Voltage Sensitive Split Charge Relay - 12V 140A

  (27 Reviews)
Price:  £36.34   (£30.28 Exc. VAT)

Product code:  P00705



In stock

Thinking of installation a split charge system? Why not check out our Made-To-Measure Split Charge Kits


12V, 140A rated voltage sensitive relay for split charging applications in camper vans, motorhomes, 4x4s and boats. Allows charge to flow into one battery (or bank of batteries) only when a charging voltage is detected at the other battery (dual sensing operation).

  • Dual sensing operation - charges from starter battery to leisure battery when alternator is running and charges from leisure battery to starter battery when mains charger is connected.
  • Relay connects when sensed voltage reaches 13.7V or higher
  • Relay disconnects when sensed voltage drops to 12.8V or lower
  • Maintains battery isolation when not charging, so starter cannot be drained by leisure use and vice-versa.
  • Ignition protection to UL1107
  • Fully automatic operation
  • E Mark approval
  • Virtually zero voltage drop
  • Protects sensitive electronic equipment from harmful engine start-up spikes
  • Well proven design with 1000s of units operating in the field
  • Terminal connections marked on inside of unit for easy installation

Note: The benefit of this type of relay is that it does not require a connection to the alternator or any modifications to the existing vehicle electrical system.  Simply connect the +ve terminals on each of your batteries to the terminals on the relay and the black relay wire to a common -ve point.

An LED indicates when the relay is ON (contacts closed). Fixing holes in the body allow the unit to be mounted to a bulkhead and body cut-outs offer various cable routing options.

Fully encapsulated electronics make this unit splashproof and particularly suitable for harsh environments (marine use, vehicle engine bays etc.)

Sold individually. 

IMPORTANT NOTE: These relays are not suitable for vehicles with 'smart' or 'intelligent' alternators. As a guide this applies to vehicles having engines that comply with Euro5 emissions standards and onward, often also incorporating regenerative braking (if in doubt please consult your vehicle manufacturer to confirm). If your vehicle has a smart alternator then you will need to use a battery-to-battery charger instead of a VSR.


  • Sensing mode: Dual (2-way split charging, starter to leisure and vice-versa)
  • Voltage rating (nominal): 12V DC
  • Current rating: 140A
  • 'Cut-in' voltage: 13.7V
  • 'Cut-out' voltage: 12.8V
  • Terminal size: 2 x M6 studs and nuts
  • Other connections: Ground wire to connect to common -ve
  • Ground wire: 1mm2 - 50cm long approx.
  • Fixing hole dia: 5mm
  • Overall dimensions: 67 (W) x 67 (H) x 50 (D) mm


For more information on our battery-battery chargers and VSRs check out our YouTube Video 

Part Number:  4015

Average Rating (27 Reviews):  
Write a Review and share your opinions!

Split charger
Wednesday, 14 August 2019  | 

Great service and very helpful. Replacement for an old one. Easy to install and it was straight up and running. Early days yet as its only done one short trip, but all seems great and just what was needed.
I have used 12V before and have found them to be an excellent, knowledgable supplier. The get my vote.

Excellent Product
Wednesday, 26 June 2019  | 

Relay works as expected. Good product

The best
Thursday, 7 March 2019  | 

My problem was audio equipment.
My power capacitor would drain my battery over time, especially in the cold.
It would not last a nite in winter, resulting in not enough power to start the car in a morning.
I had an inline fuse/RCD device from my battery, and I had taken to flipping that off to isolate things. I often forgot though, resulting in flat batteries.
I contacted 12 Volt Planet describing what I needed, and this deice is what was recommended.
It works brilliantly. Since fitting it, my battery maintains a good healthy charge at all times. I no longer even worry about it. I literally have to do nothing at all to isolate things.
It cost a little more than I could really afford, but it is one the best things I have bought as far as audio gear is worth.
Maximum points, stars, kudos for their patience. Craig was awesome, and his advice was perfect.

Split charge relay
Monday, 20 November 2017  | 

Easy to install. The holes for the wire entries could have done with being larger for my installation

Excellent, needs good earth!
Monday, 13 November 2017  | 

I fitted this and thought I'd done a neat and perfect job but something was wrong and the relay kept clicking on and off whenever I had a load on the leisure battery. Checking everything still didn't help until I discovered that the leisure battery earth was just a little insecure and wasn't giving me a good connection. Problem sorted. This is a very simple and efficient method of charging the leisure battery and I would heartily recommend it.

Friday, 21 July 2017  | 

seems to have cured my battery charging problem

Voltage sensing split charge relay
Wednesday, 28 June 2017  | 

After reading through the free useful info on the website I bought a VSR. Three connections to make and it's done. Definitely the easiest way to sort out charging of a second battery.

As described- and well made
Tuesday, 6 June 2017  | 

Comes with diagram showing wiring options.

very pleased
Sunday, 4 June 2017  | 

the product is everything 12 volt planet said it was. i am very pleased with the delivery time and performance of the product. i will definetly order more from 12 volt planet as and when i need them.

Split charger relay
Friday, 31 March 2017  | 

As they say, it does what it says

Read all 27 customer reviews...