Portable Solar Panels

Submitted: Friday, Jul 22, 2005 at 19:53
ThreadID: 24973 Views:6391 Replies:13 FollowUps:13
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Does anyone have experience with portable Solar Panels? We’re off again to the Kimberley next year and will be camping in an isolated area on a cattle station for at least two weeks.

I’m currently looking at the Suntech 80 Watt unit which retails for around $990.

Both 4wd’s have dual batteries and run a 40L Engel each. We also have a 2KVA Honda generator. However, there are days when I don’t want to listen to any noise.

Will a 80 Watt panel handle the discharge from two Engel’s (assuming sunny conditions).

Any advice would be much appreciated


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Reply By: Boeing - Friday, Jul 22, 2005 at 20:01

Friday, Jul 22, 2005 at 20:01
Hi Kim, If you do a search you will find a wealth of info on this subject. But having said this, to provide the correct answer you will need to advise if the fridges are in the sun or shade,estimated temp and if you will be going for a drive which will charge up the batteries. But a 80watt panel will not cover the enrgy used by the Engels on its own. You will need to run the genny with a (preferred) 3 stage charger to top up.


AnswerID: 121653

Reply By: porlsprado - Friday, Jul 22, 2005 at 20:03

Friday, Jul 22, 2005 at 20:03
Lots better answers to come but i have 2 x 40watt panels that pull out in full sun about 4.6 amps per hour which is great for one fridge but if running two engels up there in say 40C heat then i await the engel owners (presuming tne newer better insulated models with the 2amp current draw) to see how much they would use. In summary i think with an 80watt panel you'd put enough into the batteries to stop them from draining too much for about a day before you'd be advised to top them up properly. Not a green solution but i think you'd be better investing in a 25 amp 240 volt charger and putting up with the noise for just a couple hours.
AnswerID: 121654

Follow Up By: kimprado - Friday, Jul 22, 2005 at 20:23

Friday, Jul 22, 2005 at 20:23
Thanks Porlsprado
Must admit I'm out of my depth with Solar technology. From what your saying we need two panels?
Can I also ask how robust they are? Each year we travel down some pretty rough tracks up North. The panel would be strapped to the side of the Engel with high density rubber between the frig and floor of the drawer set?
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Follow Up By: Grungle - Saturday, Jul 23, 2005 at 09:02

Saturday, Jul 23, 2005 at 09:02
Hi Kimprado,

I went through the same exercise 6 months ago. I documented everything I learnt and put it on my website Grungles Homepage.

I agree with polsprado and suggest buying a high amperage 240v 3 stage battery charger. You can run this for around 2 hours every couple of days from a generator or from mains power but has the added advantage of keeping the batteries healthy when the camper is in storage. You can connect and leave it until the camper is next used. I bought a 30A one for $370 and is great.

Solar is a technology that very few people understand. There are many factors that determine how succesful one is in getting the most from a setup. One thing that people need to know is that solar panels are not efficient and you will never get the output that manufacturers claim. I only rely on panels when I am in an area where generators are not allowed to be used and if I am in camp to constantly move them for optimum performance.

If you still want to go the route of solar then I would suggest an exceptional book on the subject from Collyn Rivers. This will arm you with all the knowledge required to setup a system that meets your needs.

FollowupID: 376886

Reply By: Member - Jimbo (VIC) - Friday, Jul 22, 2005 at 20:47

Friday, Jul 22, 2005 at 20:47

Firstly, $990 for an 80 watt panel is extortion. The going rate, if you bargain, is about $500. Add on $110 for a regulator and decent cable at $2 a metre.

As for whether it will handle the load of 2 x 40L fridges; there are a lot of varaibles. A Suntech panel in the Kimberley will only work at about 80% efficiency, they drop off when the temp exceeds 25C. Therefore you will only get about 64 watts (about 4.6 amps) whilst the sun is out. Say 8 hours of good sun per day if you are lucky, equals about 37 amps.

Depending on how high you set you fridges they will use diifering power, but from tests these use an average of 1.6 amps per hour. Therefore, 2 fridges X 24 hours X 1.6 amps equals 77 amps. Clearly you will fall short. Probably not by as much as the maths tells you as I have found from personal experience.

I have an 80L Waeco which is supposed to average 84 amps per day, but in summer I can power it happily with a 64 watt panel (amorphous panel that is).

However, you will still be keeping some charge into the battery and will therefore not need to use your genny too often.

Have a look, as an alternative at the Unisolar panels. View the archives under "Jimbo" or "Solar" about December 2004. I posted on some tests I did.

I would suggest start low and see if it works. You can always add another panel. Dealers can, at times, oversell.


AnswerID: 121671

Follow Up By: kimprado - Friday, Jul 22, 2005 at 21:14

Friday, Jul 22, 2005 at 21:14
Thanks Jimbo. Good advice.
If you think the price for the Suntech is a rip off, you would'nt beleive what I was quoted for a roof top unit installed on a camper trailer.
Who distributes the Unisolar panel in Victoria?
Many thanks for your help.
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Follow Up By: Member - Jimbo (VIC) - Friday, Jul 22, 2005 at 22:50

Friday, Jul 22, 2005 at 22:50

Try Award Caravan Accessories in Ferntree Gully. Talk to Rod, he knows his stuff. Good bloke to boot.

He'll do you a Unisolar 64 watt for low 500's. Could be less these days as prices have come down. I paid $545 late last year. Don't pay anymore than that.


FollowupID: 376851

Reply By: BigO- Friday, Jul 22, 2005 at 22:40

Friday, Jul 22, 2005 at 22:40
Hi Kim,
I use an 80 watt solar panel with 2 x 100 amp/H deep cycle batteries to run my 60L Evakool fridge and some lights and find this allows me to be away at least a week without any other form of charging. I live in Victoria and have puchased all my batteries, chargers and solar panel from Solar Panel Xpress in Queensland. They can courier them down here much cheaper than I could buy them in Melbourne. They have a great website with heaps of info (www.solarpanelxpress.com.au).
AnswerID: 121684

Reply By: motherhen - Friday, Jul 22, 2005 at 23:29

Friday, Jul 22, 2005 at 23:29
We used to travel with a generator, but a few years ago "went solar" purchasing just one 80w panel mounted it on a stand so it be set to face the sun, or put on top of the (stationery) van, depending on time of day, to get optimum sun. We had a deep cycle battery in the van which also charged from the car - but the solar panel did it much quicker than going for a drive. We had 12v lights (more than adequate for reading with) and built in an engel caravan fridge. We didn't meet bad weather though, and were touring mainly in the Pilbara. Often we'd set up the panel facing the sun, go for a walk, and get back late in the day to find it well and truly in the shade, but the battery was fully charged. If the batteries were getting a bit low over night we'd leave the panel facing East, and at first light it would start charging. We run an engel car fridge in the Nissan which has two batteries, and the second one doesn't get drained, so it can be used the jump start the car if the main one goes flat. We never missed the generator at all.
AnswerID: 121692

Reply By: kimprado - Saturday, Jul 23, 2005 at 17:59

Saturday, Jul 23, 2005 at 17:59
Thanks to everyone for your helpful advice.
AnswerID: 121761

Follow Up By: Mainey (WA) - Sunday, Jul 24, 2005 at 13:25

Sunday, Jul 24, 2005 at 13:25
like those in the affirmative above, I would recommend at least one 80 Wt panel, I use one 80 Wt solarex panel wired direct to two x 80 A/H DC batteries, was only a few months back that I started using a solar regulator, and yes I would recommend one if you want to see where the panel should be facing and improve the panel’s performance, as it shows the amps generated by the panel and going into the battery and amongst many other things also the Volts of the battery.
Link here-> http://tinyurl.com/ccxzz

As soon as the sun comes over the horizon it starts replacing the power in your battery system, I have seen, at 8am, via the LCD screen on the solar reg, there is 0.2 amps going into the battery system and it raises as the sun gets towards midday, it’s still replacing power at close to sundown.

Your Fridge should not be working anywhere near 24 hours/day, while the solar panel is working from sunrise till sunset to *some* degree, and replacing power during this time.
As Jimbo has stated the mathematical numbers do not stack up with solar panels and he has tested his system on various occasions and posted the results on the forum confirming this.

As with most things, actual life experience is where realistic answers will come from!
FollowupID: 376988

Reply By: Member - Collyn R (WA) - Wednesday, Jul 27, 2005 at 12:05

Wednesday, Jul 27, 2005 at 12:05
May I suggest you check my article 'Solar Thar Really Works' posted a few days ago on this site.

Click on 'Electrics' on the 'Topic Search' panel on the left of the page.

Incidentally $880 for an 84 watt module is hugely over the top. Should be closer to $600.
Trust this helps
Collyn Rivers
AnswerID: 122268

Reply By: kimprado - Wednesday, Jul 27, 2005 at 19:09

Wednesday, Jul 27, 2005 at 19:09
Thanks Collyn,
I'll have a look at it. Obvioulsy the first two prices were way over the top.
AnswerID: 122359

Reply By: Member - Gary W (VIC) - Thursday, Jul 28, 2005 at 13:56

Thursday, Jul 28, 2005 at 13:56
We have a 120w Kyocera Solar Panel charging a 110Amp/hr Deep Cycle Lifeline battery. The fridge is an Evakool ED90 (Danfross compressor). In most circumstances the solar panel keeps the battery charged but does not fully charge it. The only time we have had problems is in hot weather and shady conditions.

I wouldn't want to have a smaller panel.

AnswerID: 122541

Follow Up By: kimprado - Thursday, Jul 28, 2005 at 18:53

Thursday, Jul 28, 2005 at 18:53
Many thanks Gary,

I have a 40 litre Engel which probably does'nt draw as many Amps as a 90 litre.
After a lot of advice I'm looking at a portable 80 Watt unit. I take it from what your saying, this may be too small?


FollowupID: 377765

Follow Up By: Member - Gary W (VIC) - Friday, Jul 29, 2005 at 07:55

Friday, Jul 29, 2005 at 07:55
The ED90 is based on a 90ltr Evakool Esky - the compressor takes about 15ltrs so the real volume is 75ltr. I't not sure about the amps it uses.

One of the thing people can over look is that to prevent battery damage the fridges normaly cut off when voltage drops. The reality of this is that a 110amp/hr battery will only supply about 50-60 amp/hrs to a fridge before the voltage drops and the fridge shuts down.

In short I would not be confident that you 80w unit is big enough - you might be disappointed.

FollowupID: 377820

Reply By: Nick (QLD) - Saturday, Jul 30, 2005 at 13:02

Saturday, Jul 30, 2005 at 13:02
The engel 4o ltrs will pull about 3.5 amps each per hour, as a fridge, and will cycle approximately 8 hours in 24. This gives a daily draw of approximately 60 amps for the fridges and lets allow say another 25 for lighting, pumps etc. So, for want of a figure lets say you guys pull about 85 amp per day.

When sizing battery capacities to suit a solar system i work on roughly 4 times the averag daily draw. There are two main reasons for this. The first is the deeper you discharge a battery the less number of discharge/recharges you will get. So, working on this theory you will only discharge approx. 25% per day. The second reason is that in days of rain your system will be able to support itself initially instead of merely collapsing. For these reasons, i suggest no less than 225 amps and will work on that figure for the purpose of this exercise.

The average 80 watt panel will give you approx. 4 amps per hour and this is only for about 6 hours of the day. So lets asssume each panel will give you 25 amps per day. I would suggest two 80 watt panels at a minimum giving approx. 50 amps per day. Bp solar has a rebate scheme going at the moment for any system over 145 amps. You are elligible for 50c's per watt for every panel install so, 2 x 80's will give you an $80 rebate. The panels sell for about $700. Bp panels are the old solarex ones with a few improvements including higher out put voltage (closed circuit) and a silver nitrate backing to prevent energy loss due to heat. Not to mention Aussie made!!!

So, your daily draw is 85 amps and your solar input in the same time frame is 50 amps making your theoretical daily draw now 35 amps.

This means that with no other input into the battery you will last approx 8 days. In saying that you would be better running the generator every couple of days for an hour or two rather then once a week for a whole day. Re: point 1 on battery sizing.

The only other point worth mentioning is charger sizing. This should be no less then 10% of your overall battery capacity. So in your case 20 amps is sufficient. (10% of 225) The reason for this is that if it is too small the unit will never reach 'float' or full as far as the charger is concerned. It will sit there for hours saying "I think i can, I think I can" but it cant!

Any further queries let me know. Nick
AnswerID: 122861

Follow Up By: Jimbo - Saturday, Jul 30, 2005 at 14:46

Saturday, Jul 30, 2005 at 14:46
With all due respect Nick, what you have posted is factually incorrect.

An Engel 40 has been independently tested in harsh conditions and averages 1.6 amps per hour, ie 38 amps per 24 hours. I reality they use less. An 11 watt fluoro (versa or similiar) will draw less than 1 amp and be used for maybe 5 hours per day.

I get by with a 64 watt Unisolar panel and a 100 amp AGM battery to run a Waeco 80L and lights. I've posted my results here previously.

All the theory in the world cannot compare with actual use.


FollowupID: 378034

Reply By: kimprado - Saturday, Jul 30, 2005 at 17:29

Saturday, Jul 30, 2005 at 17:29
Hi guys,

Before I start, i want to thank every body for their helpful advice. I've learnt a lhell ot a lot from the contributions. Your all been terrific.

I've decided to buy a portable 80 Watt unit. The reason for doing so is:

We tend to camp in isolated areas (therefore generator noise is not a problem( except for me).

The units are compact and easy to store

I can move it around to follow the movement of the sun.

Finally, if it doesn't work, I've only got myself to blame.

Hope to see you on the track



As previously mentioned I also have a dual battery set up.
AnswerID: 122897

Follow Up By: Mainey (WA) - Saturday, Jul 30, 2005 at 17:42

Saturday, Jul 30, 2005 at 17:42
Why a 'portable' panel ?

Where will you store it ?
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Reply By: kimprado - Saturday, Jul 30, 2005 at 19:01

Saturday, Jul 30, 2005 at 19:01
Hi Mainey,

Firstly, because of the advice I've received from this site and where its led me in discussions with retailers.

Secondly, as previously explained, we often set up a base camp and could be away from there for well over a week. Therefore, its important I can take the unit with us.

Next year we'll be in very remote country up in the kimberley well off the tourist trail and therefore need to be self sufficient.

Hope I've answered your quesrion



AnswerID: 122912

Reply By: Alan Southport QLD - Tuesday, Aug 09, 2005 at 17:07

Tuesday, Aug 09, 2005 at 17:07
Hope everyone remebers that you wanted portable! Obviously, all panels are flat and can be stored. There are fold up / briefcase open/shut with little stands types might be ones that were the high price you were quoted.

There are ploy and Amophorous (Can't speel), types. The AM type give out more but wear out over time and don't do well in the heat - most portable types are AM. The polys are better, last longer, and are much better at heat levels.

Previous replies, mention about morning and facing sun and stuff. This is fact: The energy output stated on the panel will be less than what you get. IE: if it says 4amps then you will get (in real life 4.4amps), they are all under rated for legal reasons. But AM types will give upto 30% more, but then go gradually lower (maybe 4 months), as they 'settle in'.

So if you have an 80watt panel which way do you face it? They only get peak power if they are directly FULL ON IN THE FACE of the sun. That's why some rich people have Solar Trackers. But obvioulsy in your case you don't need that - I'm only making a point.

You should only pay for a 80W Ploy panel $600. Get 3 and have one facing the morning sun, the other to collect the midday and the third to collect the setting sun.
if you are around the area, then moving all 3 to face the sun full on as time goes by, then great!
But if you don't want to be moving them all the time, then i suggest the 3 panels. Don't forget that if you get ONE cloudy day, then maybe judge about having a 4th panel to cater for that.
AM type panels are better for cloudy days, but Poly does ok anyway within reason.
That way you cannot go wrong and should meet your power requirements.

As for regulators, thickness of cable and quality of batterys, they all have a percentage of loss and as any good solar guy will tell you - your loss with be at LEAST 50%, for a final power given (what is should give you), to what you need (What you actually get out at the end).

If you have the money and don't care about longivity and a bit lower energy due to 35-40C° days and a working usable life of 10 years, then go AM type. If you want
good all round performance go the Poly type, but i am not sure about the 'portable' side of it.

Lastly, with your roof top quote, just get 2 80w polys and make a frame.

Hope that helps.

AnswerID: 124454

Follow Up By: Jimbo - Tuesday, Aug 09, 2005 at 18:13

Tuesday, Aug 09, 2005 at 18:13

A couple of errors in that.

It is poly panels that do not like the heat. Clearly written on the back of Kyocera brand poly panels is they lose 20% efficiency over 25 C. Amorphous panels love the heat.

Amorphous panels operate at 10 to 15% ABOVE their rated output for the first 8 weeks of continuous use and then revert to their actual output. They do not "wear out".

Also amorphous panels are not a sensitive to being angled directly at the sun as poly panels.

Hope this clears a few things up.


FollowupID: 379370

Follow Up By: Alan Southport QLD - Wednesday, Aug 10, 2005 at 09:10

Wednesday, Aug 10, 2005 at 09:10

Yes i can see some errors, The Polys are not as tolerant to the sun, but i thought the temperature was higher than 25°C, around the mid 30's to low 40's.
I was being conservative about he Rated output in the first settling in period.
As for the life span, i was not aware that any AM types have a warranty - but the polys do.

In your conclusion as for the better panels to buy (And AM types are cheaper), then why would anybody buy the Poly types here in Australia where 80% of land (particulary the outback) gets way beyond 25°C?

If the AM types are cheaper, better shade tollerant, higher output, do not wear out, and are not as affected by the higher temperatures, then why choose the Ploy type of panel?


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Follow Up By: Alloy c/t - Wednesday, Aug 10, 2005 at 11:04

Wednesday, Aug 10, 2005 at 11:04
Alan , I have and use both types of panel , a 64w UNISOLAR [same as Jimbos] and a 120w KYOCERA , heat issues aside , the main difference is SIZE , the 64 unisolar gives out in near perfect conditions 3.7amps ,its SIZE =1366x742x47 and weighs 8kg ,,,the 120 kyocera in the same conditions 7.1amps yet the SIZE is not much bigger at 1425x652x52 and 11kg , pay 2/3 the $ for 1/2 the amps yet the same size , each to their own.
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Follow Up By: Jimbo - Wednesday, Aug 10, 2005 at 19:17

Wednesday, Aug 10, 2005 at 19:17
All very interesting and like everything there are no absolute rights and wrongs.

See post 25476 and the response by Collyn Rivers, the Guru on this topic. He has forgotten more than most of us know.

Alloy your comments on the Kyocera vs U/s are valid in perfect conditions. My understanding is that in partial shade or overcast conditions a poly panel stops dead, whereas an amorphous panel still gives some output. Therefore if you forget to move your poly panel and 10% of it is shaded it stops, whereas the amorphous panel in the same circumstances will produce 90% of its output.

As you said, each to his own.


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