12V Solar Panels; how much do you really need?

I’ve heard a number of people say that you can never have enough solar when it comes to 12V systems, and always had a bit of a chuckle about it. I mean, surely there’s a point at which you don’t really need more solar?

My tune has changed a fair bit though, with a substantial solar array that is not keeping up with our demands, even though it was absolutely killing it a few months ago. So, what’s changed, and why is more solar better?

Our solar setup

We have two independent systems, that can be used to share the power demands. Our Dmax has a 200W solar panel on the roof racks, with a 230aH lithium battery in the back, charged off the solar and a Renogy DCDC Charger. We have a 2000W inverter that gets used occasionally for induction cooking, but its mainly just the fridge, camera batteries and some 18V batteries for our power tools that gets charged.

On our Reconn R2 Hybrid Camper, we have 720W of solar panels (3 x 200W Renogy solar panels and 1 x Thunder 120W panel), which feeds into 340aH of Renogy Lithium Batteries. On top of this, we have a 200W kings solar blanket (which performs pretty badly), giving us a minimum of 720W of solar all the time, and often 920W if we get the blanket out.

We run an induction cooktop as needed full time, an 82L freezer, lights, water pump and a toaster when we want toast. Now, this is a fair bit of demand, but I sized the solar and battery bank to be able to handle it under most circumstances, and knew we could always revert to gas cooking if the batteries got low.

Why does it not keep up?

When we left on our Lap of Australia, we were absolutely killing the solar and battery side of things. Just our 600W of Renogy solar panels would keep up with our usage as we travelled through the bottom of WA, and spent 4.5 months in South Australia. It was running so well that I never even bothered plugging the camper into the Dmax when we were driving along, and entirely relied on the solar to charge the camper batteries.

The only times we had issues was with multiple days of overcast weather, or if we parked in the shade, which would happen from time to time, and we just swapped to gas and all was good.

However, since hitting Victoria, NSW and now Queensland, the solar panel performance has dropped substantially, and that’s due to a combination of things. For starters, its much warmer, and that hurts your solar panel efficiency considerably. Then, you have a much lower angle of the sun, which also hurts the generation ability.

The hit was so much that I started running our extra 120W solar panel (by plugging two Andersons in each time we set up), and using the Dmax alternator to charge the camper batteries via the Enerdrive DCDC.

However, what really took it to a whole new level was the number of overcast days, and the number of camp sites that had very average levels of sun in Queensland.

I naively thought that far north Queensland would be like the northern parts of WA in the dry season; not a cloud in the sky for months on end, and certainly no rain around. How wrong I was, with so much of our visit in Queensland having overcast, or raining days, and when it was sunny, we were often camped with trees hindering the solar panels ability.

What’s the solution?

Honestly, this is going to be so dependent on your setup, and what you run, but I think if you rely on your battery levels you’d be mad not to travel with at least one decent quality solar blanket.

I refuse to idle my car to charge batteries up; we just swap to gas cooking, and move if we have to when the batteries get low.

What would we do differently next time?

I’ve always gone down the path of oversizing my battery and solar needs, but I think next time I’d take it another level again and fit some more 12V solar panels, and a slightly bigger battery bank. Of course, the trade off is weight and cost, and that is always heavily on my mind, but I think a bit more solar, and maybe a smidge more lithium power would hugely help to keep our power levels up.

I could have fit 1000W of solar on the roof of our camper trailer, but it would have been a whole lot of extra cost (flexible panels to keep the weight down), or a whole lot of extra weight, and with the roof being on gas struts with no assistance, I didn’t want to push the friendship too much.

I think I’d also go for a bigger panel on the Dmax, or two panels if I could keep the weight down. Perhaps two flexible panels, putting in around 300 – 400W would have been better.

It’s not really an issue

Overall, this is not much of a problem at all. We move every couple of days, can easily run on gas cooking as needed and most of the time we’re fine for using our electrical system to the maximum, but I was surprised at how many times in Queensland both the Dmax and the camper batteries got run right down, and I can see some sense in the idea that you ‘can never have too much solar’.

Of course, you can have too much solar, and it’s a balance between your level of storage, how much you consume each day, where you travel, how critical power levels are, what you want to spend and weight.

The simple take away though, is that more solar is generally better!

How many 12V solar panels do you run? Is it enough?

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