Split Charge Relay - Voltage Sensing
140 Amp Relay. Senses voltage from the Alternator and when it starts charging connects the 2 Batteries together.
Simple connection - Connect Starter Battery to the Red connector, Second Battery to the Silver connector, and the Black wire to a shared earth (usually the body).
No trigger from the alternator is required.
Relay will automatically disconnect once the alternator stops charging so you cant flatten your starter battery when parked.