I purchased a surplus Rayovac PS133 Nicad AA/AAA battery charger, but had trouble getting it to work. The LEDs which indicate that it is actively charging would not light up. After looking around a bit inside, I made the following changes: 1) Add a resistor to the LED for the first battery, so you know when 1 is connected (glows at half brightness). 2) Add some solder to the positive connectors, so that the batteries can make contact. Without the solder or some type of material on the positive contacts, the batteries would not make contact with the case on. My particular batteries are Panasonic N-700AAC Nicad batteries.. See the following video.