SOLAR POWER BASICS

Thanks for that Frank.

- I was thinking 240w Monocrystalline panels - any brands you can suggest?
- An MPPT Controller
- Upgraded cables to minimise voltage loss
- Not sure which battery to purchase or how many - any suggestions

I was thinking of getting something good quality, we do camp a lot and plan to extensively in the coming years, a number of sites we visit have no power.

We use three way fridges so have gas when needed, but can run 12v when needed.

Small tv every now and then, refitting everything with LED to minimise power draw.

Your thoughts on Anderson Plugs - are they worth doing.

Cheers

Heath 1
Unless you are able to power the 3way firdge/s off the car while travelling
which may be sort of ok, perhaps maybe, the solar is not going to run a fridge when stopped.

To run both while travelling will mean a large cable/anderson plug supply to caravan from vehicle, DUAL battery system solenoid, as they will be drawing in excess of 25amps from the alternator while driving and still not much, if any, Cvan battery charging happening.

240w panel in full sun might run one fridge but only in ideal conditions and have nothing else left in output capacity to charge a battery.
At night no solar output so gas is a must.

3wya fridges and solar just aren't compatible re energy requirements.

Ross M

I think you'll find Collyn Rivers' article here of great benefit.

Firstly, and pretty much as Ross said in his last line, forget about running your 3-way fridge(s) off 12V while camped. They draw 10 to 15 amps and run nearly continuously, so think 240 to 360 amp-hours per day!!!! No practically sized solar can keep up with that kind of demand. The 12V part of 3-ways is basically only for transit, to be powered by big cabling off your tug's alternator.

Having said that, 240 watts of solar will support an otherwise pretty large and hungry outfit (in electrical terms). I had 240 watts adequately supporting 320 Amp-hours of batteries in a caravan with a compressor fridge. It's the fridge that's the killer, and yours will be gas while camped so the fridge is out of the equation, leaving just lights and a bit of TV and maybe radio/CD and water pumps.

Based on what you've said in your Follow-up, I've estimated your useage at about 18 amp-hours a day:

Lighting 2.0 amp-hours
12V sockets 5.0 (extras like charging phones, cameras, running outside camp light.)
Water pump 1.0
TV/radio 10.0
Total 18.0

That's very modest. Is there anything else?

I used a solar spreadsheet calculator to see what sized battery and panels might be appropriate. It suggested that 120 watts of solar and a 100 amp-hour battery would be more than adequate. In sunny weather in all seasons it suggests you will never run out of power.

How long you will last with no sun depends on how much you are prepared to discharge your batteries. According to all the literature, 50% discharge is the best compromise between practical use and longevity of the battery. In that case a 100 amp-hour battery will give you 3 days. 200 amp-hours will give you 6.

With the above useage and 120 watts of solar, you would be oversolared - slightly in winter, considerably in summer. The benefit of this is you wouldn't need perfect solar days to keep up.

So if I were doing your system I'd go for

- 1 x 100 amp-hour deep cycle battery. More capacity if you want to be self-sufficient for longer in no sun.
- A controller such as this one from Jaycar or on eBay.
- 10m of pretty heavy sheathed twin-core cable, eg the 5825 found here

This system is expandable - if you want to add batteries or panels you can, without changing the solar controller. Batteries in parallel, of course, and the same with the panels.

Anderson connectors are very practical. Rugged, reliable, fool-proof. Only real disadvantage is they're not waterproof. I use them throughout my system and have never had a problem and I think many others would say the same.

Cheers

Thanks very much for that, starts to make much more sense now, gas for the fridge did seem like the best option when i first looked so i will continue to operate it like that (last trip with fridge freezer running i got 20 days with gas to spare, so that should be fine)

Looking at the amp hours i will need i think that i will invest in solar for running my other appliances. Pumped.... i think it looks like a much better option than carting a generator around.

Cheers

Heath,

"So if I were doing your system I'd go for "

I left out the most important bit (distracted by babysitting the grandies) :

- 120 watts of solar panels.

I strongly recommend you get them with no controller attached. You can often get a good deal on panels with an attached controller, but first investigate if it's easy to bypass the on-panel controller and use your own.

You can easily upgrade if you need to by adding one or more panels of any wattage in parallel, so it's easy to tailor your solar to your needs. Just plug them together with Andersons. To keep this option available it is most important that your panels all feed into one controller.

I found that with my 240 watts in two pairs of 120 that it was best to have each pair on its own 10m cable, joining up with a double Anderson adapter at the controller. That keeps the current in the panel cable down (fewer losses) and gives maximum flexibility for chasing the sun.

Cheers