For extended trainings with your Delta or Delta Sport dog device?? bring an extra lithium-ion battery?? or purchase this as a replacement</br>This long-lasting rechargeable battery lasts about 3 months per charge</br>Excellent backup for those long field days</br></br>Product Description</br></br>Delta Dog Device replacement/extra battery</br><br/>http://www.amazon.com/gp/product/B00BJFCYTK