I had an old Aimpoint that I bought in 1998. In 2001 I ended up moving back to my hometown where all my guns were banned, so I stored them elsewhere for a few years. When I got them out of storage, I had a similar problem; my battery appeared to have corroded against the contact points. I took the battery out, got a wooden dowel and glued some sand paper to the end. I used this to break up the corrosion on the contact points inside the Aimpoint. Then I just blew out all the debris.
But after that the Aimpoint still had problems. It had a bad connection and would turn itself off randomly from recoil. I ended up selling it on eBay several years ago for $180. (Don't worry, I fully disclosed its problems to the buyer; eBay's a good place to sell broken electronics.)
0331: "Accuracy by volume."