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
5/10PCS TP4056 Lithium Battery Charger Module 1A Portable Battery Charger Panel Type C Micro USB 4.5V-5V for Lithium Batteries
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
BMS 20S Lithium Battery Charger Protector Module 48 V Wiring Detection Light Board Lithium Battery Charger Protection Board
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
ISDT PC-4860 Lipo Battery Charger 1-8S XT60 Safe Parallel Charge Board Balance Charging Plate for RC 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. When your engine is switched off, the relay will isolate your leisure battery(s) from your main starter battery.
eBay
12.6V 2A Lithium Battery Charger Portable Charger DC 5.5*2.1MM 110-220V Lithium Li-ion Battery Wall Charger Dc Cable 1M
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
24V Li-ion Lithium Battery Charger 7 Series 29.4V 2A Lithium Battery Charger DC Plug Connector 29.4V 2A Charger
Aliexpress UK
Maximum solar input current: 20A.
eBay
67.2V 3A Lithium Battery Charger 16S 60V 3A Charger Li-ion battery Pack Charger Fast Charging DC-GX16-GX12-XLR-RCA-IEC-4Pin XLR
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
21V 5A Lithium Battery Charger 21V5A For 5Series 18V Li-ion battery pack Electric drill Battery Charger DC 5.5*2.1mm Connector
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
TP4056 Lithium Battery Charger Module 1A Portable Battery Charger Panel Type C Micro USB 4.5V-5V for Lithium Batteries
Aliexpress UK