12V Guru – can I use a generator to power the AC-DC charger?

Question to 12V Guru

Hi Dave, some months ago I decided to buy a portable generator for my 2014 Jurgens Lunagazer caravan for those free camping times when the solar receives no sun. When I purchased the van 3 years ago, I upgraded the battery charger. I installed a Projecta 7 stage, 25 amp smart charger. I wanted a generator just to run the battery charger to recharge the battery, not necessarily to power the whole van.

I read countless articles both online and via this magazine, and they all recommended a Pure Sine Wave unit. Let the search begin. I saw an ad on eBay from a large Aussie company that specializes in caravanning gear. I contacted them, told them my requirements and the application. Their reply was that these generators are not suitable for this application yet the ad specifically says that they are for caravans. I then contacted Projecta and was told that “We do not recommend using a generator with smart chargers”.

I see so many vans that come with a generator, as standard, and they all have a smart battery charger installed. From what I have seen, this type of charger is the norm. I also see many fellow travellers using generators on their vans. Could you tell me the facts, and advise what is suitable,

Thanks, Mark, Quakers Hill NSW

12V Guru answers:

Hi Mark,

Thanks for your question.  Being from Victoria I can certainly sympathise in not having enough solar for getting those batteries charged. In these circumstances a generator can be a very helpful partner in ensuring you have enough energy for a few days and also in the warmer climates where RVers want to run their AC’s and enjoy a good night’s sleep.

In order to determine if you can use a generator to power the AC-DC charger the first question to really understand is what type of generator are you planning to utilise.  Typically, there is the older style generators that are relatively noisy and hum along at the same noisy level regardless of what power is actually required. 

This is definitely the case when you think of generators used at building sites or other light commercial applications. The generator motor will normally run at a constant speed of around 3600 rpm and this produces the 240 volts at 60 Hz to produce the current (Amps). The speed of the motor nor the noise does alter as otherwise it would alter the frequency of the output.  In this case I would agree with the technical advice given by Projecta that this is not suitable for today’s modern electronics with their state of art operation.  Older style transformer-based chargers maybe!

Inverter Generator

However, this is where we love technology and have seen the advent of newer products such as the inverter generator which is very suitable for your application. Earlier last year we trialled one of the Briggs & Stratton P2200 inverter generators and certainly found that it was very suitable for charging the complete array of electric devices such as laptops and ipads.  The inverter generator versions are very suitable for being able to connect to a smart charger to recharge batteries.  We used it on the BMPRO BatteryCharge25 to recharge our Lithium batteries and it worked flawlessly.

These inverter versions of the generator create AC power but this is then converted back to DC power and then “inverted” to the AC power that is “clean” and suitable for smart electronics. There are some great advantages of these newer types of inverter generators. As these generators vary their speed to match the required output in amperage there are claims that they can be up to 40% more fuel efficient as they are not always running at high rpm.  Secondly this makes them a lot quieter than older generators. Lastly, the suitability for use with modern electronics makes them a great solution for powering smart battery chargers or the range of RV power management systems that are installed in most caravans.

A couple quick tips though in the use of a generator (this applies to all types)! 

  • Firstly, store the fuel in a non-glass safety container which is properly labelled
  • Allow generator to cool before refuelling
  • Only operate generator in well ventilated area outside of RV or awnings
  • Ensure all electrical cables are properly connected, suitable for use and safely positioned
  • Cables must be suitable rated for total requirements of loads and regularly inspected
  • Never let children use or play in area local to generator
  • Ensure all generator and electrical connection are not in rain or inclement weather
  • NEVER connect a generator to try and backfeed into a house

And … always be mindful of your neighbours!

Safe travelling! Cheers, 12V Guru

The article first appeared in Caravan World Magazine

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3 thoughts on “12V Guru – can I use a generator to power the AC-DC charger?”

  1. David, another important point to note that Once your Generator is hooked up to your caravan 240V input your Caravan RCD (safety switch) device no longer works because of a lack of Earth connection. Extra caution is needed when running Caravans on Generators.

  2. The problem above as stated can be overcome by replacing the RCD/RCBO at the entrance to the caravan with an RVD-SAFE RVD-EMR-16A a combination RVD/RCBO that works safely with both mains power and isolated power such as Generators and Inverters and also has Reverse Polarity Rejection covered when on mains power and the RVD-EMR-16A is a simple quick retro fit replacement by your electrician.

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