Does anyone know whether I need a ML2032T25, ML2032T26 or a ML2032T17 battery? I have no idea what the difference is, and these are the ones I've found. My keyboard is now having trouble charging. It's placed in an area where it doesn't get any direct (sun)light, so I have to place it in the window for half an hour or so before it works... It's about 4 years old, but have not been used every day!