According to today's test, the box can run during exactly 70 minutes powred by this 18650 battery (the one I tested is a 4500mAh not 5600 mAh):
I use it with this charger module :
So this 70min-battery life is just okay, but not super great...
We'll need to experiment with other batteries / power banks.
Just 3 or 4 hours would be enough!
3.7V sounds a bit on the low side, I don't know where the RPi will cut off, maybe 3.5V? In which case there is not much headroom for this battery before it drops below the cutoff value. 5600mAh is pretty meaty.
You might be better off having two in series and running them through a regulator to give you a solid 5V.
I also have a DC-DC step up converter that converts the output of the battery to 5.00V.
I'll try if it gives better result with this.
I first wanted to avoid it because
3.7V battery ==(DC-DC converter)==> 5V ==> RPi ==(built-in converter) ==> 3.3Vbut it might help... I'll give a try.
(PS: the battery I tested is finally a 4500mAh, not 5600mAh.)
I tried this, but no luck. It looks like the RPi is working fine, but the USB Audio DAC requires 5Volts to operate correctly. This probably depends on the DAC you are using.
But I tried it with a USB Power Bank and it works fine as expected. I haven't measured the runtime though.
If you can do a runtime measurment with powerbank, this would be cool. Btw what model do you use?
I did a runtime measurement with the Mipow SP3000 (3000mAh). It works more than 2 Hours.
I didn't run it continously, but in several sessions. It added up to more than 120 Minutes.
I am using an 16x2 LCD display to show which instrument is selected instead of the LED display, but that shouldn't be much difference.
Interesting video (in french) to do a portable battery.
https://www.youtube.com/watch?v=Q_04ieSHOzk [French]