Marsh,Good to know, will charge all my batteries tonight. Haven't used some of them for a while.
Rechargeable NiMH, NiCad or Li batteries seem to have an utter dislike to be fully discharged. I have various chemistries of these cells and if I leave them discharged and uncharged for a couple of months, they will totally fail.
Case in point, I have a "yellow brand" portable electrical drill and the battery was fully discharged and I took it out and left it uncharged for a couple of months because I have a second battery I can use. Now, I can't charge that battery again. Other NiCad batteries I used for model cars are the same.
It seems that there is a small discharge of battery power while in circuit, whether the device is turned on or off. This is what would fully discharge your battery. That the cells out when you're not using the device. It is also the best way to protect any battery (primary or rechargeable) operated equipment. Sometimes, the batteries leak and the chemicals will corrode the contacts in the equipment, and damage the instrument if the leak is severe.
Can you imagine what the landfills look like when we throw the dead cells away? Hope they're properly recycled.
Hope your YN still works.