Images for the exchange's on the net. Did it just in 15min made: no problem at all. One must however be "tender" with the fine going into the plastic of the controller screws be. Procedure: Remove 5 Phillips screws on the back; are all the same. After the housing Carefully unfold. The old battery falls by itself out. Pull out the best law firm connector to a telephone pliers. The new as pure (note polarity black / red wire!). Position a new battery in the holders. Fold housing. And then: very tender the 5 screws reindrehen again. To find the right position trick: first turn against the closing direction until it fluppt. After easily hand tighten. At the end all over again 1/8 turn to cross. Finished! After that, the battery-weak controller comes back to, twice long life. Have Fun!