last van had 1 x 50 w and 1 x 80w ex Yachts. 2 x 85 w new. Plus 1 x 85w floater. through 30a Reg. never a problem in 14 yrs of usage. Battery's always floating by lunch. (2 x 110 AGM) As long as they all inside v'age limits with a decent reg, and H\Duty wiring. You won't have a problem. They all trip out at around 17+ and float around 14.2ish v. Reg's normally cover to 24\28v. some 48v. The operative word being "UP TO" so many volts. and inside max combined amps.
This van has 200w wioth same 85w floater. They work ok together through same reg.
Now some will probably come up with all the figures to suit. Me. I just keep adding till I have enuff. or get a red light. Then back off a bit.
Over 40 yrs..Still works for me..
-- Edited by macka17 on Monday 22nd of May 2017 06:16:35 PM
In very simple terms can some body explain why/if panel output is effected if mixing panels.
Eg: 120watt with 80watt.
Thanks in advance.
Kezngaz.
Hi Kengaz
If the panels have similar output voltages then you can run any wattage panels in parallel together. Big or small. They only have to be similar really, not identical either.
In the past like others I have used combinations of 40 to 100 watt, 2, 3 and 4 different panels together without any problems. Even mono and polly crystal too. Panels are not picky like people can be about their specs They just work when the sun is out !
I am led to believe that you must only have the one regulator
All the panels must be wired, as others have said, in parallel
All the positive (red) wires must go together, and all the negative (black) wires, must go together
These wires are then fitted to the regulator
If each panel was to have its own regulator, then one regulator would think that the battery was fully charged, as it would be reading the voltage from the other regulator
If I have got this wrong, then I hope that others will come along and correct me
A single panel, of any wattage or size, is a package of lots of individual solar cells. Those cells are wired into parallel and series strings and grids to result in a designed or specified output voltage at the panel terminals. Multiple panels are no more than a number of packages of individual solar cells. If paralleling panels of different nominal power specs, it is best to try for panels that have a similar Open Circuit output voltage. In use, the short circuit current output from different wattage panels will vary in proportion to the the nominal wattage of the individual panel.
Iza
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Iza
Semi-permanent state of being Recreationally Outraged as a defence against boredom during lockdown.
Hi all and thank you.
My understanding is, as long as all individual panels have an open circuit voltage of above 14.8 and all panels go through the same regulator, then there shouldnt be a problem.
All the amps add up together and the lowest voltage becomes the total output voltage.
Thanks once again to all.
Kezngaz.
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Commitment shows. Quality is what is done when no one is looking.
But there is conjecture from very knowledgable folks as too why. Others have posted of issues with one controller coming off float or bulk and the other staying, etc, during cyclic loads whilst also charging.
My rig has two 30 amp controllers side by side, inputting to different ends of the battery and it works fine. Initially they were both inputting into the same terminal and they argued with each other.
IF you want to do it then be prepared to observe the chargers a bit to ensure they do not compete with each other under all conditions. Ensure your system has independant over-voltage battery protection.
So the bottom line is that it can certainly work but its probably not a project for beginners.
In the light that I am not an electrician, but eager to learn about 12 volt systems Can you please give a link to an independent over-voltage battery protection switch, for AGM batteries
The ones I found on the internet, all mention lithium batteries I have only found, low voltage cut off switches, (for AGM) to stop a battery draining
My CTEK DC/DC solar panel/engine battery charger, relies on a heat probe near the positive terminal of the battery, which is supposed to stop thermal runaway, if the battery gets too hot due to (I assume) overcharging
Panels of different output watts, Vmp and different amp outputs can be linked in parallel using a PWM type regulator and all will be fine. You can not do the same thing with an MPPT controller, in parallel the panel with the highest Vmp will take control to the detriment as far as output from the other panels. I have such a set up here at the workshop at the moment, 2 x 250w x 30.5v VMP (STC) and 1 x 195w x 36.7v Vmp (STC), all connected in parallel to a MidNite Solar KID MPPT controller. These controllers are up there with the best on the market, the KID just has less features than the Classic model but still has all the good gear in side. One of the 250w panels is on a roller slide so it can be deployed when free camping but slide back in and over the top of the 195w panel for travelling. With the 195w panel covered by one of the 250w panels the solar harvest from these 2 x 250w panels is around the 25 amps @12v nom. mark, when the 195w panel is exposed the solar area goes up to 695w yet the harvest drops to around the 11 amp mark. Why? The 195w panel has a higher Vmp so the MPPT controller uses that as the reference voltage, 36.7v is very close to the 37v open circuit for the 2 x 250w panels, so they produce virtually zero output.
If the panels were in series the combined voltage would be 97.7v STC, but the 2 x 250w solar panels would be restricted to 195w each max because the smallest panel in the series string is 195w.
As far as this system is concerned, the only real fix is to either replace the 195w panel with a 3rd 250w panel with the same Vmp, or, a second MPPT controller that can be linked in a master/slave configuration for the 195w panel. Far cheaper to replace the panel but unfortunately it won't fit in the spot where the 195w panel is mounted, so over $1,000 for the second controller and linking cables.
This is yet another example of designing the solar array with expansion in mind, you can simply add any size panel to a PWM style controller or have multiple PWM controllers working together, to add a second MPPT controller because mis-matched Vmp to battery voltage panels were used becomes very expensive as only the top of the line MPPT controllers are designed to work in master/slave configuration.
Yes, the Victron 100/30 MPPT controllers can be linked in master/slave configuration but it requires quite a lot of other Victron gear to be purchased and quite a bit of reprogramming to achieve it so not a simple or cheap option, but at least it is an option that has now become available, there was no way of doing it previously.
T1 Terry
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" 2 x 250w x 30.5v VMP (STC) and 1 x 195w x 36.7v Vmp "
Hi
Thanks Terry for putting that up. When I said any similar panels would work together and I have done so successfully, I did not attempt to do what is described here.
It is unwise to link two different type panels which have VMP which differ by 20%. In fact I would go further and say the first panels are house type panels with only 60 cells and the other is a regular 72 cell panel for battery charging. The problem is not the MPPT regulator getting confused but the silly match. I see it is into a 12V battery system so a MPPT regulator is required to make the big panels work into them. Perhaps the answer is to short out some cells in the odd panel ??
So lesson to learn is be reasonable in your selection of equipment, just like you do with your tug or caravan. If you know nothing then ask someone who does for advice first !!
Jaahn
PS the easy answer is to get another 60 cell panel which fits in the required space.
-- Edited by Jaahn on Tuesday 23rd of May 2017 06:51:35 PM
That also answers the question I came on here to ask, unfortunately it's not exactly the answer I was looking to get.
I'm in the situation where I have two 140 watt panels on the roof of the van going to a MPPT controller, and a folding 120 watt portable panel with a separate ? controller which I believe is not doing much good plugged straight into the battery as is, and a pain to cart around when you have storage space issues.
So I was going to also fix them on the roof and just wire the panels in parallel with the other two panels running the lot through the existing MPPT controller but reading what has been posted it's obviously not a real good option.
Cheers, Tom
-- Edited by greyhoundtom on Wednesday 24th of May 2017 05:00:32 AM
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I had a thought but it got run over as it crossed my mind.
Hard to say whether it will work or not without more information. If the VMP of both types is similar then it probably will be good. Google the information or look at the panel specs with a mirror or a phone camera. Look at the panels and count the individual cells as they sit in their visible grids. If the cell numbers are the same, normally 30/60(12/24V) or 36/72 then you are at first base OK. There are some other cell numbers for house panels but not common.
Jaahn
Of course the portable controller/regulator has to be removed and some decent wires run to your MPPT reg.
The latest issue with these Midnite Solar Kid MPPT units, the wire connections are suited to 4.35mm sq cable, fine for the solar in as it is at high voltage and low current, but the battery out cabling is the same size where the voltage is only 12v nom. and up to 40 amps..... through 6mm auto cable? Add to that the voltage sensing is internal rather than separate voltage sensing wires..... what were they thinking to make such silly mistakes on a high end unit?
T1 Terry
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You can lead a head to knowledge but you can't make it think. One day I'll know it all, but till then, I'll keep learning.
Any links to any sites or products is not an endorsement by me or do I gain any financial reward for such links
Thanks Jaahn, much appreciated and will check it out a bit more thoroughly.
PS. Sorry about the late reply but being on the road full time can at times make an internet connection a bit unreliable.
Cheers, Tom
Further to the above; I checked both types of panels, that is each half of the folding panel and each roof mounted panel has 36 individual cells. Which i believe gives me a couple of options to make the solar system a little bit more efficien, and that is to mount one half of the folding panel next to each of the roof mounted panel and connecting it in parallel, or running the appropriate wiring from the controller to an Anderson plug on the drawbar and connecting the folding panels minus their controller to that when circumstances demand additional and better sun focussed solar input.
Thanks for your help.
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I had a thought but it got run over as it crossed my mind.
Good news ! If they are all the same number of cells then they will run in parallel OK. If you want to use the portable controller then I would remove it and wire it so it is as close to the battery as you can get it. At the anderson plug connection if that is your best plan ! If the batteries are down below controlled voltage, having two will be OK.
The MPPT regulator may work OK with the 4 panels in parallel too. Depends on the regulator. Most cheap MPPT regs are not really MPPT so ?? Try it and monitor the current output, while throwing a rug over each pair at a time. Let us know ! Hard to say from my computer keyboard, not having seen your setup
We have a 19' Roadtrek and there is very little real estate for solar. So our son designed and fabricated a system that utilizes a 315 W and a 100 W panel. This required two separate MPPT controllers which send power to 4.8 kW-hrs of LFP (two batteries of CALB cells at 12 nominal in parallel). This has worked extremely well on 14 weeks in Newfoundland and Labrador and then 14 weeks in southern and western Mexico.
5th wheel has, as written on earlier posts, 1400 W of solar which is sent at 90 V to MPPT controller to 9.5 kW-hrs of LFP at 48 V nominal.
Reed and Elaine
They just work when the sun is out ! 
There are some other cell numbers for house panels but not common. 
