Different brands or lower quality sourced regulators can have less or more voltage change. The yellow wire gets connected to an ignition switched 12V+ source to turn the alternator on and off with ignition and the blue wire with ring terminal gets connected to the alternators threaded output stud. This harness can be used with engine swap applications where the stock alternator harness is not available, and you just need a way to turn the alternator on and off through a 12v switched connection.
This harness may also be used WITHOUT THE BLUE WIRE CONNECTED as previously stated if you are currently running a regular battery but plan to upgrade later to a Lithium battery later in your build.
NOTE: This unit is NOT FOR USE ON STANDARD 12V AGM BATTERIES. This module will increase the charging voltage by 2.5 Volt and WILL DAMAGE 12 VOLT AGM batteries. Please check with your battery manufacturer to verify the proper charging voltage before installing this module! Not all Lithium type chemistries require higher voltage charging!