I am going to mod my novation ultranova to use with a battery pack. just trying to be sure of the specs as the manual says the wall wart is 12vdc 1250ma BUT it can also be powered by usb which is only 5vdc at.5a . so what would be the best choice to be able to get a nice long lasting power supply on it? (I would like to just make up a battery pack that I can plug into the dc connection on the UN)
My suggestion would be to buy a sealed lead-acid battery, say 5 AH, which is fairly small and light, and try it out to see how long it lasts, maybe good for 5 + hours but you just don't know till you try it. . If it doesn't last long enough then you can buy another and connect them in parallel ( +ve to +ve and -ve to -ve) which will give twice the running time. A word of warning: A lead-acid battery, even a small one, can deliver a huge current if it is shorted by accident, this is what causes a lot of car fires. It's very important to put a fuse in the circuit to avoid the risk of burns or fire. Place it right next to the +ve terminal. A 2amp fuse in an in-line fuse holder will do fine. You will also need a small battery charger, your wall wart will probably do that job ok for such small batteries, see if you can get a gender changer so your power connector from the battery can connect to the ultranova AND the wall wart.
Use an gell cell/AGM battery. Those are around 12V, and can run for hours depending on your chosen capacity and load drawn. An 18Ah battery might last 6-10 hours. It might help if you say why you need to run it without utility power, and for how long you need it to run.
