What Is a Smart Alternator?

Smart alternators are common in modern vehicles and dictate which type of battery to battery charger you can use. Take our simple smart alternator test to ensure you choose the right battery charger for your campervan.


What is a Smart Alternator?

‘What is a smart alternator’ is a common question asked when converting a campervan as it dictates which type of battery to battery charger you can purchase.

This blog will help you to run a simple test. This will give you the knowledge necessary to figure out which type you have. After that, you can purchase a corresponding battery to battery charger for your campervan electrical system.

Also, you’ll be glad to know that you don’t need to go it alone. Our team at Vunked have created thousands of campervan electrical systems for adventurers like you. We have created a super simple free tool to build your own campervan electrical system in minutes.

Enough shameless plugging – let’s dive in. We hope you’re sitting comfortably. 

The basics

Firstly, as a rule of thumb, smart alternators (also referred to as a variable voltage or ECU controlled charging system) are common throughout modern vans (2015 onwards). For example, smart alternators are commonly found in T6s, Transit customs, Renault Masters and Mercedes Sprinters, amongst most other new vehicles.

Key facts

  • Efficiency: Smart alternators and more efficient and help the manufacturer to comply with low emission regulations.

  • Variable voltage: Unlike a traditional vehicle alternator, which supplies the battery with a constant voltage of between 13.8v – 14.4v when the engine is running, a smart alternator voltage is variable.

  • Reduced voltage: The smart alternator reduces the voltage supplied to the battery when you are driving. This helps to reduce emissions.

  • Fast charge your car battery: When you lift your foot off the accelerator, the voltage output of the alternator spikes to 17v–18v which will fast charge your car battery in stages. This encourages better overall efficiency.

This is important because the voltage spike of a smart alternator is not compatible with older battery to battery charging technology. For example, voltage sensing relays. 

Do I Have a Smart Alternator?

Smart Alternator Test

Follow the instructions below to test and see if you have a traditional alternator or a smart alternator. In fact, all you need for this is your van (which we assume you have handy) and a voltmeter that can read 12v DC.

Generally, if your vehicle is manufactured from 2015 onwards, you most likely have a smart alternator installed but it is worth testing.

  1. Locate your vehicle’s battery
  2. Ensure all lights, fans and radios are switched off and start your engine
  3. Take a voltage reading using a voltmeter and note the result
  4. Leave the engine running for 5 to 10 minutes and then take a second voltage reading of the battery

Reading your results

Traditional alternator: If your first and second readings are the same, around 14.4v, then you have a traditional alternator.

Smart alternator: If your first reading is around 14.4v but the second reading is lower, around 12.5v-13.5v, you have a smart alternator.

Do I have a smart alternator? | Take our smart alternator test

Battery to battery charging and alternators

Whether you have a traditional alternator or smart alternator, you can still use battery to battery charging in your vehicle to charge your leisure battery while driving.

What charger do I need for a Smart Alternator?

If you have a smart alternator, you will need to use a DC-DC charger.  The variable and high voltages of a smart alternator are not compatible with older voltage sensing relay (VSR) chargers. The best option is to use Victron’s Orion-Tr DC-DC charger. These are more efficient and easy to install.

What charger do I need for a Traditional Alternator?

If you have a traditional alternator, you can still use a DC-DC charger like Victron’s Orion-Tr charger but you also have the option to use a voltage sensing relay (VSR). The latter is often the cheaper option. As a trusted Victron partner, we can support you to buy what you need as part of your bespoke campervan electrical system build. 

Without a doubt, there are many different factors to consider when planning your campervan electrical system. We hope this blog has helped. Our team are dedicated to making campervan electrics as simple as possible. As always, please get in touch if you have any questions. 

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