MetaWear Battery life

i have tested Metwear board with sample IOS application which you provide, when i kept metawear board on connected mode with iPhone, battery level decreased 4% point at each 10minutes. even i have not used any continuous communication with metawear board (like accelerometer record). after 3 hours battery level completed down.
Final result : 3 hours battery life with connected mode.

how to save battery life? whether we need to follow any configuration from mobile app or any hardware change required (better standard battery for long life). 


  • edited September 2014
    We would need more information such as how your product is behaving and how it is configured.
    These types of devices last a long time because 90% of the time they are sleeping; BLE is off, LED is off... If you have BLE and the LED on then the battery will drain very fast.
  • Apologies @samsgates don't mean to hijack your thread but would like to address the same problem. With the factory default settings, sample iOS / android application and full battery charge, what is the expected lifetime of the metawear board? Is there a difference between the uptime on iOS and android? The biggest issue addressing wearables today is battery life.
  • Similar question here...  I've found that if i charge my metawear overnight, and then leave it sit for about a week (nothing connected to it, basically doing nothing) it's dead.  That seems surprisingly short to me....  perhaps I have a bad battery?  What would you expect to see under those circumstances?

  • Mine will last a week on a single charge doing almost nothing (a demo or two a day). Perhaps try a different battery?
  • I'm also seeing battery challenges.  I tried to present this at a conference and it didn't last the 1/2 hour window.  Granted I had a 3d case and I think part of my problem was that the charger wasn't pushed in far enough but even at home testing I have to charge every few hours.  I'm lighting up the LED though.
  • @Ideluca,
    Yes the LED will halve the battery life very quickly since it's an ultra-bright LED (with a lot of current demand).
    You can always power your board with a much larger lithium battery since they are all standard, take a look at this website:
  • So basically this (from the faq) was significantly ambitious... Multiple months (without a different battery) isn't even in the ballpark of feasible.

    "The battery lifetime is highly dependent on the use case and can be anything from multiple weeks (as indication jewelry) to multiple months (as a beacon) on a single charge. "
  • @bmp, my recommendation is to experiment with your setup. Everyone will get different product lifetimes!
  • With MetaWear app on IOS we can get the battery indication in percent. It decreases very slowly and not linearly. Never get an indication below 90%, MetaWear stops before. Are you making a measure of the voltage of the battery? How do you get the battery charge level?
  • @cpignol-- sounds like they're doing strictly a voltage measurement (This is a guess based on the description in the hardware data sheet), which will not give a reasonable idea of remaining battery life due to the relatively flat discharge curve for a lithium cell.  Fine for determining when it's full but not so great for anything else.  The only way to get an accurate reading would be to implement a coulomb counter like the LTC4150 (, just an example) to record the actual watt-second power usage, which would require more circuitry if they didn't already plan to include this functionality.  
  • @lbattraw, Thanks for your answer. For this kind of device, power management is fundamental and the battery indication based on voltage doesn't really help. 

  • sam,

    What about the baattery life .. Still are you facing any challenges.
  • Replacing the battery with a bigger one, let's say 300mAh or more, will increase the charging time, right?

    Are there any other things to consider?
    Maximum capacity, type of battery, ...

  • Yes, bigger battery = longer charge time.  With a 300mAh battery, the charge time will be around 3 hours to 80% and 6 hours to 100% charge.

    The battery charger supports lithium ion and lithium polymer type batteries, of the "1C" aka single cell variety.  They have a nominal voltage of 3.7V, but you will occasionally see them rated as 3.5V or 4.2V.

    If you are using the ultrabright high current LED on MetaWearR, you will want to have a battery that can continuously source 50mA.  If you are using the vibration motor, you will want to be able to source around 70mA, and bursts up to 100mA for motor startup.  Most 50mAh and larger lithium polymer batteries will have no problem here.

    The battery charger is configured to charge at 90mA constant current, so the battery must be able to handle this rate.  For a 90mAh battery, it will need a max charging rate of 1C or greater. 

    There is no real maximum capacity, other than how long of a charge time you can tolerate.  If much larger batteries are required, we would recommend using an external battery charger.  It is generally safe to connect a secondary charger directly to the battery while it is connected to the MetaWear, it will not interfere with the on board charger (but I would not recommend plugging in the MetaWear USB while doing this).

    On special request, the charge current of the on board charger can be adjusted down or up to a max of 300mA for MetaWearR and 500mA for MetaWearRG.  However, MetaWear cannot communicate over USB to request currents exceeding 100mA.  This means for a smart device like a laptop or tablet, the charge rate will likely still be limited to 100mA. Many dumb charging devices, like the USB charger included with many tablets, may supply more current.
  • A general note for those still looking into battery life:  A firmware fix to an issue in one of the device drivers has significantly improved the idle/standby current consumption.  This was released in early 2015, so any firmware you are running now is bound to already have it.  All devices can standby and advertise at low intervals for many months.
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