Help N7 dischargeing while charging??

[systemofadown]

Hi fellow N7 lovers
Ever since the 4.4.4 update my N7 has been struggling to charge fully. I've owned this unit for exactly 2 years now (Stock Rooted for about that long too). After the last update I reRooted & all was running fine as usual - then I noticed it was taking more than a day powered down to reach "almost" fully charged. Powered on & plugged into the OEM charger it slowly dies while saying Charging... My OEM charger still clicks tightly into the charging port & the battery does not get the slightest bit hot. I did manage to get one full charge & it lasted as long as when the tablet was new. I wiped the cache & Dalvic cache last night to no avail..
Screen time still shows to be the main battery killer & android processes show around the normal 3-5% or so.. I have very few apps on my tablet..
I would think maybe a bad charger but its been very well taken care of. Though it still could die like any other component over time..
any ideas?

 

[John Bean]

You mention the OEM charger but what about the USB cable?

My experience of the N7 is that it is very fussy about both the charger output and the quality (ie low resistance) of the USB cable. All it takes as a dirty contact and/or a suspect cable to drop charge levels below that required for operation while charging.

It's definitely worth trying a different cable.

 

[systemofadown]

Thanks for the input Sir Yep I'm using the stock USB cable/little black box combo that came with the N7 (I've never used anything else as I knew the N7 was picky about the current required to charge the battery). Both items have never been abused & the lockup between the N7 to micro USB is ultra tight as is the lockup between the USB to the wall charger.
This issue popped up right after the 4.4 update - could be coincidence I know but I've searched around the web & found a few others that had this same problem after the update & no solution as of yet. Just wondering if any users here have the same issue or found a fix..
in the mean time I'll try a couple differed charger setups

 

[John Bean]

It's a long time since anyone called me sir

One point to remember is that the USB connector on the N7 is a weak point, so if it gets used a lot it can develop a bad connection even when it feels tight. Trying a different cable can be a good indicator of wear since the "wear points" are unique to the exact combination of plug/socket. I'd stick with the original charger though.

If changing the cable helps at all I would consider buying a charge-only USB cable - often called a "quick charge" cable - which uses much thicker power wiring but has no data connectivity. I discovered these quite recently and use one to great effect with a portable battery pack, which recharges my N7 faster than the OEM charger and cable.

 

[systemofadown]

I took your advice & tried different setups. First off I plugged my n7 into my Laptop's USB port with the OEM cable. It started charging right away. Seems the charging block is to blame.. Thank you guys

 

[John Bean]

No problem

At least you now know where the problem lies, although before writing off the faulty charger it's worth checking this post in a different N7 charging issue. Maybe yours has a similar simple solution.

 

[systemofadown]

I may have spoken to soon.. I went out last night so I plugged my Nexus 7 back up to my laptop - just got in a few minutes ago and it was only at 50% where I had left it several hours ago... It was powered up yesterday when I first tried the laptop & got her to take a charge. if I power it down and plug it up it seems to charge sometimes & discharge others.. It's a strange situation...

 

[John Bean]

Are you sure the laptop provides USB power when asleep? Mine doesn't, so if I plugged my N7 into it and left it the charge would stop as soon as the laptop went to sleep even if it's on mains power.

Just a thought

 

[systemofadown]

Thanks for that tip . I had figured that since my portable external batteries charge even when the computer is sleeping that my Nexus would too. That may not be the case as you said- I'm keeping an eye on things & will report back with my findings.

 

[John Bean]

Many computers keep power on the USB port when sleeping but of course there's no data connection - which is ignored by "dumb" devices like batteries but most "smart" devices stop charging from a USB port in the absence of a data connection.

The solution is cases like this is to use a so called "quick charge" (charge only) USB cable which loops back the data connection in the same way as the mains charger does, fooling the device into thinking it's connected to a dedicated charger instead of a computer USB port.

It's also possible that the laptop has a single dedicated charge port designed to charge even when sleeping (often a BIOS setting) so one port may work while the others may not. My Samsung does that, causing me much confusion until I resorted to RTFM

 

[hawkwind212]

I had the same problem with both of my Android phones, and I really want to blame this issue on the custom rom, since I had this problem every time I switch over to the custom rom, but I guess that's not a scientific way to go about investigating a problem. This issue of discharging while charging only accords every once in awhile, and I usually solve the problem by swapping out the battery (oh, wait, you can't do that on the nexus line of phone, well that's too bad ). Otherwise I will just let it discharge all the way to 0, and most of time the device will reset itself.

 

[John Bean]

I will just let it discharge all the way to 0, and most of time the device will reset itself.

Never, ever do that to a Nexus 7 (2012), it can (and does) cause severe problems recovering from a "flat" battery that can in some cases can take days on the charger to make the N7 usable again. In a few rare instances the device doesn't take charge at all, no matter how long it is left on charger, requiring a return for repair.

This problem is pretty well documented; best practice with a N7 is to avoid low-battery situations (where it may power itself off) and never deliberately let it fully discharge.

 

[hawkwind212]

Never, ever do that to a Nexus 7 (2012), it can (and does) cause severe problems recovering from a "flat" battery that can in some cases can take days on the charger to make the N7 usable again. In a few rare instances the device doesn't take charge at all, no matter how long it is left on charger, requiring a return for repair.

This problem is pretty well documented; best practice with a N7 is to avoid low-battery situations (where it may power itself off) and never deliberately let it fully discharge.

Due to the scenario you described, I will never buy a device where I can't swap out its battery.

 

[UncleMike]

I've got a similar issue - while using my Nexus 7 in the car for navigation, it discharges, even though it's plugged in and "charging". Using one of these meters, I found the following:

1. When plugged into the OEM charger and cable the Nexus 7 draws 800ma while charging, while my Moto X draws 1000ma.
2. When plugged into my Belkin car charger and included cable, the Nexus 7 draws only 430ma, while the Moto X draws 1000ma.
3. According to System Panel, both devices believe they are connected to AC (not USB) on both chargers.

Any ideas on what the problem could be?

 

[JCWren]

Same problem here. I use mine in the car, the charger is capable of 2.1 amps, and I've loaded tested it to prove it. I didn't measure the current draw of the N7, but if I start out on a 6 hour road trip running Waze and/or Google Maps, at the end of the trip, I'm down to about a 40% charge.

Exit the app, turn the screen off, and and a few hours later, it's charged. Basically, it appears the N7 is using more power than it's willing to draw from the USB connector. Maybe that's to avoid damaging cheap chargers and PCs that don't current limit their USB ports.

With the navigation apps, I'm betting the processor doesn't get to sleep as much as if you were just using it for email and such sitting on a desktop. Backlighting also pulls a significant amount of current, relatively speaking. Maybe try turning down the backlight as far as you can tolerate will help some.

Update: Saw this post about an in-line USB current meter, which led me to a reference about charging cables. That led me to this link. Perhaps replacing your cable with a charging cable that signals to the N7 that it can do a high-current charge will help you. I'm going to give it a try.

 

[UncleMike]

I came to the same conclusion and the cable makes all the difference. I ended up buying this cable:

Amazon.com: PortaPow Specialised 5ft 22AWG Charge Only Micro USB Cable for Blackberry, Xperia, HTC One, Google Nexus, Other Fast Charging Devices: Cell Phones & Accessories

and this charger:

Amazon.com: SCOSCHE USBC242M 12 Watt USB Car Charger for iPhone/iPad/iPod Lightning/Micro - Retail Packaging - Black: Cell Phones & Accessories

The combination works well, but the same cable combined with my Belkin charger (rated @ 2.1 amps) worked equally well.

I also did some testing, and the stock Nexus 7 has the data pins shorted in the charger itself, which tells the Nexus that it's okay to draw more power - and it draws up to 800ma.

As best I can tell, Apple is the cause of all this. STANDARD USB charging specifications require the data pins to be shorted to indicate that more than 500 mA can be drawn. But Apple devices don't seem to like it when the data pins are shorted, so charger manufacturers don't short the data pins in order to be "Apple compatible". Even the above-linked charger is "Apple compatible", and will only charge the Nexus 7 at ~430mA without the right cable.

It's a sad state of affairs when a single manufacturer influences manufacturers of what should be UNIVERSAL accessories, making them no longer universal. It's BS like this that fuels the Apple haters - including me. I don't even own any Apple products, yet they're still screwing up my experience.

To summarize, the above-referenced cable should make any charger rated at 800 mA or more charge your Nexus 7 at its full 800 mA rate.

Now the question is, why does the Nexus 7 have a maximum charging rate of only 800 mA - only slightly more than that required to maintain its current charge level when using it for navigation?