It's Here! Finally...A reliable rechargeable battery. The Invisicell battery is truly a first. It runs 30 days on a charge, has a low battery light, and will last 5 years plus! Check it out here. Save yourself some money and free yourself from that expensive Invisible Fence® Brand battery plan you are on from your local Invisible Fence® Brand dealer! We have batteries to fit your Invisible Fence® Brand collar as low as $8.95! (when purchasing the 12-pack) These batteries are guaranteed 100% compatible with your Invisible Fence® Brand R21, R22, R51, and MicroLite™ receiver. Our batteries batteries are an exact aftermarket replacement to the Invisible Fence® Brand Power Cap® battery. Satisfaction guaranteed! You’ll get quality batteries manufactured right here in the USA by Perimeter Technologies, Inc (not manufactured by Invisible Fence, Inc.). All of our Invisible Fence® Brand compatible batteries meet or exceed the original manufacturer’s specifications. Many dogs report getting a 6 month battery life out of each of our Invisible Fence® Brand compatible batteries. The shelf life on these batteries is at least five years.