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.
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100% /Original 21700 NCR21700T Lithium Rechargeable Battery 4800mAh 3.7 V 40A High-discharge Battery High-drain Li-ion Battery
Aliexpress UK
The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped. RELAY EQUIVALENT PART FOR HC-CARGO 160477 & DURITE 0-727-10.
eBay
New For Green Battery 24V 8.0AH GreenBO Lithium Ion Battery (works Battery) The original product is 100% brand new works
Aliexpress UK
Another thing to note about these batteries which is vital is that when charging and discharging they have 250 life cycles. ALL ORDERS WILL BE CANCELLED.
eBay
18650 21700 32650 Li-ion Battery Insulation Gasket Barley Paper Battery Pack Cell Hollow Insulating Electrode Insulated Pads 100
Aliexpress UK
The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped. 1.5mm sq red cable (2m long) - To Switch relay.
eBay
100% New 3800mah 1.5V AAA Alkaline Battery AAA Rechargeable Battery for Remote Control Toy Batery Smoke Alarm with Charger
Aliexpress UK
The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped. 1mm sq red cable (2m long) - To Switch relay.
eBay
100% New Original Battery 21.6V 12800mAh lpega Dyson V7 Battery Pro Vacuum Cleaner Replaces Rechargeable Battery
Aliexpress UK
1.5mm sq black cable (2m long) - Earth for relay switching. Also suitable for many other applications. The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped.
eBay
16.8V/18V 100%New Battery Brushless Small Steel Gun, Starter, Brushless Lithium Battery Starter for Dongke JAVN Battery
Aliexpress UK
1.5mm sq black cable (2m long) - Earth for relay switching. Also suitable for many other applications. The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped.
eBay
DCF512 100% Original 20V Dewalt- batteries 20V 6000mAh battery MAX Premium 6.0Ah Lithium Ion Power Tool Battery 18650.00
Aliexpress UK
The kit has everything that you need to install a split charging system in your vehicle including a relay that prevents your main battery from draining while the engine is stopped. 1mm sq red cable (2m long) - To Switch relay.
eBay
100%Original 18650 Battery 3.7V 2000mAh Rechargeable Li-ion Batteries with Charger for Electric Pointer Doorbell Flashlight cell
Aliexpress UK