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buying this 2nd hand PV panel
By dinges, Section Solar Posted on Fri Dec 16, 2005 at 10:12:23 PM MST
what do you think?

G'day,
Today I placed a bid on this PV panel. 75E (about 65US$) for this 20W panel. Apparently, this model was first made in 1976 by Philips (model BPX 47A, if that means anything to youse); I don't know how old this particular panel is. According to the seller, it's in excellent condition. It does look a bit archaic to me, though.
See this link (in Dutch, but should be understandable for non-Dutchmen)
LINK
What do you think of this price, and the age of the panel? It will be used to charge my newly acquired (& to be acquired) bank of batteries; it will be about 200Ah in the end, if I get my way, so this panel won't do much more than trickle charge; should be enough to keep it loaded in case of a power outage?
Looking forward to your opinions.
Peter,
The Netherlands.

buying this 2nd hand PV panel | 13 comments (13 topical)

Re: buying this 2nd hand PV panel (3.00 / 0) (#1)
by Clifford on Fri Dec 16, 2005 at 05:08:29 PM MST

I guess it depends on your goals.

20W may be the max in the summer under perfect conditions.
But, don't count on lots of Amps in the winter.

It would be great for working in the winter.

You should target $3 to $4 / watt. Remember if you add shipping, that adds to the price. Small panels seem to be a bit more expensive, although I did see a few "trickle charge" panels at Harbor Freight which appeared to be a good price, don't remember quite what it was, but that was here in the USA.

It probably would be ok for low voltage needs... say you want a few 12V lamps on for a few days a month. But, not good if you want it to sustain your entire household 24x7.

Don't know the comparisons between new and used panels. That one has some "wasted space" between the cells. But, in theory panels last a long time so that should be ok as long as they are working. The easiest way to test panels is to measure both open circuit voltage and short circuit amps.

Re: buying this 2nd hand PV panel (3.00 / 0) (#2)
by Clifford on Fri Dec 16, 2005 at 08:37:23 PM MST

BTW

I like your exchange rate.

How many Euros would you be willing to change at the rate of $60 for 75 Euros?

The last I checked, $1 was less than 1 Euro (.83 Euros/dollar, or 1.2 dollars/euro)

A 75 Euro bid would be about $90

So....

You are offering about $4.5 / watt for a 20 yr old panel.

I like the clear plexiglass (or glass). It just looks COOL!!!

Anyway, small panels seem to go for up to $10 / watt.

Once you throw in shipping, it will probably push it to over $5 / watt... still acceptable for a small panel, and it sure does look cool !!!!

Re: buying this 2nd hand PV panel (3.00 / 0) (#3)
by dinges on Sat Dec 17, 2005 at 02:32:42 PM MST

Clifford,

Did I mention I was an economist (blush). This is what you get with those quick conversions from memory (more blush). You'd like me to fill in your tax return? ;-)

There would be no shipping costs, since it's in a city that I visit regularly.

BTW, I still calculate with 3$/W, as I've seen here about 2 years ago. However, that price seems to be very far behind us.

The panel looks nice, but it has a lot of 'empty space', with no solar cells. It also looks archaic, with its round solar-cells. But if it works, who cares. Not maximum efficiency per square meter, but I can live with that.

Thanks for the replies,

Peter,
The Netherlands.

[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#4)
by dinges on Sat Dec 17, 2005 at 02:34:25 PM MST

What I really meant to ask: a 20 year old PV panel is still a good investment? I know they're normally guaranteed for about 15-25 years.

Do you guys experience lower output from your older PV panels? What's the oldest PV-panels you have that still work satisfactorily? Any older ones you're not happy with?

Peter,
The Netherlands.

[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#6)
by ghurd on Sun Dec 18, 2005 at 11:24:10 AM MST

It looks new to me.

The cell coloring looks new.
I would be concerned if there was any 'yellowing' or fading of the cells themselves, because failed panels of that style usually have a yellow tint around the cell edges. Maybe heat damage yellows them?

Is the sticker on the front of the glass? Maybe it was never installed.

The frame looks good too, not like it has been outside for 20 years.

Having 34 cells, the wire to the battery should be heavy or short. There is not a lot of extra volts to lose in wire losses.
Standard is 36 cells, some even 40 cells.
The 30 or 32 cell panels are so called self-regulating and don't work very well.

Looks OK to me, if you feel the price is good.
G-
Ghurd.info
[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#7)
by dinges on Sun Dec 18, 2005 at 02:06:12 PM MST

Thanks Ghurd.

How much voltage should a 34-cell panel put out? I can always keep wiring losses to a minimum. Just yesterday, I installed new connections on my UPS to use the new batteries I found; the extra resistance was measured to be 5.1 milli-ohm on one cable, 6.3 milliohm on the other one :-)

What 'headroom' do you have with 34-cell panels? I remember my tiny-tiny panels put out 2V for 4 cells; so should it be .5V/cell; in that case, 17V should be more than enough? About 3V available for wiring losses (1ohm would be very much already, at 1A that's only 1V), plus some headroom for a regulator (will build a shunt-type, not series), so no headroom for the regulator would be necessary?

And yes, it looks pretty good to me. Won't make it possible to get off-grid, but at least it should keep the batteries (100-200Ah) topped up. Recharging would be quite a different story (unless you could wait a month for the sun to do its work).

Besides, all this reading & writing on PV panels makes me want to do something with them! My hands are itching, especially now I've got the batteries for it.

Peter,
The Netherlands.

[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#9)
by ghurd on Mon Dec 19, 2005 at 09:22:59 AM MST

I figure the peak power will be at about 16.5V, and 1.2A. Not sure how standard the rating systems were 20 years ago. That 1.2A will be for a short time each day, so it could be OK to figure average losses at 1A.

Personally I am not big on shunt controllers. Have seen much better results from PWM. Maybe not worth the cost on a small panel. Maybe a SG-4 controller could be had over there for a decent price.

Have you heard of the STMicro chip 'PB137ACV'? I have had very good results for panels around 500 to 750ma, using only the chip, no caps even. Some of the literature states 1A, other states 1.5A. Maybe it could be used with a bypass transistor, but that would use up some 'headroom'.

G-
Ghurd.info
[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#10)
by dinges on Thu Dec 22, 2005 at 03:19:38 PM MST

Ghurd,

Do you know of any circuit designs of PWMs? Or could a plain old PWM power supply be used in this circuit (i.e., TL494 or U3852 (?)). I know MAXIM semiconductors make some nice ICs that could do it, but any proven circuits around, intended for RE, that can be built by a DIY-er? If so, I'd be interested.

Why you're not fond of shunt-controllers? They seem much better to me than series-controllers; hadn't thought about PWM yet. Higher efficiency? Or does it have MPPT characteristics? IIRC, an MPPT is usually a PWM, but a PWM is not necessarily a MPPT.

Peter,
The Netherlands.

[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#12)
by ghurd on Thu Dec 22, 2005 at 10:45:50 PM MST

I have seen a few homebrew PWM circuit designs for.
IIRC, Forest Mims had a couple versions. Maybe Home Power magazine too.
Never built one. Parts cost more than a factory made unit that works for sure.
(funny, I spent more on stepper motors I figured would NOT work, than a half dozen TDMs cost. A hobby is a hobby. You may enjoy building one.)
Plus I use a lot of them, so making (or repairing!) them would take too much time.

Sandia labs did a big long term test a few years ago.
Series (on/off) controllers lost. Shunt did better.
It is PWM for me, until the MPPT get cheaper, or the systems I install get bigger.
Higer efficiency, built in de-sulfator, less stratification, cheap enough, etc.
And a very inexpensive one is available for panels up to 60W.

Results for MPPT seem related to 'who' does the test. Tom in NH likes his MPPT, and thats the most reliable and trustworthy information I heard in quite a while.

"MPPT is usually a PWM, but a PWM is not necessarily a MPPT"
Correct. It can get confusing in their advertisements.
G-
Ghurd.info
[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#5)
by DanG on Sat Dec 17, 2005 at 03:02:14 PM MST

If that was a indoor demo or 'conversation piece' without visible corrosion on backplane you may have a good panel - though I suspect the wiring pig-tail conductors have weakened from handling just at the point they exit the panel, or insulation is failing at that point perhaps allowing moisture intrusion...

I have cells now 25+ years-old that still output exactly what I measured & recorded on them back in 1983 but they have been sleeping in cardboard box in basement the whole time.
-
-

Re: buying this 2nd hand PV panel (3.00 / 0) (#8)
by Dreadstar on Mon Dec 19, 2005 at 01:20:35 AM MST

Not sure what the shipping would be but i have a 80 watt Solec 12/24 volt panel for $300 if you are interested. My zip is 92802 if you wish to check panel is 21lbs but would be a large box. figure 27lbs or 13 kilo for it and packing.
Take out the (at) and substitute @ for replies via email

Re: buying this 2nd hand PV panel (3.00 / 0) (#11)
by dinges on Thu Dec 22, 2005 at 03:25:48 PM MST

Thanks everyone for your opinions.

I have bought the PV panel; had a nice discussion with the seller too (he was installing 600W of PV capacity (when he showed me the panels, I got the proverbial bulge in my pants :-) ), the maximum over here apparently if you want to go grid tied without commercial installers. He also was running back the meter. And he had built a Savonious turbine (small one, from PVC) which he intended to connect to a car alternator. Quickly 'educated' him, and pointed him to this board & windstuffed.

The panel was installed inside of a RV, so out of the weather; it looks good, no yellowing, but I haven't been able to really test it: no sun here for days, only grey overcast. 10mA is not much :-(

Only downside was a slight damage of the wire sleeve in a particular place (thanks for pointing out to check where the wiring exits the panel!), but it's not a major problem. Will strengthen this bit though, so it won't be subjected to too much stress.

Now all that's left to do is build a small alu frame to mount it outside (really need to learn TIG welding now :-) ) and start enjoying the sun...

Peter,
The Netherlands.

[ Parent ]

Re: buying this 2nd hand PV panel (3.00 / 0) (#13)
by ghurd on Thu Dec 22, 2005 at 10:51:48 PM MST

Leave a lot of clearance all around the panel. like 20cm.

When the sun comes out, you will watch the meter for hours... 0.9 amps, 0.9, 0.92 (Oh Boy!), 0.92, 0.98 (Wow!)... I still do it. :)
Ghurd.info
[ Parent ]

buying this 2nd hand PV panel | 13 comments (13 topical)

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