Doing a little problem solving today. There was a little illuminator light that came with my Donegan Opti-Visor kit. It can be attached to the visor for use while using the magnifier. I grabbed a couple Eneloop AA rechargeable cells and installed them. No bueno. It wouldn't light. So I grabbed a couple alkaline AA cells, and it worked just fine. I don't like to use alkaline batteries because they sometimes leak. How many devices have you destroyed because of battery leaks? So what was the problem? Normally when using AA or AAA cells the holders usually have a spring loaded contact for the base (negative terminal). This battery holder had a spring loaded contact for the positive end of the battery. It was just wide enough to prevent contact with the terminal of the battery. The AAA alkaline battery has a wide metal part to the positive terminal (left) which makes suitable contact with the holder. The middle battery is an unmodified Eneloop AAA. I cut away the insulation from the Eneloop at the right revealing a large metal surface. When installed, contact was made and the light worked just fine. I guess I could have squeezed the coil with a needle nose, but I was having too much modifying the battery. The black thing on the right is the top of the battery holder. I figure this is not the first instance of a customer encountering the problem. Maybe I should write the company.