Review on High-Capacity 2 Pack Replacement Battery for Sony BP-HP550-11 Headphones (700mAh, 2.4V, Ni-MH) by Charles Stennis

I put them in my Sony headphones and was disappointed that they still wouldn't charge. I was very surprised as I thought I had confirmed for sure that my original batteries were defective! After spending a little time I realized that there was a flaw in the design. The tops of the cells are too thick/wide/flat to hook the contacts on the headphones; and that was the reason. I ended up just taking the items out of the "packaging" and found that they weren't charged YET. I then discovered that this was due to the fact that there is a protective tab inside that allows you to charge only the batteries that are in the "package" design. Then I split the pack in half, leaving only the negative side. This pressed the safety latch to allow charging and also allowed the positive side to mate with the ports in the headset. Three stars might be too generous considering all this, but the price was cheap so I think it's worth the extra star :)