The batteries are built in and rechargable. I have not had a battery failure yet and I have used one set for 3-4 years now. I get a good 8+ hours hunting and if I am going to hunt longer I have a cigarette lighter style
plug-in inverter so I can charge them in my vehicle while taking a break or driving to the next hunting spot. I have 3 sets of the first ones in my pics above. I have bought a couple off of eBay for around $25.