a little silly question, but can you add extra factory batteries to the prius? so that you can use electric power longer/more and have it regenerate/capture more battery power? it would be different than a plug in where as you won't be able to plug it for power but you could regenerate power in more quantity??? i don't even know if that's even possible? and if so, i'm sure there would be a lot of people trying that mod!! is it a lot more worth while to get a plug in kit?
You would only 'need' a larger battery if you routinely descended slopes with more than a 600 foot vertical drop. Vegas is not that mountainous, but parts of Utah would be. With your current Prius if the HV Battery fills, it uses engine braking to help the disc brakes. Plug in kits fill with house current, so they do not rely on big mountains to get full.
