Hi, Does anyone know which external battery is the best for SP2? I heard Intocircut 26000mah is good and can provide two fully charge for SP2. Anyone has it? Is it truth? Anyone know what is the DC output connector for that battery? Is it 5.5mm*2.5mm? Which of the following cable fit for the external battery WITHOUT adapter? Wall Charger Cable for Microsoft Surface RT Surface Pro | eBay New Power Charger Adapter Cable Fit for Microsoft Surface RT Surface Pro | eBay Thanks!!!