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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New LiitoKala LII-CH4 4-slot Battery Charger for 3.7V 18650 21700 26650 1.2V AA AAA NiMH 1.5V Lithium-ion battery
Aliexpress UK
Maximum solar input current: 20A. Compatible with Multiple battery types : AGM, GEL, Flooded, and Lithium. 6way Fuse Box with 12 fuse blades & Label Stickers. 2 x MTA Midi Fuse holders. Battery capacity: 18 - 250Ah.
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3W 12V/6V Trail Cam Solar Panel 360° Rotation Build-in 5000mAH Battery Solar Battery Charger Kit for Hunting Camera/Deer Feeder
Aliexpress UK
Maximum charging current of target battery: 30A. It is not compatible with 24V batteries or a combination of 12V and 24V batteries. - Easy battery type selection: with the use of dip switches, the unit can be switched between Lead Acid, AGM, Gel, LiFePO4, or Lithium-ion battery types.
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DC 12V/24V Li-ion Battery Mini Compact Car Charger Cigarette Lighter Plug With LED For Makita 18V LXT Battery BL1860 BL1830
Aliexpress UK
A rubber cover to prevent dust from entering. What's in the box.
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LiitoKala Lii-ND4 Lii-NL4 NiMH/Cd AA AAA Charger LCD Display and Test Battery Capacity For 1.2V and 9V Batteries.
Aliexpress UK
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12V -4000mAh Rechargeable Lithium Ion Battery plus Charger for Electric Screwdrivers, Drills, Mini Angle Grinder 18650 Batteries
Aliexpress UK
The Renogy 20A 12V DC to DC Battery Charger Lithium AGM Gel Dual Battery Maintainer is a high-quality, efficient charging solution for a variety of battery types including AGM, Gel, Flooded, Lithium-iron Phosphate, and more. With a maximum output current rating of 20A and a charging efficiency of 94%, this charger is designed to effectively power up your batteries while also offering protection against reverse polarity, overvoltage, and overdischarge. Its compact dimensions and lightweight design make it easy to transport and store, while its operating temperature range of -4℉ to 122℉ ensures reliable performance in a variety of environments.
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Premium Screwdriver/Drill Battery 12V 4.0Ah for DKCD Angle Grinders and Impact Wrenches Li-Ion Battery + Charger
Aliexpress UK
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Turmera 12.6V 16.8V 21V 25V 2A 18650 Lithium Battery Charger DC5.5*2.1MM for 3S 4S 5S 6S 12V to 25V Screwdriver Battery Pack Use
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
100% New 3S2P Protection Plate12V 50Ah Battery Pack 12V 5000mAh 18650 Lithium ion DC 12.6V Super Rechargeable Battery + Charger
Aliexpress UK