iPhone 5S Motion Co-Processor Still Tracks Movement After Battery Dies



According to a post from Reddit user Glarznak, Apple’s iPhone 5S apparently continues to track your movement even after the battery dies. The Redditor noticed this when he was traveling abroad and his lightning cable broke.

Glarznak had another four days left before he returned home and he decided not to charge his dead iPhone 5S, instead he threw it into his backpack. His post suggests that even though the battery was dead the phone continued to track his every movement.

On his post, Glarznak writes:

While traveling abroad, my iPhone cable stopped working so my 5s died completely.

I frequently use Argus to track my steps (highly recommended if you have any health bands or accessories) since it takes advantage of the M7 chip built into the phone.

Once I got back from my vacation and charged the phone, I was surprised to see that Argus displayed a number of steps for the 4 days that my phone was dead.

I’m both incredibly impressed and slightly terrified.

Apple first introduced the iPhone 5S in September and includes the M7 co-processor that was designed to track users’ movements, including steps taken and distance traveled. With the help of third-party fitness apps, the co-processor aims to help users improve their health and fitness levels.

It is well known that your iPhone will shut off before your phone’s battery is completely drained, normally around the three to five percent mark. This gives the phone a chance to save the contents of memory, so that you do not lose any of your current data. Even with only three to five percent of battery left and the phone completely powered down, the M7 co-processor was still able to keep track of the Reddit users’ motion for four full days, probably because the co-processor requires very little power to operate.

Apple is expected to release an iWatch along with iOS 8 later this year, which will reportedly focus heavily on fitness and health applications. It will be interesting to see if and how Apple will tie in the M7 co-processor with the rumoured iWatch.


  • Al


  • techguy01

    Why do you say that? It is possible that the iPhone after it shuts off will continue to track your movements. The M7 processor probably needs so little power that Apple enabled such a feature.

    People who are into fitness tracking would appreciate this feature (assuming it is actually true).

  • Al

    4 days on < 5% power, triangulating GPS location non-stop? I don't f'n think so.

  • techguy01

    No one said GPS! Motion tracking has nothing to do with GPS. Taken a users steps does not have anything to do with GPS. Sorry but you are completely wrong.

    Even distance traveled can be calculated without the use if GPS.

  • Al

    Sorry – My mistake.

    Having said that… Measuring non-stop motion? On < 5% power? Seriously?!

  • andrew boon

    wow great !

  • SFlsf

    Not very accurately, but yet it can be done (it’s called inertial navigation) and would take significantly less power than a GPS chip. The problem is INS systems can be thrown off pretty easily. I’m a engineering grad student, with experience in this field, and think it’s possible. I’m assuming this isn’t default behavior though. It’s likely only doing this because of the fitness app.