Solar set-up

[bazzaboy]

Still working on my solar set-up. Considered a solar blanket but am now thinking of a permanent set-up with a sliding panel under my roof rack. My current arrangement is a wet start battery, and a wet auxiliary, with a third AGM auxiliary in a box in the rear, if needed.

Changing is working successfully via my Redarc solenoid and keeps all batteries charged while driving. The solar charging will only be used while stationary ( extended camping ), to keep batteries charged.

Components:

Redarc solenoid
200W Mono Solar panel
30amp MPPT Solar regulator
Two wet cells and one AGM ( All similar 110A batteries )

Questions :
Is this workable, when stationary?
If so, is it enough solar power to keep two fridges ( 40ltr & 65ltr ) and a few LED camp lights powered?
Will the Redarc solenoid keep the start & auxiliary batteries isolated, on will it link them together?

I've noticed that when connect my 25amp 240V home charger directly to the auxiliary battery, the solenoid eventually links the start battery. Will this solar set-up do the same? If so, is this an issue?

[trev zd30]

If I understand what you've written, you mean you have a wet cell battery in the cabin of your patrol? If so this is not a great idea. As the battery charges and discharges it will give off gas. This gas is harmful to you and is flammable.
The only batteries safe for in cabin use is a fully sealed one such as a gel or AGM.


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[bazzaboy]

If I understand what you've written, you mean you have a wet cell battery in the cabin of your patrol? If so this is not a great idea. As the battery charges and discharges it will give off gas. This gas is harmful to you and is flammable.
The only batteries safe for in cabin use is a fully sealed one such as a gel or AGM.


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Sorry, misrepresented myself. Two wet cells under the bonnet, and a AGM in a battery box in the back of the wagon ( occasionally ) *edited original post

[PeeBee]

BB, seems like this topic comes around on a regular basis, but we all have different locations and uses, hence why the answer is specific to your case. Here are the issues you are facing.

1) the 200w panel is based on a solar rating or light density of 1000w/m2 to achieve the 200w output and i am guessing around the 11 amps output - similar to mine? Unfortunately these ratings are lab derived and there is nowhere on the planet with this light density(possibly a carry forward from the space race where panels are operated in the absence of cloud and smog). I suggest you consult a solar map and work out where you are going to spend most of your time, then it will tell you the light density for that area. This will then allow you to get a handle on the actual panel capacity. You can already see its not going to 'cut it' as its flogging out 210a/hr of battery sitting on a 25amp charger - get where I am coming from?

2) temperature will derate the panel performance, so above 25 deg c and the output drops, generally, there are a couple of panels that stabilise and plateau and dont drop, but they are more expensive

3) you only get around 4 - 5 hours a day at peak watt density anywhere in Australia, hence you are not going to be able to do a simple calc and say I get 14 hours of sunshine at full panel capacity, hence when its dark, I am ok - not true.

4) Ambient temperature and physical location of the fridges will determine how long they run per hour. I know my older 60L Engel runs around the 50% mark in 35 Deg C+ temperatures and it is inside the vehicle, with an auxiliary air circulation fan to keep the hot air moving. I also know that when we were in the Kimberley in 40+ and high humidity the fridge ran most of the time, probably around the 80% mark, so your environment has a lot to do with the load. Also, if the fridge is only partially full, you lose efficiency as air is a great insulator, but it does not help when it is in the environment you are trying to keep cool - if that makes sense.

5) So will it be enough? You need to do some homework along these lines

a) say the fidges pull 2.5a/hr and 4.5 a/hr , 7 amps/hr total. Your nominated location has a watts density of say 500w/m2, for ease of the maths, so you can expect say 6 -7 amps out of the panel for 4 hours, then as the sun angle decreases, and remember this is at the start and end of the day between the max output period, you are going to get some fraction of this, so lets say 14 hrs sunlight, less 4 hours peak, so 10 hrs sliding scale, so make it simple work on 2.5a/hr av for these 10 hours.

b) You now have a total supply capability, only during light hours of 4x7 plus 10x 2.5 = 28 +25 = 53amps/24 hour period, as the fridge is possibly going to be running at night - mne certainly does unless its turned off.

c) OK, so lets say your fridge is running 40% of the time average for every hour, 24 hrs x 7 amps/hr consumption x 0.4 = 67.2 amps

So you can see from a supply perspective you are behind the 8 ball regardless of how big your battery bank is. As you deplete the battery storage, you are now minus 14amps over 24 hr period, the battery voltage drops, which means if you start the recharge process again at first light, you are chasing the -14 plus the 67, which you know you have only 53 amps/day charge capacity. ( probably why we need to run the car for a couple of periods/day or take it for run to punch in the alternator amps as well) For good battery life and recovery you want your DOD - Depth of discharge to be as shallow as possible, ie dont draw down to 11v and think the battery is going to love you for it - it won't - check the solar publications on the web and there are numerous curves about typical battery life profiles V DOD - you will be surprised at how detrimental DOD is.

Ok, after all that long winded PEEBEE dribble, you basically need a bigger panel array to sustain the load and keep the power balance correct. For my system, I am running 400w of panel, to chill a 60L Engel. I expect the energy balance to be in the order of 108a/day solar and 75amps per day fridge draw, but this is speculative of course and assuming i am based camped in a spot that affords good coverage to the panels all day. This gives me spare capacity for the couple of hours I might need to run a light. I hope this helps, and I think simply do some investigation and the research will give you a better match to your situation. We have not touched on cold weather use either, but funny enough you can still run out of power as the watt density is drastically lower when cloudy.

Good Luck!!

Ok, thinking about this further, imagine you are in hot stinky weather and its overcast? The fridge is pulling for long hours and your panel capacity is greatly reduced.

[GQtdauto]

Great summary Peebee and possibly one of the best I've seen , I run a 45 litre evercool as a freezer and an ARB 60 litre as a fridge , the evacool has an external fan helping to cool the cabinet the ARB has a fan on the fridge box extracting the excess heat both fans are ex computer fans and use bugger all power but help reduce run times on the fridges .
While up north on the last trip we had mostly overcast days but hot and the solar struggled to the point I ended up buying a small genny .
I've got 300 watt of solar hard mounted but can remove and position a 200watt panel to chase the sun .
Two gel cel batteries in the GQ and two in the camper all linked , I do need to get a better regulator (mppt) although I found as I got closer to Alice Springs the solar was working overtime and charged the batteries no trouble at all but reduced air temps and a good part of oz for solar was the reason I'm sure .

[Yeti's Beast]

I’ve found over the years many people increase battery capacity to ensure they have lots to Run their fridge but forget about how the are going to keep those batteries charged.
Excellent write up Pee Bee
Have you guys read any on the books by Collyn Rivers?
He is also a very smart person when it comes to solar.
What’s your real name PeeBee? Is it Collyn.


Proud BTrol Owner
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[PeeBee]

I’ve found over the years many people increase battery capacity to ensure they have lots to Run their fridge but forget about how the are going to keep those batteries charged.
Excellent write up Pee Bee
Have you guys read any on the books by Collyn Rivers?
He is also a very smart person when it comes to solar.
What’s your real name PeeBee? Is it Collyn.


Proud BTrol Owner
Sent from my iPhone using Tapatalk Pro

Good one, Its Phil, and yes I have read and applied what i have read from Collyns 3 books that i have and refer to directly. He is a very knowledgeable fella for sure, and practical.

[Mc4by]

Wow! Brilliant write up PeeBee.