BMCracer

Nexus 7 - Ongoing battery drain

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2013 ( second series ) Nexus 7 in a 2007 Legacy. Got a DC/DC step down tranny plugged into the cigerette lighter feed ( no power to cigerette lighter anymore ). USB OTG Y cable into DC/DC output. USB OTG Y cable goes to Nexus. 3rd leg of USB OTG Y cable has  the output from the Tactrix. I have the Tactrix with the cable, so cable is plugged into the cars' OBD2 port, not the wireless one. Got Timors ROM on the Nexus, it's in the FI mode, and does the "suspending" thing when the power is taken away ( car turned off ).

 

The Nexus was at 100% last night, 6pm ( had it out of the car for a while but exactly the same thing was happening before ). This morning 6:30 am, it's at 73%. How does it loose 27% just sitting there, supposedly asleep? I drive 25 minutes to work, and it's up to 86%, but will loose another 25%-odd while I'm at work today, small charge on the way home, loose more tonight, so by about Sunday it'll shut itself down due to flat battery, and I'll have to pull it out of the dash to be able to press the power on button once I've recharged it. 

 

All I run on it is BtSsm and Google maps ( offline ) at the moment. Any ideas appreciated.

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Try an add-a-fuse as the power source direct to the fuse box. Mine was originally like yours, using the wires off the back of the ciggy lighter and never charged as well as it should have.

 

After being off for a few hours what is the on time counter at in powereventmanager?

 

 

 

 

Doesn't help with the power issue but let's the tablet turn on by cycling power to it so you don't need to pull it out of the dash when it goes flat.

 

https://legacygt.com/forums/showpost.php?p=5478955&postcount=32

 

Plus a bit more info from Pharnos as to how you do it.

 

Hey man,

So yeah you need the adb and fastboot android tools on your computer.

some good instructions here:
http://forum.xda-developers.com/show....php?t=2317790

http://lifehacker.com/the-easiest-wa...-to-1586992378

Once this is all setup, you can then connect your nexus (on, at the main menu) to your computer and run that command in my post "adb reboot bootloader". This will restart the nexus to the little green fella. Once there (fastboot mode) you can run the next command "fastboot getvar all". This just shows the current settings. This next command makes the change "fastboot oem off-mode-charge 0". Then you can reboot the nexus. done.

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I don't think it's a charging issue, as when it's charging it's always pretty good - I've checked the charging current in the power event manager each time and it's always good, like 0.8 - 1.1A. I think it's more a case of either it's not going to sleep when it suspends, something is still running in the background, or something is draining it somehow. I'll check the on time counter later, might go to the car at morning tea time to check it.

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This is what the power event manager screen told me this morning:

 

USB Host mode: Active

External Power: Yes 1200mA max

Charging battery: Yes 52% 734mA

Powering slaves: No

 

Fast Charging: yes

Firm sleep ( disable wakeup alarms: no

Disable secondary USB audio device: No

ADB over network port 5555: no

Auto activate cam by device detection: no

Auto activate cam by FTDI detection: no

 

USBDisk media Server support: no

Auto-mount USB drives: no

 

Last screen off duration: 14 hrs 05 min

Suspended 100.00% / Awake 0.00% (0.00 sec)

Battery charge level / change: 77% -33% =44%

External power reconnect counter: 28

Timur's Kernal v4.0 build 105

(c) 2016 Timur Mehrvarz https://timur.mobi

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I reckon something in that power circuit is causing a small power draw. I know mine will be flat after 7-10 days if not driven at all if just turned off when the acc power is cut. But lasts 2 weeks plus if I flick the switch I installed between the transformer and the tablet 

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So all those settings above are correct?

 

I'll see if I can put an ammeter inline to see if there is any leakage.

 

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Most are right. 

I have firm sleep and disable secondary USB audio device selected which are the only differences.

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OK, Had the nexus in and out of the car more times than I care to count. Last 4 days before it's flat. So I disabled as many apps as I could, turned other stuff off, basically had as little as possible available to run. Didn't make squat difference.

 

Then I had a thought the other morning at 2am, as you do. When it's in the lounge charging, and I unplug the power for a day to test it, it loses 2% maximum ( over about 14 hours ). The only difference between when it's in the car and when it's the lounge, is that the BtSsm isn't plugged in to the Nexus. So last night I put the Nexus back in the car, and this morning it hadn't lost any charge. So I enabled all the apps again, turned on google maps again and turned on location again. Then today after work, it hadn't lost any charge either.

 

So it looks like the BtSsm is what is draining the battery. But how, why, and what to do to rectify that? I have the OBD2 extension cable plugged into the cars' port in the footwell, and run up in the dash into the device, with the usb cable coming out of it into the OTG Y cable. So as far as I can tell, the car is powering the device through the OBD2 port, becuase when the Nexus is out of the car, the device is still powered because it has lights that change colour like a disco. So the nexus shouldn't be powering it?

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Nice find. With your OTG cable only the data wires should be going to the Tactrix anyway so no chance of powering it unless you have a cable that does send the power that way too? 

Or it's just the data source somehow keeping things from fully shutting down even though the uptime doesn't seem to think so.

 

Get a powered USB hub. Mine loses the data connection if the hub isn't plugged in so killing the tablet power supply it is also connected to cuts it.

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I too was suffering the same issue, I ended up adding a relay to the ODB2 cable in effect disconnecting the main power line between the ODB2 cable and the hub/tablet. IT does slow the drain but still not enough if you don't drive daily. Next step is hard wiring :/

 

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OK so it's update time.

 

I got a powered 4 port hub, and plugged that into the dc/dc convertor, and then fed the Tactrix and the Nexus from it. and you know what, finally it works!!!!!!!!!!!!!!!!! The battery doesn't drain 30% overnight. Now when the car is parked during the day at work, or overnight at home, it loses 3% at worst, but most times either nothing or 1%. So a big thanks to Andy_Mac for that tip.

 

Tonight I put in the FSL21 unit I got from Japan via Import Monster, the Beringer 202 I got from ebay, and also ran a USB extension lead to the centre console ( from the 4 port hub ) so either charge a phone in emergency, but more to be able to upload music to the Nexus without having to pull the dash to bits.

 

So it's 99% there, I just need to figure out why google maps doesn't work offline most of the time.

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OK so yes I am a retard. And I know it. I went to here Pharnos' thread https://legacygt.com/forums/showpost.php?p=5478955&postcount=32 as linked by Andy Mac

 

and then I went here https://developer.android.com/studio/releases/platform-tools.html and downloaded the SDK Platform-Tools for Windows. Next I plugged the Nexus into my PC, and turned the Nexus on by pushing the power and volume - buttons together to enter Bootlogger mode. Moved to option "Restart Bootloader" press power button, it did it. But it comes back to the same screen. Where / how do I type in the code " adb reboot bootloader " to get to the next screen so I can change the off-mode-charge from yes to no? 

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@pharnos should be able to clear it up. I was super confused when doing this too. 

Just realised those links didn't work when I copy and pasted from legacygt.com The XDA one was super helpful

 

https://forum.xda-developers.com/showthread.php?t=2317790

 

https://www.lifehacker.com.au/2014/06/the-easiest-way-to-install-androids-adb-and-fastboot-tools-on-any-os/

 

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So using the links from Andy_Mac, and Pharnos' instructions on LegacyGT.com, I got that ADB and Fastboot installed on my PC, and sorted out the off-mode-charge setting. 

 

Pharnos, mate you're a bloody legend for working that out and posting it up, and Andy_Mac, you're a legend too for posting up the links to it. Thanks heaps guys, that made my night tonight 😊

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Good to see a positive turnaround with this thing finally haha
 

The only extra thing I've done is added a switch for the positive wire to the power supply which when the tablet goes flat allows me to restart it while driving.

It will need a few mins of driving to get the charge high enough to boot but won't as there hasn't been an power on/off situation during the time it has had enough power to actually boot.

Turning the car off the back on works but gets super annoying doing it that way when you won’t know if it is actually ready to boot or not until you try. The switch allows you to quickly flick it off for a sec then back on at which point it'll either boot or flash the battery on the screen to say it needs more time. 

 

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13 hours ago, Andy_Mac said:

Good to see a positive turnaround with this thing finally haha

 

Couldn't have done it without all your help!! Honestly, the thing would have been thrown on the driveway then had a sledgehammer put through it. But happy days now finally, touch wood. 

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I'm going to put this here because it's all part of the Nexus install problems, so people can hopefully find several answers in the one place. Maybe a Mod can change the title to "Nexus 7 Fixed Install Problems"?

 

It's been going well since the above posts. Then the car started using a little more petrol than usual, used to be around 10.6/100, but it went up to 11.4/100, for no apparent reason. So I looked at the codes, and it had 2 error codes up ( I will start a new topic for this in the appropriate section )

 

IAT too low 

MAF too high

 

I forget the code numbers, and I may have got the too high and too low around the wrong way, but anyway. So I reset the ECU while sitting at a set of traffic lights, then continued on. The fuel consumption went back down to 10.6/100, and the car *seemed* to have a bit more go. I did some logs before and after I reset the ECU to see how much timing it was pulling out. When I got home and turned the Nexus Wifi on to connect to the house wifi, so I could email the logs to my PC so I can post them and hopefully get some advice on the problem and what to do about it. Ever since then, the Nexus has s*** itself ( again ), more specifically the FI mode, and it won't sleep when the power is cut to it etc etc. I've had this several times before, and the only thing that seems to fix it is a new USB OTG Y cable. So I took the cable to work and ground off all the rubber insulation around the 3 plugs, and then cut all the other bonding stuff away, hoping to find a microchip that is fried. But no, there is nothing but the wires going between the plugs. So I've put another ( I started buying them 5 at a time ) new USB OTG Y cable on the Nexus now, and it magically works again. I'm guessing as long as I don't connect the Nexus to the wifi, it'll be good.

 

So I've got 2 questions.

 

1/ How do you brick a cable that is only copper wire and plastic insulation?

 

2/ How else do you connect to the internet? For maps etc? Do you use your phone as a hotspot and connect the Nexus to your phone, and somehow having your phone between the Nexus and the internet provides some kind of barrier that stops the internet bricking the OTG Y cable? And then bluetooth the files from the Nexus to your phone, then you can email the files from your phone to whoever / wherever?

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1)

current draw too high for tiny wires since powered all the time. I’ve seen this as most older cables are for 5v .2a or .5a and new devices can take 2amps. It can melt the insulation off until it shorts internally

or

vibration from the car wearing the cable out

 

 

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There's no way going on the internet has ’bricked’ an OTG cable. Do you have auto updates on for apps or anything like that? Something updating when you went on the net is the only thing I can imagine that may cause a compatibility issue. 

 

Have you force rebooted the Nexus from powerevent manager?

 

My phone was always used as a hotspot with bluetooth split so the phone could be connected for calls and the Nexus for music. With the Nexus connected to the net i’d just upload logs straight from BTSSM to Google drive for later viewing.

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