Solar Panels and Shading

[BroncoHauler-SMB]

...I made a storage box for it mounted under the rear shelf

Brilliant way to keep it accessible and keep it safe.


Herb

 

[TomH-SMB]

Brian F. (SMB-W) just told me that they are going to have some new panels that are less susceptible to partial shading killing off as much power. No details yet.

 

[Scalf77]

Sunpower Solar makes solar cells that have a built in bypass diode. They generally make grid tie only solar panels, and generally cell in the home systems market.

They do dump a lot of their B-grade solar cells on the open market, and can be picked up on Ebay. Many people use these to build DIY panels. I have seen multiple sellers that have flexible panels using there cells.

There was one company that was discussing using their cells for a hard panel.
http://www.sportsmobileforum.com/forums/f20/solar-panels-that-are-not-susceptible-to-shade-shut-down-18975.html

That said, the bypass diode only does so much and when it does you would still loose the current and voltage of that cell. The issue being that you would still be limiting the all the cells to the same current as the partially shaded cell(s) until the shading was bad enough to make the bypass diode kick in.

Don't get me wrong, they would still be an improvement.

-greg

 

[1der]

Greg - perhaps you can shed some light on the combining of panels of different wattage. I have read what I consider very informed information about the inefficiencies of combining panels of differing wattage. Say a 100 watt additional panel is added to a my 300 watt panel. I am of the understanding that the 300 watt panel will be restricted by the 100 watt panel and thus the system will be 200 watts not 400. Is this correct? Does it matter if they are hooked up in parallel or series?

The other question is the practice of adding a portable panel to an all ready installed fixed system This is where the panel leads from the portable panel are added to the PV-In terminals on the existing solar controller. What happens here and is it really different from the above? Thanks!

 

[Scalf77]

Greg - perhaps you can shed some light on the combining of panels of different wattage. I have read what I consider very informed information about the inefficiencies of combining panels of differing wattage. Say a 100 watt additional panel is added to a my 300 watt panel. I am of the understanding that the 300 watt panel will be restricted by the 100 watt panel and thus the system will be 200 watts not 400. Is this correct? Does it matter if they are hooked up in parallel or series?

The other question is the practice of adding a portable panel to an all ready installed fixed system This is where the panel leads from the portable panel are added to the PV-In terminals on the existing solar controller. What happens here and is it really different from the above? Thanks!

Ray,
Sure, mixing panels of different specifications can lead to issues, and worse it can be easy to do because we tend to focus on the wattage rating of the panel. The wattage rating is really made up of two major specifications of the panels Vmpp x Impp = Wattage.

I previously had an Kyocera Panel 140 watt panel it had Vmpp of 17.7 volts and Impp of 7.91 amps to get 140 watts (17.7 X 7.91= 140.007). I was looking to upgrade to a second panel and looked at Grape Solae 180 watt panel. This panel had a Vmpp of 19.67V and Impp of 9.71 Amps.

The simple math would sat that I have 180 + 140 = 320 watts. But lets dig deeper, since I have an MPPT controller I could have put the new panel in series or in parallel, either one of these could give me different results. If I chose to put them in series I would added the voltage 17.7 + 19.67 = 37.37 Volts. The current in series would be restricted to the lowest current panel, in this case 7.91 amps from the Kyocera Panel. If I do the math 37.27 X 7.91 = 295.6 watts. That is a Far cry from the 320 watts expected.

If I chose to go in parallel I would now add the currents, 7.91 + 9.71 = 17.62 Amps. For the voltage we would take the lesser of the two panels, in this case 17.7 volts. We do the math, 17.7 X 17.62 and we get 311.87 watts. While again this is not the 320 watts that we expected it is better than 295, we would have produced in series. In short, I decided to sell the Kyocera and purchase two new GS– 180 panels, so that they were matched.

Now if you were to take some panels that were mismatched even worse, the problem gets even worse. Take a LG 300 watt panel Vmpp = 32 volts x 9.4 Amps & a Renogy 100 watt panel Vmpp of 18.9 X Impp of 5.29 amps. The specs are much farther apart, so let’s do the math again.
First in Series: 32 + 18.9 = 50.9 X 5.29 Amps = 269.261 Watts.
In Parallel: 9.4 + 5.29 = 14.69 X 18.9 Volts = 277.641Watts.
In both cases the combined output of the mismatched panels is worse than original 300 watt panel.

Generally, if you are hooking up a portable panel it is done in Parallel to the hard-wired panel and it is done at the controller. Will this be a perfect solution, a lot depends on the specs of your panels, generally if they were close it won’t be so bad.

Hope this helps

 

[Twoxentrix]

Wow - Thats certainly more involved than the math I was using (1+1=2). Appreciate you guys clarifying this prior to buying my auxiliary panel. Thought I had read enough to perform an effective upgrade. frustrating part is now I know I dont know crap about what I should - starting to appreciate the comfort of ignorance.

 

[seasmith]

I have a Renogy 100 watt panel with
Renogy Wanderer -- 30A Advanced PWM controller i leave hooked up to the single house battery, while parked at the high camp in CO.

Thinking of getting a small BatteryMinder 5 watt unit to hook to the starter battery, as there is strong sun up there all morning.
Would this be in effect a parallel circuit config ?

Any one see a looming disaster in the works ?

Thanks

 

[1der]

Greg, awesome explanation, best one I have read because of the calcs and examples you included! Thank you!!

 

[1der]

I have a Renogy 100 watt panel with
Renogy Wanderer -- 30A Advanced PWM controller i leave hooked up to the single house battery, while parked at the high camp in CO.

Thinking of getting a small BatteryMinder 5 watt unit to hook to the starter battery, as there is strong sun up there all morning.
Would this be in effect a parallel circuit config ?

Any one see a looming disaster in the works ?

Thanks

I think we need a bit more info:
Are the two battery banks completely separate or are they connected together either directly or through a separator/isolator? If a separator/isolator what is the model?

 

[Scalf77]

I have a Renogy 100 watt panel with
Renogy Wanderer -- 30A Advanced PWM controller i leave hooked up to the single house battery, while parked at the high camp in CO.

Thinking of getting a small BatteryMinder 5 watt unit to hook to the starter battery, as there is strong sun up there all morning.
Would this be in effect a parallel circuit config ?

Any one see a looming disaster in the works ?

Thanks

This configuration does not fall into either Parallel or Series Panel configuration.
The Battery Minder 5 watt panel is it's own controller. So the above panel discussion were all based on the panels going to the same controller. Not that multiple controllers can't be a issue in their own right.

As Ray says we really need to understand you Battery/Isolator/Separator solution. In general if while camped your house and starter batteries were isolated from each other this would be an acceptable solution.

If you have bidirectional voltage monitoring separator, the Battery Minder would be redundant, as Renogy system would raise the voltage and cause the Batteries to be joined in parallel. This allows the renogy system to take care of both your house and starting batteries. That can be considered a plus or minus, depending on what you are intending and preference to taking care of your batteries.

The two solar controllers in parallel would could be a negative. If we take a look at most solar controllers (or any batter chargers) they tend to monitor voltage of the battery to determine what charge state to be in, if you have multiple controllers this could cause them to work against each other.

The common misconceptions is that multiple controllers would added to each other, that in most cases is wrong. There are systems that are destined to be connected, with stacking or master-slave solution.

-greg

 

[seasmith]

Sounds like it would be piddling in the wind..
Have a Surepower 1315-200 seperator and it usually engages/links whenever the microwave is used (i tossed the fridge a while back).
So guess what i'm wondering is when the batteries are Not separated, will either controller be damaged ?
When separated, there should be no issue ?

 

[1der]

Seasmith - if there is sun on your roof panel then it will be charging both house and starter batteries. The 5 watt will do nothing. If your roof panel is not in the sun and you place the 5watt in the sun, then the 5 watt (less than 1/2 amp) will provide a less than 1/2 amp charge to the battery it is connected to.

When you refer to using the microwave the BlueSea “engages”, it actually is disengaging the two battery banks as the inverter is drawing your house battery bank down below 12 volts, even with the solar panel receiving full sun. It is doing this to protect the starter battery. Turn off the microwave and then solar charger can again provide higher than 12.7 volts (or whatever) and the BlueSea engages the two banks again. I

You shared you get lots of sun on the roof panel lots of the time. It is taking care of both batteries. No need for the 5w thing at all. Is there something else going on that is making you concerned about charging? Personally, I would see what could be done to get another (or two) 100 watt panels up on the roof.

 

[ShuttlePilot]

Personally, I would see what could be done to get another (or two) 100 watt panels up on the roof.

Sorry, couldn't resist.

 

[MSD-SMB]

Gar- I think the long term longevity, or lack thereof, of the flexible solar panels out on the market has been well documented over the years. I could be wrong but it looks like the panel you referenced is of similar design in that the solar cells themselves are flexible. Even if the cells are small rigid units mounted to a flexible panel, I would still be cautious of it holding up long term. The connections between each cell will be flexed when deploying and when putting away for storage, something that will no doubt put stress on those contact points.

I supplemented my roof mounted 137W Kyocera with one of the Renogy suitcase units, they are available with/without their own charge controller. It works great as a supplement to my mounted panel and gives me some flexibility to maximize my solar input.


Without controller

https://www.renogy.com/renogy-100-w...lline-foldable-solar-suitcase-w-o-controller/

With controller

https://www.renogy.com/renogy-100-watt-12-volt-monocrystalline-foldable-solar-suitcase/

It also looks like they have one with a waterproof controller
I added an external plug in that is connected to my charge controller

I made a storage box for it mounted under the rear shelf

I like that suite case set up and the storage for it. Nice and clean, plus having a suitcase set up allows you to park in the shade and put the suitcase in the sun if needed.

 

[seasmith]

You shared you get lots of sun on the roof panel lots of the time. It is taking care of both batteries. No need for the 5w thing at all. Is there something else going on that is making you concerned about charging? Personally, I would see what could be done to get another (or two) 100 watt panels up on the roof.

Thanks 1der,
Actually it is the hood area that gets strong AM sun, and what i'm looking for is some fairly portable setup to harvest that morning sun, and also be easy to derig if we need to move quickly.
The 100w Renogy is mounted on a ground-based easel facing South, so gets its main sun midday.
I have been starting the engine when microwaving, so as Not to draw down the starting battery, and that is what I'm trying to get away from doing.
Guess there are no simple options ...

 

[1der]

seasmith - I am guessing your setup is as follow:
Inverter connected to the house battery, Blue Sea separator located between the house battery and the starter battery. Microwave plugged into the inverter running off the house battery.


If the foregoing is how the system is configured, then starting the engine when microwaving is helpful to the house battery if the rpm's are held at or above 1100/1150. The separator may provide alternator current to the house battery with the engine running, certainly if the rpms are high enough.

Running your inverter should have no impact on your starter battery when the engine is off as the separator will disengage it from your house battery once the house battery is being drawn upon to invert for the microwave usage.

 

[seasmith]

Ider- I don't know from Blue Sea, it's a SurePower 1315-200 separator, but yes that is the set up. I think the rpm's are high enough, that's why i said the batteries are connected when running microwave, but will double-check that when have the chance.
I think i follow what you are saying here, but the ultimate aim remains to augment the power fed from the Renogy 100W through the house battery;
with a small, semi-portable solar system fed through the hood/starter battery, without disconnecting the Renogy controller.

Any ideas on that pipe dream ?

Thanks

 

[Scalf77]

Ider- I don't know from Blue Sea, it's a SurePower 1315-200 separator, but yes that is the set up. I think the rpm's are high enough, that's why i said the batteries are connected when running microwave, but will double-check that when have the chance.
I think i follow what you are saying here, but the ultimate aim remains to augment the power fed from the Renogy 100W through the house battery;
with a small, semi-portable solar system fed through the hood/starter battery, without disconnecting the Renogy controller.

Any ideas on that pipe dream ?

Thanks

Your Solar Controller has more capacity than (1) 100 watt panel. If you purchase another 100 watt panel to use as a portable that would work. You just need to match the specs of your existing panel. You can mount the portable panel in parallel to the existing one. Because it will be in parallel you want to make sure the voltage output of the panels is close. You can probably go about .5 volt higher and be OK, (You generally have a little more voltage drop in a portable setup because the wires are longer).

-greg

 

[seasmith]

.

Thank you Greg and 1der

 

[Bear in NM]

New to the forum, have been doing solar for a few years. Last year I added a Goal Zero foldable panel to my fixed 135w panel. I thought I was a pretty smart feller by testing shade issues while connected in parallel and series. I came to my decision, but recently learned of this diode issue. Pretty sure if I had tested shading understanding the diode construction, I surely would have tested differently. Great thread to sticky.

One little trick I have been doing these few years is using Anderson power pole connectors for my solar suitcase and my cargo trailer solar installation. I like them like potato chips, can't eat just one. One handy use is when combined with an inline volt/amp meter (I like the Amazon GT Power RC 130A) device. I have 3 or 4, all wired with Power Pole connectors on each end. This lets me place the meter anywhere in my system, at the panel, before the controller, at battery etc.

Many of the solar controllers on the market are not terribly useful to see what is actually going on. Red light needs charging, green light fully charged is really not useful for testing or trouble shooting. The in-line meters are also easier than fiddling with a multi-meter. And a properly installed shunted meter is a must, but a meter like I noted sure comes in handy.

Craig