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4 Step Simple Smart Alternator Test

19529 Views 17 Liked
4 Reviews
Rating:
5.0
Posted on: October 3rd 2018
By: James Withams

Please note 25/04/2020: We will no longer be updating this article as we've moved it over to our help centre. You can view the most up to date version here

What is a smart alternator and do I have one?

 ..

This is something that’s coming up more and more frequently these days as vehicle manufacturers seek to get their emissions down to meet Euro 5 & 6 regulations.  These are common place in T6s, Transit customs, Renault Masters and Mercedes Sprinters, amongst most other new vehicles.

A smart alternator, also referred to as a variable voltage or ECU controlled charging system, runs at a lower voltage to a traditional alternator and then increases the voltage dramatically when the driver lifts off, this high voltage (around 17VDC) quickly charges the battery. This is similar in principle to the regenerative breaking used in F1 cars.

The problem this causes for us self-converters is that the lower voltages stop us from using voltage sensing split charge relays which are only activated at 13.8V. Now you might be thinking, well I can use an ignition triggered relay rather than a VSR. This, would link your batteries, yes. However, if you try charging a leisure battery at a lower voltage (around 12.5V) it will charge about as quickly as a glacier moves, or in other words, you might as well not bother. Using conventional relays on smart alternators also poses a risk as the relays won’t be rated to take the higher voltage bursts.

..

So how do I know if I have one and what’s the solution?

The test, mercifully, is much simpler than the science behind the smart alternators’ use. You will need a multimeter capable of reading 12V DC.

1.      Locate your main vehicle battery

2.      Start the engine, ensuring any fans, radio, lights etc. are turned off.

3.      Take a voltage reading across the main vehicle battery

4.      Leave running for around 5/10 minutes, then repeat step 3

 ..

If your readings are around 14.4V DC then then you most likely have the traditional, non-smart alternator.

If your reading is closer to 12.5-13.5V then it’s likely that you have a smart alternator.

 ..

If you do happen to have a smart alternator this isn’t an issue. Here at Rayne Automotive Ltd, we use a CTEK D250SA DC DC charger specifically designed and wired to charge leisure batteries from smart alternators. It’s also great because it doubles as an intelligent 20A Solar charge controller.  Check out our range of products including the CTEK chargers here.

 ..

Please leave any comments below, thank you for looking.

Tags : Conversion, Split charge
Posted in: Archive - How to Guides
Author: James Withams

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Comments

  • Smart Alternator Test - Question regarding instructions
    By : Philip Merlier On March 2nd 2020
    Rating:
    5.0

    You state that we are to test the voltage twice. You then say the voltage readings determine what type of alternator we have. Questions 1) Is this for a fully charged battery that has not been sitting --- or does it make a difference? 2) Is the voltage reading result (that determine the type of alternator) that you refer to the first (after initial start) or second (after 5/10 minutes) reading? Thank you

    Replied by : Rayne Admin Hi, Thanks for getting in touch. Both of the voltage readings should be taken with the engine running. The reason we take two is as the smart alternators have a variable voltage, it is possible to take a reading whilst it's in a range which would appear the same as a traditional alternator. By taking two or more readings we lessen the chance of this happeneing. I hope this helps and if you get any more questions, please let me know. Thanks James.

  • Vsr questions
    By : Paul On February 17th 2020
    Rating:
    5.0

    Right im getting 13.5v at van battery ,i dident get to take for spin yet ,most likely a smart alternator? And also i bought a durite SMART vsr will this work with both non smart and smart?

    Replied by : Rayne Admin Hi Paul, Thanks for commenting. That sounds like it will be a smart alternator. Do you have a part number for the durite unit, it's not one we stock so I wouldn't be able to say. Most battery to battery chargers are fine to run with both old and new alternators. Thanks James

  • Split charger
    By : Glen On July 23rd 2019
    Rating:
    5.0

    Hi, what type of split carving system will I need on my 2014 Mercedes sprinter as I’m doing a van conversion, many thanks Glen

    Replied by : Rayne Admin Hi Glen, Thanks for your comment, I would say that it's likely to be the older style alternator, but I would definitely recommend carrying out the test to be sure. Kind regards James

  • alternator
    By : Mark sansom On April 6th 2019
    Rating:
    5.0

    so if you don't have a smart alternator is the ctek charger still ok? or is this for smart alternators only? regards Mark

    Replied by : Rayne Admin Hi Mark, Thanks for getting in touch. The CTEK will work fine with the older vehicles, it's a very good charger and will often charge faster and better than the traditional split charge relays. It's only if you have the smart alternator that you must have the CTEK charger, but it's great for all vehicles. I hope this helps James.

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