Looking at the rear of the FNB-83 there are 3 terminals, from the left going to the right they are as follows.
Positive (Through Diode) | Negative | Temperature sensor
If you measure using the Positive and Negative terminals you will see a voltage that is lower than what the radio displays due to the voltage drop through the diode. i.e. 7.75V, not 3.75V.
If you measure from the Temperature sensor which is 10K you will read an even lower voltage.
Ignoring what voltage the radio says, take the battery off the radio, measure across the Positive And Negative terminals on the back of the battery.?
Write down this voltage or remember it.
Flip the battery over and measure across the other terminals that connect to the radio. these are on the top of the battery pack, these terminals do not have a diode inline and are connected directly to the battery. You will see the actual voltage of the battery pack.?
