Solar The Solar Panel Thread

[Macca_75]

I know when we installed Solar on the house years ago, the sparky had a little tool. plugged some readings from the roof into his laptop and made some predictions. We were within 2% of that after 12 months - frigging great.

Anyway, maybe @ericmil wanted to compare 12v Caravan panels to the higher voltage house panels??? Would need a good MPPT regulator to take advantage of the higher voltage but I suspect there won't be a huge difference - solar technology is solar technology.

Although higher voltage panels would mean cheaper (thinner) wiring could be used.

 

[jazzeddie1234]

I mentioned earlier that my cheap ebay flexible panels have lasted around 12 months before failing and my last working panel has developed an opaque surface. Dr google suggests EDPM panels have a greater durability and there are more of these being sold - some marine quality are very expensive but there are some in the affordable range. Has anyone tried EDPM and have any views on them? I'm 70% leaning to installing good old rigid for peace of mind but they are heavy...

 

[BrokeInBendigo]

How do we calculate for my house quantity solar cells? I found only this review websolarguide.com/passive-solar-energy-pros-and-cons/

Hi Eric, @Boots in Action summoned me regarding a formula to calculate how much solar you need. It's not necessarily difficult to do but you'll need spend some time testing things.

Firstly, you need to figure out how much power you use daily. You have 3 main options:

1. Look at the power requirements of all of your appliances and devices. They will have a wattage listed. Multiply that by the number of hours the device will be powered on during an average day.

2. There are many devices that can measure the actual power usage of a mains appliance, for example one is called a Kill-A-Watt, you plug it into your mains power outlets and then plug your appliances into it. It measures the actual current draw of the appliance. Sometimes an appliance's wattage is inaccurate for real-world use. What you have to do is spend a couple weeks measuring an average day's worth of power usage for all appliances in your home.

3. The final option is to look at your power bill to see how much power your home uses over a month and average that out per day.

Use this formula to calculate wattage if you don't have your numbers already in watts. Watts are the best, most sensible way to represent power usage.

Watts = Volts * Amps

When you have the wattage per day (it may be in watt-hours or kilowatt-hours, adjust your math accordingly), you can determine how much solar you need. Solar panels are rated in watts, which in practice means the solar panel can generate that many watts per hour, in perfect conditions (which never actually happens for a number of reasons, many of which are unrelated to the quality of the panel) so you'll really want 50% more wattage of panels than your daily requirement. Also, you will not have sun for 24 hours - more like 7 hours of usable sunlight on a good day is reasonable. Finally, inverters are not perfect and have some efficiency loss - usually they max out around 90% efficiency. So you lose 10% of your wattage to the inverter. You also lose some power from your solar charger but I won't factor that in.

Let's say you calculate that you use 10000 watt-hours per day.

So:
(10000 watt-hours / 7 hours) * 1.5 * 1.1 = 2,357.14 watts of panels needed to provide your power needs for 1 day, on a good sunny day.

How, how big, like square meters, will that require? Do you even have enough roof!?

Well, wattage ratings of panels are calculated by assuming that the sun puts out 1000 watts per square meter. Average decent PV cells have an efficiency of 20%. So one square-meter of PV cells would give you 200 watts in perfect conditions (light is perpendicular to the solar cell and it is 25 degrees - heat decreases efficiency). So you'd need 2,357.14 watts / (200 watts / sq meter) = about 12 sq meters of PV cells. Keep in mind that a 1 sqm panel is rarely 100% PV cells.

In summary, a super generalised and rough formula to get the area in square meters of solar panels needed:
((daily power use in watt-hours / 7) * 1.5 * 1.1) / 200 = area of solar panels

Ideally you have a battery bank that can provide a few days' worth of power or else the lights go out when there are a few cloudy days in a row.

Whew, sorry I got a bit excited with all those numbers. I hope that makes sense.

Check out diysolarforum.com for some great resources on all this stuff. I'm an amateur but there are real solar gurus on that forum. Also check out Will Prouse on YouTube, he's great (and I think he runs that forum actually).

 

[Drover]

I mentioned earlier that my cheap ebay flexible panels have lasted around 12 months before failing and my last working panel has developed an opaque surface. Dr google suggests EDPM panels have a greater durability and there are more of these being sold - some marine quality are very expensive but there are some in the affordable range. Has anyone tried EDPM and have any views on them? I'm 70% leaning to installing good old rigid for peace of mind but they are heavy...

My roof panel is about 8 years old, my portable is about 5 or 6 years old still going well and soon as this damn rain buggers off an extra 220w will be added to the roof, all nice hard panels, have never trusted the flexy panels and price only means a lighter wallet as they all seem to crap out.......... though have been told by some their flexy panels have lasted 4 years and are still in good nick, mind they get used for a few weeks a year so hearsay is to be taken with a grain of salt I think........... My roof tops sit in sun all year and the portable gets about 3 mths or so.... How heavy are mine I have no idea, can't be too much as I can sling them around one handed.

 

[Crusty181]

Question for the solar gurus, way above my pay grade. I have a Redarc bcdc1220 (cant afford the expensive ones) and as a punishment for being a cheap ar$e, Redarc don't put solar input/regulator in the poverty model so Im using a PWM controller strapped to the top of the battery

If the Redarc max input voltage is 32v, and 160w fixed panel on the car has a VOC of 20.57v can the Redarc be connected directly between the panel and battery and skip a regulator altogether.

Redarc's customer service/tech support are A1, and would be onto this with 30min ...... but it's Sunday and Ill have moved onto a completely new idea by tomorrow

 

[Drover]

While I'm only a dumb truckie, I would surmise NO and I would connect the solar reg direct to battery by-passing the Redarc ........... My simple reason would be the Redarc wouldn't like the erratic supply from the panel, I think the panel wouldn't supply enough actually and connecting a regulator to the Redarc wouldn't work either, as it wont see the battery..... the reg needs to see the state of the 12v power to work.....
So either buy a proper DC-DC charger or solar/reg direct to battery........................ of course someone will reply with a more fluent techno tome.

 

[Crusty181]

While I'm only a dumb truckie, I would surmise NO and I would connect the solar reg direct to battery by-passing the Redarc ........... My simple reason would be the Redarc wouldn't like the erratic supply from the panel, I think the panel wouldn't supply enough actually and connecting a regulator to the Redarc wouldn't work either, as it wont see the battery..... the reg needs to see the state of the 12v power to work.....
So either buy a proper DC-DC charger or solar/reg direct to battery........................ of course someone will reply with a more fluent techno tome.

I've no done it, I read a resident Professor at Facebook University recommending to the uneducated masses. Although it's seems like it should work, it still just doesn't 'feel' like you should do it. I don't know why, or enough about it either way.

I have a fixed panel on the roof of the Troopy, and its connected directly to the Aux battery via its own cheap pwm controller. (One fixed panel doesn't warrant a lavish mppt controller for my Aux battery setup). The Redarc bcdc is connected independently to the Aux battery directly from the start battery per the std recommended Redarc wiring guide.

Redarc charges while driving, and the panel when parked up. (although i have to connect the panels cable .... im not quite ready to bore holes in the Troopy just yet)

 

[Drover]

I had same on Colorado, panel on roof cheapy reg all hooked up to auxillary and if I wanted it to charge from car battery as we drove along I just flicked a switch, simple toggle job outside the shed and bingo the battery charged, the Engel ran all was happy.......... was always going to get a Cetek 250D, still am, one day, in the fullness of time.... i also had an Anderson plug outside which I could either plug a portable panel in for extra ooompf or run a light/compressor/extra beer fridge.
Be a devil thats why we buy Mine Trucks, drilling holes is what they are made for.........want aerial here, whine, growl, bingo hole for aerial lets have a light here, same again add grommet for cable and t looks better................ Toorak tractors like this Jeep, drill a hole an airbag will go off or some damn electronic gizmo has a hissy fit......... after 40 odd years of me drilling holes Mrs D now just shakes her head, took awhile though.......

 

[mikerezny]

Hi,
I did a Google search on "redarc bcdc1220 solar panels.
If you do the same, you will see that redarc have a forum and this question has been asked and answered by Redarc a number of times.
Here is on of the threads:

https://www.redarc.com.au/forum/discussion/7483/using-solar-with-a-bcdc1220

The answer from Redarc, appears to say no and does give some explanation.

I didn't read all the threads and none of them extensively. However, it does seem that this will be an adequate reference for your question.
I would suggest that if your query is not answered on these threads, to post it on that forum. The Redarc staff seem to be quite responsive.

I hope this helps.

take care
Mike

 

[Boots in Action]

While I'm only a dumb truckie, I would surmise NO and I would connect the solar reg direct to battery by-passing the Redarc ........... My simple reason would be the Redarc wouldn't like the erratic supply from the panel, I think the panel wouldn't supply enough actually and connecting a regulator to the Redarc wouldn't work either, as it wont see the battery..... the reg needs to see the state of the 12v power to work.....
So either buy a proper DC-DC charger or solar/reg direct to battery........................ of course someone will reply with a more fluent techno tome.

Hi "dumb truckie" @Drover , and for your info @Crusty181 , a more fluent techno answer, although what @Drover says is mainly correct. For starters, just because the RED ARC has a max input voltage (from alternator) of 32 volts, does not mean it cannot accept any lower voltages. In fact, most ordinary portable or fixed (roof top type) solar panels have an open circuit voltage of around 22.5 volts. But it is the WORKING VOLTAGE in solar panels that matters - when a load is placed on circuit - and working voltage whilst producing current with load applied is usually 17 or 18 volts depending on quality and bypass diodes used. Schottky type have a lot less loss in that regard and means higher operating voltages if two parts of folding panel are involved.

The RED ARC Dc to Dc charger is mainly set up as a transformer to convert output voltage from alternator (generally only 13 to 14 volts or even lesser in modern tugs) to a higher level (at the expense of current) available to charge van battery, while a solar regulator's task is to REDUCE the higher solar panel voltage down to battery voltage (or just above that) to put current into battery for charging. A MPPT controller does the same thing BUT it does not waste the excess voltage and turns this into extra current!!
So as your cheaper unit (@Crusty181 ) is not wired for both types of upgrading or down grading input voltages, any other inputs such as a separate solar panel must have its own solar controller in circuit (series) between solar panel and battery connections or connected through existing solar regulator wiring. This would already be happening with any power generated by roof top panels (if in sunshine and not in shadow or darkness) as that power would be going through your Epever solar regulator before reaching van battery, even while the Dc to Dc charger is also charging battery/ies by tug alternator.

Dc to Dc charging is all about getting a higher voltage from tug to van (overcoming losses in wiring/connections) and Solar regulators PWM or MPPT are all about charging the van battery/ies themselves, although both end up charging the battery/ies. Hope that clarifies that in simple terms. No offence to you @Drover. @mikerezny might like to bring up a few more point I have missed.

 

[Drover]

None taken the answer is the same just you used more words................NO it won't work.......... I actually found someone who tried and spoke to the Redarc mob who confirmed it, he then sold his unit and bought the model that does the solar, he's one of those annoying people who sell for more than paid and got the new one on special..................

 

[BunchOfHunts]

I have read most of this extensive thread and appreciate all the great input people have had.
I have been researching solar heavily for the last 3 months as we are currently full time on the road in our expanda.

I currently have 140ah AGM in the van which is used for lights, fans and charging devices.
I have a Dometic PLB40 40ah portable lithium battery for charging the Waeco 40litre fridge.
I have 1 x domestic 150w solar blanket with an mmpt charge controller.
I use the car to charge the PLB40 via the cigarette socket.
I don't have a dcdc charger.

My main weakness is obviously not enough solar for the system as if we have a couple of days where we don't drive (especially if it is hot) then I only have 1 blanket to charge the van and the portable battery.
On heavy load days like when we spent a week at Litchfield I just wasn't able to keep up and had to turn the fridge off for periods. Otherwise the battery system has been keeping up pretty well.

I strongly considered getting an upgrade to a 150ah lithium battery and roof top solar for about $2k but not sure if we need that much as we will be chasing the Sun around the country.

Any suggestions on how I can fix my problem of not enough solar?

Should I just buy a cheap 200w solar panel with an attached regulator eg Kings? Or should I buy an expensive panel (eg red arc) and a victron (100/30) regulator? Or should I be looking to get some roof top solar instead?

I think the cheap panel would probably do the trick but I don't love the idea of lugging around a 1m long 21kg panel.

Any advice greatly appreciated. Sorry for long post, just trying to add detail.

 

[mikerezny]

Hi,
from my first read:
1: I would suspect that a 40Ah Lithium battery would be barely capable of providing enough power to run your Waeco for 24 hours
They typically draw an average of 2A over a 24 hour period, so 48Ah per day. This very much depends on the ambient temperature and the load on the fridge (how often it is opened and how it is used).

2: A solar controller supplied with a panel is unlikely to actually be an MPPT controller, regardless of what is printed on the front panel. So, I would assume it is a normal, rebadged, PWM controller. So the current into the battery will not exceed solar current in.

3: A 150W blanket, may deliver about 7A in direct sunlight on a clear day. Assume a maximum of 5 hours per day. So a maximum of 35Ah per day.
This is not enough to recover the power used by the Waeco (48Ah), let alone recovering anything taken out of the van battery.

Here is a copy of what I just wrote on another thread in this forum. It may be of some help to you:
Note, if you are considering forking out $2k, I would suggest a modest investment of about $100 in a digital multimeter with DC clamp (might be about $80 nowadays) and an inline 12V power analyser (about $20).

The three step process to setting up a 12V system for off-grid use is roughly:
1: Determine your average daily 12V requirements in Ah.
2: Determine the maximum number of days you want to have power assuming no sun for solar power. This is a tough question with many side issues. One consideration is the power source for the fridge. If it is gas, the food in the fridge will not go off if the 12V system fails. If one has a generator AND a high capacity 30-40A charger, it can be used to maintain the batteries until the sun comes back.
From this you can estimate the battery capacity needed bearing in mind that the most economical use of batteries is achieved by avoiding regularly discharging them below about 50%. Deep cycle batteries don't suddenly die if deeply discharge, but their life is determined by the number of discahrge cycles AND how deeply they are discharged. My Ritar RA12-100DG GEL battery is rated to provide roughly 450 100% discharge cycles down to 9.6V. At which time the battery capacity will be down to 60Ah (60%). In comparison, if discharged to only 50%, the battery is rated to provide about 1,100 discharge cycles. Bear in mind that the expected life of these batteries when used in caravans is about 6 years, 300 weeks. So if the batteries are 100% discharged once every weekend they would die from old age before they die from being discharged 400 times. There are numerous charts around showing the relationship between battery voltage and SOC for various types of batteries.
3: Once the first two items are determined, then the solar system is designed to ensure the batteries are recovered each day with some spare to catchup when the batteries were not fully recovered on previous days. Rough rule of thumb, assume a maximum of 5 hours of sunlight per day, add some more to allow for camping spots that do not get direct sun every day, then allow some more if considering roof mounted solar since the panels are NEVER optimally aligned or regularly cleaned.
4: (Yeah, I said three, but I lied.) Ensure you understand every aspect of your usage, battery capacity, and solar system and have the necessary tools to measure voltage and current.

If this sounds daunting, just start at the beginning and work slowly through it. Time spent at home reading manuals, getting familiar with the equipment and documenting in the comfort of your home will greatly enhance your ability to have camping trips that are not frustrating or result in cutting a trip short because the 12V system goes pear-shaped. There are spreadsheets around in previous posts to help with the calculations.

Just as an example:
Step 1: My average daily requirements are 4Ah. I have measured and recorded the current draw of every 12V device we use when out camping.
Step 2: Battery capacity is 95Ah.
Step 3: Portable solar panel is 40W, maximum output current is 2.2A.
Step4: I have copies of all the manuals: Setec, Solar controller, Solar panel, deep cycle battery. A digital clampmeter that can measure DC current, A power analyser that can measure charge voltage, charge current, and accumulated Ah charge into the battery.

From that, I can survive for a maximum of 24 days (100% discharge), but preferably no more than 12 days (50% discharge). I need 2 hours of direct good sunlight to recover 4Ah each day and I have the capacity to provide about 10Ah per day with 5 hours of direct sunlight. Armed with that information, I can exist indefinitely as long as I get two good days out of 5 days.

I hope this has been of some help. It is a very short summary of what I have learnt from the input of people on this site over the past 5 years. In that time, I have never had a 12V problem and never had to cut a trip short or compromise a camping experience in any way due to 12V problems. In that time we have spent well over 300 nights off-grid.

take care
Mike

 

[Boots in Action]

I have read most of this extensive thread and appreciate all the great input people have had.
I have been researching solar heavily for the last 3 months as we are currently full time on the road in our expanda.

I currently have 140ah AGM in the van which is used for lights, fans and charging devices.
I have a Dometic PLB40 40ah portable lithium battery for charging the Waeco 40litre fridge.
I have 1 x domestic 150w solar blanket with an mmpt charge controller.
I use the car to charge the PLB40 via the cigarette socket.
I don't have a dcdc charger.

My main weakness is obviously not enough solar for the system as if we have a couple of days where we don't drive (especially if it is hot) then I only have 1 blanket to charge the van and the portable battery.
On heavy load days like when we spent a week at Litchfield I just wasn't able to keep up and had to turn the fridge off for periods. Otherwise the battery system has been keeping up pretty well.

I strongly considered getting an upgrade to a 150ah lithium battery and roof top solar for about $2k but not sure if we need that much as we will be chasing the Sun around the country.

Any suggestions on how I can fix my problem of not enough solar?

Should I just buy a cheap 200w solar panel with an attached regulator eg Kings? Or should I buy an expensive panel (eg red arc) and a victron (100/30) regulator? Or should I be looking to get some roof top solar instead?

I think the cheap panel would probably do the trick but I don't love the idea of lugging around a 1m long 21kg panel.

Any advice greatly appreciated. Sorry for long post, just trying to add detail.

@BunchOfHunts , I have 3 portable solar panels - 1 X 180w, and 2 X 200w. None of them weigh more than 12kgs and a 10 meter extension cable of good quality and proper gauge cost me around $30.00. 200w folding solar panels are available on Ebay for around $120.00 on special, but look for the ones with the highest working voltage, usually around 18.0 to 18.3 volts. Anything under 17.8 volts would not be a good buy. And PROPER MPPT solar controllers 30A capacity can be purchased also on Ebay for around $150.00 and they are worth the money in getting the most out of your panel, especially in dimmer conditions or cloudy days.
So for around $400.00 , you may be getting closer to covering your electrical needs.

 

[BunchOfHunts]

Thanks for replies. As @Boots in Action suggests I think I have a solar problem and a good controller and the right panel is where I should be looking. As we are full time in the van I'm tempted to just buy an awesome panel, spend my $1k on that and controller and then I can be confident that I have what I need.

 

[Macca_75]

I have read most of this extensive thread and appreciate all the great input people have had.
I have been researching solar heavily for the last 3 months as we are currently full time on the road in our expanda.

I currently have 140ah AGM in the van which is used for lights, fans and charging devices.
I have a Dometic PLB40 40ah portable lithium battery for charging the Waeco 40litre fridge.
I have 1 x domestic 150w solar blanket with an mmpt charge controller.
I use the car to charge the PLB40 via the cigarette socket.
I don't have a dcdc charger.

My main weakness is obviously not enough solar for the system as if we have a couple of days where we don't drive (especially if it is hot) then I only have 1 blanket to charge the van and the portable battery.
On heavy load days like when we spent a week at Litchfield I just wasn't able to keep up and had to turn the fridge off for periods. Otherwise the battery system has been keeping up pretty well.

I strongly considered getting an upgrade to a 150ah lithium battery and roof top solar for about $2k but not sure if we need that much as we will be chasing the Sun around the country.

Any suggestions on how I can fix my problem of not enough solar?

Should I just buy a cheap 200w solar panel with an attached regulator eg Kings? Or should I buy an expensive panel (eg red arc) and a victron (100/30) regulator? Or should I be looking to get some roof top solar instead?

I think the cheap panel would probably do the trick but I don't love the idea of lugging around a 1m long 21kg panel.

Any advice greatly appreciated. Sorry for long post, just trying to add detail.

Having just finished nearly 4 months on the road (trip was cut short) I would suggest

1) Definetly swap the regulator out for a Victron MPPT (size appropriately)
2) Add permanent panels to your roof - only use portable as a last resort. (can get stolen, you need to pack and unpack, they don't work if they are packed up, etc).
3) If you want a portable panel, ensure the voltage is the same as the fixed ones on the roof (+/- 1v) VoCC - then wire an Anderson (not grey/black) directly into the MPPT controller you fitted in step 1. You will then be able to plug your portable (with the same color - but not black or grey, Anderson into it unregulated). Let the MPPT do it's thing.
4) If you have the budget maybe look at replacing the "12v" panel/s on your roof with house panels (even second hand) - higher voltages like house panels are where the MPPT's really shine and you will get more bang for your buck.

Personally we left with 1 x 110ah AGM and 1 x 160W roof mounted and 1 x 200W Kings panel. The van has the regulator swapped to MPPT. We soon found after 1 or 2 days of cloud cover and no travel (ie no charge from the car) it was no where near enough solar to top the battery up. We had a 2nd 160W fitted (so 320W on the roof) and never had an issue after.

 

[Macca_75]

Thanks for replies. As @Boots in Action suggests I think I have a solar problem and a good controller and the right panel is where I should be looking. As we are full time in the van I'm tempted to just buy an awesome panel, spend my $1k on that and controller and then I can be confident that I have what I need.

Won't be $1K - Victron 100/20 or 100/30 is all you need for a controller. The difference between "average" and "really good" panels doesn't justify the cost IMO. The controller/regulator makes the difference.

 

[BunchOfHunts]

Thanks heaps for your reply @Macca_75
I am a bit worried about shade hitting the rooftop panels and making them basically redundant. I'm also a bit worried about having to clean the panels regularly as I don't carry a ladder with me so access is a bit tricky.

You reckon if I get 2 x panels on the roof and a decent regulator then I won't have to worry about that? I do have a portable blanket that could supplement it if needed.

I do like the idea of not having to lug around another portable panel and constantly stress about chasing the Sun with it.

 

[Drover]

Well @BunchOfHunts , with all that info on how and why's my suggestion for a set up since you are full timing and I assume a lot of off grid and if you say the van battery is just for lights, pump and charging phones then the 140ah battery should be okay, I would get 200w of solar on the roof connected to a decent MPPT reg, one that has a display as well, fiddling around with wifi can be a pain and often means another plug in, one like the Epever or the one Boots has are good, the battery for your Waeco is a bit small for that job I think but if it was plugged into the portable all the time it might just keep it up to speed, ideally leave it as the aux in tug for fridge when travelling , up the storage and panels on van and plug the waeco into the van via an anderson when in camp............

I camp off grid for weeks at a time 95% of the time and do find a portable (120w) to have my batteries charged up by 0900 mostly, the roof tops can then charge cameras, phones, laptop etc without drawing on batteries.......and if they cop shade its not a biggy....... genny need to come out after 3-4 days of full time rain/overcast.... my van can eat about 40amp/day, so thats my rule of thumb............. I have a 200w 10 yr old panel and 240w of Kings panel on roof with an Aldi 120w 6 year old portable which gets brought out for stays of a couple of days or more, the solar is basically the only means used to charge up my batteries, genny is mostly used for the washing machine and the odd charging but not often...... The onboard 240v job rarely if ever used............... The protable is set up to catch the first of the morning sun while I'm still ZZZZzzzzzing and gets moved during the day if I'm around but its not a must, reposition in arvo to catch those last little bits of gammas is actually fun not a chore, since I dont have a panic..
Originally I had just one 110ah battery with 200w on roof and 120w on ground and it worked well, as demand increased so did my storage, extra panels followed later, now I don't have to fuss about it......it's set and forget .

 

[BunchOfHunts]

Thanks @Drover that all makes sense. I have to make a decision in the next few days as I'm finally hitting Cairns which is the last big town that I will see for a while. At this stage I only need to last about a week off grid.

I have an Anderson plug that goes straight from the battery to my draw bar. I plug this into the car when driving and plug my portable solar blanket into it when stationary. I don't have a DC/DC charger and probably won't invest in one.
Does plugging it into the car when driving do anything/do much?
If I get a solar controller do I have that Anderson plug connected into it and then stop plugging it into my car while driving? Or do I need another Anderson plug on the draw bar?

I do have another Anderson plug on the awning side which I sometimes use for the solar blanket or plugging in the fridge.

Also, has anyone noticed that it's more difficult to lift/drop the roof with panels on top? As we are full time on the road the roof gets a fair work out.

At this stage I'm looking at:

A recycled roof top panel
A victron 100/30 mppt controller with Bluetooth (I do have a visual battery monitor already installed so I can track voltage, just a cheapo one)

Then just use my current blanket and potentially add another portable panel depending on how it all goes.