2nd solar panel connect together or wire up separately

Submitted: Friday, Dec 07, 2007 at 14:22

Member - michael H (NSW)

Have just purchased another 64w panel and want to know your thoughts /preferences/ideas how to wire up.
The panels will be transported on top of a trak shak camper without rack system or on top of car.
If I wire them up seperately I could take 1 or both or spread them around campsite to chase the sun or if away for the whole day face 1 east & 1 west (laying flat on ground ideal but then it could be stood on or driven on)I have mounted an old adjustable tent pole to prop up and if at camp I could adjust as needed.
On the other hand the first panel has a pl12-10 regulator which may be O.K for both panels ?? If not I'll buy a bigger regulator then all I have to do is chuck some hinges on them set them up and forget. Any feedback will be appreciated

Thanks Michael
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AnswerID: 275497   Submitted: Friday, Dec 07, 2007 at 14:34

Member -Signman replied:

From my understanding to align solar panels...Is to lay them facing North, tilted at the approx. latitude. That means (say) Sydney the angle would be about 34 degs, Brisbane about 28 degs- and if you were on the Equator they'd lie flat..
I assume there would be some variance from summer/winter.

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FollowupID: 539255   Submitted: Friday, Dec 07, 2007 at 16:30

Member - michael H (NSW) posted:

Thanks Signman, Gee I must have looked funny last year on hols moving the panel around every 10 mins following the sun (na not really). Facing north well now I know.

Thanks Michael
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AnswerID: 275500   Submitted: Friday, Dec 07, 2007 at 15:17

bruce replied:

If you lay them flat on the ground you will only get approx. half the output...facing north at approx. 45 degrees .....depending on where you are , is in my experience gives best output..and of course they must be in full sun . I made up a bracket leg that is attached at the back on a hinge and a length of rope back to the bottom of the panel , just pull the leg out and it is set at the said 45 degrees....we only move it about 3 times during the day to keep it more or less pointed at the sun...it is a 85w suntech...cheers
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FollowupID: 539259   Submitted: Friday, Dec 07, 2007 at 16:39

Member - michael H (NSW) posted:

Hi Bruce, I have a bracket already on an old adjustable tent pole but that length of rope is a good idea.

Thanks Michael

ps. I have loaded a couple more piccies in my rig pics of the solar panel set up. I'm always looking at other peoples rigs and setups to get ideas that suit my type of camping
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FollowupID: 539352   Submitted: Saturday, Dec 08, 2007 at 09:50

bruce posted:

Another..trick ? is to have the panel/panels sitting length ways on ground...especially a glass panel like mine , then if they/it do/does happen to fall or get knocked over then they/it have not got so far to fall and hence less chance of damage...cheers
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AnswerID: 275557   Submitted: Friday, Dec 07, 2007 at 21:24

Member - John and Val W (ACT) replied:

Hi Michael,

My technique for optimum angle - Adjust so that the panel throws the biggest shadow, i.e. intercepts the maximum amount of sunlight. The angle is not very critical. (A mathematician would point out that we are dealing with a sine curve, and that's pretty close to it's maximum over a fair angular range.)

Wiring - I use 2 panels. Simply wired in parallel. You won't exceed the 10 amps which (I think) your controller is rated at.

I find moving panels to follow the sun is worth doing a few times per day, certainly not as frequently as every hour.

An interesting fact that I'd overlooked until recently -
My camp uses about 35 Ah per day. A 60W panel will provide about 3.5 A in good sunlight, that's about 20 Ah per day, which is some help. With my 130Ah storage (and using only 2/3 of that in order to preserve battery life), I can remain stationary with the 60W panel for about 5 days instead of 3. If I could harvest 40 Ah per day I'd have ample to last until the sun stops shining. I've added another 85W panel, and now have more electricity than I need. The two turn in about 9 amps in full sunlight, over 50 Ah per day, so aiming them accurately at the sun is not an issue - I can afford to be suboptimal.

(I expect an argument about the above statement that a 60W panel only supplies about 3.5 Amps. Fact is it's a fact! Solar panels are rated at their highest power output, which occurs at about 17.5V. Hence a 60W panel provides about 3.5A x 17.5V = about 60W. But for battery charging we can only use up to about 14.4V, not the full 17.5. The 3.5 Amps is available, but because of the reduced voltage, the 60W is not.)

I'd suggest that you best approach is to keep the two panels together, both looking approximately at the sun from around 9am to 3pm - simply facing north and angled for biggest shadow should do it. It's important to use heavy gauge cable since you will be moving a few amps and can't afford much voltage drop.

HTH

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein
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FollowupID: 539318   Submitted: Friday, Dec 07, 2007 at 22:54

Gronk posted:

Ahh, the joy of having too much power !!!!!!!

If I could get 2 x 85W panels for $500, then solar would be the go for me !!!!!
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FollowupID: 539320   Submitted: Friday, Dec 07, 2007 at 23:16

Member - michael H (NSW) posted:

Hi John,

Exactly the feedback I was after I might try and see if I can put a plug in the back of the first panel to piggy back the second panel then I have a choice of taking one or two panels using the single regulator and maybe padlocking the two together to slow the honest thief down ha ha.

Thanks again very helpful info

Michael
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FollowupID: 539331   Submitted: Saturday, Dec 08, 2007 at 06:42

Member - John and Val W (ACT) posted:

Hi Michael,

Your piggyback proposal is exactly what I've used. Mine slide into slots on the (custom) roof rack, one above the other. On the road the top one is exposed to the sun and feeds into the lower one which is then connected via a controller to the battery. In camp the two stand side by side and both harvest sunlight. Both have handles on one end. Pass a heavy steel cable through the handles and padlock to the vehicle (trailer in your case) and you have a little security, though as you say, only ok for an honest thief!

The thing I didn't say too well above is that one 60W panel gives an extra day or two, while two 60W panels give permanent independence while ever the sun shines! It's a major step which is obvious, but I only discovered with hindsight!

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein
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