Foldable panel output voltage & MPPT SCC

[sunrise]

I did some search on amazon for an ~100w foldable solar panel, as an addition to roof top rigid panels. I found most of popular/highly rated ones has 'output voltage' of 18v, does anyone know if this is Voc or Vmp?

I am wondering how folks use them to charge their trailer lithium batteries with MPPT. if the 18v is Voc, then it won't even high enough to kick off MPPT charging as my victron needs battery voltage + 5v to start charging.

 

[Forbisher]

So called 12V 100 watt panels have a Voc of about 20V to 22.5V
Most are about 21.xVoc and about 18Vmp

 

[snoobler]

+1 with Forbisher

And to say it another way, It's almost certainly Voc, and you'll get Voc with very little light, so the Victron won't have an issue with its +5V requirement.

Since you're presumably talking about mixing panels - foldable and your rooftop array. There are more considerations. If you're connecting to the same charge controller, your "foldable array" and rooftop array need to be compatible.

If they are all in series, they need to have about the same current. If they don't, they will all work at the LOWEST CURRENT of all panels in series.

If the foldable is in parallel with the rooftop, it needs to have very similar Voc & Vmp.

 

[sunrise]

@Forbisher - I just checked one of the popular brand 'Rockpals' 100w foldable, Voc 19v, in fact I found several videos and reviews people with MPPT SCC with Lithium battery only get 22w out of the 100w panel, while a PWM SCC can get 55w out of it. In the mean time, the same MPPT controller gets 64w from Jackery 100w foldable with 21v Voc.

@snoobler I will use a separate MPPT controller for the foldable panel. Victron has 75/15 SCC for $118, with bluetooth, it would work very well if the foldable panel has proper Voc.

 

[snoobler]

How critical is foldable? If these are for temporary trailer use, what about flexible or stowing rigid panels.

A spare SCC may not be necessary if you shoot for compatibility with the rooftop array.

 

[sunrise]

How critical is foldable? If these are for temporary trailer use, what about flexible or stowing rigid panels.

A spare SCC may not be necessary if you shoot for compatibility with the rooftop array.

I tow my 16 feet camper with a mid-size SUV, so space is important - it's easier to find space in my SUV if it has more than 2 folds.
If my plan is sound and I execute it well, I would have over 200w on rooftop, so if I have reasonable exposure to sun at campsite I won't bother to take out the foldable. If I have to take it out, most likely the rooftop panels are in shades and I am not sure if they will drag down the foldable panel if they share one SCC?

 

[snoobler]

If you parallel your "deployable" array with the shaded rooftop array, they will function independently of one another even on the same SCC assuming it can handle the voltage and current of both.

I'm not sure what kind of "trailer" you're dealing with, but it seems to me that sliding a couple of flexible 100W panels into a crevice would be a triviality. Many flexible panels with the proper coating for durability are offering 5 year manufacturing warranties and 20+ year performance warranties. They're more expensive than rigid, but cheaper than foldable and perform better than foldable.

 

[sunrise]

If you parallel your "deployable" array with the shaded rooftop array, they will function independently of one another even on the same SCC assuming it can handle the voltage and current of both.

I'm not sure what kind of "trailer" you're dealing with, but it seems to me that sliding a couple of flexible 100W panels into a crevice would be a triviality. Many flexible panels with the proper coating for durability are offering 5 year manufacturing warranties and 20+ year performance warranties. They're more expensive than rigid, but cheaper than foldable and perform better than foldable.

It's a Airstream Bambi 16RB, the only place I can think of for a 100w flexible panel, is hanging it on the outside of bathroom door. that's why I need a foldable solution so I can put it in the SUV.

 

[snoobler]

Sounds like a great place to me. That's a slick little unit. Pretty sure I'd have to poo with the door open or I'd never fit in that bathroom. That's a statement more about me than the trailer.

 

[rin67630]

I did some search on amazon for an ~100w foldable solar panel.

The only valid place I can imagine for all foldable/flexible crap on the market, is the next dump yard. Sorry.

 

[sunrise]

I'd be looking at a proper 250-300W panel or 2 and make a rack underneath the Trailer that you could slide the panels in and out of while traveling and lock them in place with a couple of spring latches. They wouldn't have to be slide outs, just something like C channel that you just pushed the panels into. Should take up exactly zero space when carrying them and the weight would be nice and low as well.

100W panels are a waste of time and money. Get something that will give you some real and useful power especially when you need it most in bad weather.

This is our weekend camper and I have a fairly modest goal, without using hair dryer and microwave, I want to be able to last 3-4 days without electricity anxiety - we could be very conservative for other things but not the fridge, which is electrical only and draws 2.4ah. I have done the math of add all things draw electricity and I think the 230w rooftop + 100w portable should serve us very well.

Thanks for the under trailer rack idea, I might not use this now but down the road I might use this on a different RV. need to do a bit more research on this though, how to prevent debris damage the trailer, and I don't want to have to wash it every time I take it out to use it. Also Airstreams have lower ground clearance than most trailers. I have seen folks paid decent amount money to install 'lift kit' to raise it by 3 inches so they can go to places that road are less forgiving.

 

[snoobler]

I assumed propane on the fridge. Please give detailed power consumption info on the fridge. "2.4ah" doesn't make sense in this context. If you have to run a fridge off batteries and solar, that may be a big challenge.

If you can link to the model, that would be best.

 

[chrisblessing]

I have 13" Scamp. I obviously cannot mount a "household" framed panel, so I mounted a 160 watt flex panel to the roof to charge, via an MPPT controller, a 100 Ah LiFePo4 battery which is inside the camper. Like you, I also have a 12v-only (2.5-3 amp draw) refrigerator/freezer and have sufficient power to keep things cold or frozen as well as powering my furnace fan, lights, fan and device charging.

I also ran a positive/negative wire pair, terminated with an XT60 plug, to the outside of the camper. When parked in shaded sites I plug a 120w suitcase panel, (with its own PWM controller) into the external plug. I can place the suitcase panel up to 12' from the camper. The two panels are independent of one another, are both pretty efficient and allow me to boon dock without concern for all my power needs. They are decidedly not "crap".

 

[sunrise]

I have 13" Scamp. I obviously cannot mount a "household" framed panel, so I mounted a 160 watt flex panel to the roof to charge, via an MPPT controller, a 100 Ah LiFePo4 battery which is inside the camper. Like you, I also have a 12v-only (2.5-3 amp draw) refrigerator/freezer and have sufficient power to keep things cold or frozen as well as powering my furnace fan, lights, fan and device charging.

I also ran a positive/negative wire pair, terminated with an XT60 plug, to the outside of the camper. When parked in shaded sites I plug a 120w suitcase panel, (with its own PWM controller) into the external plug. I can place the suitcase panel up to 12' from the camper. The two panels are independent of one another, are both pretty efficient and allow me to boon dock without concern for all my power needs. They are decidedly not "crap".

Thanks for your comment and glad to hear your setup works well for you - I am pretty confident the modest sized panels (rigid or foldable) would work well for me as well. We made conscious chose not to go big rig, our small trailer give us access to some very best camp in PNW that bigger rig would not fit.

 

[sunrise]

You ought to see the thing My Neighbor just bought. Not the biggest van out there but probably 3 times the size of what you have. I wouldn't like to be dragging the damn thing around that's for sure. All the comforts of home but if that's what you want, farking stay home!

I think I took the gloss off things a bit when he was telling me about the capacity of the water tanks and I said that's half a ton right there and the House batteries and gas bottles were almost another 1/4 ton to drag around. It's a beautiful set up and he seems to have no trouble towing it round but I think I'd be wanting to start with something small and work my way up with a bigger vehicle than what he has.
The King size bed I think is stupid. Bedroom takes up about 1/3rd of the vans length. I have a king size bed but I'd be looking at something a bit more compact or at least something you could fold away if it was that big to give more "daytime" Room or a larger shower that gave enough elbow room to reach up and wash my hair.

The thing has a BBQ that slides out, speakers for the stereo on the outside, led Lighting for the remote control fold out awning, an outside tap and sink.... It's quite amazing but I think a bit overkill just the same

We did manage to put a KW of panels on the roof of the thing though between the AC, hatch and TV antenna. Makes plenty enough power in the shed to keep the batteries charged right up just though the sun that comes in the skylight in shed roof.

I know there are folks who live in these big rigs full time and these were designed to provide comfort as close to a house as possible. Multiple slide outs, king bed like you said. These are great products, the only time I hate them is when I have to park right in between 2 of these

Thanks for sharing your experience, BTW.