I have just bought a used - excellent condition - D 610 from a reputable camera store. I fully charged the battery with the Newell charger the they sent me with it. When inserted it showed 96% in the battery info menu. Without firing the shutter I sat and literally watched the charge percentage plummet before my eyes down to 46% in about five minutes. The battery info stated that the battery was new so I was amazed. Recharged it to full a couple of more times with the same result. It's a Nikon Li-ion 1.0 EN-EL 15. Just thought I'd seek advice in case I'd missed anything obvious before going back to the store.