How is this different from a simple diode isolator?

A diode isolator only blocks backflow. This relay switches based on voltage you set, so the auxiliary battery can also recharge the main one, and it adds a delay and a live voltage display.

Does it work with lithium batteries?

Yes. The start and stop voltages are adjustable, so you can set thresholds that suit lithium as well as lead-acid charging profiles.

What does the delay function do?

It holds the relay from switching on and off repeatedly when voltage is unstable, which protects the relay and the batteries from constant cycling.

What is the 300 amp rating for?

It is the current the relay is built to carry, so it can handle heavy loads such as winching or a large inverter between the batteries.

Can I switch it manually?

Yes. It runs in automatic mode or manual mode, so you can force the connection or disconnect when you want.

What do I need to install it?

The kit is the isolator itself; you supply the wiring, fuses and mounting for your vehicle or boat, and set the voltage thresholds for your battery types.

KFFKFF Dual Battery Isolator Kit, 12V 300 Amp

Best price now

$114.99at WalmartChecked Nov 12

Prices are checked against each store and labelled with when.

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KFFKFF Dual Battery Isolator Kit, 12V 300 Amp

Best price now

$114.99at WalmartChecked Nov 12

Prices are checked against each store and labelled with when.

Visit Walmart

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Price facts

Last seen at $114.99 at Walmart on Nov 12.

Our take on the KFFKFF Dual Battery Isolator Kit, 12V 300 Amp

The KFFKFF Dual Battery Isolator Kit is a voltage-sensitive relay that links a main and an auxiliary 12V battery, letting the auxiliary recharge the main when its voltage drops. It has adjustable start and stop voltages, manual and automatic modes, a delay function to stop rapid switching, and a real-time dual-voltage display. It works with both lithium and lead-acid batteries and is rated to 300 amps in a plastic case. It suits overlanders, van and boat owners, and off-grid setups that run a second battery; the adjustable thresholds and display put it ahead of fixed-threshold isolators, though the brand is lesser known than established names like Blue Sea or Redarc.

Best forVan, camper and overland dual-battery setupsBoats and off-grid 12V systemsOwners running lithium or lead-acid auxiliary batteriesDIY installers who want adjustable voltage thresholds

Pros

Adjustable start and stop voltage settings
Works with lithium and lead-acid batteries
Manual and automatic operating modes
Delay function reduces frequent switching
Real-time dual-voltage display
300 amp rating covers heavy loads

Cons

Little independent testing or long-term owner feedback
Plastic casing rather than metal
Setup requires understanding of voltage thresholds
Brand support and documentation thinner than established rivals

KFFKFF Dual Battery Isolator Kit, 12V 300 Amp prices at every store

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$114.99Free shippingChecked Nov 12
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KFFKFF Dual Battery Isolator Kit, 12V 300 Amp price history

Lowest price we've seen: $114.99 on Nov 12 at Walmart. Tracked across 1 store since Nov 12.

About the KFFKFF Dual Battery Isolator Kit, 12V 300 Amp

This dual battery isolator kit is a voltage-sensitive relay (VSR) for 12V systems with two batteries. It lets both batteries charge at the same time while power to your devices stays uninterrupted. It works with lithium and lead-acid batteries and regulates charging voltage automatically based on the battery type.

Start and stop voltages are adjustable. It has automatic and manual modes, and a delay function reduces frequent switching caused by unstable current. A dual-voltage real-time display shows battery conditions. If the starter battery is drained, manual mode lets a charged auxiliary battery reverse charge it, so you can start the engine without jumper cables.

The casing is durable plastic that resists impacts, and the design helps keep water and dust out. The unit is compact and made for installation in off-road vehicles, RVs and boats, including under the hood.

Model: VSR005-1
Rated power: DC 12V, 300A
Battery types: Lithium and lead-acid
Modes: Automatic and manual
Material: Plastic PA6 isolator, copper wire
Color: Black
Dimensions: 3.5 x 3.5 x 3.1 in (90 x 90 x 80 mm), L x W x H
Weight: 7.3 lbs (3.3 kg), including all accessories
In the box: 1 x dual battery isolator kit, 1 x user manual

Specifications

color: MulticolorSource

Questions and answers

How is this different from a simple diode isolator?: A diode isolator only blocks backflow. This relay switches based on voltage you set, so the auxiliary battery can also recharge the main one, and it adds a delay and a live voltage display.
Does it work with lithium batteries?: Yes. The start and stop voltages are adjustable, so you can set thresholds that suit lithium as well as lead-acid charging profiles.
What does the delay function do?: It holds the relay from switching on and off repeatedly when voltage is unstable, which protects the relay and the batteries from constant cycling.
What is the 300 amp rating for?: It is the current the relay is built to carry, so it can handle heavy loads such as winching or a large inverter between the batteries.
Can I switch it manually?: Yes. It runs in automatic mode or manual mode, so you can force the connection or disconnect when you want.
What do I need to install it?: The kit is the isolator itself; you supply the wiring, fuses and mounting for your vehicle or boat, and set the voltage thresholds for your battery types.
Where is the KFFKFF Dual Battery Isolator Kit, 12V 300 Amp cheapest?: At Walmart, for $114.99, as of our latest check.