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[Q] Nexus 7 in car

OP Ted_rivers

23rd January 2014, 07:12 AM   |  #1  
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Hi, I have recently installed my Nexus 7 (running CM10.2 on 4.3.1 and leanKernel) in the dashboard of my car. I installed a cigarette socket behind that dash that provides power to the device when the vehicle is running. When the vehicle turns on i have tasker set to lock the display on, start my music and torque. The problem I am having is when the N7 is one and receiving a charge the battery is still discharging (approx. .8%/h according to battery stats app). I have used 3 different charges, two which are 2.1A and the third is 150w dc 12v to 110v ac power inverter which i have used 2 different usb chargers in, but i am still seeing the battery discharge while I am using the tablet. i can rewire the cigarette socket so it is constantly charging the device but since I am not able to reach the power button on the tablet i dont know how ill be able to toggle the screen. i have tried to under-clock the cpu and gpu (currently have the device running on 1 core) but still havent seen an improvement. Any idea what i may be able to do to rectify the problem?

I was also going to try to upgrade the tablet to 4.4.2 but adb and fastboot cannot see the tablet anymore. i updated the usb drives and it was working perfectly fine up until a week ago so i am not sure what is happening.

Thanks for the help.
23rd January 2014, 05:11 PM   |  #2  
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Quote:
Originally Posted by Ted_rivers

Hi, I have recently installed my Nexus 7 (running CM10.2 on 4.3.1 and leanKernel) in the dashboard of my car. I installed a cigarette socket behind that dash that provides power to the device when the vehicle is running. When the vehicle turns on i have tasker set to lock the display on, start my music and torque. The problem I am having is when the N7 is one and receiving a charge the battery is still discharging (approx. .8%/h according to battery stats app). I have used 3 different charges, two which are 2.1A and the third is 150w dc 12v to 110v ac power inverter which i have used 2 different usb chargers in, but i am still seeing the battery discharge while I am using the tablet. i can rewire the cigarette socket so it is constantly charging the device but since I am not able to reach the power button on the tablet i dont know how ill be able to toggle the screen. i have tried to under-clock the cpu and gpu (currently have the device running on 1 core) but still havent seen an improvement. Any idea what i may be able to do to rectify the problem?

I was also going to try to upgrade the tablet to 4.4.2 but adb and fastboot cannot see the tablet anymore. i updated the usb drives and it was working perfectly fine up until a week ago so i am not sure what is happening.

Thanks for the help.

Hi, do you have a dcdc-usb? I know Who did your work (n7 in dash car) normaly have that, with a otg-y cable and normaly use USB ROM with Timur's kernel, which is a dedicated rom for car 's installation. Try to search info about that.
Unfortunatelly development is stopped to android 4.2 (the release before 4.3) But it' s very good rom.
If your installation is fixed, in the night u will lost about 1-2 %
Ps can you upload some photoes about your dash ?

Inviato dal mio Nexus 7 utilizzando Tapatalk
Last edited by furious84; 23rd January 2014 at 07:46 PM.
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23rd January 2014, 10:32 PM   |  #3  
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Quote:
Originally Posted by furious84

Hi, do you have a dcdc-usb? I know Who did your work (n7 in dash car) normaly have that, with a otg-y cable and normaly use USB ROM with Timur's kernel, which is a dedicated rom for car 's installation. Try to search info about that.
Unfortunatelly development is stopped to android 4.2 (the release before 4.3) But it' s very good rom.
If your installation is fixed, in the night u will lost about 1-2 %
Ps can you upload some photoes about your dash ?

Inviato dal mio Nexus 7 utilizzando Tapatalk

I dont have a dcdc-usb as the power to the tablet is coming from 2.1A car charger or a 150w power inverter. i dont have a otg-y cable but i do have the means to easily install one if i ever need it. I never knew about USB rom and Timur's kernel. ill flash those asap and hopefully that will fix the battery drain. As for pictures i only have this one from when i first installed the the tablet but know i have my dashboard disassembled. hopefully this will hold you over for now .
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23rd January 2014, 11:13 PM   |  #4  
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Uhm i can say to u try the USB ROM,i haven't other idea
Ps nice work

Inviato dal mio Nexus 7 utilizzando Tapatalk
26th January 2014, 01:35 AM   |  #5  
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Ted, you need to flash a kernel that supports fast charge and enable it. I have the same issue, after flashing a 4.4 rom I lost my fast charge and over the duration of a long drive the battery is discharged. Apps such as fanco kernel updater have the option to enable fastcharge, if the kernel supports it. Great setup BTW, I have mine mounted on the dash.
26th January 2014, 04:21 AM   |  #6  
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Quote:
Originally Posted by ryar

Ted, you need to flash a kernel that supports fast charge and enable it. I have the same issue, after flashing a 4.4 rom I lost my fast charge and over the duration of a long drive the battery is discharged. Apps such as fanco kernel updater have the option to enable fastcharge, if the kernel supports it. Great setup BTW, I have mine mounted on the dash.

Hi ryar,
Thanks for the help. I've flashed a few different kernels that have fast charging enabled. The latest is Timur's kernel which says fast charging is enabled. Sadly my tablet is still discharging when its in use so I've decided I'm going to have it set to charge at all time and use a magnet to switch the screen on when I need it.
26th January 2014, 04:58 AM   |  #7  
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Quote:
Originally Posted by Ted_rivers

Hi ryar,
Thanks for the help. I've flashed a few different kernels that have fast charging enabled. The latest is Timur's kernel which says fast charging is enabled. Sadly my tablet is still discharging when its in use so I've decided I'm going to have it set to charge at all time and use a magnet to switch the screen on when I need it.

Are you trying to charge in host mode or just using the USB came that came with the nexus 7? I could help you solder power and volume to some switches so you can toggle screen on off that way? I bought a Samsung branded car charger and it works great for car charging. I made a y cable that you can turn host mode on and off with a switch. I could help talk you through it or do it for u if you buy the stuff its pretty cheap fairly simple to do if u have patients. Most of Those 2.1 amp dual port chargers only supply 1 amp to android devices, this could be your problem.
26th January 2014, 09:44 AM   |  #8  
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Quote:
Originally Posted by b3ltazar

Are you trying to charge in host mode or just using the USB came that came with the nexus 7? I could help you solder power and volume to some switches so you can toggle screen on off that way? I bought a Samsung branded car charger and it works great for car charging. I made a y cable that you can turn host mode on and off with a switch. I could help talk you through it or do it for u if you buy the stuff its pretty cheap fairly simple to do if u have patients. Most of Those 2.1 amp dual port chargers only supply 1 amp to android devices, this could be your problem.


I am just charging the tablet straight up no host mode. ive used a variety of chargers: two different branded 2.1a chargers and both the stock nexus 7 wall charger and another tablet wall charger plugged into a 150w power inverter. Thank you for the offers! If its fairly simple to solder the power switch I would prefer to do that regardless of the discharging problem so that i can hard reset the tablet if i ever need to.

Thank you for the help!
26th January 2014, 10:31 AM   |  #9  
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Quote:
Originally Posted by Ted_rivers

Hi ryar,
Thanks for the help. I've flashed a few different kernels that have fast charging enabled. The latest is Timur's kernel which says fast charging is enabled. Sadly my tablet is still discharging when its in use so I've decided I'm going to have it set to charge at all time and use a magnet to switch the screen on when I need it.

Fast charging on Timur's rom work with otg Y Cable

Inviato dal mio Nexus 7 utilizzando Tapatalk
20th April 2014, 12:34 AM   |  #10  
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Quote:
Originally Posted by Ted_rivers

The problem I am having is when the N7 is one and receiving a charge the battery is still discharging (approx. .8%/h according to battery stats app). I have used 3 different charges, two which are 2.1A and the third is 150w dc 12v to 110v ac power inverter which i have used 2 different usb chargers in, but i am still seeing the battery discharge...

I've had my Nexus 7 "in my truck since last year. I at first had it sleep via Tasker, but I was having issues if I left my car for awhile. The batterywwould be low and if I didn't have long drives, I could never rechargeit to ssufficient battery fullness.

I changed my setup to have the tablet power on upon receiving AC ignitionpower using this adb command:

Quote:

there is a Fastboot command that you can issue to the bootloader to make the tablet power on once plugged it.* “fastboot oem off-mode-charge 0” makes the unit power on the instant its connected to AC. “fastboot oem off-mode-charge 1” returns to normal state,* so fitting an external switch isn’t 100% necessary, but i decided i wanted one anyway. I’m using Tasker to switch the unit on and off* with the ignition, but having the external switch is a handy addition.

Then I have Tasker turn it off after minute not being used. I'm sure it's not good for the Nexus 7 to always be at 100% power, but I don't care about the batter health because I purchased this for my truck only.

My only concern now, is the safety of the battery in AZ summer heat. I don'twant it to explode, and iI'm wondering if the tablet will function with AC power only, then I could remove the battery and not worry about it.

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