Help to ID a Solarex Panel needed

Submitted: Wednesday, Jan 19, 2005 at 21:59
ThreadID: 19597 Views:4186 Replies:4 FollowUps:16
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Hi,

A mate gave me a solarex solar panel, but the label was worn off and I need help to ID it.

It is a 36 cell, 620mm square panel with a rubber back and an alloy frame.

Laid flat in the sun on Saturday in Adelaide it pushed out 20 Volts unloaded and 3.1 Amps shorted.

I just need to find out the approximate wattage so that I can get a suitable regulator. (and yes I know 20V x 3A = 60W, but what would it be rated at?)

Thanks also to whoever suggested using wheelchair batteries as a portable power source. I picked up 2 x 30Ah gell cells for $50 from a shop on south road. He even load tested them for me.

Thanks

Paj
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Reply By: John - Wednesday, Jan 19, 2005 at 22:51

Wednesday, Jan 19, 2005 at 22:51
Dear Paj
From the size you quote (0.38m2) I would expect it would be about 40w. Your multimeter may be out of calibration. The current 60w Solarex module is 1110 x 500( 0.59m2). The 40w is 764 x 502 (0.38m2)

However any regulator with a higher Amp rating than the solar pannel is fine. The smallest quality regulators are generally about 6A and your pannel wont put out more than this. It is often worth buying a higher capacity as it alows you to connect more pannels or a bat charger at a later date (often 10A units are only slighly more expensive than 6A).
A quality regulator will get more out of the pannel. I use is the Plasmatronics PL20 (it will handle up to 20A with lots of great features, programable, with display), but would be a bit expensive (at $300) for your set up. The Morning star 6A unit is only a single stage regulator but is PWM and at only about $80 (from memory) may be a good choice for your small set up.
Cheers John
AnswerID: 94006

Follow Up By: paj - Wednesday, Jan 19, 2005 at 23:03

Wednesday, Jan 19, 2005 at 23:03
Thanks,

40W sounds about right seeing the 20V was unloaded, so if it sustained 3A at (say) 13V under load it would work out almost exactly.

Cheers

Paj
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FollowupID: 352960

Follow Up By: John - Thursday, Jan 20, 2005 at 09:51

Thursday, Jan 20, 2005 at 09:51
Dear Paj
Solar panel manufaturers are a sneaky lot. They quote the watts at 19-20V which means for most real world situations you have to derate the output. The Solarex 40w pannel will put out a max of 2.37A. The 3.1A you measured is not possible from a 40w pannel, but from the size you have given I carnt see it being much more.
Cheers John
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FollowupID: 353013

Reply By: Member - Jimbo (VIC) - Thursday, Jan 20, 2005 at 08:01

Thursday, Jan 20, 2005 at 08:01
Paj,

Make sure that the regulator you get is designed to charge Gel Batts. The Morningstar, SS-10L-12V, that I have has a clip which when fitted dops voltage to 14.1 for Gels, or removed 14.4 for normal wet cells, cost $115. It's a 10 amp job.

A call to the bloke at Federal Batteries confirmed 14.1 is better for Gel/AGM.

Cheers,

Jim.
AnswerID: 94023

Follow Up By: hl - Thursday, Jan 20, 2005 at 08:20

Thursday, Jan 20, 2005 at 08:20
Hi,

The 14.1 voltage would be for stand-by use. When using it in the field for short periods and continously cycling, the higher voltage would be more appropriate.

Cheers
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FollowupID: 352984

Follow Up By: Member - Jimbo (VIC) - Thursday, Jan 20, 2005 at 17:53

Thursday, Jan 20, 2005 at 17:53
hl,

That statement is at complete odds with what Morningstar and a National Importer and Disributor of Gel Cells and AGM Batteries recommends.

Might you please explain to us your qualifications for making such a statement?

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FollowupID: 353104

Follow Up By: hl - Thursday, Jan 20, 2005 at 18:03

Thursday, Jan 20, 2005 at 18:03
Hi,
Well, read my post, Jimbo.
I did say short periods and continous cycling. It probably makes no difference anyway, as in that scenario the battery would not reach full charge ever, and setting the regulator a bit higher might give some extra charge.
Most Gel batteries have a standby rating and a cyclic use rating.
The cyclic use voltage is usually .5 to .8V higher than standby rating.
cheers
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FollowupID: 353106

Follow Up By: Member - Jimbo (VIC) - Thursday, Jan 20, 2005 at 19:01

Thursday, Jan 20, 2005 at 19:01
Might you please explain to us your qualifications for making such a statement?
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FollowupID: 353123

Follow Up By: hl - Thursday, Jan 20, 2005 at 21:36

Thursday, Jan 20, 2005 at 21:36
Hi Jimbo,

No particular qualifications, actually.
Just all round genius.

Cheers
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FollowupID: 353151

Follow Up By: Member - Jimbo (VIC) - Thursday, Jan 20, 2005 at 22:11

Thursday, Jan 20, 2005 at 22:11
I rest my case.

You need to heed the words of my dear old Dad;

"Better to keep your mouth shut and be thought a fool, than to open your mouth and confirm the fact".
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FollowupID: 353162

Reply By: Magnus - Thursday, Jan 20, 2005 at 10:10

Thursday, Jan 20, 2005 at 10:10
Paj,

According to the Solarex site it is probably a 20 or 30 watt panel. Check out the site It has pics of their panels that may help you as well as complete drawings etc.

Cheers

Magnus
AnswerID: 94051

Follow Up By: paj - Thursday, Jan 20, 2005 at 18:51

Thursday, Jan 20, 2005 at 18:51
Thanks Magnus, that was my first try, but my panel is not one of the current standard sizes. It is an older unit that has come out of a remotely operated pump station (legally! - the company changes them out every couple of years)

Cheers

Paj
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FollowupID: 353117

Reply By: Mainey... - Thursday, Jan 20, 2005 at 10:59

Thursday, Jan 20, 2005 at 10:59
paj,
If you read the entire Morningstar website you will find that -ALL- tests done actually compare various solar regulators, obviously for showing how much better they believe their regulator is, however I could not find a comparison between a regulated battery and an UNregulated battery.
This however is at the far end of the Morningstar website;

http://www.morningstarcorp.com/support/Why-PWM/why-pwm-6.shtml

ANALYSIS - Are charge controllers really necessary?

“The systems described in this paper have battery capacities equal to -4 days of load requirements and are typical of many PV systems used for residential or outdoor lighting applications. The function of the charge controllers in these systems is to protect the batteries from overcharge or over discharge.

There are PV designs which operate satisfactorily without charge controllers. As an example, when load requirements are much smaller than in the systems described here, it is often economical to omit the charge controller entirely and use a battery with a capacity of ~30 days of load requirements instead.
The U. S. Coast Guard has used this type of design in many navigational beacons. While the batteries in these navigational systems do suffer from the effects of overcharging and over discharging, the relatively large battery capacity allows these systems to continue to operate reliably”

Where you put more into the battery system than you remove you will have a battery in a state of charge, and as has been stated elsewhere and often a battery will only accept the charge required. As to boiling the battery, remember the battery is powering a fridge and various accessories, therefore being Discharged and Recharged continuously, not only being charged during the few 'sunhours' available daily.
AnswerID: 94062

Follow Up By: John - Thursday, Jan 20, 2005 at 12:18

Thursday, Jan 20, 2005 at 12:18
Dear Mainey
I would not recomend an unregulated solar system with the small battery capacity found on 4wd and camper trailers unless the solar panel was less than 10w as a maximum.
As you describe systems can be designed without a regulator using small panels, usually with less than 36 cells to limit voltage and large batteries that have been designed so they wont suffer thermal runaway, but these systems dont have much relavence here.
Even if the discharge is higher than the input it is still very easy to reach damaging voltages. (for example you arrive at a campsite with a charged bat and the fridge has cycled off. Connect a 40W solar pannel and you can reach 18-19V)
Remember this will not only damage the battery, but can fry other connected electronics.
If the discharge out is always greater than the solar input use a cheap regulator. (There is no advantage in using an advanced multi level regulator in these cases.) For $80 its cheap insurance. The regulator wont have any effect on performace ( efficency is typically 95-98%. There is a very small power consumption from the regulator (mA) but they will also typically disconect the panel at night).
Cheers John
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FollowupID: 353054

Follow Up By: Mainey... - Thursday, Jan 20, 2005 at 17:10

Thursday, Jan 20, 2005 at 17:10
John, I can only speak from my own personal experience, as I have only ever used an 80wt Solarex panel without direct regulation for 9 years now, and I am only on my second set of batteries in that time so I believe the chance of frying the battery is not that high!
Note; in that 9 years it is only 7.5 years of constant use (not 9)

Consider your scenario, you arrive at a camp site, and I assume you have driven there with the vehicle alternator recharging the Auxiliary battery at it’s maximum of ~14.2v, it would also be possibly 3.30pm, mid afternoon and according to 0zi, post ID:19129, the 'solar hours' are about to loose all chance of recharging the battery from the solar panel for the rest of that day, if it was late afternoon there would be no 'solar hours' to power the battery, however there would still be many hours of beautiful sunlight left.

With no added power from the solar system the battery would have been discharged all night by the fridge and the lights etc, till the 'solar hours' start again next day, possibly about 10am till 3.30pm, a total of 5.5 hours by the 'solar hours' chart which does cover most of the northern section Australia, when during the day the panel has to restore the charge lost during the night and replace the charge used daily by the fridge.
The voltages you mention are not possible with any of the panels I have looked at?
Another thing to consider is Maximum Volts are not generated from daybreak or even from the start of the 'solar hours' time period, frequently the maximum volts are not generated at all on some days.
hope this clarifies the situation
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FollowupID: 353102

Follow Up By: hl - Thursday, Jan 20, 2005 at 17:38

Thursday, Jan 20, 2005 at 17:38
Hi,

The maximum voltage quoted is the open circuit voltage, and will never exist once a battery is connected. The most you will measure with a fully charged battery and an 80W panel in full flight would be on the low side of 15V. The battery would start gassing, but it would take a fair while to do any real damage. As Mainey said, when you arrive at your campsite in the avo, the first thing that will happen is drain, there will not be sufficient charge from the panel to do any damage to a reasonably big (>60Ah) battery, even if the fridge has cycled off.
So, you can safely save your money.
cheers

0
FollowupID: 353103

Follow Up By: John - Thursday, Jan 20, 2005 at 19:00

Thursday, Jan 20, 2005 at 19:00
Dear Mainey
I think you have misunderstood the meaning of “solar hours”. 5 solar hours means that a typical solar panel will produce 5 times its real A output in AHrs over the total daylight hours. It is a means of allowing for cloud and doesn’t imply that the output is only over 5 hrs in the middle of the day.
At this time of year an 80W solar panel will produce over 3.5A at 3.30 pm. This is enough to raise the bat voltage of a fully charged battery to a dangerous level.
If you are not convinced by my example consider what would happen if your fridge stopped drawing power and you didn’t realize (eg plug pulled out, turned off by accident, broken etc).
The fact that you have run the system for 2 year without damage doesn’t convince me in the same way as if you had shorted all fuses and run for 2 years without problems.If you are always drawing more out of the battery than you are putting in the regulator does nothing, but if the above sort example occurs it will be a lot of expensive damage.

Please at least make sure your battery is well ventilated and has no ignition sources near it.

Cheers John

Dear hl
I guess we will have to agree to disagree. In my opinion An 80 W solar panel will take a charged 60Ahr battery well over 15V. I have personally seen a Voltage close to 17V (and still going up rapidly) on a boat with an 80Ahr gel battery and a 46W “self regulating “ solar panel.
Cheers John

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FollowupID: 353122

Follow Up By: Mainey... - Thursday, Jan 20, 2005 at 20:57

Thursday, Jan 20, 2005 at 20:57
John,
(Quote)I think you have misunderstood the meaning of “solar hours”.
5 solar hours means that a typical solar panel will produce 5 times its real A output in AHrs over the total daylight hours(end quote)

John, can you please post a "Link" to any official site where it is clarified as it would also have other relevant information on similar subject matter.
Thanks…..
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FollowupID: 353139

Follow Up By: John - Thursday, Jan 20, 2005 at 21:39

Thursday, Jan 20, 2005 at 21:39
Dear Mainey
My hard disc fried itself a couple of months ago (perhaps the battery went over voltage :) ) and I can not open many of my scrapbook pages. (they are back up but will not open. Its a macintosh if anyone has any ideas).
This may help however.
http://www.jxj.com/magsandj/rew/2003_05/sun.html
Cheers John
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FollowupID: 353152

Follow Up By: Mainey... - Thursday, Jan 20, 2005 at 23:22

Thursday, Jan 20, 2005 at 23:22
John,
that "link" was also posted in the same thread where 0zi mentioned "solar hours" for the first time, and I reiterate it does not explain the said "sun hours" terminology, also each solar specialist I have contacted are all unaware of the precise terminology of the term “solar hours” but yes they all say “it must be possibly the number of hours per day of practical sunshine available to power a solar panel to generate enough power to recharge a 12v battery”

I believe there would be technical formula to associate with the term “solar hours” and that is obviously what I am seeking here, if it in fact exists.
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FollowupID: 353175

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