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Thread: Nexus 7 - charging problems

  1. #1
    Constant Bitrate
    Join Date
    Mar 2008

    Nexus 7 - charging problems

    Hi Everyone,
    So, I moved from a PC-based setup to Android - all is more or less OK, except I am having some charging issues.
    Here's my setup:
    Tablet - Nexus 7 (1st Gen)
    Power - DCDC-USB (up to 10A) overvolted to 5.4V
    ROM - USB ROM / Timur's Kernel with Fastcharge enabled
    Self-made OTG cable with charging enabled
    Devices connected: 256Gb USB memory stick, 7 port D-Link HUB and a DAC.

    USB ROM does a really good job - my tablet doesn't lose much charge - usually it doesn't even drop a single % overnight.
    However if it DOES drop some charge, the tablet doesn't get charged on my way to work (it's only 2 miles "unfortunately").

    I experimented outside the car - it takes about 5 min for the tablet to even START charging. Then it starts charging quite fast (1.2A or so) but soon the Nexus ramps down the charging rate to 0.8A and then even lower. Sometimes it starts charging at 1.8A right away (as it supposed to be) but it doesn't happen often. Sometimes it starts charging at 0.5A and then it takes forever to get even 1% back.

    Apparently, it's a known problem... But maybe some smart soul here knows something I don't?

    I overvolted the power supply. I use shorter and thicker cables. Not much change.
    Thanks for reading!
    Below is a screenshot of my homescreen (just to show off. work in progress):

    Name:  Screenshot_2014-04-14-23-13-28.png
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Size:  186.6 KB

    Last edited by maxthebuilder; 04-15-2014 at 02:54 AM.

  2. #2
    Maximum Bitrate
    Join Date
    May 2012
    Grandville, MI
    Is this a new Nexus 7?

    If so you need a different kernel to allow OTG and charging at the same time.

    As far as I know OTG charging is not included in that kernel.

    Also, if you are powering a hub and other devices off your tablet you may find you can't do it all and may need some different options.
    There are powered hubs available and some other cool stuff.

    I will give you a link that is refering to a hacking platform for the Nexus 7 (2013) but there is much information in that thread about powering the device and some custom wiring etc to make it all work.
    I think you will get all you want and more from this thread if you read it all. Also I hope you have the 32gig version... Although the 16gig version will work the 32gig version has more flexibility.

    I have three ROMS loaded on my nexus and still have over 24gig available on the device.

  3. #3
    Constant Bitrate
    Join Date
    Mar 2008
    -1st Gen Nexus. 32Gb
    - OTG charging IS enabled and working
    - the USB peripherals are powered by the power supply not the tablet
    - It DOES charge but slower than it potentially could
    - Since my power supply is overvolted it actually charges a bit faster than the original asus wall charger but still slow
    - The main problem is that it doesn't start charging right away - it takes about 5 min to even start charging.

  4. #4
    Newbie mackey's Avatar
    Join Date
    Mar 2014
    timur has a thread on rootzwiki that may be of help

    hopefully the answer's there

    if i were to spitball, it may be a pin connection issue in the tablet since it's not consistently charging

  5. #5
    Maximum Bitrate
    Join Date
    May 2012
    Grandville, MI
    You might be better off asking directly on the xda-developers forum in the nexus 7 forum. You might find all sorts of cool stuff you want to add.

    They generally have much more experience in dealing with android tablets.


  6. #6
    Constant Bitrate
    Join Date
    Mar 2008
    Thought it would be nice to revive this forum...

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