Some time ago i got an old Logitech Harmony 1000 Remote but without a chargin cradle or an original battery. I found out, that an old battery from a Nokia Mobile would work to although the remote couldn't charge it, neither on the cradle nor via USB. So i built my own charger around a simple Li-ion charging IC from Maxim.
In various boards on the net i read, that some harmony remotes had problems to charge the battery after a while, this will fix this problem, too. (With some aditional steps)