Roof top Solar panels

[VK3GJM]

Hi All,

This break I managed to study the effect of sun exposure, efficiency of Poly vs Mono panels. The Topaz has 2 x 120 watt Poly from Projecta. They are great panels with a good overall exposure to sun, so Poly is better used in higher sun days, Northern Aus.

I also have a set of folding Poly 2 x 135 watt panels, they develop a greater output during typical Victorian days and locations where sun can be patchy, say high country camping at comet flats Woods point even at ground level.

I am now seriously thinking to replace the Poly panels with the same portable units, Mono panels are more expensive but have far better temp and sun exposure characteristics. I found Poly panels on the roof simply does not keep any battery topped up. Luckily the new single 200 amp LiPoFe2 has great deep discharge characteristics without affecting cycle life, we managed to get through without having to run a generator, the second set did help keep the battery above 50% SOC.

Low energy developments make a great panel 135watt Mono with a small foot print that is light and can be fitted between TT,s brackets. I used these panels as my folding array.

I am keen to hear from others, Southern states, would more relevant as the selection of panels is based on sun hours, cloud etc.

Poly is cheaper and the ability to work well over a wide temp range vs Mono panels is well documented.

[Chuin]

Regardless of the efficiency of the respective poly/mono panels, my experience has been that it is how the panels are used that seems to make the difference. I have the Topaz 2x120 rooftop and 2 lithium's. I also carry 2x120 mono 'portables'.

I use the portable panels when i am parked in shade (full or partial) as I have found any level of shading significantly affects the output of the rooftops - with the long lead on the portable panels I can capture the sun easily. This is a 'set and forget' placement - I don't chase the sun around as others do.

I've found that cloud cover affects both types similarly. I can have 3 days of heavy cloud cover before the batteries drop to about 60% - regardless of how I have the panels set up. Having said that we are very light on usage - the fridge is the most power hungry and the rest is lights and recharging phones/modem.

This has been up and down inland NSW. Not tested in Winter as yet.

[Harry Lissimore]

Chuin,
Slightly off topic and I was thinking of putting another subject up for discussion but I have just checked my rooftop Topaz solar panel and it appears to be deteriorating.  I can see tracks of corrosion of fine wires.  These tracks are about 0.5 mm wide and about up to 100 mm long.  There's at least a dozen of these.  Have you checked yours lately.  My Topaz is 4 years old.

Harry

[Chuin]

Apologies for off topic. 
My Topaz is 4 months new so shouldn't see anything like your tracks. However I'm off on a trip mid Feb so will check roof top just before then anyway.

[VK3GJM]

Hi Chuin and Harry,

Harry, sorry to heat about your panels. Good panels should have a sound IP68 rating and water should never penetrate conductive layers and supporting ceramic substrate. Generally, damage you describe could be from a hairline crack or water wicking through unsealed edges, sometimes this can also be due to a corner cracked, and might be hidden. There are many mechanical issues with poor mechanics assembly of solar panels, generally associated with lower cost units.

Chuin, I am surprised that you have 2 Lithium cells, I hope you do not have them in parallel, one with stronger charge characters will deprive the other over time from getting a full charge.

You cannot parallel Lithium batteries unless each battery BMS can be linked or you charge each one separately and during discharge you combine, however and charge will potentially deprive one from optimal levels for cell equalisation. The Internal BMS will shut off, the Charger will see a sudden drop in current and assume battery is full.

Anyway, it is common practice not to put Lithium in parallel unless a inter-BMS via CAN bus, RS-485 or some other kind of data comms between respective cell packs with integrated BMS can be connected together...

Anyway, southern Vic on prolonged cloudy days in the high country with tree cover, I need to continue to chase sun to keep them topped up to levels to maximise SOC / discharge life cycle. I find the roof panels not enough and during heat, they very quickly derate, symptom of low grade Poly type cells.

I purchase Mono panels from low energy developments, I have had a slim 80 watt unit, but puts out more like 90 watts on the roof of 4WD for 5 years now, panel is as good as new and it has travelled around Aus on some extremely rough roads.

Have a wonderful safe trip.

[Nomadic]

I don't think any of the solar panels are perfect. Luck of the draw when it comes to quality.  I wanted to avoid the heavy glass panels on the roof so I went flexible. My cheap semi flexible don't put out anywhere near their rated power but I expected that from the eBay sellers. I badly scratched one of my flexible panels under trees but it still works. I may have smashed a glass panel under the same circumstances. They are all a compromise.
The biggest downside I have found with the semi flexibles is they are uneven and pond water. Did you know water and red dust makes mud? Well that's what I found and it means regular cleaning of the panels. Not easy on my topaz roof because it's now 2.8m off the ground.
For me Keeping the panels clean is the difference between getting the battery back to 100% by 9.00am or mid day. Dirty panels on an overcast day means putting restrictions on my wife's Nespresso coffee intake or use of her hair dryer.

Gerald, I'd be interested to know what regulators you are using for your different panel types and if they are using the same charge profile? I'm finding not all regulators perform equally either.

Re the LiFePo4, I personally don't like the Fusion style drop-in black box replacement lithium batteries but agree avoid running in parallel if you can. Some people like the redundancy two 'black-box' banks provide and it's the only way they can get enough current out of their banks to run a small inverter.

I prefer individual cells with external BMS. It's not an issue paralleling cells and at least you can verify cell balance and fault-find easily. Also means you can use a decent relay and not be constrained by mosfets limiting the charge or load current like some of the 'black-box' Lifepo4 Batteries. Not an issue for light loads like a couple of fridges and lights but a concern if running bigger inverters.

[VK3GJM]

Hi Nomadic,

When I optioned the Van, I had TT install a 200ah Enerdrive Lithium. TT installed a Redarc BCDC1240D DC/DC for vehicle charge and with MPPT for solar and the default 50 amp Projecta AC mains to 12 V charger is LiFeP04 ready.

The hardwired roof panels and portable panels via RHS Anderson plug parallel to the 1240D very close to the battery, the 1240D has Lithium charge profile set and it does a good job.

I do not use PWM or MPPT devices located on the panels themselves. I also use a 6mm2 double insulated black outer sheath cable that is 20 metres long to ensure I can tap into sun away from van location, the voltage drop is not enough at the input to shut most good regulators down, even at low light

I only use Victron MPPT regulators.

Although the cost may seem high compared to others, but you get what you pay for. Low Energy Developments sell a very good 135 watt panel,

http://www.lowenergydevelopments.com.au/solarpanels-poly-mono?product_id=404

for 5 years now I also run another slim solar panel on the roof of the vehicle, also very good quality mechanically. Connected to the Viltron it behaves more like 85-90 watt panel. These guys make this slimline, very unique shape.

http://www.lowenergydevelopments.com.au/solarpanels-poly-mono/75-Watt-12v-SLIM-Solar-Panel-Monocrystalline-Pickup


Cheers. 

[Mark Cauchi]

Hi VK3GJM

I am currently getting a van built from TT and your post has me intrigued.

Did TT charge you a lot more for the changes and if so do believe you have seen the benefits.

Thank you

Mark

[VK3GJM]

Hi Mark,

Depends on the mods you are looking for?

Send me a pm.

[Greyghoster]

Hi Nomadic, I am interested in adding solar panels to the roof of my Topaz II. The 120W panel needs supplementing which my mobile 160W panel helps out fairly well but extra built in panels seem to be a better alternative. When you added panels to your roof did you have difficulty with the existing solar panel wiring? did you need to run heavier cable, install blocking diodes etc? 

[Nomadic]

Hi Greyghoster,
My set up is a bit different to most as I wanted full redundancy with  independent solar arrays and controllers.
Incidentally I just had a set of semi flexible panels fail on me after less than 8000km. After that experience I have just replaced with a set of conventional panels. Unfortunately it means extra weight on the roof but I'll see how these go.

Each set of panels has its own cable running down to the controller. It's easy to run a new cable from the roof top through a hole in the aluminium roof extrusion (outboard of the canvas) and down through pockets in the canvas into the van. My cable runs along the top of the upper cupboards and into the robe where my controllers are mounted. I have a manual reset circuit breaker on each solar array cable before the controller. I didn't add any extra blocking diodes and I may live to regret it. Time will tell.

Both controllers can contribute to the charging the battery but normally I only ever have one switched on. The other is a back-up or if we have a few days of rain or overcast weather. I have three fridges running all the time but the 3rd (a small 18L cab fridge) gets switched over to the vehicle supply when on the road.

[IsuzuTopaz]

Hi Everyone. We have a 2012 Topaz and found the fitted flexible panels totally inadequate and mucking around with portable panels cumbersome so we did total refit.
As glass panels are relatively cheap now and technologies improved we got 2 X 200w with a new Redarc 40w DCDC charger with duel input to handle the higher current flow. I am sure many consider this overkill but when you only get limited sun hours this will punch in enough to keep you going and not running down especially if running 2 fridges.
The extra weight in lifting the roof was balanced out by fitting stronger gas struts.

[Nomadic]

Hi IsuzuTopaz, sounds like the same panels I have now. Any  recommendation on the best gas strut pressure? My struts are new with 500N. I can lift roof OK but it's still a bit on the heavy side for the wife. Thinking of trying 650N on the just the heavy end but worried about extra effort required to pull down.

[Phil G]

Incidentally I just had a set of semi flexible panels fail on me after less than 8000km. After that experience I have just replaced with a set of conventional panels.

Join the club!  I had a 100W flexible one that died after 6 months.  Then one of my travelling companions had 3 fail on his Exodus hybrid van.  They were replaced and the second set all died as well.
So it's glass mono panels for me.  They last forever. 

[IsuzuTopaz]

Hi Nomadic. I just checked and the struts are 700NM my preference was 600 as the originals were 400 but they weren't available when I was ready so we got the 700s of Ebay, they weren't very dear. I keep a lookout at the mounting pins and to this time (12mths) it has been fine. The 2 panels weighed in at 30kg and the lifting was just a little lighter than original.