Voltage at Cigar Lighter is 13.8V But Torque Pro reads 12.3V

13.8V would be too high for a 12V battery at rest, however it is close to what the battery should read when the car is in Ready mode. You didn't say that you were measuring the voltages by the 2 different methods with the car in Ready mode, but I'm assuming that you were.

Even if the the car was turned off (i.e. not in Ready mode) when you were measuring the voltage, a "surface charge" may remain at the points of contact with whatever gauge was being used for the measurement, if the car had recently been running. It does not represent the true charge state of the battery, but rather a disproportionate distribution of electrons near the surface of the battery's negative terminal. This would usually dissipate after some time had elapsed, from a few minutes to a few hours. That is why we speak of measuring the battery's voltage at rest, probably at the jump points under the hood after the car has been sitting overnight with the hood unlatched.

Yes, using a voltmeter at the front jump points is the best way to measure the voltage, rather than relying on some other method.

 

It can be confusing to refer to the 12 V battery as "low voltage".
Measuring with any "app" can't be trusted.
And measuring with anything while in ready mode or actually running is testing the charging voltage from the converter.....and NOT the battery itself.

 

It only matters what you measure at the front jump points. Because That is after many connections a 100 amp fuse ay the battery and a very long b+ line to the front fuse box snd finally the bolted down L bracket that is used to clamp on a jumper cable if need be. So voltage measured there is through all those devices and is the ultimate test of the working voltage of the battery.

Now go one step further. Measure the volt at the front jump point with car off.
Write it down
With car still off turn on the headlights in high beam. Leave them ion for exactly 5 mins.
After 5 turn them off and with car still off measure dc at front jump point.

On my car with 3 year old yellow top it did not drop one volt.
Any drop in volt after this very minor load on the battery means your battery is highly suspect.
If you own a battery charger with anti sulphation mode it may help.

If your battery is near 5 years old it will fail this test.

 

Here we go again spewing out incorrect and misleading information.

First, significant voltage drops for 12 V automotive batteries are measured in TENTHS of a volt, not whole volts.

After the test that you specified, ANY battery in ANY condition including new and perfect, should be expected to show at least a slight drop in voltage. Having the high beams on for 5 full minutes is NOT an insignificant load.

And lastly, while a battery that has seen 5 years of service won't perform like new, it still may be perfectly good for a while longer.