!function(f,b,e,v,n,t,s){if(f.fbq)return;n=f.fbq=function(){n.callMethod? n.callMethod.apply(n,arguments):n.queue.push(arguments)};if(!f._fbq)f._fbq=n; n.push=n;n.loaded=!0;n.version='2.0';n.agent='plepages';n.queue=[];t=b.createElement(e);t.async=!0; t.src=v;s=b.getElementsByTagName(e)[0];s.parentNode.insertBefore(t,s)}(window, document,'script','https://connect.facebook.net/en_US/fbevents.js'); fbq('init', '1335701559822839'); // Insert your pixel ID here. fbq('track', 'PageView');

12V Voltage Sensitive Relay 125A

In stock
can be shipped within 02-Mar days

 Price, plus VAT & delivery



  • Voltage Sensitive Relay (VSR)
  • Instructions
  • Mounting Screws
Dual battery charging made easy.
Protects electronics on house battery circuit from engine start up spikes.
Fully automatic.
Continuous : 125 Amps
Intermittent : 140 Amps
Sense : Dual
Voltage System : 12VDC
Cut in/cut out 13.7/12.8VDC
The voltage sensitive relay (VRS) allows two batteries to be charged at the same time. When the engine is started and the battery reaches 13.7 volts, the VSR engages, allowing two battery banks to be charged simultaneously. When the voltage drops below 12.8 volts ( eg the engine is stopped) , the VSR disengages, separating the batteries.
The system eliminates the possibility of draining the wrong battery & protects sensitive electronic equipment powered from the house battery from harmful engine start up spikes. 



Once your main starter battery is sufficiently charged, it will begin charging the second battery. 

  • A voltage sensitive relay (VSR) is the best way to ensure you can always get your dual-battery vehicle started.
  • Surface or panel mount options provides flexibility when installing.
  • No voltage drops comparing to battery isolator diodes (0.6V).
  • It has a solid glass fiber reinforced nylon shell.



Material: Nylon

Colour: Black

Size: 7 * 7 * 6cm / 2.8 * 2.8 * 2.4in

Nominal Voltage: DC 12V

Combine / Open Voltage: DC 13.3V / 12.8V

Continuous Current Rating: 125A

Intermittent Current Rating: 140A

Power Consumption: 10mA (Standby) / 330mA (Engage) / 0mA (Storage Mode)

Certification: CE IP67

Package Weight: Approx. 234g


Functional Features:

After the engine stalls, the left House battery discharges to the upper left load device, and the VSR disconnects when the battery voltage drops below 12.8V. The Start Battery on the right will not discharge to the device. When the battery on your left is not charging, it is used up. At least there is a little battery on the right that allows you to start the engine.




Product Note Status Price
273pc Assorted Electrical Terminals & Crimping Pliers 273pc Assorted Electrical Terminals & Crimping Pliers
£8.33 *
500A Winch Soleniod 500A Winch Soleniod
£34.99 *
Low Voltage Cut Off Module Low Voltage Cut Off Module
£21.99 *
12/24v Cree LED Orange Amber Strobes (4 LED) 12/24v Cree LED Orange Amber Strobes (4 LED)
£20.00 *
Mini LED Digitial Voltmeter Mini LED Digitial Voltmeter
£6.50 *
17" Straight LED Light Bar 17" Straight LED Light Bar
£27.99 *
Prices, plus delivery
Display accessory details

Customers who bought this product also bought

Prices, plus delivery

Browse these categories as well: Expedition & Overland, Electricals, Solar Panels, LED Spots and Worklights, LED Upgrade Packs