If your dog's training collar battery dies, Fido can run off or bark at will, and all that training could be lost. However, if you had an extra PetSafe Lithium Battery - 2 Pack, you'd be back to full power immediately. Very few can gauge when a battery will run out of juice, so why take the risk? Make sure you have a PetSafe Lithium Battery - 2 Pack around for when it happens. There's just no reason not to.Features 3 volt lithium battery for use with: PDT00-13882- PetSafe Obedience Trainer and SD-105S- SportDOG YardTrainer for Stubborn Dogs Specifications Type: Lithium Battery Power: 3V