12V Guru – Best setup for caravan battery charging

Question to 12V Guru: What is the best setup for caravan battery charging?

Hi Dave,

Can you please advise the best and most cost effective setup for vehicle and caravan battery charging. I have seen two main configurations:

  1. solar panels and regulator mounted on vehicle charging two AGM batteries (one start and one auxiliary) connected to caravan with Anderson plugs and caravan solar and regulator to batteries on the caravan.
  2. DC-DC charger with solar input between start and auxiliary battery on the vehicle and DC-DC charger with solar input for the caravan batteries and solar panels.

Typically fridges in vehicle and caravan are the main power users.



12V Guru answers:

Hi Ray,

The two setups you have described for caravan battery charing sound quite creative in what they are trying to achieve.  I am guessing that there is probably an easier way to setup an adequate solution.  What I am missing from the question is the ultimate goal you have in your setup.  You mentioned in the beginning that you were after the most suitable setup for charging a caravan battery and a vehicle battery. 

The vehicle battery is already managed by the alternator in your car so let’s assume that you mean a deep cycle style battery for powering the fridge that resides in the rear of the car.

Powering fridge with deep cycle battery

Let’s cover this battery first – the simplest solution you could utilise here which is cost effective and best suited to the application is to install a simple DC-DC charger in your vehicle to manage what should be a deep cycle battery.  There could be two possible setups in this scenario – one where the battery is mounted under the bonnet of the vehicle or where the battery is mounted in the rear of the vehicle in a secure ventilated location such as behind a seat or a drawer setup.

Battery under bonnet

If the battery is mounted under the bonnet and setup as a dual battery setup you will need to find a DC-DC charger that is suitable to be installed under the bonnet of the vehicle. This means it will need a high IP rating to withstand dust and water but also must be rated to handle the extreme temperatures that can be generated under the bonnet of a car which is driven for hours through high temperature in outback Australia.

Battery in the rear of the vehicle

The second option is where you select a DC-DC charger that does not hold such a high IP rating and is then mounted internal to the car beside a battery that is stored normally in the rear of the vehicle. In both scenarios you will need to ensure that it is a latest model DC-DC charger than can handle smart alternators installed in modern cars which lower their voltage once the primary battery is charged.

You would only need to install solar on the roof of a car if you were planning to stay in one location for a few days without driving the car and in which case many DC-DC chargers will take both the alternator and the solar as an input to charge the battery in vehicle.

So, in summary – DC-DC charger than handles solar and alternator input.  Use movable panels on Anderson connector to position for best charging.

Charging your caravan battery

It is not possible to have both batteries charged by the same device unless you install some type of isolating switch between the batteries and this is generally not effective. Therefore, you will also need a charging source for the battery in your caravan.  Again, the most cost-effective way to do this is top utilise a DC-DC charger which can handle solar and the charge available from your car.  This time the choice is clear in that you can choose a DC-DC charger with a lower IP rating install right beside our battery.

Set it up with proper fusing and correct wire size from your Anderson plug connection from the vehicle and you should enjoy heaps of charge from either your car or solar panels – fixed or movable.

You could even have the same charger in both setups. Of course, you could move to fancier full power management systems but to get away with a smart, cost effective and highly suitable solution for caravan battery charging – 2 x DC-DC chargers could cover you. There are a multitude of displays and 12V output distributions that need to be considered but you could just run all these directly from the battery.

Safe Travels,

12V Guru

The article was written for Caravan World Magazine.

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