arrow11 Comments
  1. Philip
    Jul 12 - 1:35 pm

    I presume that if one is out and about town with one’s phone, it would still pay to turn off wi-fi so that it’s not burning power by constantly (and fruitlessly) seeking out wi-fi connections. Does my thinking seem to be correct?

  2. Jim Szymanski
    Jul 12 - 3:35 pm

    True Phillip. Most of my time is spent between home and office, so the little time I spend out and about, I don’t bother to turn off WiFi. If I know I will be away froma signal for an entire day, I probably would turn it off though.

    The trick used above will automatically turn off WiFi as soon as you leave the range of the currently connected access point. If I were to build a feature for Windows Phone, I would keep WiFi running in the background, as it works today, but I would maintain a connection with an access point until it was out of range. Once out of range, WiFi would go back to sleep until you woke the phone again and it was able to connect to a new access point, and remain connected until you were out of range again. This would be an efficient method for implementing persistent WiFi.

  3. Xsever
    Jul 12 - 4:40 pm

    Hey Jim.

    Thanks for the results. I was expecting them since I was running my own tests too.

    Please note that I do not have a data plan so before this trick, my phone one would remain disconnected at night. My Nokia Lumia 900 averaged 0.828%/h without wifi.

    After trying the wifi trick, my drain average overnight is 1.046%/h. That is with hotmail set to fetch as items arrive, and whatsapp running.

    This is very acceptable and convenient for those without a data plan and your findings are even more surprising. Microsoft needs to look into this!

  4. Jim Szymanski
    Jul 12 - 9:20 pm

    Interesting results Xsever. I am still trying to figure out what uses the juice on my non-SIM HTC Surround, but your numbers are not that far off from mine. On the Surround, I forced WiFi on and let the phone sit for nearly 3 days, 71 hours total. I dropped a total of 86%, or 1.21%/hr over that time period, but remember the Surround only has a 1230mAh battery. Converting the percentage to the L900s 1930mAh battery, and the number equates to a total drop of 53%, or 0.75% per/hr.

    I only had Hotmail push and 2 internal background tasks (Network Dashboard and Battery Meter) enabled. I received multiple emails that I opened daily. And on the second morning I had 26 app updates waiting for me to install (it’s been a long time since the phone had a connction for 24+ hours) , which I did do, forgetting the phone was under test. Actually, I had updates waiting every morning. So of that 0.75% per/hr average in L900 battery life, WiFi was probably not responsible for more than about 0.2 to 0.3% per hour. Easy to understand how a persistent WiFi connection could actually save you energy.

    Glad you can now make better use of your phone.

  5. Xsever
    Jul 12 - 9:27 pm

    I also forgot to mention that next to the Hotmail email account, I have my university’s email account set to fetch every 15 minutes. This makes my numbers even more impressive.

    I have also been using my HP Touchpad charger to charge the 900. Where the original Nokia charger manages 650 ma, the Touchpad’s charger pushes 850 ma until the battery reaches the 90% range where the rate drops to trickle charge. This allowed me to fast charge the phone and I do not notice any excess of heat of anything.

    Back to the WIFI trick, it is really amazing and I am very glad that I can stay connected now. I like your idea at the end of the article about the WIFI policy. I thought of that too since on campus, you get handed from an AP to another and that requires applying the trick again.

    We need to get in touch with MS and show them our results. After Stephen Elop (NOKIA’s CEO) replying to my email today concerning something else, I believe we are a great feedback source for both Nokia and MS!

  6. The Truth About Windows Phone Persistent WiFi « Windows Phone News
    Jul 13 - 7:36 am

    [...] My previous baseline tests have resulted in an 16%, or 2% per hour, battery drain in an overnight 8 hour test. For clarification, my Background Tasks include; USA Today, Fox News, Weather Channel, Mehdoh, Urban Dictionary, Network Dashboard, Clever-To-Do and Battery Meter (a homebrew app set to update every 10 minutes). Continue to read the full story… [...]

  7. Joker
    Jul 13 - 11:52 am

    Its called connected standby in windows phone 8 and windows 8

    what is described here is a bastardised version of that.

  8. Jim Szymanski
    Jul 13 - 8:48 pm

    Interesting Joker, and good news assuming the info is accurate. Hope Microsoft gets it right the first (well, second) time.

  9. joker
    Jul 13 - 10:07 pm

    basically wp8 connected standby is based on system on chip wifi.

    but if someone can edit the wp7 registry to poll and connect with phone screen off periodically or after disconnect when moving to a different place with a different wifi AP …that will be great..

  10. [...] can inadvertently trigger persistent WiFi) or as part of the WP7.8/8.0 refresh. In yesterday’s Truth article, Joker added a comment indicating that Microsoft has rectified this issue with something called  [...]

  11. QC
    Nov 06 - 4:07 pm

    I’ve found a solution to this. Keeping the search app open in the background will keep the WiFi connection live.

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