The Dogtra BP20R battery is a replacement battery for many Dogtra collar receivers.   It is rechargeable and user replaceable. 

Battery Voltage:  3.6 V

Capacity:  350 mAh

Type: Ni-Mh

Fits Dogtra Collar Receivers (RX):

• 175NCP
• 200NCP/202NCP Gold Series,
• 280NCP/282NCP Platinum Series,
• 300M/302M Element Series,
• 7000M/7002M Series,
• Surestim M Plus
• EF-3000 Fence (old style only) What does that mean?  If the dial knob for the collar receiver is on, the wall mount transmitter you need this battery
  

Package Includes

• One BP20R replacement battery