Use batteries of the same type, voltage, capacity, and age if possible
Turn off all loads and charging sources
Wear appropriate safety gear
Identify the positive terminals and negative terminals on each battery
Connect the positive terminal of one battery to the positive terminal of the next battery
Connect the negative terminal of one battery to the negative terminal of the next battery
Use cables of equal length and proper gauge
Connect the system positive lead to one positive terminal
Connect the system negative lead to one negative terminal
Tighten all connections securely
Check that all connections are correct before powering on
Measure the total voltage to confirm it matches one battery’s voltage
Inspect for heat, loose connections, or damage after startup