• A 12V 140A voltage sensitive relay by NARVA, with a blue label on top displaying part number and other specifications.
  • Narva voltage sensitive relay in packaging with blue and white design
  • Diagram of a power adapter with labeled power input and output, dimensions, and connectors.
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Narva Voltage Sensitive Relay 12V 140A

Narva Voltage Sensitive Relay 12V 140A

SKU: EL094

$99.00
$99.00
Sale Sold out
GST included.

The simplest and most reliable way to charge your house battery while driving. The Narva VSR monitors voltage automatically — when the engine runs and the alternator charges, it connects both batteries to share the charge. When the engine stops, it disconnects them instantly to protect your starter battery from house loads.

Benefits:
• Fully automatic — no switches, no manual intervention required.
• Protects starter battery from being drained by house loads when parked.
• 140A capacity handles high-current charging from modern van alternators.
• Works with AGM, gel, calcium, and standard lead acid house batteries.
• Compact and weather-resistant — suits under-bonnet or behind-seat installation.
• Connects at 13.7V, disconnects at 12.8V — safe thresholds for all battery types.

Features:
The Narva VSR requires only three connections — starter battery positive, house battery positive, and ground. No complex wiring, no programming. When voltage rises above 13.7V (alternator charging), the relay connects. When voltage drops below 12.8V (engine off), it disconnects. LED indicator confirms relay status. The 140A rating exceeds the output of most van alternators, meaning the VSR will never be a bottleneck in your charging system. Weather-resistant housing suits installation in engine bays and under-van locations.

Note: for lithium house batteries, a DC-DC charger is recommended over a VSR for correct charge profile management.

Pair with the 12-Way Fuse Block and CAMEC 120Ah AGM Battery for a complete dual battery system.

Specifications

• Brand: Narva
• Voltage: 12V
• Current rating: 140A
• Connect voltage: 13.7V
• Disconnect voltage: 12.8V
• Compatible batteries: AGM, gel, calcium, standard lead acid
• LED: Status indicator
• Housing: Weather-resistant
• Application: Dual battery charging from alternator

Downloads

Narva VSR Manual

View full details

People are asking

What is a VSR and why do I need one?

A Voltage Sensitive Relay (VSR) automatically connects your starter battery and house battery when your engine is running and the alternator is charging, then disconnects them when the engine stops. This allows your alternator to charge your house battery while driving without any risk of draining the starter battery when parked. It is one of the simplest and most reliable ways to charge a second battery in a van build.

What voltage does the VSR connect and disconnect at?

The Narva VSR connects the batteries when voltage rises above approximately 13.7V (indicating the alternator is charging) and disconnects when voltage drops below approximately 12.8V (indicating the engine has stopped). These thresholds protect the starter battery from being drained by house loads while the engine is off.

Is a VSR suitable for lithium house batteries?

A VSR works with lithium batteries but is not the ideal solution. Lithium batteries charge faster and at different voltage profiles than AGM — a DC-DC charger (also called a B2B charger) is the preferred method for charging lithium house batteries from your alternator, as it regulates the charge profile correctly and protects both the alternator and battery. For AGM house batteries, a VSR is a reliable and cost-effective choice.