Most electric golf carts use 6-volt, lead-acid batteries that are basically smaller automobile batteries. One needs to understand the quality of the batteries will dictate their lifespan and efficiency. A quality battery will tolerate a higher number of discharge cycles than a cheaper, less expensive one. Unfortunately, over time, batteries will not hold as much charge and thus not go as far, no matter the quality.
The biggest killer of battery power is disuse, which will deep discharge them and affect their longevity. If not used, lead sulfate crystals form on the plates inside the battery and lower efficiency. This process is accelerated in hot weather, the climate in which most cart batteries are used. Low water level, acid buildup on the terminals and leakage because of a cracked case are other issues that can cause a battery to malfunction.
When battery terminals need cleaning, safety is very important. Remove the battery cables, making sure not to touch the terminals with any metallic objects. Using a wire brush and a solution of tap water and baking soda, clean them thoroughly. Be sure not to let any of the solution get into the battery. Once completed, apply a thin coat of petroleum jelly on the terminals and reattach the cables to the battery, making sure they are on firmly but be careful not to over tighten. If possible, remove the caps from the batteries and check the water level. If any need water, use distilled water as tap water will adversely affect the performance and battery life. Do a thorough visual inspection of the battery case. Any that are cracked or leaking need to be replaced; unaddressed leakage can drain down other parts and cause more problems.
Two of the easiest methods of maintaining the batteries are making sure all devices are off when the cart is not in use and completely discharging the batteries as seldom as possible. It is also vital to keep the water level filled. If the cart sits idle for long periods of time, attaching a trickle charger helps greatly. It's a device specially designed for the job, keeping a constant flow of energy but not allowing the batteries to overcharge.