About Impedance Matching :
We are taught that the maximum transfer of power occurs when the impedance of the source equals the load. This is true. However it does not mean that this match is the most desirable. Folks are always trying to match their microphones impedance to their pre amps input or audio drive to modulator etc. what they should be trying to achieve is a match of the desirable impedance.
For example: A crystal microphone has an internal impedance of about 50Kohms. If you try to attach it to a pre amp of less than 1 meg ohm input it will sound very bad.
The plate resistance of a pentode tube is 50Kohms but it will work into loads of 2 to 5 Kohms. ( Recommended plate load impedance)
It is very confusing.
Matching the impedance of a car battery to a load would probably cause a fire and explode the battery, but maximum power would be transferred to the load, at least till something burnt or exploded.
A audio amplifier designed to work into an eight ohm speaker will produce almost twice as much power if connected to 2 eight ohm speakers in parallel, but the quality of the audio will surely be reduced.
A 12 volt car battery will drop its output voltage 1 to 2 volts while starting a car @100 AMPS but will not show any measurable drop in voltage while running a transistor radio.
A 12 volt lantern battery will also run the transistor radio with very little drop in voltage but you will probably see it drop to near 0 volts if you try to start your car with it. This all has to do with the internal resistance of the batteries
This diagram below may help out.