Things not considered for modern vehichles back to the mid 2000s.
Battery Mangement Systems are now the norm from 2015 on.
The sensor is located either in the positive or negitive lead for these systems.
If you hook directly to the battery posts, the radio is not sensed in the oveall battery control design for the vehichle.
This will have an effect on battery life calculations the Mangement does via the Sensor over the long term.
Those vehicle that have auto stop/start are most affected by low battery state of charge to the point of function failure.
Usually an AGM battery is used in these systems, and for a number of reasons are not kept or charged to `100% like a Flooded Lead Acid normally might be.
The state of charge in a late Ford F150 is desiged to be about 60 to 70% of full charge the battery is capable of. An AGM strill has a lot of power even at this SOC.
The battery type, the wide temperature range they are subjected to and attempts to improve vehichle fuel mileage and unload power robbing of the motor are some of the major reasons why. As the battery ages from all the various effects, the capacity goes down and charge rates are reduced to extend the life.
For instance, an AGM should never be charges at voltage above 14.6+/- and never be charged if the core is very cold in winter temps until it warms up.
The sensor tracks this and sends to mangement, that controls the field winding of the Alternator.
There is more to the system opration but you get the jist of the explaination as presented, I hope.
It's not the good old days any longer.
Your 13.8 volt equipment operates at 14.6+/- most of it's time in mobile under these conditions. Tx power is up along with Current draw.
Good luck.
