You may have a grounding issue. You may want to remove you ground and slightly grind the grounding point. I know this will cause a battery to discharge and actually permanently fail on hydraulic systems. A cart should be no different. Check your ground and then, have each of your batteries tested. This problem will typically burn a cell in at least one battery. If it is bad, you may be able to pull off a free replacement if they are new enough and you don't disclose EVERY detail.
