The Surface 2 has a weird power connector. That makes it difficult to charge it from a battery power pack. This blog outlines creating one from a DC 12V 36W Car Charger Adapter for a Surface 2. Building it wasn’t too difficult. This means I can now use my Surface 2 on long journeys without need to access main power to charge it. Cost about $A40 apart from the Surface and Power Bank.
The Surface 2 has a wired power connector so can’t directly use laptop battery power banks when travelling.
You can purchase an adapter wit the above socket to charge your Surface 2 from a vehicle 12V (cigarette lighter) socket, Its not hard to adapter the Surface 2 adapter to connect to a Power Bank.
The Car DC Adapter
The Power Bank
The only thing to make sure of is that +V on the lighter socket goes to the centre of the DC plug.I did a static test on the connector before attaching to my surface:I had another 12V Car adapter that has a DC plug on the other end (for running a TV in my car!). I connected this into my 12V socket with that plugged into the Power Bank which was turned on and set to 12V. A multimeter showed that the adapter was correct because the inner part of the extra adapter’s plug was +12V wrt to the outside.
Disclaimer: No responsibility taken for any reverse polarity when connecting to your Surface 2. You must check and recheck the polarity before connecting. Make a number of alternative checks, powered and with a multimeter on Ohms for connectivity.