When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery. So it does not drain your main starter battery and you will always be able to start your vehicle.
eBay
Remote Battery Disconnect Switch 12V 200/250A Remote Control Battery Switch Relay Anti-theft Car RV Boat Battery Kill Switch
Aliexpress UK
When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery. So it does not drain your main starter battery and you will always be able to start your vehicle.
eBay
Car Battery Separator Coupler Power Switches 4Pin Dual Battery Isolator Relay 200A 12V Battery Circuit Cutter Wm686 M6 Terminal
Aliexpress UK
When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery. So it does not drain your main starter battery and you will always be able to start your vehicle.
eBay
Car Relay Tester Voltage Tester ANENG RT01 Universal 11-25V Automotive Car Battery Check LED Indicator Light Relay Diagnostic
Aliexpress UK
When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery. So it does not drain your main starter battery and you will always be able to start your vehicle.
eBay
ANENG RT01 Universal Car Relay Tester Voltage Tester 11-25V ar Battery Automotive LED Indicator Light Relay Diagnostic Checker
Aliexpress UK
Battery disconnect switch rated current: 240A. Disconnect Switches can solve the power consumption caused by such problems, and can extend the battery power and service life of cars. Disconnect Automatically (12V).
eBay
ANENG RT01 Universal Car Relay Tester Voltage Tester 11-25V ar Battery Automotive LED Indicator Light Relay Diagnostic Checker
Aliexpress UK
NOX SENSOR FOR RENAULT MASTER MK3 III 2.3 DCI (2014+) VAN DIESEL 227903557R NEW. 1x Remote battery disconnect switch. Front 3 Point Seat Belt Driver & Passenger Side Retractable Extension Seat belt. Battery disconnect switch rated current: 240A.
eBay
12V 140A Adjustable Dual Battery Isolator Split Charge VSR Car Relay LCD Display Digital Voltage Sensitive Relay Voltage Setting
Aliexpress UK
When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery. So it does not drain your main starter battery and you will always be able to start your vehicle.
eBay
Auto Relay Tester for 12V - Durable Car Diagnostic Tool with Battery Clips, Fits 4-Pin & 5-Pin Relays
Aliexpress UK
Dual Battery Isolators also feature surge protection and a L.E.D indicator designed to alert the user when the unit is engaged. - Suitable for most 12V charging systems- Surge protection. When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery.
eBay
12V 140A Dual Battery Smart Isolator Split Charge Voltage Sensitive Split Charge Relay LCD Display VSR Car Relay Voltage Setting
Aliexpress UK