The Invisible Fence® Brand Computer Collar® is powered by a small 3 volt lithium battery called a Power Cap®. Invisible Fence Brand Power Cap batteries are specially engineered to offer consistency, reliability and superior quality to guarantee your pet's safety 100% of the time. Official Invisible Fence Brand patented Power Caps are the only safe battery to protect your pet. Failure of the receiver due to usage of an unauthorized battery would make your system inoperable thereby putting your pet at risk. By using Invisible Fence® Brand genuine parts and components, you can be confident that your pet containment system will work correctly and all the time.