From Freightliner ambulance to RV - we hope!

[patoz]

Now, that makes better sense. I've been looking at these Panasonic VBHN325SA16 HIT N325 Monocrystalline 325 Watt Solar Panels. If I can get four of them up there, that will give me 1,300 Watts of power. Probably overkill, but I'm like Tim the Tool Man Taylor... 'More Power!'

I don't plan on carrying anything on top, but I will raise them up enough to allow air flow and to be able to clean under them. I live in an area with lots of Oak trees and things will mildew overnight once the tree spores land on them.

 

[Coachgeo]

Now, that makes better sense. I've been looking at these Panasonic VBHN325SA16 HIT N325 Monocrystalline 325 Watt Solar Panels. If I can get four of them up there, that will give me 1,300 Watts of power. Probably overkill, but I'm like Tim the Tool Man Taylor... 'More Power!'

I don't plan on carrying anything on top, but I will raise them up enough to allow air flow and to be able to clean under them.....

Don't plan on anything on top either. As well am a bit of a "reasonable overkill" person myself hmmm ... wait.... does that mean I am an oxymoron.. (reasonable overkill) lol. Am going 1000w but would have been more if I did not pull trigger too fast when I saw 100watt panels on sale and got 10 of them. Now am seeing the larger ones like y'all have for cheaper per watt (though barely cheaper so maybe with my free shipping the price was equal? I can pretend right) going 24v and will separate into several arrays maybe one array of two on the cab.... and two of four each on ambo top. who knows.... might overkill and wire it up with as 5 array of two each. Either way plan to wire in switch to kill lowest producing array so it won't drag down the others. (shaded array for example).

Assume ya'll know.... but in case not..... over all; each array output always drops to lowest common denominator of the bunch that make it up. So if one has an array of 4 panels and one panel is shaded ..... total output will drop in ALL the other panels to same output as the shaded one. Granted you could put a charge controller on each panal (or group of panels- aka: array).... but that starts getting very spendy real fast compared to some switches.

 

[patoz]

My ideal goal is to be able to run my A/C on solar power, but we all know that's an oxymoron because in order for the solar panels to work properly you have to park directly in the sun if the panels are mounted on the roof, which makes the A/C unit work much harder and draw that much more current. Some experts say it can't be done efficiently, and some say it can. The panels I'm looking at are 19.7% efficient with 20.0% being the best you can get, so maybe I can get close.

For anyone looking for slightly used panels, check with this company Sun Electronics. They are in Miami, FL and sell mostly panels that have been used in solar farms, etc. From what I understand the panels get changed out on a regular basis and also any time one panel is damaged in a bank, the entire bank must be changed out. I guess that is like batteries in a bank.

 

[Coachgeo]

My ideal goal is to be able to run my A/C on solar power, but we all know that's an oxymoron because in order for the solar panels to work properly you have to park directly in the sun if the panels are mounted on the roof, which makes the A/C unit work much harder and draw that much more current. Some experts say it can't be done efficiently, and some say it can. .... For anyone looking for slightly used panels, check with this company Sun Electronics......

thanks for info. am considering an awning...... that is part solar panel. That way it makes power but also shades the rig's side making it's AC not have to fight so hard.... ANDD you can tilt it to get most advantage. Disadvantage is unless it is deployed.. if it sits above or below other panels on roof....... you only got part of available panels working.

Course then again if all were on the awning hmmmm....

 

[Mattersnots]

Now, that makes better sense. I've been looking at these Panasonic VBHN325SA16 HIT N325 Monocrystalline 325 Watt Solar Panels. If I can get four of them up there, that will give me 1,300 Watts of power. Probably overkill, but I'm like Tim the Tool Man Taylor... 'More Power!'

I don't plan on carrying anything on top, but I will raise them up enough to allow air flow and to be able to clean under them. I live in an area with lots of Oak trees and things will mildew overnight once the tree spores land on them.

This is the set up I have. I've been meaning to see if the panels can keep up with the A/C. It looks like they will during peak sun. My panels make almost 10 kilowatts per day and my A/C uses about 1100 when the compressor is on. Now it's all about the variables like cab windows in the sun, pass through door insulated enough, etc. I still don't have my window shades on so I've got a giant greenhouse going too. I'm confident that I could run the A/C 3 to 6 hours a day at least without shore power. I can easily keep it on for a nap or mid day meal. But there's no way it's going to keep up in Houston during mid summer.

 

[rossvtaylor]

I'm also aligned on the air conditioning. The CruiseAir (now Dometic) system in our rig draws 7-8 amps, so about 840-960W when running. I measured this with my clamp-on meter and was actually pleasantly surprised, since it's on a 30 amp circuit. That makes it viable to keep the back cool while stopped for lunch. Once I get the AC recharged, so it runs cooler, we'll do some real world testing and see what happens.

On a related note, I did add 4 more batteries in the back and have a disconnect option between those and the 4 batteries up front.

Ross

 

[Coachgeo]

Due to amp draw of AC's combined with no cab ac in my truck for cab am using a cool suit(s) or vest that will only draw about 4.5 amps?.. For ambo box will use that also when elec bank dictates; otherwise only maybe a small 5000 watt ac for rest times. This set up is another reason am going with no new windows in ambo (only door windows on it).... to combat temp losses thru the glass etc. to lower demand on any ac or heat system.

 

[Britboaters]

Coach - your point about shaded panels bringing down the whole array.....
I'm planning 4 x 305 watt panels each wired separately to a "combiner" (individual breaker for each panel so they'll all wired in parrallel, so about 30 volts).
Am I right to think that if one panel is shaded it won't affect the others, 'cause they're in parrallel ?
Or should I wire them in series, to get 120 volts ?
Thanks
Bob

 

[Coachgeo]

Coach - your point about shaded panels bringing down the whole array.....
I'm planning 4 x 305 watt panels each wired separately to a "combiner" (individual breaker for each panel so they'll all wired in parrallel, so about 30 volts).
Am I right to think that if one panel is shaded it won't affect the others, 'cause they're in parrallel ?
Or should I wire them in series, to get 120 volts ?
Thanks
Bob

https://www.gonewiththewynns.com/Sailboat-Solar-Series-Parallel-Shading

 

[Britboaters]

Thanks Coach. I knew shading was bad but didn't realise how much effect it had.
I am planning 2 panels fixed and 2 panels that can be tilted, using gas struts. This will probably be a fixed angle for simplicity of installation. I should have some photos over the next few days, if I can figure out my TIG welder....
Bob

 

[rossvtaylor]

Ah... shading. Just placing an index card on a panel can cut the whole array's output significantly, as can enough bird poop. I did some troubleshooting on some installations of single-panel solar, mounted on telephone poles. Since the panels weren't mounted above the wires, the wires cast a shadow across the panels for much of the day. That single, narrow shadow bisecting the panel killed output. This whole issue led to the popularity of small inverters for each panel, micro-inverters, so that if one panel is shaded the others still contribute to their full potential.

 

[patoz]

... This whole issue led to the popularity of small inverters for each panel, micro-inverters, so that if one panel is shaded the others still contribute to their full potential.

I was going to mention micro-inverters, but I just started researching them and don't know enough yet to provide any useful input. Download the Owner's Manual which has much more info in it.

Magnum Dimensions MicroGT 500 Inverter

 

[dwh]

I was going to mention micro-inverters, but I just started researching them and don't know enough yet to provide any useful input. Download the Owner's Manual which has much more info in it.

Magnum Dimensions MicroGT 500 Inverter

Um...no.

Most (if not all) micro-inverters are "grid-tie" inverters that sync phase and frequency to the grid. If they don't detect grid power to sync to, they shut down their AC output.

The manual for those Magnum Sensata units describes a way to fool them into working in the absence of grid power. You feed a normal inverter from batteries, and the micro-inverters sync to the output of the battery-fed inverter.

Not really practical for most mobile installations. Plus, how you gonna charge the batteries with that kind of setup?




There is something hinky about that Gone with the Wynns series vs. parallel test - but I haven't thought it through enough to spot the flaw.

Still...in series, shading one cell should not drop the output of the array of two panels to zero.

I'm pretty sure they goofed up the test somehow.

Edit: Could be that the Outback charge controller only does an MPPT sweep (adjusting array load voltage to determine Vmp) every sixty seconds. If so, they would have to shade a cell, then wait for the next sweep.

In parallel, shading wouldn't change the array voltage (array Vmp), so the MPPT wouldn't need to readjust the load voltage. In series, partial shading would change the array Vmp, so the MPPT would have to find the new Vmp.

So maybe they just didn't wait long enough for the MPPT to adjust...

Dunno. Prolly have to sleep on it.

 

[patoz]

Dwh, I read some more about those micro-inverters after I posted that, and started coming to the same conclusion as you did, and the biggest one was how to charge the batteries. When I read what their output was, I realized this was a different animal all together.

Oh well, at least I learned something new today! ?

 

[rossvtaylor]

Ah, yes! Sorry, I was only referencing the micro-inverters to explain the shading issue and attempts to address that. But, as DHW said, they're for grid-tied (grid interactive) installations and require a line connection to which they synchronize - they are not for mobile installations like ours.