Every electric cart should get a gauge so that you understand how much battery power you have left and as part of maintenance to prevent over discharge which shortens battery life. Here is a recent post which I think works in this thread:
Best Electric Cart to buy: post re: battery meter
Even with a meter I always keep the pack fully charged. The rule of thumb I have read is 10 - 15 minutes of pedal time justifies a charge. I also have a Battery Minder which I use in stead of the bulk charger to charge the cart when I make a short trip.