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Old 02-05-2016, 10:29 AM   #15
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maybe a remote recepticle

Don't mean to hijack the thread but this seems like an appropriate question. I am going to mount 2 100W panels on the roof and have them wired thru a controller. Would it be possible to prewire a recepticle that is wired thru the controller and have the recepticle easily accessible on the outside of the A/S so that you can just plug in a suitcase solar array? That way you can just plug in the extra solar panels or not as needed? Tom
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Old 02-05-2016, 10:38 AM   #16
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For 200w on the roof, combine them and send the cable down to the solar controller location to another combiner box. Then lay cable with a quick connector from that combiner box to outside the trailer for the portable panels. Disconnect/remove any controller on the portable panel. Then connect that combiner box output to the solar controller inputs. Disconnect any controller mounted on the portable panels.

I'm planning to do this hopefully this year; 200w on the roof plus my 200w Zamp portable.

Kelvin
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Old 02-05-2016, 02:44 PM   #17
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Be sure to use an A/B selector switch just ahead of your solar controller, as 2 sets of non-matching panels will not play nicely together into a single controller.


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Old 02-05-2016, 04:55 PM   #18
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Really? So I can't really get 400w with say 2 AmSolar GS100 on the roof and two Zamp 100 of portable running together connected to either a Bogart SC 2030 or a Blue Sky controller?

I guess I need to buy two Zamp 100w panels for the roof if thats true.

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Old 02-05-2016, 05:14 PM   #19
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You can if all the specs match.
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Old 02-05-2016, 07:07 PM   #20
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Quote:
Originally Posted by twh731 View Post
Don't mean to hijack the thread, Tom

Of course you did, but that is ok. The thread was dead.
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Old 02-06-2016, 06:56 AM   #21
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Originally Posted by BoldAdventure View Post
You can if all the specs match.
What specs? When I look at specs from 100w panels offered by various popular companies:
AMSolar:
Here are the SF 100 panels
Pmax = 100 watts @ maximum power

Vmpp = 18.0 volts @ maximum power point
Impp = 5.55 amps @ maximum power point

Voc = 21.6 volts @ open circuit
Isc = 5.93 amps @ short circuit

Here are the GS100 panels
Pmax = 100 watts @ maximum power

Vmpp = 17.7 volts @ maximum power point
Impp = 5.7 amps @ maximum power point

Voc = 21.2 volts @ open circuit
Isc = 6.10 amps @ short circuit

Length = 40.8" (1037mm)
Width = 20.7" (527mm)
Depth = 1.38" (35mm)
Weight = 14.5 lbs. (6.6kg)

Here is the popular Renogy 100w panel
Built-in Components
Renogy 100 Watt Monocrystalline Solar Panel IP65 Rated waterproof junction box
Panel Leads (Pair): 12AWG IP67 Rated waterproof MC4 connectors

Specifications
Maximum Power: 100W Maximum System Voltage: 600V DC (UL)
Optimum Operating Voltage (Vmp): 18.9V Open-Circuit Voltage (Voc): 22.5V
Optimum Operating Current (Imp): 5.29A Short-Circuit Current (Isc): 5.75A
Weight: 16.5lbs Dimensions: 47 X 21.3 X 1.4 In

Grape Solar 100w panel:
Characteristic Details
Max System Voltage 1000 V
Max Peak Power Pmax
100 W (0%, +6%)
Maximum Power Point Voltage Vmpp
18.0 V
Maximum Power Point Current Impp
5.56 A
Open Circuit Voltage Voc
21.9 V
Short Circuit Current Isc
6.13 A
Module Efficiency (%)
14.63%
Temperature Coefficient of Voc
(-0.32% /ļC)
Temperature Coefficient of Isc
(0.04% /ļC)
Temperature Coefficient of Pmax
(-0.45% /ļC)

Are they all incompatible with each other?

Thanks

Kelvin
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Old 02-06-2016, 07:44 AM   #22
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Kelvin,

You need to match the MPPT voltage figures (Vmppt) as closely as possible across all panels to be effective when using an MPPT controller. A difference of more than 0.2VDC in panel output voltage will confuse the MPPT function.

If you want to use panels with a greater voltage differential, stay with a PWM controller. In any event, I would not use any panel in a PWM system that has more than a 0.5VDC differential.


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Old 02-06-2016, 08:18 AM   #23
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Lewster,

If your MPPT controller has only one set of panel inputs from the panels and two panels are paralleled upstream from the controller...and they have more than .2 V difference in Vmp, how does that "confuse" the controller?

My understanding is the the two different voltages will result in the lower Vmp panel "dragging" down the combined Vmp of the system somewhere lower than the higher panel.

Example: (numbers pulled out of the air):

Panel 1 - 18.9Vmp
Panel 2 - 17.9Vmp

They are paralleled upstream from single controller posts

Observed Vmp of system 18.2Vmp.

How does that confuse the controller? I know there would be some loss of MPPT efficiency as system voltage has been dragged down.
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Old 02-06-2016, 08:22 AM   #24
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Quote:
I am going to mount 2 100W panels on the roof and have them wired thru a controller. Would it be possible to prewire a recepticle that is wired thru the controller and have the recepticle easily accessible on the outside of the A/S so that you can just plug in a suitcase solar array? That way you can just plug in the extra solar panels or not as needed? Tom
That is exactly what I did plus one. Last summer I planned a system to meet my needs- a triad setup with three controllers and it works fine. At first I was told you cannot have more than one controller. Then I had an appointment call with two different solar peeps- one a solar engineer. One of them was from GoPower; any who, I was told that it would be fine as long as the charge "rates/cutoffs" were similar. They are so it works for me. I have the 100w suitcase, a 50w single panel for battery/storage and a 150w roof unit. It is true that that one particular may cut off at a certain point BUT it would be doing that anyway and read the battery charge as complete. I have sat and watched the suitcase charge monitor and it reads the battery voltage while the other panels are charging without issue. It also cuts off when I plug in the trailer to power which makes sense. I added pigtail connectors on the side of my battery box for quick connect/disconnect. This week I am returning the flexible panel to Renogy for a different option as it is not charging but that is another issue. I may get the 60w suitcase instead of another panel to have to temporarily mount. Still deciding. I would steer clear of the flexible panels.
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Old 02-06-2016, 09:06 AM   #25
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I have a couple of 25 year old no name brand (the labels fell off years ago) flexable panels that as I recall are around 35 watts that I picked up in Georgetown, Bahamas. They still put out about 2.5 Amps in direct sun light. I used them and the 75 watt panel on my boat full timing down island for years. I realize that opinions differ here but I know plenty of boat folks that swear by flexable panels and have never had any problems with them.
By the way, I talked to Renogy yesterday about my crazy idea. They said using the two controllers the way I had in mind was a bad idea. They did have a couple of suggestions as to how to add an additional panel to the suitcase. But did not recommend using the old 75 watt panel.
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Old 02-06-2016, 11:51 AM   #26
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So, I have been googling the voltage difference between panels discussed above and am unable to find anything definitive. Relative to parallel hookups of arrays, they all seem to say the panels should have "similar" voltages, but do not define "similar". They then go on to discuss issues with 17 Vmp and 24 Vmp panels. I know Lewster likes the .2V difference as a bogie, but I wonder if that is the "perfect world" spec and if "similar" carries a larger V difference for discussion. All say the the system voltage will be dropped to the lowest panel (array) in the parallel system.

Has anyone seen discussion (links please) as to one array being at 17.9 Vmp and one at 18.9 Vmp, for example? Is that "Similar"?
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Old 02-06-2016, 12:35 PM   #27
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Sure would be nice if someone would come out with a book like this for us complete solar deficients.
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Old 02-06-2016, 02:41 PM   #28
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Originally Posted by dznf0g View Post
So, I have been googling the voltage difference between panels discussed above and am unable to find anything definitive. Relative to parallel hookups of arrays, they all seem to say the panels should have "similar" voltages, but do not define "similar". They then go on to discuss issues with 17 Vmp and 24 Vmp panels. I know Lewster likes the .2V difference as a bogie, but I wonder if that is the "perfect world" spec and if "similar" carries a larger V difference for discussion. All say the the system voltage will be dropped to the lowest panel (array) in the parallel system.

Has anyone seen discussion (links please) as to one array being at 17.9 Vmp and one at 18.9 Vmp, for example? Is that "Similar"?
Here is the 'least technical explanation' of how MPPT works in the real world: http://www.blueskyenergyinc.com/uplo...at_is_MPPT.pdf

This is on the Blue Sky Energy web site. Since the maximum power point voltage is the determining basis for 'solar boost' from the controller to the batteries, anything over a small differential will cause the MPPT function to operate more like a PWM unit, or will fixate on the lower Vmpp voltage panel and you will loose the advantage of the higher output panel(s). Output also depends on the specific algorithm that is used for the MPPT sampling: some use a rather slow sampling ( a minute or two) while others sample at several times a second.

This has always been the mantra at AM Solar, and I would expect that they have conducted real world testing (as they do with all of their offerings) before arriving at a position statement.

While some may be tolerant of lower panel output to your batteries, most of the folks that I work for expect to achieve the maximum output from their systems. After all, that's why they hire me. This is why I'll stick with my 0.2VDC differential…..no guess work and I know it works as designed!
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