Are 250w panels on a vehicle mounted system a good idea?

lillharold

New Member
Joined
Nov 18, 2021
Messages
5
Hello,

Forgive me if this is a silly question. I have a camper trailer whose roof I plan on filling with Solar panels.

I was originally looking at 100w panels and estimate I can fit about 21 panels on the roof. These are the 100w panels I was looking at https://www.amazon.com/HQST-Monocry.../B08SVXMK3V/ref=psdc_2236628011_t1_B018BOK9WU . However while reviewing this site I found out I could buy 250w panels used. For about half the cost, and about 25lbs more. Due to the increased size of these panels I would only be able to fit 9 on the roof. I was looking at these panels https://store.santansolar.com/product/santan-solar-t-series-250w/ .

This 250w panel weighs about 41lb vs 16lbs of the 100w panel, and would be about $10 cheaper per panel. So when “mathing” it out, going with the 250w options means I would be adding about 30lbs more in total, but saving almost half of the cost of the 100w choice.

My question here is would this be a good idea to buy the 250w panels and mount them to the roof of my camper trailer? I am mostly worried about how well 250w panels fair on the roof of a system that might move here and there.

If it helps I plan on going with a 24v all in one system, and 24v LitFePo4 battery.

Any insight would be appreciated thanks.
 

Rocketman

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Sep 27, 2020
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698
My Dad has two of those panels on his 5th Wheel RV, and we installed one of those on a brother-in-laws camper.

The panels will hold up just fine, the real question is how are you planning on attaching them. In both the above situations we had plenty of room, used self made brackets- (1-1/2 alum angle -2 pieces bolted to make a Z-bracket), and used lots of brackets (6 to 9 per panel).

The fewer the panels - the less the mounting hardware is needed.

How were you thinking of attaching your panels?

Also, what are the specs of the solar charge controller? That’s the real question of how many can you use?
 

Bud Martin

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Aug 27, 2020
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You may want to see this thread and ask LtDan.
One reason for less panel: Less panels = less connectors to fail and less mountings.
 

Rocketman

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Sep 27, 2020
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698
9 panels = 2,250 watts of power - that’s a lot of power for a RV - those are BIG panels for a RV - will they fit?
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
Messages
10,692
Those Santan panels are 153W/m^2, 15.3% efficient. You can get 20% and higher efficiency, 1/3 more power per unit area.
Especially for an RV, I would favor lighter weight and more power per unit area.

It may be that adding ribs to stiffen the panels, avoid flexing glass, might extend their life.
We don't know for sure, but some brands have warranties that exclude mobile applications.
 

lillharold

New Member
Joined
Nov 18, 2021
Messages
5
You may want to see this thread and ask LtDan.
One reason for less panel: Less panels = less connectors to fail and less mountings.
Thank you for replying and this post is definitely helpful thank you.

I was originally planning on using brackets on the roof but I am thinking that uni strut method is the way to go.
 

lillharold

New Member
Joined
Nov 18, 2021
Messages
5
G'Day



What 24v solar charge controller are you going to buy ?
My Dad has two of those panels on his 5th Wheel RV, and we installed one of those on a brother-in-laws camper.

The panels will hold up just fine, the real question is how are you planning on attaching them. In both the above situations we had plenty of room, used self made brackets- (1-1/2 alum angle -2 pieces bolted to make a Z-bracket), and used lots of brackets (6 to 9 per panel).

The fewer the panels - the less the mounting hardware is needed.

How were you thinking of attaching your panels?

Also, what are the specs of the solar charge controller? That’s the real question of how many can you use?

The roof is rubber with aluminum studs and wood beneath it.
I planned on using brackets originally to the roof. However I might install a unirail system like Lt. Dan did in the post linked above.


The charge controller I planned on using is included in the all in one.

Growatt 24V SPF 3000TL LVM
https://watts247.com/product/spf-3000tl-lvm-24p/


But reviewing the data sheet I may need cut the number of panels to 8 to fit the spec
Those Santan panels are 153W/m^2, 15.3% efficient. You can get 20% and higher efficiency, 1/3 more power per unit area.
Especially for an RV, I would favor lighter weight and more power per unit area.

It may be that adding ribs to stiffen the panels, avoid flexing glass, might extend their life.
We don't know for sure, but some brands have warranties that exclude mobile applications.

Price was a huge consideration for me when I was looking at those panels. Since they were used/ blemished they were cheaper than 100w panels. Do you have any recommendations on a specific panel with a higher efficiency?

9 panels = 2,250 watts of power - that’s a lot of power for a RV - those are BIG panels for a RV - will they fit?

I am redoing the roof completely along with removing some of the original roof installments. This would give me the empty space I need. Dimension wise I can fit a max of 9 of those panels.


Thank you all for replying.
 

12VoltInstalls

…myself everything do I…
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am thinking that uni strut method is the way to go.
It’s a bit more time and money- but edge mounting brackets to hold whatever ‘strut’ or frame material you use are imho a much better choice.
I view it like utility trailer ladder/material racks. Many people want to mount to the roof, but the usual trailer manufacturer’s (much more expensive racks) mount to the edges of the roof and sides. There’s a lot of strength there and it’s easily waterproofed. And they don’t come in for warranty service.

Plus the flex issue mentioned. RV roofs move a surprising amount. Long strut mounts or edge mounts do not. Happier panels!

It’s more money to do 100W panels but on a moving vehicle or trailer the smaller form reduces the likelihood of a cracked (failed) panel imho
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,692
Price was a huge consideration for me when I was looking at those panels. Since they were used/ blemished they were cheaper than 100w panels. Do you have any recommendations on a specific panel with a higher efficiency?

PV panels have come down in price to where they are almost the cheapest part of a PV system. Batteries are the most expensive.

I went with SunPower 327W E20 panels.
The SunPower panels are supposed to be particularly good and long lasting. They are of a silicon doping type which degrades more slowly in the sun. However, being opposite type from most, they are best used positive ground rather than negative ground to avoid "PID". Earlier models discovered this problem with rapid degradation. Recent models are "PID free" which means greatly reduced but not eliminated.

Battery systems with DC SCC are probably all negative ground. My system is GT AC PV transformer type and can be grounded either way.

Several model panels are in the 20% to 22% range, often some at SanTan. They have large quantities of used panels, and small quantities of brand-new excess from jobs (priced more like $0.50/W)

You can read about test results of prior year models, try to select one highlighted as performing well in reliability tests.

 

Fast1one

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Joined
Mar 3, 2021
Messages
27
Those Santan panels are 153W/m^2, 15.3% efficient. You can get 20% and higher efficiency, 1/3 more power per unit area.
Especially for an RV, I would favor lighter weight and more power per unit area.

It may be that adding ribs to stiffen the panels, avoid flexing glass, might extend their life.
We don't know for sure, but some brands have warranties that exclude mobile applications.
Watts per unit area is a very important consideration for an RV. So is watts/pound. The larger the panel, the less overall weight for a given amount of efficiency in general. I think it’s because there is less framing material per unit area.

The OP panels were 250W and 41 pounds which is about 6.1 watts/pound.

I purchased Qcells L-G8.2 425 watt panels locally for $233 each which is about $0.55/watt. They are a hefty 55 pounds but that comes out to 7.7 watts/pound so lighter overall.

@lillharold you should definitely look for panels through your local distributor if you haven’t already. We had a CED Greentech and it was affordable and they offered free delivery to my work.
 

chrisski

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Joined
Aug 14, 2020
Messages
3,267
I am redoing the roof completely along with removing some of the original roof installments. This would give me the empty space I need. Dimension wise I can fit a max of 9 of those panels.
Please take into account spacing between panels. For my RV roof mounted panels since They are tilting and I need to access the screws to move up and down. This needed a fist worth between each panel. I don't recommend the tilting panels; huge waste. Just add another panel and you don't need them. There still is a manufacturer spacing spec to allow for expansion when installed. Could be 1/4"
The roof is rubber with aluminum studs and wood beneath it.
I planned on using brackets originally to the roof. However I might install a unirail system like Lt. Dan did in the post linked above.
Not sure what type of roof this is, but I recommend some sort of two sided tape and anchoring system. My roof is EDPM covered by wood with wood crossbeams. Best anchoring point would be the crossbeams.

Done right, I see no problem with 250 watt panels.
 

Browneye

Dr. WattSon
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Nov 2, 2021
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Southern California
I just went thru this quandary, liked the good value on the Santan panels, but they are REALLY large. It becomes a challenge to fit them and rack them as well. I found they just wouldn't fit right on my rig.
Plus those are grid-tie (high volt) so you have to consider how you'll group them and feed to an mppt SCC.

Home Depot has their NATURE POWER 215w panels back on sale right now thru the weekend - they are $154 or 71cents a watt which is pretty good. They're larger than standard 100w obviously, but still lighter and more manageable than the grid-tie poly ones.

You must be wanting to run a residential fridge and AC or something, that's a LOT of power. We use about 50-80Ah overnight, actually have gotten by with a pair of GC2's for the past 15 years, mostly boondocking.

Attaching to the roof is always a challenge - and of course you want to make sure they don't blow off - some guy in CA lost one and it caused an accident and killed the driver of the car it hit.

Here's my two on my roof - I used strut channel with vhb and #14 screws to attach the longitudinal racks, then cross bars for each panel.

IMG_4078.HEIC


And the specs on the HD PV's, they're 58x26.5", so comparable to all the 180-200w 12v panels out there:

215w.JPG
 
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lillharold

New Member
Joined
Nov 18, 2021
Messages
5
It’s a bit more time and money- but edge mounting brackets to hold whatever ‘strut’ or frame material you use are imho a much better choice.
I view it like utility trailer ladder/material racks. Many people want to mount to the roof, but the usual trailer manufacturer’s (much more expensive racks) mount to the edges of the roof and sides. There’s a lot of strength there and it’s easily waterproofed. And they don’t come in for warranty service.

Plus the flex issue mentioned. RV roofs move a surprising amount. Long strut mounts or edge mounts do not. Happier panels!

It’s more money to do 100W panels but on a moving vehicle or trailer the smaller form reduces the likelihood of a cracked (failed) panel imho
Thank you very much for this input this makes sense to me.
PV panels have come down in price to where they are almost the cheapest part of a PV system. Batteries are the most expensive.

I went with SunPower 327W E20 panels.
The SunPower panels are supposed to be particularly good and long lasting. They are of a silicon doping type which degrades more slowly in the sun. However, being opposite type from most, they are best used positive ground rather than negative ground to avoid "PID". Earlier models discovered this problem with rapid degradation. Recent models are "PID free" which means greatly reduced but not eliminated.

Battery systems with DC SCC are probably all negative ground. My system is GT AC PV transformer type and can be grounded either way.

Several model panels are in the 20% to 22% range, often some at SanTan. They have large quantities of used panels, and small quantities of brand-new excess from jobs (priced more like $0.50/W)

You can read about test results of prior year models, try to select one highlighted as performing well in reliability tests.

Appreciate the link and info
Watts per unit area is a very important consideration for an RV. So is watts/pound. The larger the panel, the less overall weight for a given amount of efficiency in general. I think it’s because there is less framing material per unit area.

The OP panels were 250W and 41 pounds which is about 6.1 watts/pound.

I purchased Qcells L-G8.2 425 watt panels locally for $233 each which is about $0.55/watt. They are a hefty 55 pounds but that comes out to 7.7 watts/pound so lighter overall.

@lillharold you should definitely look for panels through your local distributor if you haven’t already. We had a CED Greentech and it was affordable and they offered free delivery to my work.
I was actually having trouble with finding some local sellers, turns out there is a CED Greentech not too far from me. So I am going to explore what they have to offer. Thanks.
Please take into account spacing between panels. For my RV roof mounted panels since They are tilting and I need to access the screws to move up and down. This needed a fist worth between each panel. I don't recommend the tilting panels; huge waste. Just add another panel and you don't need them. There still is a manufacturer spacing spec to allow for expansion when installed. Could be 1/4"

Not sure what type of roof this is, but I recommend some sort of two sided tape and anchoring system. My roof is EDPM covered by wood with wood crossbeams. Best anchoring point would be the crossbeams.

Done right, I see no problem with 250 watt panels.
Understood, I had a template I used to mock up the panel size. The template was a few inches larger than the panels I was looking at. To hopefully account for spacing. Thanks
I just went thru this quandary, liked the good value on the Santan panels, but they are REALLY large. It becomes a challenge to fit them and rack them as well. I found they just wouldn't fit right on my rig.
Plus those are grid-tie (high volt) so you have to consider how you'll group them and feed to an mppt SCC.

Home Depot has their NATURE POWER 215w panes back on sale right now thru the weekend - they are $154 or 71cents a watt which is pretty good. They're larger than standard 100w obviously, but still lighter and more manageble than the grid-tie poly ones.

You must be wanting to run a residential fridge and AC or something, that's a LOT of power. We use about 50-80Ah overnight, actually have gotten by with a pair of GC2's for the past 15 years, mostly boondocking.

Attaching to the roof is always a challenge - and of course you want to make sure they don't blow off - some guy in CA lost one and it caused an accident and killed the driver of the car it hit.

Here's my two on my roof - I used strut channel with vhb and #14 screws to attach the longitudinal racks, then cross bars for each panel.

IMG_4078.HEIC


And the specs on the HD PV's, they're 58x26.5", so comparable to all the 180-200w 12v panels out there:

215w.JPG
This is also super helpful thank you. I plan on adding some anchor cables to whatever I put on the roof just in case. Not even sure how I would be able to process/handle accidentally killing someone like that, I would rather avoid having to do that. I figure I could also do periodic checkups on the mounts to make sure nothing is going wrong.
 

HRTKD

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During the planning phase of my PV project I created a CAD drawing of the roof of my RV trailer. I then placed on that drawing various panels to see how they fit. My original plan to put four 200 watt panels wasn't going to work. There was no way four panels could be arranged to fit. I ended up using two 320 watt panels instead and that is working out quite well.

I used Z brackets to mount my panels. Unistrut or a similar rail system would have been nice but I decided to with the Z brackets for the simple design and low weight. Should you use Z brackets, be sure to include the width of the brackets when test fitting the panels on your virtual roof. The brackets add as much as 3" to the width of the panel. Because of the size of my panel, I used six brackets instead of the usual four.
 

Bryanbr

Solar Enthusiast
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Sep 27, 2021
Messages
93
Home Depot has their NATURE POWER 215w panes back on sale right now thru the weekend - they are $154 or 71cents a watt which is pretty good. They're larger than standard 100w obviously, but still lighter and more manageble than the grid-tie poly ones.

I ordered 4 of those Nature Power 215w panels.

How are they performing? Can get close to 200watts in full sun?
 

Browneye

Dr. WattSon
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Messages
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Southern California
I ordered 4 of those Nature Power 215w panels.

How are they performing? Can get close to 200watts in full sun?
I am planning to install the controller and run the feed wires tomorrow, try them out.

Oh, and we had a 200 mile trip in the RV today, out north of LA for my son's Spartan Trail run. It's always windy on the Grapevine pass - probly saw forty or fifty mph winds, and 60mph on the freeway. They're still up there. LOL
 

BretS

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Mar 30, 2021
Messages
168
I have six 350W Hanwha Q panels on mine, and plan to add four 210W panels. I just saw the above for the 215W panels from HD, but unfortunately they are sold out now...
 

OffGridInTheCity

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I have 4 x 300w panels 'flat' on my 7 x 14 cargo -> camper conversion. They're 2s2p (so 1 string will work even if the other is shaded as in the pic). In full summer sun I'm getting ~5kwh/day. Using an MPP Solar 3048LV. These were used panels from @santansolar on Ebay
1637545534735.png
The only downside of 100% flat is that water pools on the panels due to the 1/8"? edge of the frame. When it evaporates, it leaves dirt residue. IF you can somehow mount them with a slight slope so the water will run off - it would avoid this issue. Turns out I can lower the tonque jack enough to have the water run off - but that's not good for 'level' situation :)
 

Impatient

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I hope this isn’t considered a highjack:

currently I have a 160w Carmanah/GoPower panel on the roof of my van. 6 yrs old. It’s been great, though i now think it’s a bit “underpowered,” at least with my PWM controller. the panel was expensive in its day (as was the Morningstar p15m) but dealer said it was one of the few whose warranty covered vehicle use. (sucker???). I’ve considered various parallel or series arrangements to add power, and keeping in mind that moving from PWM to MPPT introduces the 5v startup penalty (possibly a consideration when used with LiFePO). All this to lead up to me finding a SunPower (semi-rebranded…from FabTech / Santan?…picture shows Sunpower specs, but warranty disclaimer…FabTech only, not Sunpower). Hopefully not fake. But the really great news is it only marginally larger dimensionally, but much higher voltage, and therefore 250w vs 160w. Thus, no real estate concern, no 5v concern.

my 2 main concerns are: #1 is the advantage just “marketing?” I mean, Sunpower claims 20% efficiency, which could be an outright …ahem… “exaggeration.” Will I really get 50% more power than with the Carmanah? Are there any disadvantages, or vanishing advantages to the higher voltage approach, when used on a van which may be parked in the (partial) shade. And #2, is the quality going to be lacking? More susceptible to snail-trail or other damage? The price is cheap…until shipping is factored in…which more than doubles the price.

to be clear, I would be REPLACING the Carmanah…I only have room for one panel. And a Victron 100/20 MPPT is what I envision for a controller. if I’m camping in the woods, I have to go out of my way to find more sun; my loads are such that I am OK if I have a really good charge just before sunset, but if not really charged up, batteries can be a bit low next morning, and may not completely recover by that afternoon. Oh, this is part of an AGM to LiFe upgrade. So, the money is flying out of my wallet pretty fast. Any advice appreciated. And the particular Sunpower panel is the 3rd from the bottom on attached.

***Since I didn’t get any responses to this, I decided to start a new thread: “Comparing “old” 160w panel to “new” 250w panel and other considerations upgrading to LiFePO4.” Please comment there if responding to my questions.***
 

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