Acer w510 battery drain and apps stability - solved

I have Acer w510 device (tablet + keyboard dock). I love the device - lightweight, excellent battery life, nice combination of the true tablet capabilities with micro-laptop (when connected to dock). And it runs my regular windows apps!

I bought the device last fall, when it just came out, and I'm using it daily.

However for a while I had some lingering problems with standby battery life - initially it was pretty good (few percent of battery drop per day of standby), but later on mysteriously it became pretty bad - up to 30% overnight. It was not too bad for me (I tend to recharge the device each night), but it was annoying. After a lot of research and tinkering I solved the problem, hopefully the solution will be useful for others.

(I also read the long thread on the battery life issue on this forum, the hint to look at WiFi driver actually came from there, but that thread is rather convoluted and unclear, so I decided to post my explanation of the problem and proposed solution as this separate message)

Also for a while I had a problem of some of the apps I tent to run all the time (e.g. Outlook) were crashing from time to time. Not often enough to become a real problem, but even twice a week is annoying - and worrying. Stable applications should not really crash. It turned out that the problem was the same as with the standby time, and the same solution fixed it as well.

The problem turned out to be associated with Connected Standby. This mode was enabled in the OS sometime in February or March in one of the updates, and since that I was having the problem. Here is some background information.

Connected Standby - how it works

As everybody knows, laptops (and most desktops) support Sleep state. Traditionally sleep state was essentially what the name suggests - CPU and all electronics is turned off, but RAM is powered and retains the state. On resume CPU and other hardware state is restored from RAM and the system keeps running. All apps, drivers and the OS are totally suspended while in Sleep state.

In Win8 there is new mode - Connected Standby. On hardware that supports it Win8 will unconditionally replace standard Sleep state with the new Connected Standby mode, and it works rather differently. In Connected Standby mode the CPU and hardware never actually sleeps - it is always powered. CPU is just sitting in the low-power state, waiting for the system timer most of the time. Applications are artificially suspended by a special OS component (DAM driver), and every 30 sec or so apps who need it are given some CPU cycles to execute background tasks or process incoming network data.

Network connection in Connected Standby mode is actually kept alive, and is processing data. You can actually ping machine in Connected Standby mode (but need to enable ICMP for it).

When you press "Sleep" button on the machine with Connected Standby, it does not actually go to Sleep. Instead it just turns off the screen and OS is going into the Connected Standby mode. And as I mentioned there is no way to switch Win8 to a regular Sleep mode - it is unconditional.

In most ways Connected Standby is essentially the mode your regular phone is operating in, but retrofitted to Windows.

The Problem

It is all nice and cool, but there are so many different components at play that things don't always work well. Specific problem on W510 is the Broadcom WiFi module and its driver. It just does not work too well in Connected Standby mode, and WiFi is sucking a lot of power while in Connected Standby.

It is not always the case - using powercfg tool you can see power usage reports and it varies. Sometimes power consumption in Connected Standby mode is great, sometimes it is pretty bad. It seems to depend on which network you were connected to before entering Connected Standby, and whether that network is still available while in Connected Standby etc. But quite often power consumption was bad for me.

Another problem happens when the data arrives while applications are artificially suspended. Instability with Outlook (and few other apps) I mentioned seems to be just that - new data arrives, but the app cannot process it properly when in Connected Standby mode, and sometimes the app crashes (typically on resume, but sometimes it was actually crashing the whole OS in the process of entering the Sleep state).

Solution

I spent quite a bit of time tinkering with settings, reinstalled OS few times, changed drivers etc. Eventual solution that seems to work fine for me is to use older Broadcom WiFi driver from Acer 1.01 driver pack.

Actual OS is clean install (I reinstalled the OS from Microsoft Win8 media but it should work with Acer image as well) and fully patched. Then I installed latest drivers (2.08) that also updates BIOS. Then I manually update just the Broadcom WiFi driver to that old version (device manager, update driver, manual, point to the broadcom WiFi driver in the 1.01 pack).

It seems that the old Broadcom driver behaves differently than the latest one - it disables WiFi while in Connected Standby mode. This fixes battery drain problem, and it also fixes app stability issues because there is no data transfer while in Connected Standby.

The drawback is that it takes 10-20 sec to re-establish WiFi connection after wakeup, but it is a small price to pay for not having other problems.

I'm using this solution for over a month now with absolutely no problems with app stability or battery drain. If you are experiencing similar problems - try it out.

(I would also suggest Acer to get the Broadcom driver fixed, and maybe push the old driver in the mean time)

With best regards

Tony