Adding a Second Solar Panel

[Bwht4x4]

Last year I added a 160 Grape Solar panel to the top of my camper. It's mounted on the Yakima tracks and is something that stays in that location...e.g. I don't ever take it off or adjust it. It's plugged into the roof top plug. The panel works flawlessly and provides enough power to run my refrig and fully charge the batteries during the day. However, if the day is cloudy or there are trees nearby the panel sometimes won't fully charge the batteries for that day and will take them up to 85% to 90%. I personally like to see them reach 100% each day.

I'm thinking I may incorporate a second, portable solar panel into my system for times when it's cloudy or there are trees shading the camper. This portable unit would plug into the camper on the rear exterior wall when I wanted to use it.

From what I understand it looks like I will need a separate solar controller for this second portable panel since it'll be a different wattage then the roof top panel. Can anyone confirm that this is true? Is there anything else I need to consider before purchasing the second panel? Wiring to the batteries?

I'm currently looking at buying one of the 100 watt flexible panels for this purpose since it'll be light weight and think I'd be able to store it under the mattress in the camper when not in use.

 

[DesertDave]

I have read that ideally you want to have the maximum power voltage (Vmp) of the various panels to be close to each other, ie. within 10%. The 100W Renogy panel Vmp is 17.7 volts - so compare that to the Vmp of your Grape Solar panel. I think the closer the Vmp is to each other, the better.

You also want to be sure that the solar controller you have can handle the additional current from the portable panel if you wire the portable to your existing controller. If your controller cannot handle the additional current/wattage, then you can either replace your controller with one with adequate capacity, or use a separate controller with your portable panel.

You should know where the rear wall panel plug wires go now. On my factory installation, they were connected to the factory solar controller. If your camper didn't come with the solar controller, then they should terminate somewhere.

In my personal example I have the factory Zamp 15A controller that they rate to 255 watts. Connected to it I have a Zamp 100W panel with a Vmp of 17.9V and a Renogy 50W panel with a Vmp of 17.6V, and I use the Renogy 100W panel as a portable. My rear wall plug is wired to the same controller. So I have three different panels wired to the same controller.

 

[Bwht4x4]

Thanks Dave. My current panel has a Vmp of 18.5 and the Renogy 100w flex panel has a Vmp of 17.7, which is within 10%.

I'm fine with buying a second controller for the new panel if I had to. Right now I run the SunSaver MPPT 15 amp controller and I'm thinking I'm getting close to maxing it out with the 160 watt and 100 watt panels connected to the same controller. I've seen my 160 watt panel max out once at the rated current at Maximum Power Point (Impp) of 8.65 amps. The Grape Solar flexible panel has a current at Maximum Power Point of 5.62 amps. That is 14.27 amps at Maximum Power Point, which is close to the point of my controller's rated 15 amps, but in reality how often will both panels max out? I'm betting that both panels combined will have an average max of around 10-12 amps. Plus I'd only be running both panels if I had to and not on a regular basis.

The rear wall plug wires currently terminate in the battery box so wiring it will be pretty easy. I just need to figure out if I want to go with a separate controller or wire both panels to the same controller.

 

[photohc]

I agree with DesertDave's analysis. Your setup with the additional panel to the same controller should work fine. I have the same Morningstar with a roof top 150 w Grape Solar and a Renogy 100w flexible panel. I too plug in the flexible panel when the truck is in the shade. Perfect combination. I have not exceeded the SunSaver MPPT 15 amp limit. Closes I've observed is around 12.5 amps. Like you, I only plug in when necessary.

 

[pods8]

Last year I added a 160 Grape Solar panel to the top of my camper. It's mounted on the Yakima tracks and is something that stays in that location...e.g. I don't ever take it off or adjust it. It's plugged into the roof top plug. The panel works flawlessly and provides enough power to run my refrig and fully charge the batteries during the day. However, if the day is cloudy or there are trees nearby the panel sometimes won't fully charge the batteries for that day and will take them up to 85% to 90%. I personally like to see them reach 100% each day.

Drawing down to 80% is the bread and butter of deep cycle batteries, they have LONG life cycle still at that range. Going down towards 50% starts reducing the life cycles but in the realm of recreational usage is still not a major concern. Going lower can start to factor in a bit.

My weekend warrior mindset for solar/battery sizing was if the solar keeps things above 80% for the duration of a weekend trip and/or keeps them over 50% for something like a week long boondock then I think I'm covered good enough. If I'm out somewhere with absolute crap weather I could always fire up the truck for a bit to throw a charge back into them.

Just something to keep in mind before more $$$/gear/weight comes into the equation.

 

[Bwht4x4]

I agree with DesertDave's analysis. Your setup with the additional panel to the same controller should work fine. I have the same Morningstar with a roof top 150 w Grape Solar and a Renogy 100w flexible panel. I too plug in the flexible panel when the truck is in the shade. Perfect combination. I have not exceeded the SunSaver MPPT 15 amp limit. Closes I've observed is around 12.5 amps. Like you, I only plug in when necessary.

It sounds like you're doing exactly what I'm hoping to do. Thanks for the information. When you deploy the Renogy panel where do you put it? Do you have a stand for it or do you simply lay it somewhere? For me I may need to lay it out while I'm away from camp for 3-4 hours and I'm afraid the wind could blow it around. I'm considering designing a method to attach it to a 16 foot telescopic pole and attach the pole to the jack brackets. This would get it above the dense pinyon and cedars trees where I hunt and would allow me to rotate it. The other idea was to put it in the windshield of the truck while I'm gone, but I'd have to see how it worked in this location. I only need this second panel for 2-4 hours and I think inside of the windshield could work well. A couple of suction cups could hold it in place.

Do you have a picture of the wiring to your controller? I'd be curious to see how you wired both panels to the controller. Did you pigtail off the controller to the panel wires?

 

[Bwht4x4]

Drawing down to 80% is the bread and butter of deep cycle batteries, they have LONG life cycle still at that range. Going down towards 50% starts reducing the life cycles but in the realm of recreational usage is still not a major concern. Going lower can start to factor in a bit.

My weekend warrior mindset for solar/battery sizing was if the solar keeps things above 80% for the duration of a weekend trip and/or keeps them over 50% for something like a week long boondock then I think I'm covered good enough. If I'm out somewhere with absolute crap weather I could always fire up the truck for a bit to throw a charge back into them.

Just something to keep in mind before more $$$/gear/weight comes into the equation.

Pods, Have you tried to charge a dual battery system by running the vehicle? I have not had good luck with that. From what I can tell you're not going to add much to the batteries unless you are going to be doing a 3+ hour drive. From what I've seen, idling the truck for 30 minutes adds a tiny bit more power and probably enough to run my refrig for 15 minutes!

 

[PaulT]

Thanks for the information. When you deploy the Renogy panel where do you put it? Do you have a stand for it or do you simply lay it somewhere? For me I may need to lay it out while I'm away from camp for 3-4 hours and I'm afraid the wind could blow it around. ... I only need this second panel for 2-4 hours and I think inside of the windshield could work well. A couple of suction cups could hold it in place.

I store my Renogy 100 watt bendable panel between the mattress and sleeping bag while the top is down and inside the cab if not deployed. I deploy the panel early in the morning while getting breakfast and before going out for the day. I found a folding aluminum camp table for about 25 bucks and use it with an a small cooler for ballast and support,

I place the panel in the morning sun and get a couple of hours of nearly full output while the roof mounted 100 watt factory is putting out < half power. I have about 20 ft of wire so that I can usually get the panel in full sun. The panel fits in the first slot on table and the cooler keeps it at a good angle. Just align the shadows of the front legs to fall on the shadows of the rear legs and it faces square to the sun.

In that 2 hours, I am able to restore about 15-18 amp hours of energy. Running the truck headed to the day's destination and the roof mounted panel finish the job.

Paul

 

[Bwht4x4]

It looks like the Morningstar SS-MPPT-15L can accept more than 200 watts, but cuts off the usable power at the 200 watt level. According to their documents, an array larger than 200 watts connected to the SS-MPPT-15L is actually the better way to go, but there is a cost-benefit in play there too.

http://www.morningstarcorp.com/wp-content/uploads/2014/02/MPPT-Technology-Primer.pdf

Nominal Maximum Input Power*
12 Volt 200 Watts
24 Volt 400 Watts
* These power levels refer to the maximum wattage the SS-MPPT-15L can process at a certain system voltage. Higher power arrays can be used without damaging the controller, but array cost-benefit will be reduced at power levels much beyond the nominal ratings.

Morningstar’s TriStar MPPT™ & SunSaver MPPT controllers are the only controllers that will always limit the output current regardless of input power levels. Morningstar’s patented TrakStar Technology is capable of limiting the output current, while other manufacturers’ MPPT controllers will operate above their maximum current ratings at higher power levels. Morningstar’s MPPT controllers can operate with an oversized array that is several times larger than the maximum Nominal Solar PV ratings, while still limiting the maximum battery current to the controller’s maximum current rating. Many other MPPT controllers on the market cannot react quickly enough for fast changes in solar conditions. Even at the published maximum power levels, these controllers are known to exceed their maximum output current ratings and can trip the overcurrent protection fault shutting off the controller during high power condition

Q2. Can I exceed the nominal wattage ratings of MPPT controllers? Will it void the warranty? You can size Morningstar’s MPPT controllers well above the Maximum Nominal Solar PV Input rating without damaging the controller and without the charging current exceeding the maximum output current rating. The controller can limit output current and will run at 100% of rated current output and not higher. The controller was designed with this power-shaving capability and when oversized it does not void the warranty.

Q5. Can I use a 240 Watt (60 Cell / Vmp≅ 30V) PV module with a SunSaver MPPT™ controller? Yes. Even though the SunSaver MPPT™ controller in a 12V system is nominally rated for a 200W PV array, you can use a larger PV module e.g. a 240W PV module.  For 12V systems the SunSaver MPPT controller is an acceptable option due to its ability to convert the module voltage down and charge a 12V battery very effectively. (Fact: all Morningstar MPPT controllers are buck converters—they can convert voltage down but not up, which is known as a boost converter. For this reason, the Vmp of the module must be above the battery voltage at all times or charging will cease).

This graph illustrates the output power levels of a SunSaver MPPT controller—comparing a 200W module to a 240W module—operating on a clear & sunny day at STC maximum power (Pmp).  Though the power being delivered to the battery is limited to 200W and the red area at the top of the production curve is lost, the larger module is harvesting more energy, as shown in green.  The larger module will provide better production with no power-shaving early and late in the day as compared to a smaller module.  In this case almost twice as much energy is gained (green area) than lost (red area) with 12.5% more energy available to charge the batteries than the 200W module.

On cloudy (or intermittent sunny) days there will be little or no power-shaving and the extra power will serve the battery well with more energy harvest. This graph uses real array data and is scaled to a 200W module and a 240W module.  On this day there is < 1% loss due to power-shaving (energy above the red line), so more than 95% of the excess power over 200W can be utilized for charging.  On clear days this loss of power is likely not to be missed so much.  One exception to note is where the power-shaving energy loss could be more of a factor—in colder climates with winter tilt. o In these conditions (shorter days, colder temperatures and okay ≈90° incidence angles) the array will operate above STC Max. o Power Levels and the loss of power could have a bigger impact during the time of the year when it is most needed.  Also, to avoid unnecessary stress on the controller’s electronic components, it is recommended that when the controller is installed in a sustained warm temperature climate, the controller not operate at full power, close to its maximum ambient temperature, for prolonged periods of time.

 

[photohc]

It sounds like you're doing exactly what I'm hoping to do. Thanks for the information. When you deploy the Renogy panel where do you put it? Do you have a stand for it or do you simply lay it somewhere? For me I may need to lay it out while I'm away from camp for 3-4 hours and I'm afraid the wind could blow it around. I'm considering designing a method to attach it to a 16 foot telescopic pole and attach the pole to the jack brackets. This would get it above the dense pinyon and cedars trees where I hunt and would allow me to rotate it. The other idea was to put it in the windshield of the truck while I'm gone, but I'd have to see how it worked in this location. I only need this second panel for 2-4 hours and I think inside of the windshield could work well. A couple of suction cups could hold it in place.

Do you have a picture of the wiring to your controller? I'd be curious to see how you wired both panels to the controller. Did you pigtail off the controller to the panel wires?

The second set of wires from the camper back plug, simply connects to the same terminals on the MPPT SunSaver like the roof top panel. Essentially in parallel.
As for placement of the movable panel, I just put it wherever the sun is shining. I like the front windshield if thats where the sun is shining. I mounted the movable panel on a foam core insulation material from Home Depot to keep it from getting the edges damaged. Cutting the foam a little larger than the panel, I then used aluminum tape to secure the edges.

 

[Bwht4x4]

Thanks photohc! This is exactly what I want to do and will pull the trigger on a new flexible panel ASAP.

 

[pods8]

Pods, Have you tried to charge a dual battery system by running the vehicle? I have not had good luck with that. From what I can tell you're not going to add much to the batteries unless you are going to be doing a 3+ hour drive. From what I've seen, idling the truck for 30 minutes adds a tiny bit more power and probably enough to run my refrig for 15 minutes!

Yes if either a DC-DC charger or the appropriate wire gauge is used. If you just run 12ga wires (or such) without anything to boost the voltage back up at the camper batteries then no it doesn't charge well, there is likely <2% voltage drop available from most alternators to still get a good flow of amps to the camper battery by the time you go through 15-20' of wiring/connectors.

But my point was if on average your batteries aren't falling under 80% even if they don't always get back to 100% daily then I don't think I'd worry about another panel.

 

[DesertDave]

On my 100W renogy panel, I bought a 30' MC4 solar cable, cut it in half, connected the cut ends to the wires for the plug in the rear wall. The solar panel comes with MC4 connections. I use it as a portable.

The Renogy comes with grommets in the corners of the backing. I zip-tied the wiring from the little box on the front of the panel, to each corner grommet, to act as a strain relief on the connections to the panel. I did this since the only complaint I saw in the reviews at the time I bought it was that this connection was fragile. And as a portable, there will be more wire movement than with a permanent install, although I did the same thing to protect the connection on the 50W I installed on the roof.

As far as holding it in place, I ran 550 cord between the end grommets to give me something to attach to, and if needed, I can bungie the panel to the windshield or the roof rack or whatever I feel the need to attach to.

For transport I use the original packaging it came with. Sometimes it is wet when I pack up, from rain or dew or ice, and I don't want to place something wet near my bedding if I can help it. It usually goes in the camper for travel, and the box in the truck cab while camped.

 

[DavidO]

[SIZE=12pt]I have a September 2012 Hawk with the 110 fridge. I discovered early that the fridge can and sometimes does use a lot of power. The first thing I did to address the need for more amps was add to the battery capacity. I put in 2 new AGM group 30 110 Amp batteries. This was a good addition, I don't think you can have too much battery capacity. Oh did I mention I had the factory solar. It didn't seem to do much, I thought when I ordered my Hawk with solar all my charging needs would be covered. In looking back, to me it seems that the 95 watt solar factory system would be sized perfect for someone with led lights and a 3-way fridge.[/SIZE]

[SIZE=12pt]Addition of a q4 chip really helped with charging my batteries. The batteries seemed to charge faster and they seemed fuller. I still didn't know what was going on until I installed a Trimetric meter. The first thing the meter told me was that when my batteries are down to 65% the IOTO charger without the Q4 chip only put out 15 Amps with the chip 30 Amps. It was so nice to now be able to look at a meter and see just what is going on with my batteries state of charge.[/SIZE]

[SIZE=12pt]I needed more solar power on the roof. I switched the roof panel out for a 160 watt Grape Solar panel. The new panel was way over the rating for my factory Morningstar SS-6-12V SunSaver 6 Amp Charge Controller so I installed a Morningstar MPPT 15 amp controller. The 160 watt panel has worked much better for me. It keeps the batteries charged better as it can run the fridge and add a few amps to the battery at the same time. I took the old 95 watt solar panel and controller on a couple of campouts and was surprised at the amount of power that panel put out because it could be pointed right at the sun. Often times it would put out more that the 160 watt panel on the roof. I like the power output but I didn't like carrying the bulky panel so I bought a 100 watt Renogy bendable panel which fit nicely between the extra bed cushions behind the rollover couch.[/SIZE]

[SIZE=12pt]Two 100w bendable solar panel is not much thicker than one so I got a second one now I can deploy 200 watts of solar panels pointed directly at the sun anywhere within 50 feet of my truck. I can now park in the shade or if my batteries get a little low I have extra capacity to bring them back up. If it is hot out or I hit the store and restock the fridge in the middle of a trip my fridge might run continually. Worst case scenario 4.5 amps x 24 hours = 108 amps, good news though I don't need to add any amps for the heater if it is hot.[/SIZE]

[SIZE=12pt]To deploy my panel I have a piece of 3/8" plywood about the same size as one of the panels and each panel has a couple of Velcro patches holding it to the plywood half on and the other half hanging over the edge. One leg a metal 3/8" pole from something else sticking right through the middle of the plywood holds the panels up. I used solar MC4 connector so it can only be plugged in one way, the right way. I did take a knife to the catches on those plugs so it is easy to unplug them.[/SIZE]

[SIZE=12pt]I have the factory halogen lights on the back of the camper and my wife loves them, it takes 9amps to run those lights and now if she wants to turn those on for 10 minutes its OK.[/SIZE]

 

[Squatch]

I'm still in the homework stage on solar. I'm liking the portable panels as opposed to hard mounted more and more. I really like the light weight of the Renology panels. Has anyone mounted their's to a piece of 1/4" ply wood? I was thinking that would make it easy to mount to the roof racks or use it portable. Maybe add 2 simple swing down legs that would work as sort of an easle to aim them in the sun. And hopefully the plywood backing would make them a bit more protected from breakage while still not adding much weight.

You folks just keep giving me more and more ideas.

 

[RC Pilot Jim]

My contribution is the original 60 watt panel ($78- solarblvd.com) on an aluminum frame with sprinkler pipe legs. Weight 15 pounds. Store it in the orig shipping box on the back seat of the Tacoma, secured by seat belts. Out of the way-easy to get to if needed. Run both panels (Renology 100 watt) through 20L Morningstar SunSaver controller. This summer we will camp in the mountains so probably will use the "portable" and will find out if its needed.

Vmp is 17.0 for 60 watt and 17.7 for Renology 100 watt. Within 10% range.

 

[Bseek]

The tilt support is an elegant solution. Thanks for sharing.

 

[RC Pilot Jim]

Thanks Bseek.

"tilt frame" instructions (if anyone needs them):

aluminum strapping wound around outside end 3/4" sprinkler pipe "T" connector
Material list
2 ea 3/4 " " T " connectors
3/4" pipe.
2 ea 3/4 " end caps

Legs and end caps are press fit. Took about an hour to make.
In windy conditions we stake a rope over the top.

 

[PaulT]

DavidO,

Could you elaborate on how you installed the Grape Solar 160watt in place of the factory panel? Did it require drilling new holes in the roof or were you able to modify or reuse the original mount?

Paul

 

[Bwht4x4]

PaulT,

Here's a link to my 160 panel install on the factory Yakima tracks. IMO I think this is the best and easiest install if you have the tracks.

http://www.wanderthewest.com/forum/topic/8774-camper-roof-flex-and-solar-panel-installation/