Thread: How do you know what is a good solar panel.

Just saying ... a mate used to import cheap rooftop solar panels from China and up to a quarter were faulty - it nearly sent him and his partners broke.

Originally Posted by PhilipA

Well that is why I am rewiring it from the starting battery to the second battery with relay to turn off when ign fully off.

On most/many caravans the 12 volt fridge is directly run from the car via the power wire in the 7 pin plug with no ignition relay.

The wiring is light duty and meanders around the caravan walls so will have a big voltage drop.

I am about to run an 8 gauge wire from the 8 gauge wire that runs to DC/DC charger .

The current will be quite high at about 20plus 11 amps draw , so I have upgraded the relay to a 70 amp one.

I am also including a new wire from the lithium battery in the caravan to run 3 computer fans(total 0.75 amp ) to be temporarily mounted in the exhaust duct of the fridge in hot weather.

I will just have to remember to switch the fridge to gas when we stop for lunch etc.

I don't think anyone would try to run a 3 way fridge on 12 volts from a battery for any length of time.
Regards PhilipA

99.99% of 3 way fridges are pretty pathetic when running on 12v and the 12v is only useful during transit.
I have found that having the freezer section filled with containers of ice blocks of our Dometic 3 way fridge vastly improoves it performance when we have to run it on 12v when travelling.
The gas and 240v options work very well so we either fire up the gas or plug the van in when we pull up.

Try out the ice blocks option before you start ripping the van apart upgrading the 12v setup, I think that you will be suitably impressed

Try out the ice blocks option before you start ripping the van apart upgrading the 12v setup, I think that you will be suitably impressed

Yes thanks for that. My wife loves her ice cubes and we already found in winter it will sort of keep the ice in the freezer. We will probably use some freezer bricks. We also have an old Engel 40 litre in the back of the car
After all the element at 12volts is only 11 amps or maybe 140watts when the 240 volt heater is something like 600watts.
However my wiring mod is pretty simple as I will run the 8guage under the floor from the A frame to the floor at the fridge inside 20MM underground conduit to protect it, as well as including a two core light wire for the planned fans.
I was able to set up the wire in the conduit today with only minimal loss of blood.
Regards PhilipA

This is always an option to help take the load off:

Dry Ice | BOC Gas

This is always an option to help take the load off:

I tried dry ice wrapped in many layers of paper many years ago in a cooler on Fraser Island.

Ended up with frozen veges and spritzig tomatoes which is interesting to say the least.
It did last several days though.LOL
Regards PhilipA

Originally Posted by PhilipA

I tried dry ice wrapped in many layers of paper many years ago in a cooler on Fraser Island.

Ended up with frozen veges and spritzig tomatoes which is interesting to say the least.
It did last several days though.LOL
Regards PhilipA

Originally Posted by spie

This is always an option to help take the load off:

Dry Ice | BOC Gas

I know a keen fisherman and he won't use dry ice as he reckons he can taste it in the fish from being kept in the esky.

Three way fridges are less efficient than 12/240 volt only, from what I have seen.
I recommend you keep the freezer full because that is more efficient than trying to freeze air.
When 240 volts are available, turn the freezer down to at least -15 and freeze everything solid. When on 12 volts, set the freezer on - 5 to keep it frozen.
On solar, our new pop-top caravan will have 300 watts of solar charging a 200 amp Enerdrive lithium battery to run a 95 litre dual compartment Evakool fridge-freezer, lights and water pump. So that gives an idea of what Enerdrive thinks works.
In a vehicle I would still prefer to use solar to keep the starting battery charged and then have the DBC connect the starting and secondary batteries to let the charge flow. Being able to start the vehicle is top priority, I think.

Each to his own.

Originally Posted by PhilipA

Warning ! boring for those not interested!
I have been trying to work out why nowadays that all solar panels seem to be over rated enormously.
I think I have the answer.
The manufacturers have a rating system based on an input of 1000watts per square metre.
It is printed on the panel as here.
Trouble is that the total input of sunlight is 1360watts per square metre at the edge of the atmosphere for a horizontal surface.

The ACTUAL daily watts input at Avoca Beach for a horizontal surface yesterday (source BOM at the Avoca Bowling club weather station) was 2800watts per square metre for the entire day midnight to midnight.

Seeing the main sunlight is for 6 hours lets assume , then the average watts per square metre are about 450watts per square metre.

So the output of any solar panel rated at say 200 watts will actually be less than half of that advertised if at Avoca Beach..

I really do not know how the industry got away with such a spurious set of claims .
Regards PhilipA

Testing output against 1000w/m2 is the correct basis for comparing solar panels as this normalises the results and relates to the published peak sun hours for your location which should be to the same standard.

The issue as you have noted Philip is some sellers are claiming false peak power figures. The efficiency of most of the cheap eBay mono cell solar panels will be around 17-19% at best. So the real peak power when tested at 1000w/m2 will be around 170-190w per m2. Even the most expensive panels only get 20-23% efficiency (or 200-230w per m2 under lab testing conditions).

In real life use you will then see less than this peak in the southern parts of Australia, but the power harvested a day will still be up to the peak power times by the peak sun hours for the specific location you are in. For places like Sydney and Melbourne this peak sun hours is less than 3 hours in winter and only gets to over 6 hours in summer.

Whilst it would be rare for us in the southern parts to ever see a peak of 1000w/m2 in real life, this standard just makes all the calculations simpler.