Ayman from the nature of the questions that you have asked you should do a seach on battery charging. Today there are more battery varietys than ever and You need to know what type of rechargable you are useing, or you may end up building a small unintentional bomb. Also search the Dallas/ Maxim website for both battery chargers and clock circuits. as a pasing note I have a 15 to 20 year old wristwatch with a built in calculator Terry