05-07-2013 08:54 AM
The slate is near perfect in my oppinion, with only two issues to be fixed, the first is the lack of power management.
After opening my new HP Slate7, I charged it, installed a couple of my favorite apps, setup my email accounts, charged the device to 100%, then turned it off, went to bed, and the battery had lost 80% of its charge over night. Okay, so I left wifi on, and data sync -- turned those off. Next night, same problem. Factory reset, full charge, turned off, left over night, same problem. So a factory-new unit will completely deplete the battery in 20 hours with no use.
The "apps" tab in the "settings" app indicates 80% of battery use was caused by "Tablet Idle". The only running apps were the ones that start at boot, after a factory reset.
Further investigation (using cpuspy) shows that the tablet never goes into deep-sleep, but rather idles at 200Mhz, even with wifi and sync off. By installing "DS Battery Saver" the tablet would deep-sleep sometimes, but ultimately non-deterministic.
At this point I'm waiting for a fix. I completely shutdown the device when not in use now.
Love it otherwise!
05-07-2013 10:22 AM
I am experiencing the same thing. It drains battery very quickly when not in use. Unfortunately I think we will have to wait until this device has been rooted and the kernel source is released. There is a strong possibility it already is considering this is stock Jellybean, but I don't know if any other device shared similar hardware.
Tablet: HP Slate 7
Laptop: Hp Envy 4
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05-07-2013 11:01 AM
When leaving the tablet for more than a couple of hours, turn the tablet fully off rather than putting it into standby.
Hold the power button down and select "power off".
As I understand it, in Jelly Bean, apps have the ability to silenty wake the tablet with the screen still off and check for updates.
I am an HP employee
05-07-2013 11:56 AM
I just installed "bettery battery saver plus" on the slate7, which will eventually show me which services/apps are issuing wakelocks on the device. we'll know soon enough. but I fear there's nothing we can do about it until the device is rooted or HP issues an image update.
Holding the power button down for a cold power down is not a solution, but the only workaround to a dead battery every day.
05-07-2013 12:09 PM
So far I have been fairly satisfied with the battery in the Slate 7, but that's just from general impressions. For example, yesterday I played some tunes on it at lunch for an hour or so (charged it up the night before), did some general browsing with it in the evening, did not charge it overnight last night, and sitting here a day and a half after its last charge and some fairly significant use my battery monitor says it has 27% charge. I keep Wi-Fi and sync on.
I have not done a test to just charge it fully, then track battery drain with no use. Seems like a good task to start tonight (I'll have to go back to my CM10 TouchPad while the Slate rests ).
(Note: As a top contributor to the HP Consumer Support Forums, HP provides me access to the Slate 7 at no charge so I may better respond to the questions raised on the Forum.)
05-07-2013 03:09 PM
I'm glad it's not just me having this issue. I am very disappointed with the battery life.
At the moment, after a full charge I am getting:
14hrs on battery
Battery remaining 33%
with moderate usage. In 7 more hours of none use it will be dead
In contrast, my wife's Nexus 7 with similar usage shows the following after a full charge:
1day 14hrs on battery
Battery remaining 49%
I know the hardware is different, but surely it can't be that different! The Nexus 7 has three or four times the battery life!
i really hope there's an update for the software soon to deal with this or I may be sending it back
05-07-2013 03:23 PM
Can i ask you to do something to help narrow this down?
What was the battery life you were getting on the stock image?
I was getting several days usage between charge running a mostly stock image.
I have run Factory Reset a bunch of times during testing, so I don't have many apps installed.
It will help to compare out of the box battery performance, to determine how it is being affected.
Providing the info above also helps. If you can include the build number as well.
I'm on 1.05.4_20130406_user
I am an HP employee
05-07-2013 04:49 PM
During my last round of isolation testing, I noticed that when the system goes into "never deep sleep" mode, there is a frequent kernel wakelock called "suspend_backoff". As soon as the slate7 starts exhibiting the symptom, "suspend_backoff" becomes the number one kernel wakelock.
I've been cold-starting the device over and over. If you let it boot, and not touch it, the device does, in fact, go into deep sleep. I've been testing different stimuli until the "suspend_backoff" kernel wakelock begins to happen. In my last test, from a cold boot, simply turning on wifi, then a momentary press on the power button (screen off) was sufficient to start the generation of "suspend_backoff" wakelocks, along with the corresponding symptom of never going into deep sleep.
The last experiment is inconclusive as to the root cause. Possibly the network stack, possibly the wifi hardware, or possibly the wifi network environment. Perhaps there's a broadcast on my network that provokes android into issuing this "suspend_backoff" wakelock.
I'll do some more testing based on those theories.
Looking forward to a slate7 that deep sleeps,
05-07-2013 06:18 PM
I've done a little digging on this issue, and it looks like the Slate is not alone in this issue. A thread on XDA developers for the nexus 4 also has the same problems listed using the same apps edfardos has used to see what is going on.
In their findings they saw that chrome was the cause of a lot of this, and you have to go in to settings within chrome, then developer settings, and turn everything off.
They also mention facebook as being a major cause of these problems.
The cause of the "suspend_backoff" events are when an app or process wakes the device as it goes in to sleep a certain amount of times in a set time period. Examples would be facebook as above if you have several updates coming on, or possibly chrome sending data for the developer settings. This keeps the tablet on rather than constantly sleeping and waking non stop, which explains the heavy battery usage.
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