# Battery life of Bangle J.s - in real world situations

Posted on
• The Bangle.Js looks like it could be fun - programmable in JavaScript and with GPS.

BUT, I am unsure about the battery life.

How long does it last in normal usage? Both with and without GPS (if that can be turned off)

• Thr 2021.03.18

'The Bangle.Js looks like it could be fun'

YES @user126405 the Bangle and all the Espruino original boards are fun to tinker with!

'How long does it last in normal usage?'

Simple explanation for battery ampacity

https://learn.sparkfun.com/tutorials/how­-to-power-a-project/remotemobile-power

I found the specific answer for Bangle by taking a peek at the Bangle presentation page:

http://www.espruino.com/Bangle.js

Idle, accelerometer on 1.25Hz - 0.15mA (default if not moved)
GPS on - 30mA

From there I searched to the bottom of the page at the tutorial icons and selected 'Technical Information'

http://www.espruino.com/Bangle.js+Techni­cal

350mAh battery, 1 week standby time

How to calculate from those values? Total capacity 350mA or 0.350A

At idle, 0.15mA or 0.000 150A are consumed when there is no movement. When GPS is
enabled, 30mA or 0.030 000A are consumed. Using simple division, `Total Capacity / Draw` will provide the time in milliampere-hours. Dividing that by the number of hours in a day, yields the expected number of days.

``````// * Idle *

Total capacity 0.350 000A   /   0.000 150A = 2333 hrs

2333 / 24 = 97 days

``````

Note that individual mileage may vary

``````// * GPS When full on *

Total capacity 0.350A   /   0.030A = 11.67 hrs

``````

Through your specific coding technique, GPS could be turned on and off to extend that value

'Both with and without GPS (if that can be turned off)'

Also take a look at this ongoing discussion within thread:

Bangle GPS Power management

Post #21 Bar Graph

• Hi! Did you ask on Reddit too? There's a good answer there: https://www.reddit.com/r/Banglejs/commen­ts/m7v4sc/battery_life_of_bangle_js_in_r­eal_world_situations/

I'm biased, but I find with the latest firmware around 2 weeks is sensible. If it's just sitting there doing nothing you'd be looking at well over a month, but the biggest power draws are the LCD and GPS, so how long you have the LCD on for (for instance whether it comes on automatically with hand movement) can have a big effect.

GPS doesn't normally come on unless you enable something that uses it (like GPS recording), and then you could be looking at ~10 hours usage. @HughB has done some great work on this though and with the GPS Setup app you can tell the GPS you only want a GPS fix every 2 minutes, and in that case you can be looking at almost 2 days of constant usage.

• Wow! Great info. Thanx. Looks like I will be buying one then :-)

• Yes, sorry. I posted on Reddit before I realized that there s an official forum. I presume that thsi one gets most traffic?

• Honestly, it's hard to know what gets looked at more. I'm not sure the forum is very search-engine friendly.

I do try and read the Bangle.js subreddit but I'm conscious that because I'm pretty biased it's not always a great idea for me to post replies there ;)