Thread: Permanent roof mounted solar panels

Can't comment on those particular panels, but keep in mind that whatever you choose its going to work most efficiently facing the sun, and that you're fridge will need less power if its not sitting in the sun.

I'm planning to add some solar to mine at a later stage, but haven't worried about it yet as my longer trips have been travelling ones, and I get an easy couple of days with my 130Ah aux and 80Ah start battery with Traxide controller. No drama's charging them again with the 120A alternator.

My thoughts (when I do it) were to attach the panels in such a way that they could either be tilted or easily removed and positioned in the sun (if there was shade to park the vehicle in). They would only be fitted for trips.

Steve

Originally Posted by flagg

Hi All,

I know this has been done to death all over the web, but I'm at the stage of my build now where I'm thinking about the interior (yay!). I have an Engel fridge, 2 300W inverters and a few LED lights.

There are 2 optima yellow tops (55Ah D34), and I'm planning on adding a Traxide USI-160 (and if I need it, there is room for an other D34 yellow top).

Ideally, I would like to have enough solar be able to run the fridge /indefinitely/ in reasonable weather. The inverters are for charging laptops / cameras etc so would only be on for a couple of hours a day max.

The other limitation is that I can't have the panels sticking up above the ribs on my roof ('86 110) as I have only got 25mm clearance into the garage and don't want any less than that!

For this reason, I've been looking at panels that are less than 400mm wide so I can fit them between the ribs. Can get a bunch of, say, 40W panels and run then together into a single regulator that then feeds in the ISU-160?

These panels (Mono Solar Panel Home Power Generator Battery 40W | eBay) would physically fit, and seem to be from a seller that has been around for a long while. All the 'brand name' solar panels seem to be too large.

The Engel says it draws 2.5A max, but from experience it does this 15% of the time, max. Would 4 of the above panels generate enough charge each day to to keep me going, even with a few days of poor weather?

FWIW there is no real need to have it on all the time, its just I used to get 3 days out of my old batteries (no solar) and it annoyed me as I had to drive forever to charge the batteries again! (old school 110 had a 40A alt.)

Basically you need to total up all the amps you will draw in 24hrs. To run 'indefinately' (I assume you mean not having to start the car/run the alternator as in sit in one spot for a while) you need to be able to replace your total daily amps. Your 4 x 40w panels will supply roughly 13amps per hour under ideal sun exposure (you wont achieve this with them flat mounted and permanently fixed - so you may have shading etc) so you might get around 8-10 amps per hour and around 5 hours of useful sun per day in spring = around 40 to 50 amps per day generated.

There are those who know a lot more than me on here though!! Having said that though I had a 64w panel mounted on the sloping part of the front of the 110 roof and feeding a 90 amp hour battery bank running my ARB fridge 24/7 and never ran out of power while sitting camped for up to 10 days at a time......

6 of these 24v panels will more than easily do the job, yes you can wire them in parallel.

24V 20 Watts Solar Panel With Mounting Bracket Post 5M Cable | eBay

24v panels with a MPPT solar charge controller is more efficient than using 12v panels , you should get equiv of 240w @ 12v or 160w with 4 panels,
MPPT controller will convert to 12v

even if you chose 12v panels get a MPPT controller rather than PWM, they are much more efficient.

I have a 24v 200w panel on the truck ($200) with MPPT controller. The fridge runs full time, also have a 1200w 240v inverter and a few other chargers hanging off the battery, after running all night its usually floating back at 13.6v mid morning. (even in the shade)

Also since you are flush mounting, be aware the cooler the panels are the more efficient they will be, when they get hot they slow down, bit of an oxymoron since you want them in full sun. you need an air gap under them to keep them cool so it might pay you to raise them a little or drill some cooling holes around the alloy frame for air flow .

Originally Posted by flagg

Hi All,

I know this has been done to death all over the web, but I'm at the stage of my build now where I'm thinking about the interior (yay!). I have an Engel fridge, 2 300W inverters and a few LED lights.

There are 2 optima yellow tops (55Ah D34), and I'm planning on adding a Traxide USI-160 (and if I need it, there is room for an other D34 yellow top).

Ideally, I would like to have enough solar be able to run the fridge /indefinitely/ in reasonable weather. The inverters are for charging laptops / cameras etc so would only be on for a couple of hours a day max.

The other limitation is that I can't have the panels sticking up above the ribs on my roof ('86 110) as I have only got 25mm clearance into the garage and don't want any less than that!

For this reason, I've been looking at panels that are less than 400mm wide so I can fit them between the ribs. Can get a bunch of, say, 40W panels and run then together into a single regulator that then feeds in the ISU-160?

These panels (Mono Solar Panel Home Power Generator Battery 40W | eBay) would physically fit, and seem to be from a seller that has been around for a long while. All the 'brand name' solar panels seem to be too large.

The Engel says it draws 2.5A max, but from experience it does this 15% of the time, max. Would 4 of the above panels generate enough charge each day to to keep me going, even with a few days of poor weather?

FWIW there is no real need to have it on all the time, its just I used to get 3 days out of my old batteries (no solar) and it annoyed me as I had to drive forever to charge the batteries again! (old school 110 had a 40A alt.)

Hey man, im new to all this but are you still running the old school 40 amp alternator, with all those batteries the first thing id be doing is updgrading the alternator to something with a big more grunt, there are plenty of 1 wire fit alts that do a great job. that way when you are on and running your kicking butt, if you look into c tek they have a battery charge system that can take alternator, 240v and solar in and produce a clean (smart) charge its called a d 250 or something like that I believe redarc do the same. as for your current draw just stick a multimeter in and see what your using with the fridge and what the inverters will draw add say 30% to your daily, should give you an idea of what you will need from panels, remembering you need enough AH in the batterys to get from the afternoon sun til the morning sun (prob 10hrs) without drawing the batterys down to far.
ive just put a usi 160 in my d4 love it great product and the kit is better then I would have made myself!

Are you sure your engle on cycles on for 15% of the time??......if so I wish mine were that efficient.

My only suggestion is install a relay so that the solar panels are isolated when you turn the ignition on.........I reckon it confuses the alternator at times. If I ever permanently mounted a solar panel this is the path I would go

I just spent four days camping in pretty hot weather, glad I had portable solar so that camper and defender were parked in the shade

Originally Posted by weeds

Are you sure your engle on cycles on for 15% of the time??......if so I wish mine were that efficient.

...

Blanket statements like that don't work. It depends what setting the fridge is on, what the ambient temp is, whether it is in the sun or shade, etc... If you turn the dial all the way around the engel will run constantly.

On long trips I use my engel as a freezer and take an esky for the other stuff - with two sets of cool bricks to swap between engel and esky.

If calculating requirements for solar I would assume the engel is running 30-50% of the time.

So 360 W.hrs @ 50%
An 80W (which I have) panel will probably give you 400 W.hrs under ideal conditions (80W*0.5(average pf)*10hrs) mounted on a flat roof.

What you need to look at is the flat aluminium panel like I have just fitted to my 110 or a flexible panel. You will need around 80w minimum but 100w like mine would be better.
I put mine on the roof rack but ended up making a frame for it. Do you have a roof rack? If so easy job.

x2 for MPPT. I swapped my old 10A one for a cheap as chips sealed waterproof MPPT one from ebay. I mounted it in the engine bay with cable ties 12 months ago and it still works, even though it was only rated to 50*C. Maybe don't mount it in the engine bay though...

When I was working out duty cycles, I went for 30-50% worst case.

The longest we've gone was our 6 day trip in Tassie. Copy paste:

65L dual zone fridge freezer was 3/4 full most of the trip used a total of 1400W of power over 6.5 days (Melb to Melb including ferry both ways). Most days didn't get over mid 20's temperature and it was mild to chilly at night.
65W solar panel generated 844W of power. Solar only works with vehicle off.
Most of the time it was sunny we were driving or we parked in the shade, so the solar didn't get much of a chance. I was very happy with over 800W. Between that and all the driving we did, the 100AH aux battery "indicator" never left green, meaning at least 80% charged.

IIRC the fridge draws 2.5A while running, so based on the above, (if my calculations are correct!) that is a 32% duty cycle. I.E. 7.7 hours of running per 24 hours. Tassie weather though..... mild!

I've always thought my 65W panel could keep up in most conditions, but I'd like a bit more for buffer for worst case. 80W is ideal IMO, but I plan on upgrading to a 120W just because they're cheap and I can make it fit.

I came up with all these numbers after I purchased 2 of these:

Imax Skyrc RC Watt Meter High Precision Battery Power Analyzer SK 500005 | eBay

I wired one in-line in the fridge lead and one in-line in the solar regulator. It loses memory if it's disconnected from power, but otherwise great little devices for keeping track of power stats.