When I purchased the Drifta DOT6 camping trailer I purchased the option to add a fridge and then added an additional AGM battery to cope with the power demands.  Since then I have tweaked this setup and have had over one year of use to try and perfect what I need in terms of the power setup.  Currently we are travelling around Australia for a year and my concern was the batteries falling below 50% with only a small solar panel (80 Watt) to maintain the charge when not near any other power source.  In reality I have found I have never gone below 50% with a combination of charging options.

Within the trailer my power requirements include the following:

• Evakool 40L Fridge (This stays on permanently running as a fridge)
• LED Lights used on the trailer each evening
• Charging for my laptop, mobile phones and tablets (all off 12v with no inverter required)

There seems to be lots of discussion around what is right and wrong for managing and maintaining your batteries and also lots of confusion as to what is the best setup.  Ultimately everyone is different and you need something that meets your power demands based on the type of camping you do.  If you are regularly near a power supply then you may not need such an elaborate setup or if you only camp 1-2 nights without mains power you may not need a lot of charging options/battery capacity unless you have a high power demand.

I find I don’t really drop the batteries below around 70% in reality and that’s continuoulsy travelling with not spending more than 5 nights or so in one location.  You should try not to go below 50% if possible with AGM batteries unless it’s an emergency of course to maintain a good healthy life for your batteries.  Of course sometimes this is not possible and in reality it will happen now and again.  I have an old 80 A/hr AGM battery in the vehicle and it has served me well for the last 6 years going under 50% charge on numerous occasions and is still going strong today.

Within the DOT6 camping trailer I have the following setup:

• 2 X 120 Amp/hr AGM Batteries connected in parallel
• Projecta Mains charger 10 Amp – This is only 10 Amp but does the job for what I need.  To do a full charge it may take a little longer than a 15 or 20 Amp but it is certainly adequate.  I use this in power supply mode rather than charging mode when on electric hookup since my system is always under load powering the fridge.  If I returned home after a trip I would shut down the electrics and do a full 7 stage charge of the batteries but don’t have this option at the moment with travelling for a year.
• Redarc BCDC charger for charging from the towing vehicle – I had a few issues initially getting this to work but now it runs with no issue.  I have an Anderson connector on the back of the vehicle and then on the front of the trailer connecting into this 3 stage charger.  I find on a reasonable drive I get the batteries back up to 100%, although even on shorter trips for 1-2 hours a reasonable amount of charge is supplied to the two batteries.  If you have solar panels without a controller then I would certainly look at one of the DC-DC chargers on the market which also allows a Solar Input.  I have heard good things about the Projecta 3 Stage DC/Solar Charger.
• Projecta 80W Foldable Solar Panel – Interesting this one as I thought I would need to purchase an additional panel to keep me going but 80W seems to have been just fine. On a good sunny day I can keep my batteries topped up to 100% without thinking about it.  On overcast days then yes I get some depletion in the batteries but unless you are off the grid in bad weather for a long time then this is not an issue.  A good example is I spent a mainly wet and windy week down on Wilsons prom with the Solar Panel out all the time and with around 4 overcast days and 2 sunny days I never had an issue of going below 50%, in fact I never went below 60%.  If you are setup for long periods of overcast weather then more Solar or a generator would be options to look at but in reality we have never needed this.  The solar panel has it’s own controller and I added an Anderson plug direct from the batteries and screwed it on near the battery box in the DOT toolbox.  Next mod would be to put this on the outside of the toolbox making it even easier to connect.
• Mains Inlet and Outlet on either side of the toolbox for when on electric hookup.  This goes through a circuit breaker and includes a double mains socket with 2 USB charging ports in the toolbox.  This is very handy when on an electric hookup straight into the side of the toolbox rather than putting cables over the top of the box and being unable to close properly.  Also very useful having the power and USB sockets for charging inside the toolbox.
• Victron Energy Battery Monitor to keep on top of the status of the batteries – There are a few choices here for battery monitors and it will come down to what sort of information you want to see and how much you want to spend.  I went for a Victron Energy battery monitor with and additional bluetooth dongle for monitoring from my phone using the VictronConnect app.  The monitor comes with a shunt which you connect to your battery and take all the negative feeds and inputs off one side of the shunt.  This enables the battery monitor to measure the power in and out of the batteries and maintain a percentage state of charge.  You can also set alarms for when a certain percentage of voltage is reached.  The best part is being able to monitor remotely via bluetooth rather than having to open the toolbox to check.  Of course you could stick with just a volt meter and use the voltage to determine the state of charge percentage which may be all you need to give a good guide on where you are at.  Not as sophisticated and you don’t know what’s going in and out but could be what you need and a lot cheaper.  A quick google search to find the State of Charge vs voltage will be a good guide.

I do have a small cheap inverter from Jaycar but in reality have only ever used it once when we had friends staying who needed a mains feed to pump up there luxury airbed :-).  Everything else we charge from 12V.

I think you can get very complex with battery setups and spend a lot of money on things you may not really need.  It’s all about what style of camping you will be doing and what your power requirements really are.  Best thing is to try and keep it as simple as possible with the ability to monitor your batteries and make sure they are well fed and cared for!

Richard.