The power light on my Bose QC15 headphones went out after many hours of use of an AAA battery. I just figured it was time to change the battery. I had a difficult time removing the battery and finally had to pull it out with needle nose pliers. When I put in a new battery, the power light would not come on. After reading some posts here, I tried to clean the battery casing with a dry Q tip, then water, and then 40% ethanol without success. Then I rubbed the casing thoroughly with the eraser of a new no. 2 pencil, blew out the interior with a compressed air canister and presto!, the power light came on.