Amazon.com: MPF Products BA 150, BA 151, BA 152 Rechargeable Battery Replacement Compatible with Sennheiser IR and RF Wireless Headsets (Compatible Models Listed in Description Below) : Electronics
Sennheiser BA151 Rechargeable Nickel-Metal-Hybride Battery NIP NOS new 615104041462 | eBay
Sennheiser BA 151 Rechargeable Nickel-Metal Hydride (NiMh) (004146)