I have to say that this quotation shed no light on problem discussed. Yes, reversing is possible in batteries BUT we have NO battery in case of 1,2V NiMH ones like NH-14WM(A). It's a CELL, and even shorting it lead to complete discharge but not to reversing. The same thing (dead NH-14WM(A)) happended to me recently. I got my Net-MD recorder from Japan and stick refused to charge. I did some wiring to try charge it with Smart Power Bank from GP and got flashing LED. It means battery is DEAD or alike. So apparently it's not a fault of recorder (dirty terminals or smth likes).