Solar - Permanent mount or portable?

[obiwancanoli]

As I work through the process of upgrading batteries, either a 4-jar bank of Lithium 100Ah 12V, one 300Ah + a 100 Ah, or two 200 Ah, I'm also researching the addition of more solar panels to the roof of my Class A. My boondocking plans in the years to come require a more serious look at power needs and requirements.

Currently, I have 3 - 160W solar panels - 26.1 amps total output, fixed to the roof, a 30A PWM Controller, and have room for up to 4-5 more, depending on configuration. Of course, will need a new Controller if I do so. For the solar wattage I'm considering, some sites have suggested an 80A MPPT Controller. I initially thought a 60A would do the trick, but I was basing that on the total amp output of all panels. I also have a 120W, 5.6A portable.

I'm thinking I might be better off using portable panels. As a practical matter, at 100-120W per portable panel, I'd need at least 3, probably 4 to reach my goal.

It might make sense to have some of my charging capacity in panels I can move around when shade impedes. I understand some can be hooked together, but then, there's the inconvenience of having to store, set up, and take down 4 folding portable panels. Perhaps just two?

I understand each person will have different needs and requirements, but is this a balance some strike, where solar is concerned? Or are there 'druthers out there who swear by one way or the other?

As an aside, I have a Trav'ler II mounted to my roof, but have considered picking up a portable sat dish - again, when I find myself in the trees...

[Vintage465]

obiwancanoli wrote:
As I work through the process of upgrading batteries, either a 4-jar bank of Lithium 100Ah 12V, one 300Ah + a 100 Ah, or two 200 Ah, I'm also researching the addition of more solar panels to the roof of my Class A. My boondocking plans in the years to come require a more serious look at power needs and requirements.

Currently, I have 3 - 160W solar panels - 26.1 amps total output, fixed to the roof, a 30A PWM Controller, and have room for up to 4-5 more, depending on configuration. Of course, will need a new Controller if I do so. For the solar wattage I'm considering, some sites have suggested an 80A MPPT Controller. I initially thought a 60A would do the trick, but I was basing that on the total amp output of all panels. I also have a 120W, 5.6A portable.

I'm thinking I might be better off using portable panels. As a practical matter, at 100-120W per portable panel, I'd need at least 3, probably 4 to reach my goal.

It might make sense to have some of my charging capacity in panels I can move around when shade impedes. I understand some can be hooked together, but then, there's the inconvenience of having to store, set up, and take down 4 folding portable panels. Perhaps just two?

I understand each person will have different needs and requirements, but is this a balance some strike, where solar is concerned? Or are there 'druthers out there who swear by one way or the other?

As an aside, I have a Trav'ler II mounted to my roof, but have considered picking up a portable sat dish - again, when I find myself in the trees...

I have nearly the exact set up you do except mine is 3-150's. Fixed on the roof, no adjusting. 30a controller. When I first got it the controller was up over the bed in a cabinet. It sorta kept up with my needs. Since then I revamped my set up and put new combiner box. Gather all the panels in the combiner box using 10ga duplex wire from the panels to the box. Then #4 welding cable from the box to the new controller location real close to the batteries. I think if you want the convenience of having fixed panels on the roof, no tilting or anything like that you need to build the system stout w/o compromise on the wire size and get the controller as close you your batteries as possible. That, in my opinion is the cost of "screwed down not tilt-able" solar panels convenience. My 450w and PWM-30a controller charge my 4-6v batteries very well. I do a lot of winter camping and we use our super in-efficient furnace in the trailer at night and use a Buddy heater in the morning and evening. Don't have an inverter. Don't watch TV. So for us it's the lights, pump, and furnace. I'm careful how I park regarding shade. I'm at the point that I really no longer have concern if my batteries charge. It all just works and I want for nothing power wise. But some of that is because our only high draw is the furnace.

[obiwancanoli]

Bert the Welder wrote:
I've see theft at a campground. An entire cooler of booze and some other items. Fortunately, the thieves were found. Unfortunately for them, it wasn't by the police. My future trips will include my trail camera and a portable solar charged motion senor spot light.

I like this idea... better yet, design one with a suction cup attachment, battery operated. Can stick it anywhere....

[Bert_the_Welder]

I've see theft at a campground. An entire cooler of booze and some other items. Fortunately, the thieves were found. Unfortunately for them, it wasn't by the police. My future trips will include my trail camera and a portable solar charged motion senor spot light.

[groundhogy]

Portable.
Can point them.
U can be under tree.
No cramming fuzes and all kinda extra circuits under your **** couch.
You can sell them when you are done

[pianotuna]

Hi,

I have had a theft, but not at a campground.

[obiwancanoli]

Mike134 wrote:

obiwancanoli wrote:
Interesting... I'd never given thought to the potential for theft... is this more common than not?

No more likely to be taken than a Coleman lantern I've always left out when away from the campsite.

In all the years I've been camping and backpacking, and the few years I've enjoyed the RV lifestyle, I've never heard anyone speak of, much less experience, theft, but I'm sure it's not unheard of. I've cleaned up my camp, neatened it up, but always left stuff out, with nary a problem. RVr's who have a stand-alone sat dish always leave their stuff out, far as I can tell... never heard about any issues...

But, that's no guarantee, and temptation can change a persons nature, enough to see an opportunity and go for it.

And here I go, getting pretty far off the subject...

[Mike134]

obiwancanoli wrote:
Interesting... I'd never given thought to the potential for theft... is this more common than not?

No more likely to be taken than a Coleman lantern I've always left out when away from the campsite.

[Lwiddis]

“Interesting... I'd never given thought to the potential for theft... is this more common than not?“

You leave it out, unattended...

[pianotuna]

obiwancanoli wrote:
Pianotuna,

It would also be interesting to learn if there's a means of tilting the roof panels from the ground, since climbing on the roof at my age probably isn't the safest approach, but then, securing these panels would seem to require a hands-on approach. Still cogitating this dilemma...

As for the batteries, I'm definitely leaning toward two 200Ah Li's, though I have room for the four wet cells that will come out. Others have suggested keeping all batteries at the same size and Ah...

What I'm needing more clarity on is the panel voltage, why higher might be better, how it would function with existing panels which operate at lower voltage. Mono vs. polycrystalline is also not clear to me, though a little research will solve that... some of which, by the way, suggests an MPPT Controller north of 80 amps for the panel wattage I envision...

For tilting look at linear actuators. But it still comes down to cost per watt--and panels with fixed mounting are cheaper. It definitely will be cheaper to add another panel than to have actuators on each panel.

There have been studies done on manual tilt. On average the RV'er gives up on that after only seven times. It is simply too much effort for the better solar harvest.

I live in a windy Province. Securing portable panels would not be easy, and having them blow away is really a concern.

Great decision on 2 200 amp-hour jars. Now if I could only entice you to SiO2..... LOL

Here are some ideas on higher panel voltage.

1. lowers cost of wire and lowers transmission losses.

2. charging, at least in theory, should start earlier and end later in the day. I do get charging 30 minutes after sunrise, and there is a similar shorter time at the end of the day

3. a 17 volt MPPT (nominal 12 volt) will move to PWM mode sooner. If input voltage is double that, then the unit will stay in MPPT mode longer and won't move to PWM until the battery bank is more or less charged.

4. PWM "throws away" the extra voltage and operates at the battery voltage. MPPT does not do this, which means charging, at least in theory, may be faster.

5. high voltage input makes equalization voltages easier to maintain (yes I know li don't need or want that)

6. As panels heat, their voltage output drops. By having "voltage to spare", one still gets an adequate charging current. "As the temperature of the solar panel increases, its output current increases exponentially, while the voltage output is reduced linearly."

7. "lensing effect" excursions are turned into more current sent to the battery bank.

Here are some negatives of MPPT

1. The charge controller is less efficient in MPPT mode (94 to 95%) than in PWM.

2. More heat needs to be dissipated, requiring the controller to be oversize to keep from letting out the magic blue smoke.

3. Since all MPPT controllers have a PWM "hiding inside them", the controller may be a lot more expensive.

4. Panels are now the cheapest component of a solar charging system, so adding an extra panel gets you to about the same charging capacity--but only under ideal conditions. (i.e. 77 f, no clouds)

I'm sure there are many other "trade offs". I chose MPPT because, in 2005, it was a good way to drag as many watts from the panels as possible--and the cost of panels was $5.50 per watt (and that was a GREAT buy, at the time).

I do get 5 amps of charging in the rain. I do get 7 amps in leafy shade. But my panels have bypass diodes on each and every cell. They are LARGE.

So far as I am aware, no one makes a panel with bypass diodes on each cell any more.

[RambleOnNW]

Portable 100 watt suitcase works for me for the low daily Ah use we have. Can supplement with generator use as needed. Usually we are parked in the trees so roof mount is not a priority. Keep honest people honest with braided bicycle cables and Kryptonite lock. Have got enough use out of it the last couple of years that if it was stolen I would upgrade to a 200 watt version.

I use to put the panel away at night and don’t bother doing that anymore. Just put it under the rear bumper and lock it to rear bumper.

Folded size is 20” x 27” and weighs 28 lbs. Controller and panel are water resistant so don’t have to take it down if there are rain showers.

If our house batteries are fully charged I can connect it to the chassis battery if needed.

[obiwancanoli]

Pianotuna,

I can appreciate your caveats, and they are worth considering, but, how often might it rain ? I'm less confident about roof panel's usefulness in the shade when, with 1 or 2 portables, I can easily aim at the sun, should the charging be needed. Yeah, the panels are potentially cumbersome, and storing them could be a challenge, but then, if I can store them safely - one already is conveniently tucked away - I would, I think, have only one more to find space for. This could prompt me to seek out panels of a size where I CAN store it conveniently.

It would also be interesting to learn if there's a means of tilting the roof panels from the ground, since climbing on the roof at my age probably isn't the safest approach, but then, securing these panels would seem to require a hands-on approach. Still cogitating this dilemma...

As for the batteries, I'm definitely leaning toward two 200Ah Li's, though I have room for the four wet cells that will come out. Others have suggested keeping all batteries at the same size and Ah...

What I'm needing more clarity on is the panel voltage, why higher might be better, how it would function with existing panels which operate at lower voltage. Mono vs. polycrystalline is also not clear to me, though a little research will solve that... some of which, by the way, suggests an MPPT Controller north of 80 amps for the panel wattage I envision...

[vermilye]

I also prefer both. With my small trailer, rooftop real estate is limited. I have 2 160 watt panels on the roof & carry a portable 160 watt. Most of the time the rooftop panels meet my needs - around 50 amp hours per day & a pair of 100 amp hour lithium batteries. The portable comes out when parked in the shade, and during December/January in the Arizona desert where even tilting the rooftop panels doesn't make up for the low angle sun & short days.

[pianotuna]

obiwancanoli wrote:
As I work through the process of upgrading batteries, either a 4-jar bank of Lithium 100Ah 12V, one 300Ah + a 100 Ah, or two 200 Ah, I'm also researching the addition of more solar panels to the roof of my Class A. My boondocking plans in the years to come require a more serious look at power needs and requirements.

Currently, I have 3 - 160W solar panels - 26.1 amps total output, fixed to the roof, a 30A PWM Controller, and have room for up to 4-5 more, depending on configuration. Of course, will need a new Controller if I do so. For the solar wattage I'm considering, some sites have suggested an 80A MPPT Controller. I initially thought a 60A would do the trick, but I was basing that on the total amp output of all panels. I also have a 120W, 5.6A portable.

I'm thinking I might be better off using portable panels. As a practical matter, at 100-120W per portable panel, I'd need at least 3, probably 4 to reach my goal.

It might make sense to have some of my charging capacity in panels I can move around when shade impedes. I understand some can be hooked together, but then, there's the inconvenience of having to store, set up, and take down 4 folding portable panels. Perhaps just two?

I understand each person will have different needs and requirements, but is this a balance some strike, where solar is concerned? Or are there 'druthers out there who swear by one way or the other?

As an aside, I have a Trav'ler II mounted to my roof, but have considered picking up a portable sat dish - again, when I find myself in the trees...

I would do two 200 amp-hour batteries. 2nd choice would be four 100 amp-hour batteries. I would DEFINITELY NOT do 300 / 100. I would consider one 400 amp-hour, but there is a certain comfort in two jars.

Portable panels are, in my opinion, a pain to store, a pain to set up, and subject to breakage when being moved. They are LARGE. Not too bad as far as weight goes--but wind loading needs to be considered. Do you really want to be out in a wind storm with rain trying to strike camp? Do you really want to have to move the panels off the bed--so you can grab 40 winks after a lovely lunch? There are other reasons to avoid portable panels--however theft is the very least of those considerations.

I still get 17 amps from my 2005 panels (256 watts), at solar noon. That is from a fixed flat install. Theoretically I should only see about 15.5 amps, as the panel voltage is 16.5, on a perfect solar day, with perfectly aligned panels (tracking the sun).

In your shoes, I'd add ALL the panels I could and at the highest voltage. Say 8 panels in series/parallel (4 per string). The panels, after all, are the cheapest part of the system.

Be sure to buy a controller that would allow for more wattage in the future. Why? Because should the panels break--new panels are quite likely to have a higher output.

[obiwancanoli]

Jayco, the more I think about this, the more I agree with your perspective... I suppose the reality of it is this... IF you're going to have solar, roof mount seems a good way to approach it, for at least SOME of the time, they'll be exposed to sunlight... for example, as ktmrfs suggests in the previous post.

I could opt to adding one more panel to the roof, but I think I'd also opt to have an additional portable - two I can deal with. But I might switch out my 120W for a 200W I found, and have another 400W portable, or another Zamp panel at 180W, which could add up to 30+ amps. That, plus the roughly 31 on the roof should be more than sufficient for my anticipated needs...