It sounds like they may not be broke in yet so its very important to do so and do it right. Once you put the battery charger on leave it alone until it shuts off which could take up to 16 hours ( normal ) No charging it and then unplugging it to run to the store or to the mailbox, leave it be. Make sure you put the charge receptical wires back on the right batteries. This mistake happens all the time and you end up only charging 5 batteries. Double check that, you won't beleive how often it happens. Even though they are new batteries it won't hurt to test them and load test them its not uncommon at all to get a new bad battery. After a complete charge let the cart sit for 8 hours or so then test voltage in each one and load test each one. If there's an issue you can get it taken care of before warranty runs out. What brand batteries are they? They are golf cart batteries right not just deep cycles?