36 volt XI5 with brand new Duracell agm31 batteries(3) will only last 6-7 hours. I am running a 521 ranger and pulling crankbaits at 1.8 mph avg. which I am running it pretty constantly. Is this all I can expect to get or does something sound wrong? Went to the 36 volt so I would hopefully end this problem. Thanks in advance for any advise