new batteries

I have a 2015 Yamaha with new batteries. On a level street, I can get about 30-minutes of run-time, and then it begins to slow (or die). I installed a meter, where I see 50V and 170AH after charge. In addition, each battery reads approximately 8.5V with a multimeter. It seems to get a proper...

I installed a new set of batteries and want to know what the battery voltage meter should be reading after full charge? It seems it fluctuates in the extremes.