700mAh Ni-MH Replacement Battery for Sony MDR-RF4000, MDR-RF840 and RF850, MDR-RF810 (Plus Other Models Detailed in Description) Wireless Headphones

The item was delivered as promised AAA+++

This battery pack is a complete rip off. I own two pairs of Sony wireless headphones model MDR-RF925RK, and they both came with these packs.After taking them apart, I realized they're just standard junk quality 550mAh Sony AAA batteries in a plastic holder.On my wireless headphones, there's a built in recharging function, but if you try to use standard Ni-MH rechargeable batteries it won't work. The reason is because the unit has a tiny hidden switch inside the battery compartment. If you use these battery packs, it pushes down that switch and enables the recharging function. If you use standard rechargeable AAAs, they won't push down the switch due to their shape.All you need to do to use standard rechargable AAAs is to find that switch inside your unit and superglue it in place while pushing it down with a toothpick or something. I have Eneloop AAAs in my headphones now and they last a lot longer than they did with the Sony battery packs.

If your original Sony batteries in this little pack finally die, you can replace them with regular NiMh batteries of any kind. See the review from K.Z. and my comment on it!

It was for my sony headphones and the stupid battery only powers it for about 10 minutes. The original sony battery lasted about an hour.What a piece of poop!I want my money back!

being deaf in one ear and hearing lose in other my sony ear phones are a must to have and these batteries are a great value that allows me to enjoy my earphone

I searched for quite a while for replacement batteries for my Sony wireless headphones as the originals were not holding a charge anymore. They appeared to be two lithium ion AAA batteries held in a specially designed plastic holder. The Sony parts website did not list them. I finally found the right replacements here on Amazon. These replacements were a perfect fit. After an initial 24 hour charge, the new batteries were good for up to 12 hours use before a recharge. I am very pleased with these and recommend them highly.