6 panels vs 3panels - same wattage

[flynmoose]

I may have made my first post too complicated so I'm going to post just one question.

I would like to put 600W+ on my RV roof.

Ive looked at HQST 100W compacts and Newpowa 210W (12 or 24V) panels.

Is there any advantage/disadvantage to 3 vs 6 panels? Right now - they are both basically $0.85-0.88 a watt.

I know with 6 I would have a little more flexibility with 3S2P or 2S3P. With the larger panels I'm pretty much locked into 3S I think (would need some pretty heavy gauge wiring to go 3P).

PS - I am currently considering dumping my converter, and 2KW inverter and going with this: Sigineer M3024NC but that would would require building 24V battery setup and a 24->12V buck and still leaves me wondering if I can start my generator with 24V.

 

[circus]

Fit is the only thing that hard. Everything else is easy to change. Perhaps a sketch of the real estate on your roof? Personally I don't like all-in-one units. After a couple years if a $200 gizmo dies it'll cost $800 to replace.

 

[jberger]

I haven't seen an 24V start generator except on 24V semi trucks, keep a 12V lead cell for the generator and engine start, you don't want to pull those load via a cheap buck converter.
Do you have levelers or slides? Those probably have serious inrush needs too, so think about all of your heavy 12V loads before you switch to 24V.

 

[flynmoose]

@circus Fit is the same. The 100w panels are pretty close to half the size of the 210w panels. Yes - I have thought about that.

@jberger - buck would only power the house 12V needs. No levelers. DC Fridge will run on 24V. Chassis battery/alternator stay the same at 12V. I haven't measured the rest of the house but I can't imagine needing more than 20A@12V and a buck could handle that no problem.

I'm considering 24V for inverter purposes. I already own a 2000W 12V inverter and probably don't need 3000W in a 26' coach. But 12V high charge current MPPTs get expensive fast. Fast enough to make me consider the complexity but efficiency of a 24V Controller/Inverter/Charger.

Back to my primary question ... is there any advantage or disadvantage to 6 x 100W vs 3 x 210W (30 watts aside). Cost is nearly identical. I would need more interconnects if I did anything other than 6S for the 6 panels so that is more cost I guess.

 

[flynmoose]

OK - I think I know what I am going to do.

3 x 210W 24V panels in series. Voc just shy of 40V so 120V. A couple of volt rise for colder than it will ever see at full irradiance. So maybe 132V max.

Epever Tracer4215BN. Max input voltage 150V. Rated max power 525. Overpaneling up to 1500W - 40A output.

I'll build my two 12V batteries and run them in parallel. Short runs and 00 wire, I can run 2 100A BMS in parallel and run my 2000W inverter as long as I have power.

No need to mess with the 24V stuff. (If I were truly starting from scratch I would still pursue the 24V option but I already own the inverter and the controller is decent price. Might upgrade my converter to push more power faster to the batteries if I'm running the Genset.

$600 for the panels
$200 for the controller
$300 for a new high current converter
$100 for bits and bobs (mostly I already have bus bars, cabling, terminals, power shunt/battery SOC monitor etc.)

I still haven't answered my primary question which is - any advantage to 6 100W panels to 3 200W panels if all the voltages work out to be the same? More panels - more hassle? Or more panels - more flexible? I'm leaning towards 3 because I need to make at least one tiltable for roof access. If I had 2 100watt panels I would either have to tilt each one or have a frame that connected them into one - so might as well just have a single larger panel.

 

[jpimlott]

1. 6 panels would let you have one string one direction and the other string a different if that were an issue
2. If a panel fails is it cheaper to replace one 100 watt than a 210.

 

[12VoltInstalls]

For small systems 100W panels do offer the two-directions you can face panels. No, the midday max isn’t as high. But with a fridge you want to have good charging right to sunset imho and faster recovery in the AM. You may and likely will get better charge performance with one array SE and the other SW
12V batteries are fine at the inverter output you mentioned imho

why do you need the converter?

 

[DThames]

More panels = more connections. More panels = more mounting points (I guess)

 

[flynmoose]

Given the real estate, the 6 x 100 would occupy the same space as the 3 x 200/210. I have been thinking about a movable mount system that would allow all 3/6 panels to pivot to one orientation (or possible 1 or 2 ... or 2 or 4... to be oriented the same direction. TBH though - I think I would just live with what I get flat no matter the orientation. Hence targeting 600W Max. I know I will never get tha over the long hall but the 12V refrig is power hungry so having 600w max makes a good case for keeping the batteries topped off until sunddown.

@jpimlott - that was one of the questions rattling in my head. Failure rate vs level of effort of 3 vs 6.
@12VoltInstalls - see above. Given that I would pivot 1 or 2 (200 w or 2x100w) the same way, I think this is a wash.
@DThames - that is where I am leaning. 3 panels are easier to mount than 6.

 

[12VoltInstalls]

see above. Given that I would pivot 1 or 2 (200 w or 2x100w) the same way, I think this is a wash.

If you are going 3S as in

With the larger panels I'm pretty much locked into 3S I think (would need some pretty heavy gauge wiring to go 3P).

then you can’t or shouldn’t really do multiple directions.

3P is roughly 30A (guessing at the panel specs) so that’s not impossible either. Just go to a combiner box or use 8gage cables from Y connections from the panels.

 

[circus]

@circus Fit is the same. The 100w panels are pretty close to half the size of the 210w panels. Yes - I have thought about that.

Wanted a sketch to determine if bigger panels would work. Like two 360w or something. If available, would save a lot of money and, if configured right, allow you to use your old equipment.
PS If not, how much for your old inverter?

 

[flynmoose]

These pics are not my MH - grabbed from a FB group.

Here is one with original flex panels moved from factory location plus a rigid:


And here is one that has the three 210 Newpowas I am thinking about.


Note this second solution provides no easy path to the front of the roof unless you walk on the panels. Maybe some people would be OK with that but I'm a clydesdale so that is a non-starter for me. So I was thinking of a similar orientation but instead of fixed mounts putting the rightmost and center panel on pivots so I could both angle for sun if desired and move them out of the way so I can walk forward on the roof.

 

[flynmoose]

I just read @12VoltInstalls' comments about not angling 3S - I assume unless all three are angled similarly. So if I did pivot mounts it would be primarily for roof access purposes - though I am not sure how to do pivot mounts with pins where I could not reach the "far" end. Maybe a threaded steel dowel underneath as a pin on both ends at the same time?

 

[circus]

Crowded up there. Can't glean your roof dimensions from a photo of a different rv so I'll just give you the dimensions of a 360w panel, 39"x77", and let you figure out if it would work or not. It's your choice, permanent mount oversize panels or tilting mount correct sized panels.

 

[flynmoose]

The 210w panels in the second picture are 26.5 x 64.5" You can see that three of them side by side pretty much takes up the width of the roof. (about 81").

You can also see the brown spot where the old Zamp flex panel was on the roof. The flex panels are 45.5x21.5"

I got 2 90 watt Zamp rigids as a warranty replacement on my dead flex panels. They are 40"x20". I'm not sure if they will fit side-by-side in the space where the previous Zamp was at but if they did I would probably feed those into the existing ZAMP controller and have a second controller for the larger panels. Otherwise - I think the 90W are going on the roof of my cargo trailer so I can have some power in there. I have a 1000W Xantrex inverter/converter combo unit that was a take-off from a friends rig.

Which brings me back to - I think I will go with 3 210w's like in the second picture - in series and then relocate the charge controller to a bay right next to the battery bank. Much longer wire run so higher voltage/lower current would be better.

Thanks all for the thoughts!