They all vary from vendor to vendor . The best way , is to test them , yourself , with a multi-meter . They are pretty cheap , @ walmart , or even radio shack . You can also test the voltage on your
batteries , as well . If your using 3.7 type voltages , LR atty's or cartos , seem to work best . % volts and up , either a SR , or a HR , work best . Iuse both on 6 volts , with great success .