On re-reading myself I think it was probably me that got it wrong
Sorry for the confusion - I meant a portable battery charger. E.g. the mobile phone battery banks but a more powerful one (higher voltage / amp output)
There's one on Amazon which us 20000mA with up to 19v / 3A output. I am not sure if this would be sufficient as I would be using a ultranote 2
compare it to your laptop battery, but due to how they function i would probably go for another battery instead