what type of power runs continuously from the start battery to auxiliary to charge it through the cable???

When the isolator reads the need to charge the second battery it will be charged with the alternator of the vehicle

Does this item have an internal fuse? Do I only need to fuse my auxiliary battery?

No it does not. I highly recommend installing a re-settable 150A fuse between your main battery and the isolator.

Can I use this to connect 2 RV batteries in parallel with differet amperage so that the leisure battery only kicks in when the primary battery low?

So they are connected in parallel when charging. The batteries can be of different amperages. However if the non stater battery drops below 12.8 volts it will disconnect from the system so your starter battery does not discharge. Starter and non-starter battery connections are labeled. The yellow wire coming out of the controller can be connected to a switch with the other side connected to ground. If you move the switch so yellow wire goes to ground it will bypass the disconnect and connect both batteries in parallel regardless of the voltage of either battery. Hope this helps.

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MaySpare Dual Battery Isolator Kit 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charger & Wiring Cable Kit

Product ID: 257387252

Details

Connector type
Screw
Contact material
Silver
Contact type
Normally Open
Current rating
140 Amps
Mounting type
Panel Mount

⚡140A Capacity

🔋12V Power

🔌Complete Kit

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121071CFA

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Sold byAmazon SenegalDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🔧 Power Up Your Adventures!

⚡ SMART VOLTAGE CONTROL - Automatically cuts in and out to protect your primary battery.
🛡️ LIFETIME WARRANTY - Enjoy peace of mind with our 100% quality guarantee.
🔋 DUAL POWER MANAGEMENT - Effortlessly manage two batteries for uninterrupted power.
🚗 UNIVERSAL COMPATIBILITY - Perfect for ATVs, UTVs, boats, RVs, and more!
🔌 ALL INCLUSIVE INSTALLATION - Comes with everything you need for a hassle-free setup.

The MaySpare Dual Battery Isolator Kit is a robust 12V, 140A system designed to keep your primary battery charged while allowing accessories to run from a secondary battery. With a smart voltage-sensitive relay that cuts in at 13.3V and out at 12.8V, this kit ensures your vehicle is always ready to go. It’s compatible with a wide range of vehicles, including ATVs, UTVs, boats, and RVs, and comes with a lifetime warranty for added assurance.

Specifications

ASIN	B081JL6ZXP
Best Sellers Rank	#746,925 in Automotive ( See Top 100 in Automotive ) #42 in Automotive Replacement Battery Relocation Kits
Brand	MaySpare
Brand Name	MaySpare
Coil Voltage	12 Volts
Connector Type	Screw
Contact Current Rating	140 Amps
Contact Material	Silver
Contact Type	Normally Open
Current Rating	140 Amps
Customer Reviews	4.4 out of 5 stars 369 Reviews
Manufacturer	MaySpare
Minimum Switching Voltage	13.3 Volts
Mounting Type	Panel Mount, Surface Mount
Number of Terminals	3
Operation Mode	Automatic
Part Interchange Info	Voltage Sensitive Relay
Part Number	US-Battery kit
UPC	742089521075

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