If I wire three button cell batteries in series, their voltages should be summed. Now, if a battery dies, let's say BAT3 for the sake of example, will the circuit operate at 6V or will it stop working? I would assume, due to the way series circuits are defined. that it would stop functioning, but then I realize that a battery is conductive, making me think that current would still flow, just at a lower voltage.
Which scenario would happen? I've provided a simple circuit diagram below.
simulate this circuit – Schematic created using CircuitLab
Best Answer
The circuit will continue to function at reduced voltage. Note that the voltage declines over time. It does not suddenly drop to zero. Normally, you want to remove the load from the batteries before any one cell drops to zero volts, because the other two batteries will force the dead one to discharge to negative cell voltage. This "reversed" cell may then leak electrolyte in the battery compartment (depending on chemistry and construction details). If you plan to do this, you should consult with the cell vendor to make sure it will not cause leakage or other problems.
Most of my experience is with 1.5V alkaline cells and rechargeable Lithium polymer cells, not with button cells.
You can also test it by putting a discharged cell in series with two strong cells, then discharge the series stack until the weak cell reverses.