1995 yamaha wave venture?

will not start ,will not turnover the computer does not lite up...have put two brand new batteries in it still nothing, checked the one fuse under the seat it is o.k....called the dealer and put the another battery in and as long as it is in trickle charge mode and charging it will turnover but the digital gauges dont lite up but i didnt turn it over long enough to see if it would start it .when the battery charger is not on and charging it ,it will not even turnover .....the ski is all original and only has 155 hrs on it..