I have an expensive camera ($20000) but the probelm is the rechargeable battery doesn't last long in the camera. I am thinking of connecting a power supply to the battery terminal inside the cammera but the only problem is I don't want to dismantle my current 18V supply. I have a 19V supply which I can dismantle, would the 1V difference will make a difference?
19V should not be a problem, as fully charged 18V battery has ≈20V ..
But, a battery being a voltage source, can deliver (when required) several amps of current ..
If you intend to use that 19V power supply make sure that it is also capable of satisfying current requirements of your quite expensive camera unit ..