I have to disagree with elio. I use the Energizer NiCd 9v battery for my bass(which has a bypass switch also) and have used it (the same battery) for years now. I haven't purchased a battery in years. It never even goes dead because when I've played a long service I just drop it back in the charger, pull it out and go. I can't make a claim for all RB, but for the above mentioned brand, it has saved me so much money and hastle.
Hope this post helps. Again I STRONGLY recommend RB.
Oh I got the battery for like 9.99 at Best Buy and the charger was like 20.00. Not trying to sound cheap or like a tightwad lol, but just compar 30.00 to how much you may spend in a year on 4.99 9v batteries. You do the math.