Mixing of Solar Pannels

Submitted: Tuesday, Apr 17, 2007 at 22:52
ThreadID: 44433 Views:2036 Replies:10 FollowUps:10
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Hi all,
Just wondering if there is any problem mixing two different solar panels?
For example if you had a 60 watt solarex panel would there be any problem adding a 60 watt sharp panel? These panels would run through a pl20 regulator.

Thanks in advance Chris.

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Reply By: Niffty - Tuesday, Apr 17, 2007 at 23:02

Tuesday, Apr 17, 2007 at 23:02
Cant see any problems.Just mountings to consider.Pl 20 is a great regulator.
AnswerID: 234104

Reply By: Black Shoe - Tuesday, Apr 17, 2007 at 23:31

Tuesday, Apr 17, 2007 at 23:31
I wouldn't think it would make much difference, the electricity would be the same coming from either.
AnswerID: 234118

Reply By: Alloy c/t - Wednesday, Apr 18, 2007 at 07:02

Wednesday, Apr 18, 2007 at 07:02
None at all [problems] that is , I have a 120w Kycera and a 64w Unisola running thru a Steca 20 regulator no problem.
AnswerID: 234141

Reply By: Robin - Wednesday, Apr 18, 2007 at 08:03

Wednesday, Apr 18, 2007 at 08:03
Hi Chris

Electronically they can be paralled together without issue because they have internal diodes so current only flows one way.

Different panels may have different open circuit voltages but they can be roughly modelled as constant current sources so while not perfect this doesn't matter or effect there ability to deliver current to a load much either.

Type of regulator won't make much difference in the mid cost end of the market like PL20's are - but if doing it again I'd buy a regulator whose clock has a least a bit of battery backup as PL20's are a pain if you try to use all their internal features.

Robin Miller
Robin Miller

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AnswerID: 234155

Follow Up By: Russ n Sue - Wednesday, Apr 18, 2007 at 10:05

Wednesday, Apr 18, 2007 at 10:05
G'day Robin,

I have a PL20 and use almost all of its internal features. I don't have any issues at all. Frankly I don't understand your final paragraph because if you set up the low voltage cutout for your load, there will always be sufficient supply to run the PL20.

It was a bit of a pain setting up theRS232 interface for the PC but I got there in the end. Had nothing to do with backup battery or internal clock though.

What circumstance were you thinking about where you would not be able to use the internal features?
FollowupID: 495053

Follow Up By: Robin - Wednesday, Apr 18, 2007 at 10:52

Wednesday, Apr 18, 2007 at 10:52
Hi Rus or Sue

Its been a long time since I have seen a product with no battery backup on its clock but if your familiar with product then you may know that they state that the expansion board is required to fully implement its 6 internal functions.

However they did not proceed with development of expansion board , and its a little hard to work out which are and aren't as reference documents make "interesting reading" and if you say, try and set the time while your experimenting and go one step over your time you have to press the set button 250 times to get back to where you are because it only counts decimal time and in one direction due to its single button operation.

I'm trying for instance to have something turn off for a few hours after midnight
and while this can be done , it appears not compatiable with the low battery volts disconnect function.

I.E. Under some conditions you can have one or the other but not both.

If you have an easy solution to this I'd love to know

Robin Miller
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FollowupID: 495058

Follow Up By: Russ n Sue - Wednesday, Apr 18, 2007 at 16:27

Wednesday, Apr 18, 2007 at 16:27
G'day again Robin,

I guess it depends on what you call easy. I have set my PL20 up to be programmable from my laptop. It works a treat and means that I simply set the value I want, press a button and the PL is updated. Real easy.

The hard part was getting it going in the first place - took several hours and several tries at configuring the interface cord, but now it works well.

Reply to me if you would like any info on how to set this up.


FollowupID: 495143

Reply By: Jimbo Vic - Wednesday, Apr 18, 2007 at 09:50

Wednesday, Apr 18, 2007 at 09:50
As long as you regulator will handle the combined amps, all should be OK.

After all, they are both providing DC power regardless of the brand of panel.


AnswerID: 234176

Follow Up By: Black Shoe - Wednesday, Apr 18, 2007 at 17:49

Wednesday, Apr 18, 2007 at 17:49
yeah but if the voltage is out of phase couldn't there be some negative feedback resulting in some smoke. ?
FollowupID: 495170

Follow Up By: Alan Southport QLD - Wednesday, Apr 18, 2007 at 18:34

Wednesday, Apr 18, 2007 at 18:34
Black Shoe,

As far as i know (AFAIK), there is no 'phase' issue with DC.

There is with AC.

But as in the OP, there will be no problem at all connecting different brands and watts together - as long as the Solar regulator can handle the watts.

Cheers Alan.
FollowupID: 495194

Follow Up By: Grungle - Wednesday, Apr 18, 2007 at 18:47

Wednesday, Apr 18, 2007 at 18:47
Hi Blackshoe,

PV voltage is DC so has no phase. If you mean reverse polarity then the regulator will need some sort of internal protection to protect itself as the panel is the source and not the load so will not care. Even if you short a panels +&- leads together it will not blow/kill/destroy itself.

Panels (should) have diodes across the panels outputs (within the junction box) that both allow no voltage to be dissipated back into the panel when dark (blocking diode) and also thermal destruction caused by partial shading or cell damaged (bypass diode).

I have seen the panels voltage get to less than 2V trying to charge a series/parallel bank of 6V 225AHr batteries in one of our repeater trailers.

FollowupID: 495200

Reply By: Mainey (WA) - Thursday, Apr 19, 2007 at 13:37

Thursday, Apr 19, 2007 at 13:37
Chris, as stated there is no problem with either brand of panel being connected in parallel.

I use a 80w Solarex in parallel with a 123w poly-crystalline Sharp panel, via a Stecca solar reg, the pl20 has similar characteristics.
AnswerID: 234472

Reply By: Cobes - Friday, Apr 20, 2007 at 01:28

Friday, Apr 20, 2007 at 01:28
Thanks for all replies.
I now feel confident in buying a Sharp panel to add to my Solarex.

Thanks once again.

AnswerID: 234659

Follow Up By: Mainey (WA) - Friday, Apr 20, 2007 at 22:01

Friday, Apr 20, 2007 at 22:01
how are you going to mount the two panels, as in, side by side or end to end etc.

Do they both have to be the same length or width ??
Are they going on to the roof of a vehicle or a caravan etc ??

FollowupID: 495806

Reply By: Cobes - Saturday, Apr 21, 2007 at 01:41

Saturday, Apr 21, 2007 at 01:41
Hi Mainey,
I will try not to be too long winded.
I currently have 2 x 60watt solarex pannels joined side by side and i Place them on a pole attached to my drawbar on my cub camper trailer.
I run a 40 litre engel as a fridge as well as a 50 waeco as a fride or usually freezer.
The combined pannels of 120 watts is not enough to charge my 2 x 90 amp hour batteries and run the fridges at the same time. I am considering buying a 125 watt Sharp panel for less than 1k which should enable me to be totally power sufficient when in remote areas or at unpowered locations. If I buy the Sharp panel I will probably make a small stand to allow me to rest the pannel on the ground facing the sun.

AnswerID: 234880

Follow Up By: Russ n Sue - Saturday, Apr 21, 2007 at 07:01

Saturday, Apr 21, 2007 at 07:01
G'day Chris,

Your set up will pretty much end up being the same (electrically) as what we have. We have a 40W and 50W Waeco and run the 50W as a freezer. We have two Sharp 123W panels that I carry on top of the Kimberley Kamper when travelling and lay on the ground when I get to our destination. We have 300AH of AGM batteries and this set-up enables us to go indefinitely without the need for a 240Volt supply.

I have found that I needed a 15 metre cable to get the panels far enough away from the camper to get them out of any shadows from trees, the camper itself and so on. To avoid volt drop I used 13 sq mm cables. I have also found that to get a really good charge into the batteries it is best to change the angle that the panels are facing about three times during the day if possible. I set them up at about 7AM, then change them again at around noon and again at around 3PM. (This is only if we are at the camp of course, otherwise I just leave them facing North if we are going away for the day.)

By doing this my batteries are usually on float by around 2 PM and I use the spare capacity available in the afternoon to run my water pumps and any 240 Volt gear through the inverter. (You know, battery chargers for cameras, phones, torches etc and about once a week we run a Lemair 2.2 kg washing machine.) We also run 12 Volt fluoro and LED lighting.

Our Sharp panels work really well and the Solarex/Sharp combo that you have should perform equally as well. If you use a regulator that keeps track of your charge and discharge AH, the battery voltage and your load and charge Amps you should be OK. These readings assist me to decide when I can run the more demanding electrical equipment.

happy travels
FollowupID: 495854

Follow Up By: brett - Saturday, Apr 21, 2007 at 21:54

Saturday, Apr 21, 2007 at 21:54
As the solar panel is a constant current source and the output voltage can be above 18V I thought voltage drop was not a major issue, you can afford to drop 3V from 18V and still be above your charge voltage so I would imagine you wouldn't need 13 sqmm wire.
FollowupID: 495999

Reply By: Cobes - Saturday, Apr 21, 2007 at 11:02

Saturday, Apr 21, 2007 at 11:02
Hi there Russ,
Sounds as though you have a great kit!
I have a couple of questions that I hope you can answer for me.
What type of regulator do you use and do you have a shunt runnung through it to enable you to see what your inverter useage is or do you just connect your inverter directly to your batteries? (I use a pl20)

Also do you find your battery capacity of 300 amps adequate?

We currently have only 180amps of wet cell battery capacity and I know that when I get my new panel (increaing from 120watt to 240watt) I will have to increase my battery capacity.
My current batteries are about 4 to five years old and are still working as good as new.
Do you think that I should purchase another 90amp wet cell or would the age difference be a problem and suggest purchasing an entirely new battery bank?

AnswerID: 234911

Follow Up By: Russ n Sue - Saturday, Apr 21, 2007 at 14:10

Saturday, Apr 21, 2007 at 14:10
G'day Chris,

I run a Plasmatronic PL20 as it matches the theoretical 20A maximum out of my two Sharp panels. I use a 200A shunt so that I can include the inverter usage in the overall discharge Amps/AmpHours. The shunt is bi-directional so I have set the battery charger up to charge the batteries via the shunt as well, thus I include the charge current when I have 240V available. I got the shunt kit, complete, from the 12 Volt Shop here in Perth. I can't remember how much it cost.

I also got the PC interface kit while I was at it. This enables me to use the laptop to change settings or monitor the status of the PL20 without having to push the button a million times. It was a bit fiddly to get going but once I had it sussed it was OK. (It was a case of "yeah I knew that" when I finally figured out why it wasn't working.) The PC interface and the shunt can be used simultaneously even though they have a common plug at the PL20 end.

300AH is all the battery I can fit into the camper, but I do have another 50AH second battery in the car that I could use at a pinch. My fridge/freezer combo use about 65AH per 24 hr day - about 22% of my battery capacity. This figure is a little distorted as the fridges are effectively running from the Sun most of the day and only use about 35AH after the panels stop providing energy. I guess realistically my depth of discharge is somwhere between 12% and 20%.

According to my info the batteries I have should last 2500 cycles at that depth of discharge, or about 7.5 years. We will be using batteries nearly all the time when we are travelling as the $4 or $5 we save per night by not needing a powered caravan park site will quickly build up to the point where we will have saved enough to replace the batteries and have money to spare.

None of the above allows for cloudy days and the gradual degradation of the batteries but essentially I have quite a bit of headroom.

To answer your question about the batteries you have, it doesn't make much sense to increase the capacity to charge batteries and then not take advantage of it. And that does introduce a new dilemna. The concensus of opinion among battery manufacturers and the reference material I have read is that all batteries in a battery bank should be of the same age, chemical make-up and condition. While you can add more cells, their internal resistance characteristics will be different.

Even if your batteries appear to be as good as new, the only way you could find out for sure is do a discharge test at, say, the 20 hour rate and see how they really perform.

I worked for a communications company and in the early days the theory was "one out, all out" when it came to dud cells in a battery bank. As time went by and Bean Counters had more influence over how things were done, we started changing individual cells as required. It wasn't an overly successful policy and subjectively I would say that it tended to accelerate the demise of the remaining cells in a bank. (The thing is, were they going to fail anyway? Hard one to prove.)

Certainly good quality AGM batteries are not as expensive as they once were, so if you can afford to replace them, that's what I would do.
FollowupID: 495918

Reply By: Cobes - Saturday, Apr 21, 2007 at 15:26

Saturday, Apr 21, 2007 at 15:26
Hi Russ,
thanks for all of your valuable and informative information.
I will have to sit and ponder for a bit while i decide which way to go re batteries etc.
I will however get a price from the 12 volt shop for their pc connection and a shunt.
If it is not too expensive i should be able to justify the purchase.

In relation to the batteries in the short term I might use the current ones until they expire which might only be another 12 to 18 months away as they now get fairly discharged with my current useage patterns when camped in un powered sites.
Although after purchasing the sharp panel at least they will be completley recharged at some point during the day.

It think that it may work out cheaper that way in the long term.

Cheers again.


AnswerID: 234940

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