Tennis ball machines can help players improve their game when their regular hitting partners are not available to step on the court. The latest ball machines are truly versatile and can simulate the shots of a good player or world class instructor. Cutting edge digital and mechanical technology allows ball machines to create a high intensity training session for tennis players of all levels. Ball machines are powered by batteries, and that means a limited usage time just as with any electronic gadget or tool. The typical battery life of a good ball machine is between three and four hours. The battery pack is rechargeable and can be plugged into any standard electrical outlet via a charging adapter. However, there are supplemental accessories that are available to improve the usability of a ball machine. Some machines can be directly connected to a nearby outlet with an adapter/charger. This will provide unlimited and uninterrupted power supply to the machine. The only problem is that outdoor electrical outlets are usually found only in private home courts, country clubs, and indoor tennis facilities. Of course, there is also the option of having an extra battery pack when using the machine on the court. There are also fast chargers which recharge the battery pack in a matter of hours rather than waiting half a day. The most advanced tennis ball machines have high tech control consoles that allow the user to manipulate and customize all of the machine's settings. Some common options include ball speed, spin, trajectory angle, and feed rate. Some of the best ball machines are extremely precise and can feed balls to exact points on a tennis court. Additionally, there are pre-programmed settings that simulate an actual drill or tennis lesson. Of course, users can also create their own unique programs to accommodate their own training needs. The ball capacity in most tennis ball machines ranges between 100 and 150. Remote controls are extremely useful accessories because they allow users to make quick adjustments to the ball machine's settings rather than running over to the other side of the court every time there is a problem. Some ball machines are now compatible with smartphone applications that allow tennis players to remotely control their machines. It is also desirable to have a lightweight machine with rolling wheels and handles for ultimate portability. Some great brands that produce tennis ball machines include Lobster and Wilson.