Hope your dog is ok[]
I currently use an Orion NiMH 3000 mAh 7.2 volt battery. I use an Intellapeak Charger. I have found that the smoke genarator works better and I can run the tank for about 1.5 to 2 hours befor the battery goes dead. I intend to upgrade to a 4200 mAh battery at some point. Hope this helps.