Solar Panels in the Shade!

Submitted: Friday, Mar 14, 2008 at 22:24
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Can anyone tell me an estimated % of how efficient a 120w polycrystalline panel would be in the shade or in overcast/raining weather... 30% 50% 80% ???



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Reply By: Member - joc45 (WA) - Friday, Mar 14, 2008 at 22:46

Friday, Mar 14, 2008 at 22:46
I haven't done a proper analysis of this, but my experience with my 40w polycrystalline panels reckons that on hot overcast weather (as in the tropics), output can be down to 25%, and bugger-all output in the shade.
Best performance conforming with the factory specs are in cool sunny conditions.
The amorphous panels seem to perofrm a bit better in the heat, but geez, they're huge.
Basically, it matters not what technology you have when it come to light thru clouds; if it's heavily overcast, you don't get much light. Simple physics.
Gerry
AnswerID: 292763

Follow Up By: Redbac - Friday, Mar 14, 2008 at 22:57

Friday, Mar 14, 2008 at 22:57
Thats a bit of a worry!
I'm thinking I may need to double up in the battery department to kinda compensate for this factor.
How many batteries do you have with you on the road Gerry?
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Reply By: Member - joc45 (WA) - Saturday, Mar 15, 2008 at 03:08

Saturday, Mar 15, 2008 at 03:08
Hi Redbac,
I'm currently using a 70ah N70 battery to run my 39L Autofridge, with 3x42w panels charging the battery.
In cool fine weather, I get about 7-8A into the battery, but in 45deg heat and sunny, I get about 6A. Despite the falloff in hot weather, I still have heaps to run my fridge, 2-3 flouros at night, plus the laptop. I usually wind the fridge up by day to get it colder, then back it off at night so it runs less.
But there is an issue if the weather is very hot and overcast. The panels sometimes only give 2-3A, and the fridge is running overtime, so I'm running into negative territory. Then it might be time go go for a bit of a drive to help the batteries. This fortunately doesn't happen often.
I usually run the panels with just a slight tilt, but I can tilt them up further for those cloudy occasions to optimise the angle to the sun and get extra output. Again, I don't do this often.
Gerry
AnswerID: 292774

Follow Up By: Redbac - Saturday, Mar 15, 2008 at 09:00

Saturday, Mar 15, 2008 at 09:00
Thanks for that info Gerry!

You obviously have found that your battery is sufficient for your needs?
I only ask as everybody has told me to get nothing less than a 100ah battery!

Also can I ask why have you opted for 3x42w panels over 1x120w one. Maybe you have added as you have needed to?

I am looking at getting a 120w panel from Jaycar but its not a BP or any type I have come across so far as a reputable brand, should I be looking for any particular brand you may know of ? I also will be getting a 12ah battery All suggestions welcome :)

Just one last question I promise. I have been looking at including a 20amp regulator in my setup, (btw - I would be running almost the same appliances as you), however I have read that the best regulator to get for optimum recharging is a 3 stage regulator? Any suggestions!

Cheers

Simon
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Follow Up By: Member - joc45 (WA) - Saturday, Mar 15, 2008 at 14:06

Saturday, Mar 15, 2008 at 14:06
Hi Simon,
There are a few deep-cycle batteries which quote more than 70AH for an N70 size. I earlier had a Trojan 105AH, but it was very expensive, it didn't really perform, and it was pretty-well dead after 2 years (its warranty period). Everyone reckons that it should have given a lot better performance than that; perhaps I was unlucky.
On my old Mav, I fitted two 6v 110AH Exides, and they were great. Could have squeezed them into my GU, but there was too much rearranging other bits under the bonnet.
Many people swear by AGM batteries. My only worry is that all lead-acid batteries don't like heat, and AGMs even more so. If the AGM was situated in the rear or on a CT or caravan where it's cool, then they would be the best. Fullriver is about the best value AGM.
My last choice of battery was a 70AH marine/deep-cycle, based on cost alone, and the fact that I was going to be on the road a lot rather than sitting in one place for many days. It's over 2 years old now and still going ok.
Regardless, the less you deep-discharge a lead acid battery, the longer its life, so if you can get a larger one to fit, then you're better off.
Re heat, if the battery is close to the exhaust in the engine bay, a thermal shield is a good idea. I also have a small fan which cuts in and draws fresh air from the front if the temp gets too high.
Re solar panels, I chose 3 x 42w panels coz they were ex-Govt purchase and were well-priced! No other reason (actually, that's a great reason :-) )
Re regulators, I have an older two-stage Solarex reg. Basically it regulates at 14.2v, cutting back in at about 13v if my memory is correct. But if the battery drops below 12.2v (usually overnight), then the reg will take the battery right up to 15.0v briefly before settling back to a 14.2v float. This is good for flooded lead acid batteries, ensuring that the battery is fully charged and gassing, and helps equalise the cells. Good modern regulators are cpu controlled and do a much better job of monitoring the charge-discharge of the battery, and provide nice status displays. The cheap single-stage regs do work, but you'll get better performance and battery life using the more sophisticated reg.
Derek, from Affordable Batteries is a good resource.
Cheers,
Gerry
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Follow Up By: Redbac - Monday, Mar 17, 2008 at 18:33

Monday, Mar 17, 2008 at 18:33
Thankyou very much Gerry,
I have made up my mind and going to get 2x85w monocrystalline panels, 20amp 3 stage regulator alongside 1x 120ah fullriver battery.
I have learnt so much thanks to you guys and I appreciate it.

Cheers

Simon

P.S. I am about to post a thread in the forum on the topic of 'whats the best type of mobile internet to sign up for?'
Any information you have would be greatly appreciated i.e. best coverage vs lowest price?
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Follow Up By: Mike Harding - Monday, Mar 17, 2008 at 18:41

Monday, Mar 17, 2008 at 18:41
>P.S. I am about to post a thread in the forum on the topic of
>'whats the best type of mobile internet to sign up for?'
>Any information you have would be greatly appreciated i.e. best
>coverage vs lowest price?

Any credibility you had has just been destroyed : --- that's half a smiley.

Mike Harding
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Follow Up By: Redbac - Monday, Mar 17, 2008 at 18:46

Monday, Mar 17, 2008 at 18:46
Why is that...please explain???
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Follow Up By: Mike Harding - Monday, Mar 17, 2008 at 19:12

Monday, Mar 17, 2008 at 19:12
Oh! It's been hot today and I'm a bit grumpy but there have been more posts on this forum on this subject than one could poke a stick at and I just get a bit fed up with people wanting to be nursemaided .

Mike Harding
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Follow Up By: Redbac - Monday, Mar 17, 2008 at 19:35

Monday, Mar 17, 2008 at 19:35
My heart breaks for you Mike, but if you cannot BARE to answer yet another question on a topic that you simply cannot stand....then don't reply...simple!!

You seem to be quite a prolific member on this website so if you are getting bored with the 'same type of questions' then go to a different website and stop making me feel like I have done the wrong thing by EVERYONE.

I can only assume that most posts here are from people, like me, who actually appreciate the feedback from members on a range of topics who ARE PREPARED to do so.

Given that there are currently 35864 odd members, you can bet on your life one of them will post the same question again....get over it!!
This is a great website....don't ruin it with your snide remarks!
And yes I am hot aswell.
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Follow Up By: Mike Harding - Monday, Mar 17, 2008 at 20:05

Monday, Mar 17, 2008 at 20:05
It's not that so much... more that your first question had a modicum of intelligence and novelty to it however your second (which is totally unanswerable [is that a word?] in any cogent manner) would have been better served had you chosen to perform the taxing act of "doing a search"! In which case you would have discovered, no doubt to your amazement, that we have done this subject 57,146,971,064,742,807 times before!

Just because you're a newbie here doesn't mean everyone else is.

Mike Harding

PS. 35,864 members!? I suspect I.T. Beyond P/L wishes there were....
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Reply By: Redbac - Saturday, Mar 15, 2008 at 09:03

Saturday, Mar 15, 2008 at 09:03
That would be a 120ah battery I mean !!
AnswerID: 292783

Follow Up By: jeepthing - Saturday, Mar 15, 2008 at 10:18

Saturday, Mar 15, 2008 at 10:18
Redbac,

I have 2x85 watt panels and 2x 100amp AGM batteries. The AGM will charge a lot quicker and you don't have to worry about hydrogen gas being emitted into a confined space, if that's where your battery bank will be located. The best controller will be a 3 stage one.

I got my AGM batteries through Derek Bester of ABR he advertises through this site. Got my solar panels through www.ozbudgetsolar.com.au. Both of these guys are very good with their pricing.
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Follow Up By: jeepthing - Saturday, Mar 15, 2008 at 14:42

Saturday, Mar 15, 2008 at 14:42
Redbac,
Further to my previous reply, I was going out before and didn't have enough time to go into this much detail. I run a 110l Waeco which is run on freeze all the time to keep our food frozen. We camp out in the bush for weeks at a time and I don't have a generator to do any topping up. The longest we have gone for is 6 weeks and during that time have encountered cloudy days and rain. Before I did my setup I performed some experimenting with my batteries and ran the fridge in my shed, which obviously gets a bit hot during the middle of the day. The fridge does have an insulating cover, and I got nearly 4 days out of the 2 x 100amp batteries without charging. I figured it would be unlikely that during a 4 day period I would not get several hours of charge in the battery each day.
I have a 20amp Manson SBC-7120 3 stage controller which indicates state of battery, voltage coming from the solar panels, amps going into the batteries, total amps for the days and then for a 2 day period.
The 2 x 85watt panels will put in 10amps when it is cloudy they will still put in 5amps on average. When it is raining I might get 1 or 2 but it really depends on how heavy the rain is.
I really do think you need to overpower and don't compromise on batteries, the bigger the total amps you have the more relaxed you will be when camping in the middle of nowhere.
In my view the biggest mistake people make with solar panels is having them fixed flat to the roof of their van, you will get maximum efficiency by having them at the correct angle to the sun for the latitude where you are. You can buy hinged brackets or make your own. This site has solar panel RV Mounting Racks www.todae.com.au. Also I would NOT buy a Polycrystaline panel the best panel is the Monocrystalline, this cell is of superior technology than a poly or multicrystalline and I have found it is more shade tolerant.
Anyway this is my experience and I hope this helps
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Follow Up By: Redbac - Monday, Mar 17, 2008 at 18:32

Monday, Mar 17, 2008 at 18:32
Thankyou very much Jeepthing!,
I have made up my mind and going to get 2x85w monocrystalline panels, 20amp 3 stage regulator alongside 1x 120ah fullriver battery.
I have learnt so much thanks to you guys and I appreciate it.

Cheers

Simon

P.S. I am about to post a thread in the forum on the topic of 'what's the best type of mobile internet to sign up for?'
Any information you have would be greatly appreciated i.e. best coverage vs lowest price?
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FollowupID: 558813

Follow Up By: Mainey (wa) - Monday, Mar 17, 2008 at 22:44

Monday, Mar 17, 2008 at 22:44
Simon,
what is it that has swayed you towards Monocrystalline Solar panels ?

What BRAND of Solar Panels & Solar Regulator are you going to buy ?

Mainey . . .
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Follow Up By: jeepthing - Tuesday, Mar 18, 2008 at 08:19

Tuesday, Mar 18, 2008 at 08:19
mainey,
I'm not answering this for Simon he'll have his own reasons for going monocrystalline but I may have swayed him a little.

Monocrystalline is more efficient than poly or multi. Before I chose Mono I did some extensive research. If you have a look at this site i will expalin it much better than I could.

http://www.solarbuzz.com/Technonogies.htm
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Follow Up By: Redbac - Tuesday, Mar 18, 2008 at 10:32

Tuesday, Mar 18, 2008 at 10:32
Hi Guys,
contrary to the beliefs of my good friend 'Mike Harding' (whoever he is when he is home - see above), I did my very own research on this topic outside of this forum and read that given that poly cells are 'one' cell they are not only more efficient but stronger which better suits the rigours of travel.
I am going for a Phocos 20 Amp regulator & 2x85w EnerTech Panels.
I have been given a very reasonable quote from ozbudgetsolar and intend to purchase soon.
Thanks for your help guys....not you Mike :(
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FollowupID: 558945

Follow Up By: Mainey (wa) - Tuesday, Mar 18, 2008 at 14:41

Tuesday, Mar 18, 2008 at 14:41
Redbac,
Your research showing you "poly cells are 'one' cell they are not only more efficient but stronger which better suits the rigours of travel" is not correct, but yes, it's your choice.

However, what I would like you to explain is why you believe your Solar panel choice is in any way at all superior to BP, Sharp or Kyocera Solar panels... and the benefit you perceive of the Phocos Solar regulator !!

Mainey . . .
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FollowupID: 558983

Reply By: MEMBER - Darian (SA) - Saturday, Mar 15, 2008 at 12:30

Saturday, Mar 15, 2008 at 12:30
And, according to a book I've just been reading, the 120W rating for your panel is nominal...... under ideal test conditions - virtually never encountered in field use - your true best output may never rise above 70% of that 120 figure..... then we have to consider the poor weather on top of that :-o)
AnswerID: 292805

Follow Up By: Derek from Affordable Batteries & Radiators - Saturday, Mar 15, 2008 at 17:49

Saturday, Mar 15, 2008 at 17:49
Hi Darian

Moving a panel around will increase the output. I have tested our GP80W mono panels and in full sun. In best position they produce 5.8 Amps using a Steca PR2020 and a 100 a/h AGM. If I lay the same panel flat on the ground it drops to 4.2 amps. If I cover the panel with bubble wrap to diffuse the light is halves again. (Trying to simulate o/cast weather.)

The best is to track the sun and keep the panels in full sun. This is why portable panels outperform fixed flat panels on the top of a van or 4wd.

Regards

Derek.
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Follow Up By: jeepthing - Saturday, Mar 15, 2008 at 19:09

Saturday, Mar 15, 2008 at 19:09
Derek,

I find that the RV Mounting rack I mentioned works very well particularly when camping in the bush as I can get the van in the right position to maximise efficiency. Not that good in a caravan park though most of the time I leave them flat and the difference is quite noticeable, the drop is similar to your figures.
The portable panels are certainly the way to go trouble is when you leave the camp to go out for the day they have been know to dissappear!!!
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Follow Up By: Derek from Affordable Batteries & Radiators - Saturday, Mar 15, 2008 at 19:35

Saturday, Mar 15, 2008 at 19:35
Quite true, I use a 10m welded link chain on mine. Still might find someone with a bit of time that is eager enough will just chop it off.

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FollowupID: 558450

Follow Up By: Mainey (wa) - Tuesday, Mar 18, 2008 at 16:09

Tuesday, Mar 18, 2008 at 16:09
Derek, your panels are so much more powerfull than Sharp and BP as you say ""you have tested your GP80W mono panels and in full sun. In best position they produce 5.8 Amps""

By comparison the 80 Watt BP Solar Panel has a Maximum Power of only 4.55 Amps and the 80 Watt Sharp Solar Panel has a Maximum Power of only 4.63 Amps.

Can you please explain why Sharp & BP are less powerfull ??

Mainey . . .
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FollowupID: 558998

Follow Up By: Derek from Affordable Batteries & Radiators - Tuesday, Mar 18, 2008 at 16:32

Tuesday, Mar 18, 2008 at 16:32
Our panels are mono-crystalline v/s multi-crystalline I have not tested the others in the same test on the same day but will next time I do a test.

Regards

Derek.
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Follow Up By: Mainey (wa) - Tuesday, Mar 18, 2008 at 20:52

Tuesday, Mar 18, 2008 at 20:52
Derek, I only ask because your own web site:ABR GP-80 watt solar panel very clearly states:

GP-80 Watt Specifications

Max. power: 80 Watt
Max. current: 4.45 Amps
Output tolerance: ±5%

The GP-80 Solar panel manufacturers test results are claiming a much lesser Maximum current @ 4.45 Amps, which is a long way from 5.8 Amps you claim and the GP-80W is almost the exact same number as the 80 Watt BP Solar panel which is slightly higher 4.55 Amps also shown on your same web page.

As I said, I was interested how you have recorded a much higher Maximum current than the Manufacturer can attain even when allowing for their 5% variation ?

Mainey . . .
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Follow Up By: Derek from Affordable Batteries & Radiators - Tuesday, Mar 18, 2008 at 21:08

Tuesday, Mar 18, 2008 at 21:08
Can only tell you what the Steca said. Will try a few more tests next time.
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