I can't with a clear consience recomend a battery for you. There is a battery chemistry that can do this for $400 but there is a real risk of fire that goes along with it. I suggest that you pour over the posts in the other forum you're asking these questions. I've worked with industrial automation equipment for 30 years and am cautious about the newer batteries. I probably will invest into it but not until I understand it completely.
Another $200 is a better entry level. Sorry