I responded to this in detail some months back. There are dozens of comments online. You should know I have the Harmony One, but the specifics of this battery pertain. They are not legitimate Logitech batteries and we had a miserable experience. Long post here http://www.amazon.com/review/R3P8J704QQZ9Z0/ref=cm_cr_rdp_perm?ie=UTF8&ASIN=B003TX2N14
I suggest you just bite the bullet (it's an expensive remote) and order from Logitech.
From what you describe, I would say that replacing the battery may very well solve your problem. Check the little battery style icon in the upper right corner of the display. If it shows red or possibly only a single green block after you have had it on the charger, then your battery is likely weak or failing. If it indicates that your battery is fully charged by displaying all green blocks, you may then have some other problem. Either way, a new battery is relatively inexpensive and would be well worth a try to fix your problem.