Solar panels

[Smiderman]

G'day folks

looking at buying some solar panels shortly & am keen to hear your recommendations pro, cons brand size etc.

Will be running a 80l freezer (12v /240V) which draws about 38 amp hrs/24hrs and charging the house battery. Will be running the solar through my redarc 25amp in car charger which has a MPPT regular (BCDC1225).

ps if i was to run the freezer via a 1000 (2000 peak)watt inverter (ie 240v) rather than of its own 12volt system, would it consume the amps in the battery faster or slower? guessing faster but would like to know rather that guess.

pss the house battery is currently 550cca start battery (off the pajasaurus but is in good nick) god knows how to work out what amps it has?

cheers

David

[Rovingman]

Hi smiderman
i have a 120 watt single panel $250, with a 20amp twin solar panel charger ($129). it was amazing in summer bringing in a 41amps (possible 72) that i needed to top up batteries plus run all i needed during the 40c days. i run a optima blue top under the bonnet 990cca's and a 130amp in the trailer. never close to losing voltage at any stage after 3 weeks on the beach.
I made a 2 plugs with Ctek adaptors so i just move the controller from trailer battery to car battery with one clip when one needs some juice.
they are pretty useless in winter as you have no heat and minimum hrs in the day from the sun. but you will get some day time running power.
i bought from whitworths marine as they are designed to be fixed on a boat at sea and a massive saving compared to a overpriced 4x4 shop

https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=80281&intAbsolutePage=1

https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=80026&intAbsolutePage=1

[NoWorries]

12 Volt

I had the same question about 6mths ago and did a heap of research.
Best answers and ideas are here http://forums.whirlpool.net.au/forum/143?g=371

Answers.
Run it off the 12 volt not the 240
A inverter uses power to convert so you are getting loss there
and then the fridges system with convert back to 12v again, another loss
so just pump the 12 volt direct for no initial loss.

At 38amps you will need to pump a fair amount back into the battery (or buy a bigger deep cycle battery) The 550cca (probably about 60ah or less)will probably die a quick death as the AH in a starting battery is not that high (more of a quick heavy burst battery than a long running battery).
So back to the solar panels, 120/140 seems to be the best value for money and size, you can spend 500-600 on a named brand or $220 for this 140watt set up (chuck out the pretend MPPT that comes with it and use yours) I know a few blokes who have bought this set up and all are happy, it will be on my shopping list as soon as the wife stops checking the credit card.

If you are charging the battery via a dual battery setup and driving the car everyday then you will probably not have any issues with the current battery though.

[sharkcaver]

First up, answering the OP's questions:

Yep, running by an inverter will be far less efficient than 12v direct. forget that idea.


120W will more than cover you in reasonable conditions. 160W will buy you a buffer in part cloudy conditions. Bigger again will cover you in more adverse conditions. But at the end of the day, no sized solar will cover you in all conditions.

As a reference, my 120w panel keeps me fully self reliant in most conditions and my fridge alone chews 50Ah/day. Lasted 8 days at Easter, some partly cloudy days, all but fully charged for the run home.

The 38Ah you mention is obviously with the CF80 running at fridge temperatures. I tested one recently. You can read it here:

http://sharkcaver.blogspot.com.au/2012_05_01_archive.html

2 things I need to inform you of going by others past mistakes:

1: You need panels with a Voc value of 21V. The 17Voc panels will not allow the BCDC1225 to switch over to MPPT for solar charging.

2: Your max solar input will be specified in your BCDC1225 manual. I dont know off hand, but I assume 160-200W input maximum.

And just to clear up a couple of other points thus posted:

it was amazing in summer bringing in a 41amps (possible 72)

There is obviously a decimal point between those values making them 4.1 and 7.2 respectively.

they are pretty useless in winter as you have no heat

Solar derate with heat. So this statement is false. However the amount of solar radiation and shorter duration is lesser in winter.

At 38amps you will need to pump a fair amount back into the battery

At whatever consumption, any panel that does not put about 3 times the consumption back throughout its solar day will deplete a battery. Based on 8 hours of production verses 24 hours of running. I did a day test om my 120 watter over Easter. Panel produced 46Ah and I consumed 16 from the fridge. Therefore I was at the 3:1 ratio and all was good. I believe I wrote about it in this post (You'll have to get through all the non related stuff, but interestingly, you will also note I spent some time solar trouble shooting a fellow campers issue whilst there)

http://sharkcaver.blogspot.com.au/2014/04/murchison-meanderings-2014.html

I'm sure the above reply will give you some answers.

[Rovingman]

Let me clear it up.

Quote:it was amazing in summer bringing in a 41amps (possible 72)

Quote:There is obviously a decimal point between those values making them 4.1 and 7.2 respectively.

41AH in a day sorry

Quote:they are pretty useless in winter as you have no heat

Solar derate with heat. So this statement is false. However the amount of solar radiation and shorter duration is lesser


Sorry Im just a mere mortal. I teach commercial cookery so I think in heat!!! Radiation is a heat transfer
But I found it collected poor AH was my point.

Great blog by the way

[/QUOTE]

[swamprat]

i have an old bushboy fridge that is thirsty , drawing 5amps when running , i bought a cheap 120w panel off ebay a few years back , worked well but couldnt keep up with the fridge with the battery going flat after a couple of days , i bought a second panel & a 40amp ( i think ) reg , set it all up with anderson & deuzth plugs , this system works great running my fridge & lights with plenty in reserve ,

[sharkcaver]

41AH in a day sorry

Ahhh, 41Ah, that sounds about right too for a 120W panel. I just took your amps as gospel and figured you left a decimal out.

Sorry Im just a mere mortal. I teach commercial cookery so I think in heat!!! Radiation is a heat transfer
But I found it collected poor AH was my point.

Thats ok, nobody is an expert in everything, otherwise we wouldn't have forums to ask questions from others in the know. And I wasn't putting you down, just correcting info for the OP.

But you are right, you will produce less Ah over the day in the same conditions winter v's summer due to solar insolation (not radiated heat).

Some info re insolation here:

http://www.bom.gov.au/climate/austmaps/about-solar-maps.shtml

and to highlight this, see these maps of the amount of average insolation over the continent summer V winter:

summer:

http://www.bom.gov.au/jsp/ncc/climate_averages/solar-exposure/index.jsp?period=jan#maps

winter:

http://www.bom.gov.au/jsp/ncc/climate_averages/solar-exposure/index.jsp?period=jul#maps

Great blog by the way

Thanks and cheers. beers back at ya

[Rovingman]

Cheers sharkcaver
very interesting read pretty amazing differences!!
Do you think it would be useful to put another 40watt panel with my 120 in winter?
I can wire another panel into my controller.

[sharkcaver]

Do you think it would be useful to put another 40watt panel with my 120 in winter?

Do you think you need to? Obviously, you have a method of tracking power in and out seeing you quoted some figures of your setup in summer. You would need to log the same in winter to make that assessment.

It wouldn't hurt, but its more expense and more equipment to carry and maybe unnecessary. Until you audit whats going in and out in those conditions, you really wouldn't know. Noting the fridge would be your biggest power demand, and this should use far less 12v juice in winter than summer, so the drop in solar input may be negligible anyhow????

But again I need to harp on about "you can not rely on solar alone". Two days of cloudy weather, and you could be left stranded. I've known a few who have been left stranded in the past. So you also need to have a backup plan for those times when solar goes to Sh!t.

[Rovingman]

Hi
power in but not out i need to get a AMP tracker you mentioned in previous posts.
I have the original starter battery tucked away in the trailer that can get me out of trouble for a while, I have a total of 196agm battery power so should be ok, with 66 of them in the car so tops up power when driving. But it seemed to drain quite quickly in April with limited solar radiation. Fridge in car was off in the morning. Maybe i need to set the fridge higher at 4c than 0c at night.