I would suggest that you first try a different volt meter and compare the 2 readings. I can't see how it's possible for a terminal connector to raise battery voltage.

 

It dropped back down to the 13 volt range after I drove it for a while. Thanks.

 

Regulators are designed to charge to a higher volts when first started then back off the control volts with time and ambient temperature.
-chart-

 

I put a new connector on my negative battery terminal side. Now with no lights on it is measuring 15.10 volts. I installed a heavy duty terminal and could that be the reason why?? Before it was the 13.5 range. The connections are solid and tight. Is that too high?? Please advise.


Mark

A freshly charged 12v battery will show a higher voltage immediately after charging due to 'surface charge', the battery's chemistry acting on the surface of the plates. It's normal and the higher voltage will self-discharge eventually. Most automotive electronic parts are designed to work properly with a range of voltages to accommodate normal voltage fluctuations.