I think I posted this is the wrong n7 2013 sub section. I can't delete the post but if a mod could please kindly move it to the relevant forum I'd appreciate it. Thanks!