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 A3010 Digital Pen Type Multimeter 4000 Counts Smart Dual Use NCV Voltage Sensing Automatic
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 621A Multimeter AC DC Voltage Current Smart 9999 Counts Digital Rechargeable Diode NCV Sensing
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 A3010 4000 Counts Smart Dual Use NCV Voltage Sensing Pen Type Backlight Multimeter Digital
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 M126 Multimeter Diode Detect NCV voltage Sensing Test Double Operation Mode 40MOhm Capacitor
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
M3050 M3056 Current Sensing Switch 30A Current Detection Switch Induction Relay AC Linkage Device AC
Aliexpress UK
It simply connects between the two batteries. The relay is connected between the vehicles main battery (Positive) and the leisure battery (Positive). The most important part of the circuit are the fuses!
eBay
ANENG B16 Lntelligent Sensing Digital Measuring Pen Non-Contact 12V-300V Voltage Detector NCV
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 A3010 Pen Type Multimeter digital professional 4000 Counts Smart Dual Use NCV Voltage Sensing
Aliexpress UK
1x VSR with fitting screws. 【Delay Setting Function】 —— The new delay function avoids frequent switching on and off of the isolator due to unstable current, which prolongs the isolator and battery life.
eBay
ANENG A3010 4000 Counts Smart Dual Use NCV Voltage Sensing Pen Type Backlight Multimeter Digital
Aliexpress UK