Solar The Solar Panel Thread

Boots in Action

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Mar 13, 2017
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Hi @Bellbirdweb,
ok, I had forgotten about the current generated at the output side of the MPPT controller. Indeed, it could potentially exceed 20A, and I agree a 30A controller would be needed.

So, if I understand this correctly. There are two main issues with respect to specifying a controller for a given panel setup:
1: Maximum input voltage from the array must be less than the Maximum rated input voltage for the controller.
2: Maximum output current must be less than the Maximum rated output current for the controller.

Is that correct?

cheers
Mike
Hi @mikerezny , that is how I understand it. As one TECH HEAD to another, the max input voltage must take into account the OCV too as this can be higher in cooler conditions. So one must allow about 10% for this too in calculating max voltage into MPPT controller. However most of the good MPPT controllers have safety cutoffs to protect system if parameters are exceeded.
 

Bellbirdweb

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Hi @Bellbirdweb,
ok, I had forgotten about the current generated at the output side of the MPPT controller. Indeed, it could potentially exceed 20A, and I agree a 30A controller would be needed.

So, if I understand this correctly. There are two main issues with respect to specifying a controller for a given panel setup:
1: Maximum input voltage from the array must be less than the Maximum rated input voltage for the controller.
2: Maximum output current must be less than the Maximum rated output current for the controller.

Is that correct?

cheers
Mike
@mikerezny, yes as I understand it, those are the 2 considerations.

Because the MPPT controller uses the additional volts and turns them into additional amps on the charge side, it would be necessary to ensure that current is catered for on the specification of the controller.
 
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Drover

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Hi @Drover , I too have seen solar controllers down that cheap and these are usually the PWM type with few if any settings. Suitable only for the back of some solar panels, I have also seen supposed MPPT controllers around the $50.00 mark and even cheaper, but these are DEFINITELY not genuine MPPT controllers in operation. I am sure you have seen many of the tests on Utube and that sorts out most of them as a waste of money. The MPPT controller that @Crusty181 has seems pretty good and looks very much like the LD Tracer Dream Series that I bought earlier. I paid a little more (at the time) because the specs suited what I wanted and the thought of a 2 year Australian warranty was comforting. At their going price of $200.00 now, I would not buy it, so I think @Crusty181 has a good deal as there are lots of "user " settings to adjust to your own requirements. @Bellbirdweb bought the Epever and seems to be satisfied, so I hope @Axl has the same satisfaction whatever unit he eventually buys. Go MPPT owners!!

@Boots in Action , the controller I was talking about being $10 was the type and brand that was being discussed that in Australia was being sold for $160 to $170, I would be a bit suss as to whats inside though.....................................................I don't buy direct from China and prefer to get Lecko stuff from known good Ebay places like Autoelecau , especially when paying big dollars, good quality with a real return process plus you can ask them something and get an answer .
 

Drover

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This forth coming tour @Boots in Action I will try and see what my sort of figures my controller works at without the boost from the portable panel, I know the Pro Star will work better than the TPS ? controller on the portable, it may lead to a MPPT for the portable and the TPS going to the ute, just have to work out if there will be a real gain that's worth shelling out the $$$$.....
If on a normal sunny day everything is back up to speed by 1000, then I don't think its justified, with week long stops plenty of off grid time to check the upgraded system out. Mind it won't be in anyway as detailed as your efforts....
 

Crusty181

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Just thinking out loud, I have an MPPT controller in the van connected to the vans roof mounted panel, and my portable panel has a PWM controller which I only ever use for the Engel (and never connect to the van). If I did connect the portable panel via its PWM directly to the van battery which is already receiving a charge from the vans MPPT; without load on the batteries would the higher MPPT voltage across the battery terminals trick the portable panels PWM into providing a higher rate of charge to match the higher rate of charge provided by the MPPT. This is either so technical advanced and revolutionary its beyond anyones comprehension ... or just not

Should I just shut up and crawl back under my rock?
 

Axl

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Dec 23, 2014
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I like your rock idea.....

From what I understand if you hook two regulators up to the same battery they will fight against each other and not do very much at all, happy to be proven wrong though. One delivers the other sees this and backs out then the first one backs out and the other delivers so on and so on, it becomes quite a s$^t fight between the two.
 

Crusty181

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I like your rock idea.....

From what I understand if you hook two regulators up to the same battery they will fight against each other and not do very much at all, happy to be proven wrong though. One delivers the other sees this and backs out then the first one backs out and the other delivers so on and so on, it becomes quite a s$^t fight between the two.
From my 6min of extensive research I just did on Google "can 2 seperate solar controllers be connected to the same battery" , the Inter-Google-Web has returned resounding yes you can. A couple of manufacturers of massive commercial solar arrays spoke about doing so as a matter of necessity, with a few over-riding qualiifiers about the batteries ability to handle the current etc etc

The PWM controller charges at just above the current state of charge. The voltage across the battery without a load whilst being MPPT charged would have a higher apparent voltage. Would the PWM controller react to the apparent voltage across the terminals, as opposed to actual state of charge. I presume the PWM controller can only see what a multi meter would see, and that would be the higher voltage of the MPPT controller
 
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Boots in Action

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Just thinking out loud, I have an MPPT controller in the van connected to the vans roof mounted panel, and my portable panel has a PWM controller which I only ever use for the Engel (and never connect to the van). If I did connect the portable panel via its PWM directly to the van battery which is already receiving a charge from the vans MPPT; without load on the batteries would the higher MPPT voltage across the battery terminals trick the portable panels PWM into providing a higher rate of charge to match the higher rate of charge provided by the MPPT. This is either so technical advanced and revolutionary its beyond anyones comprehension ... or just not

Should I just shut up and crawl back under my rock?
Hello @Crusty181 , not a silly question at all!! Connecting two solar controllers to the same battery is like having two cooks in the kitchen . One likes his steak rare and eggs sunny side up and the other one wants his steak burnt black and eggs flattened and dried out. One wants his meal in a hurry and the other is a connoisseur and wants to take his time!! Remember the movie "The Odd Couple"?? Well that is the best example of how to explain what can happen. The greater the difference in solar controllers and settings (made either at the factory and fixed, or user adjustable and different brands), the greater task the controllers have in sorting out charge and voltage requirements and meeting changing load conditions. It may not be particularly evident, but that is what would be happening. I would NOT recommend it under normal circumstances even if it "looks" okay.

DEFINITELY NOT not a good idea to try that with two different types of controllers ie PWM and MPPT. The PWM type drags down the panel voltage to just above battery voltage to charge at what ever the input current is. Any excess voltage from panels above battery voltage is just wasted. In fact, with a Pulse Width Modulation Type, it is really just a switch between the panel and battery, turning on and off as necessary. Whilst charging, it is basically "ON" all the time until charge voltage setting is reached and then it switches "ON " and "OFF" keeping the battery at the set float voltage. But this changes all the time according to load factors which drops the voltage and makes it start charging again to make up what has been taken out and caused voltage to drop. It is a lot more complicated than that too if you want to take in temperature of components and battery. There is a different (best) charge voltage for batteries in all conditions - the hotter the battery and or ambient temp, batteries require a slightly lower charging voltage and in colder times, a slightly higher voltage is optimum. But I digress - sorry!!

An MPPT charger is constantly changing the input current to the battery by converting any excess voltage from the solar panels into extra current (amps). This is IN ADDITION to the current being produced directly by the solar panels. Let's say that the solar panels are producing 10A on their own, but there is 6 volts from panels above the battery voltage which is SENSED by the MPPT controller.( Panel charging voltage to controller is 19V but battery voltage (sensed by controller ) is 13 volts.) The MPPT controller DOES NOT WASTE THIS EXTRA VOLTAGE (like the PWM type does), but converts this excess voltage into additional amps to add to the 10 amps already available from the panels. And this is happening all the time, constantly adjusting current available to charge or carry the load placed on electrical system. The greater the differential between the panel voltage and the battery voltage, the more spare volts are available to be converted to extra amps. So the lower the battery voltage (say only 11.8V (near battery disconnect?) and the higher the input voltage from panels, the more amps you get and the faster your battery/ies are recovered by charging. MPPT stands for MAXIMUM POWER POINT TRACKING and that is exactly what it does!
@Crusty181 , in an earlier post which even @Drover thought was a good idea was to bypass the controller on portable panel with a separate lead and Anderson plug and connect this lead from portable panel in parallel with the existing input line to your MPPT controller. So you end up with two leads hanging off the back of your portable panel - one that goes through the existing panel controller which is still suitable for charging other things, and the new cable from the portable panel (bypassing the controller on the back) which you can easily join into existing system and not lose any of the original properties/uses.

God this has been an epistle!! I hope this covers all the bases and I have not lost too many. Some "Tech Heads" cannot help themselves. Sorry!!
 
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Boots in Action

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This forth coming tour @Boots in Action I will try and see what my sort of figures my controller works at without the boost from the portable panel, I know the Pro Star will work better than the TPS ? controller on the portable, it may lead to a MPPT for the portable and the TPS going to the ute, just have to work out if there will be a real gain that's worth shelling out the $$$$.....
If on a normal sunny day everything is back up to speed by 1000, then I don't think its justified, with week long stops plenty of off grid time to check the upgraded system out. Mind it won't be in anyway as detailed as your efforts....
Hello again @Drover , I am looking forward to YOUR report on what is happening with the van charger/batteries in varying conditions. There is no great difference in output efficiency between various PWM controllers. The better ones have lots more user friendly settings and displays etc to supply info to user, but not much different in output - component quality notwithstanding. However with an MPPT controller, you are talking about an entirely different technology. Like comparing carburettor power with fuel injection. Both will give you power, one just does it better and more efficiently. Your recordings are handy to have, but you are not trying to prove anything. I WAS with my detailed MPPT reports, and that is why I did so much field testing for myself, so I could put it to the other Tech Heads on this forum who are pretty switched on, and mostly have more electrical technical experience than me. But I learn fast and do a lot of research, pester expert electrical engineers with many years' experience in solar and am able to glean a lot from their own situations faced. Only then do I have the temerity to offer my ideas which have worked for me and MAY work/be useful to others who want to see what they can do. There is nothing as good as passing on tested and proven information which will help others, just like you have done on this forum!!
 

Boots in Action

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been thinking about getting extra solar panels for when needed -

looked at these on Fleabay

any good?

https://www.ebay.com.au/itm/300W-Mo...at-Charging-USB/272827722742?mi_u=43115721358
Hi @bigcol , had a good look at these panels on Ebay for you. If I had the room to store these, I would have a set. From what is displayed, should be good value. Important things to look for are max charge voltage (18.0 volts), tolerance (plus or minus 10%), rated efficiency (at 17%) and an MPPT controller too. The Platinum Series IS a true MPPT controller, although it does not have all the bells and whistles that individual MPPT controllers may have (those that stand alone and are not connected to the back of solar panels.) I paid $279.00 for a 180w folding panel 3 year's ago( with a bogey MPPT controller attached) and just 12 months ago purchased a 200w panel with an ordinary PWM controller. Although I do not use any of the controllers on back of panels (they are bypassed), the fact that more and more solar panels now have an MPPT controller included says it all. Note that max rated output for panel under Standard Test Conditions is 16.67A, the controller is only rated at 15A, so the output from panel is unlikely to reach the rated max, and the MPPT controller would be at its limit under these conditions, even if allowing for no increase in controller output to battery. Hope you can understand this okay. Try hard and look back at some of the posts explaining how excess voltage (above sensed battery voltage) is converted to extra amps over and above standard output from panels to controller. IMHO, a good buy at that price and what you get for your dollars.
 

Drover

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This green steam is mystical stuff, where before both my roof panel and my portable with seperate controllers worked away happily when everything was connected to the battery terminals, now with everything running off a bus bar type set up with just single cable hanging off the batteries they don't want to play together one will stop charging while the other steams ahead while on the ute, plug the portable in which is direct to the battery the ute panels runs okay......................next time I run the Genny I think I will make up an anderson bypass controller lead for the portable and run an anderson from van controller to chassis to plug the portable into and the van controller will run both that will allow the portable to be still portable for other tasks..........Anyone want me to do a test on Victron Blue controller ?????????
 

Crusty181

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This green steam is mystical stuff, where before both my roof panel and my portable with seperate controllers worked away happily when everything was connected to the battery terminals, now with everything running off a bus bar type set up with just single cable hanging off the batteries they don't want to play together one will stop charging while the other steams ahead while on the ute, plug the portable in which is direct to the battery the ute panels runs okay......................next time I run the Genny I think I will make up an anderson bypass controller lead for the portable and run an anderson from van controller to chassis to plug the portable into and the van controller will run both that will allow the portable to be still portable for other tasks..........Anyone want me to do a test on Victron Blue controller ?????????
Im about to buy a Victron 75/15 for my portable panels
 

Boots in Action

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Mar 13, 2017
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This green steam is mystical stuff, where before both my roof panel and my portable with seperate controllers worked away happily when everything was connected to the battery terminals, now with everything running off a bus bar type set up with just single cable hanging off the batteries they don't want to play together one will stop charging while the other steams ahead while on the ute, plug the portable in which is direct to the battery the ute panels runs okay......................next time I run the Genny I think I will make up an anderson bypass controller lead for the portable and run an anderson from van controller to chassis to plug the portable into and the van controller will run both that will allow the portable to be still portable for other tasks..........Anyone want me to do a test on Victron Blue controller ?????????
Hi @Drover , this "Tech Head" is smiling broadly at the moment but feeling for you and your problems. It is very rarely that you are so vulnerable to be reminded of what has been put in print on previous postings on this matter. Without malice or prejudice, may I remind you of postings 790,792 and 793 regarding running two different controllers onto the one battery. And I think that post 802 by you is a classic!!! May the force be with you. Every dog has HIS day - sometimes one has to be patient, very patient!!! Do I hear the rattle of the money box getting shaken to see if there are enough shekels to buy a good MPPT controller and then you WILL really will be " all singing and all dancing". Let me know if I can be of assistance in bypassing the controller on portable panel and connecting a separate Anderson plug to connect to van, so you have both panels in Parallel, but controlled by the VAN controller. Cheers
 

Drover

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Yes @Boots in Action you have pointed out these things and I knew you would bite but until I redid things it all worked well way before the post reached 3 digits just a change in situation, and Im talking quite a few years, if I put the solar cables back onto the battery there wouldn' t be a problem...

It is sort of scary that you can quote actual post numbers though.

And no the money box isn't rattling, it isn't a problem just a new direction to take which will require 30 mins of my time, I won't be throwing money at replacing the units .
 
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Boots in Action

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Ive absorbed as much of this as I think is humanly possible. The last time around the school'in many years ago, I wasnt such a conscientious apprentice.
@Crusty181, you can never absorb TOO much on this subject!! Technology is always changing (moving forward??) and we all have to relearn things. We have moved from Flooded batteries to Gel and then to AGM type. But now there are two other types - dearer at the moment - but who knows in the future with Lead Crystal and Lithium?? We have also moved from valve operated electronics to transistor to printed circuits which are getting smaller and smaller. Dick Tracy and his comics of 60 years ago are now the norm! The trouble is as we get older, it is harder to delete "old thinking" and learn "new ways". Change is always hard (for me anyway!) But I am happy to use technology if it makes my life easier too. Sorry, off subject again.
Have a read of post 928 directed to you about how to connect your portable panel into your van system and not have two controllers fighting each other. And you still have the option of using the panel (with its own controller) to do other tasks. That is what I think @Drover will now probably do to overcome his problem for good with NO hassles. The "KISS" principal is always the best!!! Parallel hookup is so simple, but the real step up would be to connect in SERIES - a bit more difficult with the wiring though!!