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
HYTRIDE 14S 58.8V 6A Lithium Charger 14S 52V Li-ion Battery Charger 52V 6A lithium ion Battery
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
HYTRIDE 58.8V 8A Lithium Battery Charger 14S 52V Li-ion Battery Smart Protection Charger
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
XTAR VC8 Plus 18650 Battery Charger 12V DC Input 3A Fast Charging Intelligent Charger LCD Display
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
60V Fast Charger 67.2V/5A Fast Charger For 16S 60V lithium Battery Charger XLR Connector Strong
Aliexpress UK
Automatically combines two batteries when charging and isolates the two batteries when not charging, which can widely used in 12v camper van trucks, caravans, and camping applications. When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery.
eBay
for Segway SGW Lithium Battery X2/I2,Charger, Support Expansion, Rebuilt, Bluetooth APP, Battery
Aliexpress UK
CBE 12v Split Charger for Engine & Leisure Batteries. * Keeps both your leisure and engine battery charged from your Solar panels etc* * Keeping your batteries fully charged for maximum lifespan * * Charges engine battery only when Leisure battery reaches near full capacity, whilst keeping them independant of each other * * Leisure battery is constantly connected to the solar charger, engine battery receives solar charging that would otherwise have been wasted energy!* * Ideal for Caravans, Campers, House and leisure boats* * Very easy installation, two fixings and three wires. Black to Chassis of vehicle (Earth) plus one wire to Leisure battery + and one to Engine battery plus!*
eBay
36V Li-ion Battery Charger 3A Output 42V3A Charger for 36V Lithium Battery High Quality Fast charger
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
Adjustable charger 12V 100A lithium charger 14.6V 100A lifepo4 charger 0-15v 0-100A battery charger
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 60A Lifepo4 Charger 100A Lithium Battery Charger 100V-240V Quick Charging Fast Adapter for
Aliexpress UK