[bronsonj]

48v is a performance increase and it is a mild efficiency increase.

To calculate runtime is a difficult guess but to compare energy stored by the batteries is not. To compare one battery to the next look at the Watt Hours. If Watt Hours isn't available then you can calculate it by Watt Hours = Amp Hours * Voltage.

So a 36v/105ah battery is 3,780Wh. A 48v/72ah battery is 3,456Wh. Pretty close with the 48v pack a little behind. But 48v being slightly more efficient (assuming you maintain the 15mph speed) it may be practically the same. If you get a 48v/94ah that would be a 4,512Wh battery (and more efficient) and would travel further than the 36v/105ah.

Generally speaking, higher V will allow you to reach higher speeds. So you like 15mph but if you upgrade to 48v you may find 22 is more fun and 22mph is less efficient than 15mph in a golf cart (especially with the windshield up).

Another thought, if you have a higher voltage cart and want to go slower, just lift up on the accelerator a bit. If you have a lower voltage cart and want to go faster you'll need to upgrade... If the camp store is across the street and you have to play frogger to get across, that higher voltage/speed may prove useful. $0.02