Are there any alternatives that are a little more portable, smaller? Carrying a device with the size of a router + a large battery isn't exactly the most portable thing.
Also, how long do you think a battery like that will last?
My device specs:
Input power: AC adapter (AC220V-DC12V)
Output power: 13W
If the power of your device is 13w,
where P is power, I is current and V is voltage.
P=IV
I=P/V
13w/12V=1.08A
6Ah/1.08A = 5.56h
The battery will last for 5.56hours.
Remember the higher the Ah, the longer the battery lasts.