Replacement Sun-90 panel arrives but is different

[vtpeaknik]

Sun Electronics sent me another panel to replace the one that was damaged, as I've reported before.  It was shipped via UPS in a nicely-fitting cardboard box, with cardboard and styrofoam panels inside, and arrived safely.  It is not clear yet what they will want me to do with the damaged one.

But, there is a problem with the replacement one: although both are labeled "Sun 90", they are different in both physical size and electrical characteristics.  Here is the label on the one that was damaged, as I reported before it had a different junction box than the other 3 that arrived in my order of 4, but it had the same size and voltage / current specs as the other 3:

And here is the label on the replacement one:

And here are the two panels side by side:

One of the attractive features of the Sun-100 that I originally tried to order was the high efficiency, i.e., high wattage relative to the physical size.  They ran out of those, but offered the Sun-90 instead, with same size but 10% lower wattage, and (back then) a 10% lower price.  I accepted.  Now this replacement one seems to be made from the same type of cells, but the frame is about 15% longer.  This takes up more space, and in case of a multi-panel installation, does not fit right with the others.  Also, I wanted the panels as advertised because they had a relatively low voltage at the max-power point, a plus if you are using a 12V battery and a simple (non-MPPT) charge controller: the extra voltage is then wasted, so it is better to have lower voltage (up to a point) and higher current.  The promised specs of the Sun-90 were like it says the label on the old panel: max power at 17.6V, 5.12A.  The replacement panel label says 18.8V 4.82A - that's 6% less current, and also 6% less power (with a simple controller).  Also, if installed as a group with the other panels some power from the other panels may be wasted due to the mismatch.  Especially so if connected in series, where the panel with the lower amperage will limit the overall current?

 Sigh.  So, should I yet again ask for a replacement?

[halfcrazy]

Yep i would call them and explain this or copy this thread to an email. i wouldn't want the different size. that would make for a long day building a rack.

[Airstream]

I vote for selling them locally off craigs' listings or eBay local pickup only, and getting a set of what you want the way you want it

(I seem to remember you wanted to get an additional four panels?)

Life is too short, sorry here to hear of your hassles, am staying tuned for the next installment of "Will the Sun Shine?"

[dnix71]

There is real variation in all solar panels. I went to look at some on Craigslist and the variation was there on high power commercial panels that came off a roof. The ratings on the back is real world. They test each panel. You get more or less to some degree.

The replacement is 90.616, the original was 90.112, both are right one the money, watt wise.

If you are looking for better than that then you should expect to pay a lot more than $2.5 a watt.

I don't know about where you live, but things are truly tough here. We have been going through our warehouse cleaning up and using anything we can find. Sun is probably doing that, too. They may even be rebuilding panels and salvage in shop.

They offer real cheap prices on some panels, but they will not all look exactly alike.

The replacement looks like a salvage.

We are still using shipping envelopes with misspellings and outdated marketing info (covering the mistake/info with the UPS label). We have envelopes that are not even intended for shipping that we will have to tape shut, but they will get used. The only envelopes that were recycled/discarded were those no longer in size compliance at the post office.

[vtpeaknik]

I am all for thrift, on their part too.  But I want to know what I'm buying.  I assume they're surplus in some sense, that's OK, but damaged is not OK.  They advertised that they had about 500 100W panels in stock, when I tried to order they said they're out of those, but have about 200 of the 90W.  And they gave dimensions and specs.  So I expect to get that.  And I got 4 that fit the specs, first time around, it's just that one was damaged.  The replacement one has minor stains and scratches on it and is definitely not "mint", but I don't mind that, I mind that it won't fit on a rack with the others.  Am I being too picky?  I don't want to give them a hard time, but I spent over $1000 and need to get a usable set of panels out of it.  I don't know yet what they want me to do with the damaged one - if I have to send it back then definitely I should get a valid replacement.  If I get to keep it (sell it cheap locally?) then I'd say I got an OK deal, except that I still won't have a set of 4.  Four are easier to use than 3 because you can wire them in serial/parallel (24V nominal) or split into two systems.  Three can be used in a 50V serial setup, but at only 270W total that's hardly worth an MPPT controller.

[dnix71]

I understand your point.

Those panels only 32 cell panels. They were made to be used one at a time on a piece of equipment like an interstate emergency phone, night light, traffic info flasher, or maybe to keep a battery topped off on a vehicle that is infrequently used. The variation in panel dimension wouldn't have mattered then.

Those panels don't have a UL sticker on them, either, as far as I know. That means they aren't intended to be used by private parties or hooked up to a dwelling.

Strictly speaking Sun shouldn't be selling those for non-gov't use.

[ghurd]

I wondered about the 32 cells, and Vmp at 18.8V!

That's higher than most 36 cell PVs.

G-

[vtpeaknik]

I was thinking they are good for two different purposes:

• one or two (in parallel) into a 12V battery with a simple controller, or:
  
• 3-4 in series into a 12V (or 24V) battery via an voltage-converting MPPT controller.
  
  

For the first possibility the fairly low Vmp (about 17.6) seems to me like an advantage, relative to 36-cell panels with Vmp above 20V (i.e. lower Cmp).  Some people here were worried that at high temperatures the voltage will be too low to fully charge the battery.  Here in Vermont I am not too worried about that, and in the winter is when we need every last watt.

[ghurd]

I have to question how valid those numbers are.

Cells have a natural voltage where they like to work.  More cells means more voltage.  And a higher Vmp.

Compare those numbers to an 80W 36 cell BP 380.  First data sheet I opened, no hidden meaning.

Vmp = 17.6V

Voc = 21.1

UL, NEC, TUV, ESTI, etc.

BP states the Voc at 0.586V per cell.

Sun states the Vmp at 0.5875V per cell.

The Sun cells working at max power are higher voltage than the BP cells when unloaded?  

I have a hard time swallowing that.

The "normal" purpose of a 32 or 33 cell module is, after the blocking diode, the working voltage and amperage curve is so low it can hardly over charge a battery.

A 32 cell VMP at 18.8V seems like something was measured in a very non-standard format.

G-

[vtpeaknik]

I measured the output of these panels myself, held vertically facing full mid-morning sunshine.  Not max-power, but open circuit voltage was above 20V (alas I can't remember exactly, but it fit the label) and short-circuit current was about 6A for the short panel and 5.5A for the long one (but is probably not very accurate - using the 10A shunt built into my very cheap DVM).  Assuming a simple shunt controller, this should give about 5A into a 12V battery (depending on the battery voltage and the exact V-I curve of the panel), or about 60W actual power into the battery.  Higher voltage would not help at all in that setup?

Anyway, if cell voltage is pretty standard (is it?) then the two labels' Voc being so different doesn't make sense, you're saying?   These are supposedly made from SunPower brand cells which claim high efficiency (they are small for the claimed wattage, significantly more watts per area than e.g. the Evergreen panels I've bought in the past), could those have different voltages than other brands?  See here for more specs on the Sunpower 90W 32-cell panels (appear to be the same as the Sun-90? *), including a V-I curve that shows the full current is maintained up to 15V, and only about 5% current reduction at 17.5V:

http://www.bonzabuy.com.au/store/product_info.php?products_id=28

- looks to me like a charge controller is still advisable...

So should I ask them for another replacement panel or not?  This question involves technicalities, practicalities and ethics.

*) just to be clear, Sunpower is a Chinese PV manufacturer, Sun is a Florida-based PV merchant.

[ghurd]

All cells have about the same voltage under the same conditions.

Mono or multi.  This brand or that brand.  The high efficiency or the low efficieny.

That's why they almost all have 36 cells.  Some even have 40 cells.

The 32 cell panels will work at a lower voltage under the same conditions.

I am not aware of any major company making 32 or 33 cell modules anymore.  If it was a good idea and they could save the cost of 4 cells, plus the metal and glass, they would still be doing it.

I bet that new frame is the perfect size for 4 more cells.

Guessing your Voc was at near 32F (0C).  The BP 380 would be a hair under 25V.

http://www.affordable-solar.com/admin/product_doc/Doc_BP%20375%20380_20070614132538.pdf

Could work backwards from about any detailed data sheet to get the performance per cell, and then multiply it by 32 cells.

Can compare data sheets from a few companies 36 cell PVs and see what I mean.

The panels will work, but you do not want a cheap controller from HF or Northern or Ebay.  They have a forward V drop of 0.6 to 1V.

A MorningStar has a forward V drop near 0V.  Probably some other good brands will too.

That ~3/4V will make a fairly considerable difference on the carging current under many normal conditions.  About like adding 2 more cells.

If you are wondering, I would use the ProStar30.

I half expect they sent that panel because that's what the last batch China sent them look like.  

Chinese translation: "90W is 90W, you ordered 90W and we sent 90W."

I would want all mine to look the same.

G-

[Dave B]

 They are obviously trying to weed through their inventory during a possible product change. I would not accept this practice and would bag the whole idea with this company. Call them and tell them you are shipping everything back, demand your full purchase price back and have them pay all shipping besides.

 If they are smart they will realize this is a deal for them as opposed to fighting against your right to have what you paid for. Good service goes a long way for a company even if it's for returns. I know they would gain back some of my respect if they took care of your situation this way, as of now I have little confidence in their practices.

 Start over, start fresh and get exactly what you want with another company. No one deserves to be played at your own expense. Just my opinion, good luck. Dave B.

[richhagen]

Sunpower is actually a U.S. Company which employs about 3500 people in total.  .  .  .  

http://www.sunpowercorp.com/About-Us/History.aspx

The distinguishing characteristics of their cells are that there are no front electrical contacts, and they feature a high cell efficiency for the finished cells - which is why the Voc as noted by Ghurd is higher than for the BP Cells.  

Still it seems odd to me that the Voc was higher at the same time the current was lower for the two panels appearing to be made with the same cells, but cells are generally batched together based upon their voltage and current characteristics so this is not impossible.  

I have 16 of the Sun 50 panels purchaed in two different batches and I am happy with them so far.  One arrived broken and two scuffed up in the first batch.  The second batch which contained a rplacement panel for the one broken and was packed much better on what appeared to be a purpose made pallet - no problems at all with that shipment.  The 50 Watt panels are 36 Cell strings which are not center tapped.  The panels had no bipass diodes, but I added some to them across the whole of the panel string since I am operating at 48V.  My Voc was above 24V on a winter day and I was getting over 2 amps of current.  I am confident that they would meet or exceed their specification at high noon on a sunny day at a good angle to the sun.

I suspect that these panels were assembled from surplus cells that Sunpower did not use for their own branded panels, and were assembled by either Sun Electric or other third parties, which results in the at least three different designs of junction boxes observed on these panels as well as other variations.  They are then marketed by Sun Electric at their store and on their site.  

The price has now changed to about $3.60 per Watt for the Sun 50 Panels, whereas I had bought mine at $2.58 per watt, which was hard to beat.  They are not perfect, but if I ever catch the 50 Watt version back on sale for $2.58, I will be buying another batch.    

It is a bit of a bummer that they were not able to send you a panel like the previous panels that you had ordered.  The difference in current and voltage is not that great.  Were you to hook upto 4 in series or a bunch in parallel through an Mppt controller your losses because of the 2.9% current difference would not likely be that great.  The look of the array would be different of course.  Because of the minimum order quantity, and the currently higher selling prices from sunelec, I would suspect you could likely E-bay or Craigslist the panel for more than you paid for it although I find packing and shipping panels to be a bit of a hassle.  Whether you send it back, sell it, or use it, good luck with it.  

Rich

[Opera House]

I just got a SUN-90 and it is the old style.  Want to do some trading?  My camp is upstate NY and I'll be there in a couple of months.  These are sure weird looking panels, Never seen that type of construction.