11.5V = Dead Cell?

You can theorize all you want but the steps are fairly simple unless there is some convoluted intermittent that is difficult to run down

1...Charge and test the battery and or sub a known good battery

2...If the system voltage does not come up to normal then you know you have a charging problem Troubleshoot that

3...On factory "ish" wired Mopars, you have the charge path and the field path. You have the components, the alternator, the VR. Just check them all out. The charge path on stock Mopars is ALWAYS suspect, because of the bulkhead connector and ammeter. Ten seconds with a voltmeter will give you the answer. Running, charging, one probe on alternator output othe probe on battery PLUS, if there is over 1 or 2 volts difference, there is a poor REALLY poor connection someplace

4...The VR MUST be grounded to the battery NEG. It MUST see "same as battery" voltage to the sensing terminal (IGN in Mopars) with no voltage drop

5...The VR must be good that is functional. It is fairly rare for a solid state regulator to regulate "wrongly." They usually either fail or work. But this is not ALWAYS the case. What you do is, you eliminate as "much else" as you can (battery, wiring / voltage drop, connections) and if the charging voltage is wrong, you gamble and replace the VR

6...The alternator must put out rated current. There are lots of little glitches here, like partial shorts in the stator, or rotor, or one or two bad diodes, or bad brushes, etc. BUT THE bottom line is, replace it with a good rebuilt or good used or good new alternator and move on

7...On highly modified cars especially with trunk mount battery, etc, suspect everything and anything and ask yourself "did it ever work correctly?" Repeat 1-6. NEVER assume terminals are good connections. I've found bad molded terminals in fairly new (we are talking the seventies here) Mopars at the molded ammeter terminals, and down at the solenoid wire---vibrated until it broke internally. Looked great on the outside of the wire.