Moving power from our 4WD to the camper batteries

Being able to move electrical power from your 4WD to the camper, or caravan can be a pretty useful setup to have. In this post, we look at what we do, why it gets done occasionally, and a number of other comments along the way.

We don’t carry a generator, but have built up two completely independent electrical systems in our 4WD and Camper, and have a couple of ways to ‘move power’ from the 4WD to the camper, if needed.

Renogy shunt showing 140 amps being drawn
Occasionally we’ll move stored power in our 4WD across to the camper

We started using an induction cooktop on our camper trailer a while back, and very quickly fell in love with it. Inevitably though, even with 340aH of lithium and 720W of solar, we still find ourselves running short at times (and I keep a bit of leeway for our freezer to run), so we either swap to gas, or we look for more power.

Before our Renogy 2000W inverter failed, our most common method was to simply move the induction cooktop to the Dmax, and cook off the 230aH DIY lithium battery.

This results in no loss, and no extra work (except for moving the actual cooker). We are always near the Dmax anyway, as it has our 12V upright fridge that gets used for most meals anyway, so its no big deal.

Heating up a curry
We absolutely love our induction cooktop, and regularly use it on the Dmax to balance the battery storage

However, there are times when our Dmax lithium battery is nearly full, and it will be sitting in the sun for hours on end and charging from the fixed panel, or we’ll be going for a drive and the camper batteries can be topped up prior, so I’ll look at moving some of that energy over.

After all, if you can store some of the power it makes sense to do so, as you’ll always use it.

Using the DCDC

Our Dmax lithium battery has a couple of Anderson outlets, which I run our upright fridge off, and some other appliances as needed. Speaking of which, if you wanted to know what to look for when buying a 12V lithium battery, we have a great guide.

I have a 10 metre long Anderson lead which is very heavy duty (used for solar blanket extensions if needed), and I can plug this into the Dmax lithium outlets, and then just run it to the front of our camper trailer, which has an Anderson plug.

This runs to the Enerdrive DC2DC unit in the rear, and it bumps the voltage up a little, to move power from the Dmax to the camper. This is the easiest, and works the best, but you still lose a bit of power rather than using it directly from the Dmax.

Also, I’ve never been able to get the DC2DC to run at more than 23 amps input, and I assume its due to volt drop through the cable on the camper, which is likely undersized. Either way, I can take about 17amps from the Dmax battery, and its putting in about 13 or 14 to the camper battery, so it moves it across.

In essence, this is the same as plugging the camper Anderson into the rear Anderson on the Dmax, and running the vehicle. I could do this, but hate running the vehicle at camp for no reason (its not great for the vehicle, and even worse for your neighbours, and if we can do it silently, why wouldn’t you?

DCDC charger
Our camper DCDC takes power from our Dmax lithium battery, and moves it across

Using the 240V charger

When our Renogy Inverter was working, one of the easiest ways to move power across was to plug a 240V lead into the Dmax inverter, and run it to the 240V charger on the camper trailer.

This powers the charger up on the camper from the Dmax, and moves power across at 25 amps. The issue with this though, is you are converting 12V power to 240V, and then back to 12V, which results in even more loss of energy, so its less than ideal. 

Also, using an AGM battery charger to charge lithium batteries will work for the bulk phase, but when it starts to get nearer full, its not a good idea. I always make a point of disconnecting the charger when it gets to 80 or 90%, but I did forget one day and the charger went into a silly charge mode thinking the batteries were fried, which I was less than happy about.

Ultimately, don’t use an AGM charger on your lithium batteries; its not recommended by any reputable lithium battery seller.

Projecta 240V Charger
We sometimes run our Projecta 240V charger in the camper from the Dmax lithium batteries and inverter

It’s handy to move power around

We don’t do this that often, and its all based around the amount of sun that we are going to get, but Victoria has made our solar setup work really hard, and I don’t like having full Dmax batteries, and low camper batteries, so we move it across as needed.

They are completely independent under normal circumstances, but its nice to know that you can move power around if you need to! Of course, we can just go to gas cooking, and basically ignore what the batteries are doing too, but if its there, we try and use it where possible.

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