Why does my multimeter capacitance measure not show up until I lift the probe?
To test a capacitor the test meter will apply a voltage or current to the DUT (device under test) and measure the response. For example, if it applies a constant current it can measure how long it takes to go from one voltage to another and work out the C value from \$ i = C \frac {dV}{dt} \$.
If you've left your battery connected then it will sink the current (if you don't destroy it) and your reading will be nonsense.
In general you can't measure the value of components in live circuits.