I purchased a Cameron Sino 3.7V 1050 mAh Li-Ion Battery (CS-MX810RC) about a month ago for a used MX-880 I recently setup for someone. Has being doing well so far and for under $14 shipped it could die in 6 months for all I care. Not going to sweat another $14 bucks to replace the battery again, but hopefully I'll find it lasts much longer than that. Replaced the original battery which had swollen up like a grapefruit causing the battery cover to protrude. Now with the replacement battery installed the battery cover is all loose from having been stretched out. When the remotes in actual use you don't notice it that much though.