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
CITYORK 1.2V AAA NIMH Rechargeable Battery 3A NI-MH Rechargeable AAA Batteries With Battery Box For
Aliexpress UK
TX Autosport™ Universal Large Battery Tray Box Car Van 017 019 + Clamp - Duel Battery Setup. Universal Car Battery Tray/Box for all 017/019 Batteries. Supplied with all required fixing bolts as shown in photo.
eBay
5-50 Pcs Semi-circular Coin Cell Case CR 2032 2025 Button Battery Holder 3V Batteries Box 3-pin for
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
10PCS 18650 Battery Holder Box 1 Slot 3.7V Battery Storage Case Cell Plastic Container Housings
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
5Pcs Mini L1154F Battery Case Battery Storage Box Battery Holder For AG13 LR44
Aliexpress UK
1 x Leisure Battery 12v Box Tray NBB 38cm x 20cm x 8.5cm. Designed to protect and insulate the base of the battery and collect any water or acid leakage.
eBay
For Raspberry Pi 5 RTC Battery Box Real Time Clock Holder with Battery/without Battery RTC Clock
Aliexpress UK
Garden & Patio. For all your caravan and Camping needs. Battery holding box with lift-off lid for caravan leisure batteries up to 85Amp/Hour. for keeping the leisure battery in to avoid spillage and for safety.
eBay
18650/21700/26650/32650 Battery Storage Box 12V 30Ah 40Ah 50Ah 60Ah 80Ah Lifepo4 Battery 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
12V 24V Lifepo4 Battery Case 30Ah 40Ah 50Ah Lifepo4 Battery Storage Box 32650/33140 Battery Solar
Aliexpress UK
LARGE 110ah LEISURE BATTERY BOX ENCLOSURE INC. COVER & STRAP. 463mm - Length across lid at widest point. 243mm Width of lid at widest point. Designed to protect/insulate the base of your leisure battery and also collect any water or acid leakage.
eBay
Plastic Case(no battery cell)Shell Housings For Bosch 9.6V 12V Square Ni-CD Ni-MH Battery BOXs
Aliexpress UK