Low battery bugfix:

Low battery bugfix:

- when the battery is low, we have previously disabled the load,
which caused the battery voltage to increase slightly, so we never
switched the system off, and the load was switched on only for a brief
periods of time.

Now we have the following battery voltage levels:

< 3.0 V: we do not enable the load, blink the status
	LED faster, and after 60 iterations, power the system off
<3.0 V .. 3.15 V): we still enable the load, but switch
	the system off after 60 iterations of LED blink
<3.15 V .. 3.45 V): battery is low
<3.45 V .. 3.8 V): battery is OK
>= 3.8 V: battery is fully charged