How can I correctly feed a 60 amp Renogy Controller Charger with eight 12 v 175 watt solar panels?

BB.

It can be confusing, but that is why I try to talk about the how and whys, and not a single solution... Because single solutions rarely work for everyone.

Why have the trailers in two different locations (?) when connecting to one "solar shed"? Or are these to power two different solar systems? Then why parallel them?

You can certainly configure for either two trailers and one solar system or two trailers and two separate solar systems with a plug-in/wire in system... Just need to make sure that the details (array voltage vs MPPT charge controller voltages are correct for the application).

What you cannot (generally) do is connect "one array" to two different Vpanel inputs for the charge controllers... MPPT controllers assume each controller has 100% control of its mating array. The MPPT function will not work correctly if you have (for example) two MPPT controllers connected to one array.

-Bill

TellGRBill

There will be two different systems.

 One for the bus and another for the farm house.

I want a lot of flexibility: One trailer or two in either place.

Just "plug and play". LOL

I have an electrician setting up the house for the dual fuel generator and an outlet for the inverter to be connected when the generator is unplugged.

TellGRBill

Hi again,

I am at the point of considering how to convert the output of my 3000 watt 12 volt inverter from 120 volts to 240 volts to run a well pump that will require about 1500-2000 watts.  I see lots of 120-240 transformers but all I see online are transformers made for European appliances and say they are not compatible with North American 240 volt appliances.

BB.

Adding 120 to 240 VAC transformers is something I would suggest that you avoid. Between the expense (copper = not cheap), efficiency, the losses of just running a transformer with no load (somewhere around 5%), and other issues such as magnetization current (starting a transformer causes "high surge current"--needing a good size inverter to support surge)--A typical, lower cost transformer used in solar is the Auto Wound type (single transformer coil, no isolation).:

https://www.solar-electric.com/search/?q=transformer

At some point you may look at a new inverter (and for larger inverters/loads, look at a 24 or 48 VDC battery bank).

Or, look at a new "solar friendly" well pump (like Grundfos, Sun Pumps, or other VFD (variable frequency drive--A kind of "Inverter") which have no surge current, roughly 1,000 Watt max load, and are very efficient (and not cheap). Some will even run directly from Solar Panels & DC Battery bank & Genset & AC mains (depending on mfg and models).

Another way is to do "slow pumping"... Smaller/low power pump to slowly fill a cistern, and a second pump at at the cistern to pressurize water for the home (these pumps can be fairly low power too in AC or  DC--Can be a simple/low cost as an RV style water pump for smaller home, emergency backup, etc.). Standard in-well pumps tend to be "solar unfriendly" with high starting/running current and relatively inefficient. Shallow well "Jet Pumps" are also very inefficient.

-Bill

TellGRBill

Good morning Brother Bill,

Thanks for your advice again.

We have a 100+' deep well with a submerged pump at the bottom of the well, so we won't be changing the pump. 

The pump only runs for short periods when the pressure drops on the storage tank and when the water is running in the sink or toilet.

Your suggestion for a "slow pump" describes what we use for our bus/motor home.  Our windmill "slow pumps" water into our 100 gallon tanks under the bus, and on-demand 12volt pumps provide water when the faucet is turned on, relieving the pressure in the system.

But that doesn't solve the farm house water pump problem when running on 12 volt batteries.

TellGRBill

Bill B.

I'm making progress with mounting the solar panels and strengthened the mount.  What do you think of it?

BB.

It is a bit difficult to tell.... Push on the corners and see how the structure flexes... Using triangular gussets is a very good way to add strength/rigidity.

For example, push on the top corner(s) along the width of the panels... If you find flexing/movement, then adding some sort of cross bracing is important:

Ideally, the frame (without panels) should be structurally rigided without the solar panels installed. However, when you install the panels and bolt their frames to the structure they do create shear resistance (middle example above).

You also want to avoid "twist"... I.e., you pull down (or back depending on angle of panels) and see if the panels want to twist--That is not good for the panels either.

Things that can make a difference (I am not there).. The short pieces that connect the panel sides to the next panel... Make those connections with "gussets" (sheet stock like a flat piece of paper) that will resist left to right "parallelograming. The "flat stock" will resist "shear". The angle you have there now is only connected by one bolt to left and right side... That will resist pulling/pushing the frames apart or together... But any left to right forces (top of frame pressed right, bottom of frame resisting to left) will just pivot on the single bolts.

Another suggestion would be to move the tilt anchors up to the top (or near top) of frames... Anchors attached too low will allow the frames to "bend" and break the panels down low (lever action). Wind loading:


Look at at the loading (pounds per square foot) for wind and snow loading (just numbers for a random solar panel):

Each of your panels is probably (guess) almost 10 square feet.. .Or 500 lbs+ of wind loading per panel (dynamic loading). And 2,000 lbs+ of wind loading (rated) for 4 panels on a trailer. And double that for snow loading (static loading).

Moving the tilt struts to the very top of the panels, and the bottoms to the (left in picture) outside edge of the trailer will make the entire "triangular" structure much stronger.

The struts themselves... Cut different lengths (two or four different lenghts, depending on how often you want to adjust the tilt). Or make them in two pieces so you can unbolt the middle of the strut to shorten or lengthen...

Anyway, some quick observations.

-Bill

TellGRBill

Thanks for the observations.

The short pieces "The angle you have there now is only connected by one bolt to left and right side" There is a bolt in the middle connecting the brace to third (center) vertical angle frame.

I'm thinking that your observations confirm my wondering if I should add a second angle brace to each panel.

The base anglesteel is long enough to accommodate  another brace.

Bill B.

TellGRBill

Am making progress, but it is slower than in the past working outside during the winter, and  after my physical complications !  Plan to add some 45 degree braces on some of the corners. 

TellGRBill

Advisor Bill,

1. I have finished mounting the four solar panels 175watt each on our two boat trailers.  I added the 45 degree angle braces on four corners to give more side strength as you suggested.

2. I also put heavy lag screws near the hinges to make the hinges normally stationary after positioning the panels at a slope of between 32 and 45 degrees.  I was afraid that the hinge anchor was not secure enough.

3. Now I feel that I am ready to begin wiring the panels to the controller, and I'm not clear about "grounding".

My need for clarity relates to the negative lead from the solar panels and the lead from a ground rod.  When I connect the ground rod lead to the L5 outlet box on the solar panel mounted trailer, it is physically/electrically also connected to the negative lead from the solar panels through the L5 outlet box I believe, and thus to the solar panel frames.   I think that the ground rod lead should be connected to the ground connector in the L5 outlet, right?  Do I remember reading that the ground rod lead should NOT be connected to the solar panel frame? That's where I'm confused.

Student GR Bill

BB.

Regarding the wood... You may wish to paint/preserve the wooden supports too... The panels should last 20+ years. You don't want to rebuild the wood frames in something like 5 years... I assume with your additional supports, the arrays feel much more solid now?

All "exposed" metal work (frames, mounts, trailer frames, metal electrical boxes, etc.) should be connected to a ground rod--Mostly for lightning control. And to a degree, to prevent metal from being "energized" with respect to ground (i.e., walk by in tall wet grass, touch frame, and get electrocuted).

Your panels will be running something like 90 VDC or more--Enough to give some nasty burns.

What you do not want to do is ground the Negative (or positive) solar panel power leads to a "local ground". Generally, what you want is to ground your "solar shed" negative battery bus to its "local metal" and a ground rod too (again, mostly for lightning). 

The idea being that the "ground point" for your DC power system (and AC for that matter) should be a "single point" ground connection. If you connect both a negative solar panel lead (from panel to your shed), and (for example) a 6 AWG cable from panels to shed, and ground both in the shed (usually the correct location) and also ground the negative lead at the remote site (trailer, j-boxes, etc.), you have a parallel current path both through the solar panel negative cable, and the green wire safety ground. With code, this is a "no-no" to have ground circuits carrying power too. Will the solar system work this way... Yes. But I can give you multiple reasons why code (and practice) does not want this--But just take it from code--Don't "multi-point" your safety/power grounds. Single point Power+Safety Ground so that only "fault" currents flow through safety ground connections.

For ground rods/lightning control--Yes, the safety ground itself can (and should be with lightning) be "multi-point" grounded (i.e., tie trailer safety grounds/ground rod(s) with 6 AWG minimum cable back to shed ground rod(s)). Lightning wants to find the shortest (lowest "impeadence" path to ground... And it will not follow (for example) a 6 AWG cable more than 10-20 feet or so before finding a better path.

The "interconnect" ground connection should be a ground lead from the "shed safety ground" to the "remote" safety grounds.... That way if there is (in this case) Panel + to local ground (frame, trailer, etc.), the return current flows back to the shed/DC safety ground....

Ground rods are not good at carrying lots of current at our DC and AC working voltages--A ground rod can have as much as 25 Ohms (or less) and still be "legal". 100 volts / 25 Ohms = 4 amps... Not enough to "short" and trip a fuse or breaker. The green wire from shed ground to trailer grounds is to provide the short circuit return path and prevent "trailer frames" from becoming "hot". Usually suggest a minimum of 6 AWG copper cable as the "safety ground interconnect".

-Bill

TellGRBill

 Bill,

Please read the description of what I believe you described to me in more professional terms, and tell me if I got it right.

I have some trouble understanding clearly, all the professional electrical language.
I have a drawing that may help you see if I understand how you told me to wire the "ground" to my solar system correctly.

1. The panels are connected to a red Positive wire and a white negative wire.

The red+ is connected to the + (positive) connection in the L5 electrical box on the trailer
The white - is connected to the - (negative/neutral) connection in the L5 electrical box on the trailer
The bare #10awg copper wire ( in the 100' 10awg  lead  wire ) "ground" is connected to the "ground" in the L5 box AND to the ground rod next to the trailer with a #6awg wire .
The L5  electrical connection box is mounted on the trailer frame as are all the panels mounted on the frame through the angle frames.

2.. On the controller end of the 100' 10awg wire :

There will be another L5 box, but to make it simple:
a. the white wire is connected to the - Negative post of the controller
b. The red wire is connected to the + positive post of the controller
c. The bare #10awg copper wire is connected to the ground rod with a #6awg wire near the controller and the ground buss strip near the controller.
An L5 connection box is mounted on the bus frame as are the controller and inverter mounted on bus frame which is connected to the - (negative) post of the battery bank and - Buss post..

I'm trying to understand.

Did I get it right ?

BB.

Yes, you are correct above (and in the drawing).

Just to clarify the drawing--The +/- (Red/White) wiring carries through from array to MPPT controller to +/- Battery Bus to AC inverter/DC loads... All + (Red) leads protected by fuses/breakers as needed (normally, these over current protective devices are mounted "near" the battery bank/battery bus connections to protect the wiring against short circuits).

There is once ground connection from the Battery Negative Bus connection to the ground rod.

Otherwise, all electrical boxes, metal chassis of various charge controllers/inverters/etc. are also wired with Hot/Return/Green Wire safety grounds as normal).

Technically, the solar panel frames are supposed to be tied to the 6 AWG ground cable with electrical "clips". The NEC does not want "mounting hardware/brackets/etc." to be "grounding connections". They want hardwired ground wire connections.... This has to do with NEC/NRTL regulations that want safety grounds to be separate from normal mechanical connections (i.e., a service person must "consciously" undo safety ground connections on purpose--Not an accidental safety ground disconnect when removing a mounting bracket/case/etc... Again, this is just a code requirement--Your choice if you want to use the mounting framework to provide ground paths.

-Bill

TellGRBill

Thank you,

1. When you complete your van conversion, I hope that you come to Michigan and visit us.
2. Finished wiring both trailers yesterday, and wanted to duct tape the + wires against the back of the solar panels to keep them from moving in the wind.  Is there a problem with taping the + wires against the back of the solar panels?

3. I made a mistake: When connecting the trailer solar panel outlet box, I connected the + & - solar panel wires in reverse in the outlet box. The panels in trailers are in the barn and 95% covered with black plastic to protect them from any bird excrement. This morning I corrected the problem.  As I understand the mistake, the connection was a direct short.  I saw no spark when connecting and there is no evidence of heated wires.  Did i cause a problem ?

TellGRBill

I have 4 12 volt 175 watt Renogy solar panels connected in series and using my volt meter, I get 118 volts at the outlet near the panels and about 114 volts at the end of my 100' 10agw wire. I expected 48 volts at the outlet near the solar panels.  Am I reading my meter wrong?  Using the same meter on a 120 volt line voltage outlet I get 119 volts.

Problem Soived:  I was using the wrong voltage meter, or using the first one wrong.  i got out the Uni-T voltage meter that Bill recommended several months ago and found the DC selection and was shown that the panels are producing 50 volts. 

TellGRBill

After nearly a years of research, and asking questions and getting advice from advisor BILL , who has been very patient and helpful to me with his T.M.I. advice, WE ARE DISCONNECTED FROM THE POWER LINE, and the system works as we had hoped.

TellGRBill

Is there a device that can limit the amount watts that the pv array sends to the controller?

Under some conditions my solar array sends more watts than my controller can handle

littleharbor2

MPPT controllers can be over paneled. People in less than perfect solar areas do it to still get decent power. When they are getting good full sun they simply limit charging to their rated output amps.

TellGRBill

littleharbor2 Solar Expert

You said, "they simply limit charging to their rated output amps". 

That is what I would like to do.

I don't know how to limit charging to my rated output amps.

Please TellGRBill,

BB.

Guessing this is your Rover 60 amp MPPT controller manual?:

https://www.renogy.com/content/RNG-CTRL-RVR60/RVR60-Manual.pdf

Page 30:

It is not really clear (to me)--Guessing that the limit battery charging current is the 60 Amp controller output rating... Looking through the manual, I did not see any method to limit output current to a different value (some controllers have the software settings, some do not).

The 60 Amp output current is hard coded (software/hardware) in this controller. You cannot adjust, and there is nothing for you to do. This is a hard limit to protect the controller and maintain UL/NRTL safety ratings (typically).

And with "good quality" MPPT controllers, "clipping" of output current to maximum rating is safe and reliable (of course, controller needs to be an a well ventilated area and is best not under sunlight).

There are cases when it is nice to be able to program less output current while battery charging (optimum lead acid charging is around 10% - 13%--And to 20-25% maximum). Very high charging current is hard on many battery types. It tends to stress the batteries, cause them to run hot, and have a shorter operational life.

I don't remember this being an issue with your system... Large AH Battery bank, and not that large of a solar array(s).

If you "over sized" the solar array to account for poor sun in winter (where you may get 50% or less of "full summer sun wattage")--In summer the array will produce more watts (Power=Voltage*Current). That is fine, the MPPT controller will limit the output current. And many MPPT controllers will also limit output current if they are running "HOT" (reduce current to prevent overheating).

-Bill

TellGRBill

Hi Bill,

I remember you telling me that if the solar array produced more watts that the controller was rated to accept, the controller would "clip" the watt power coming from the solar array to the rated limit of the controller.

This afternoon I got a warning on my cell phone controller monitor " WARNING !! YOUR SOLAR ARRAY IS PROVIDING MORE POWER THAN YOUR CONTROLLER CAN HANDLE" CALL TECHNICAL SUPPORT.

When I called technical support they told me that my solar array could produce more watts than the rated capacity of my 60 amp MPPT controller and seriously damage the controller.   

That is why I asked the question: " Is there a device that can limit the amount watts that the PV array sends to the controller?

Checking my controller monitor I saw a reading of only 80 watts over the controller's rating of 800 watts coming a solar array.

Sincerely, Bill B

PS: the system is working as expected, pretty good.  Am learning how to manage the "load" to conserve battery energy.

Another question: when a controller disconnects because the battery voltage gets too high or too low, how is the load disconnected, by stopping the output of the inverter ?

littleharbor2

I'm back. I totally agree with what Bill B said.  At only 80 watts over your charge controller says is the acceptable wattage I have to question the quality of it, either that or shut off the monitor phone warnings. Here's an example from another "mid grade" brand of MPPT controllers.
Notice their own generous overpaneling limits?

BB.

I don't have any suggestions on a "clipping" device on the array side... Yes, there are DC to DC converters that could, in theory, clip the current/voltage of the array, but they are not "MPPT" input type converters--And could cause other issues (such as loss of harvest).

Typically, the limit on array output current is there because you don't want too much current that could "cook" the wiring if there is a controller failure or short in the Array wiring.... I.e., a 100 amp peak output array attached to a 20 amp controller.

From the manual (my quote in above post), it says it should clip. And the controller "clipping" would simply limit the current draw from the array to generate its 60 amp output current. And the controller should not "know" if the array is 1% or 100% over sized.

I guess there is the MPPT algorithm that could draw more array wattage when doing the "mppt scan" of the array (controller trying to solve the Pmp=Vmp*Imp equation) and trigger such a warning.

The short term answer would be to reduce the number of panels in the array. The longer term would be to replace the controller with a "better quality/design" MPPT controller--I would guess.

Otherwise, I have not read about that warning before and I have nothing more to add.

-Bill

TellGRBill

What about having a low voltage or high voltage disconnect connected to the on/off switch of a DC to AC inverter?

My Renogy 3000 watt inverter has an on/off switch and a remote switch called a remote control with a on/off indication.

We have both DC and AC use in our bus, so shutting down the DC inverter for a short time would not be so bad to save the batteries.

Just shut off the inverter when the batteries reach the low or high set limit ?

littleharbor2

Some inverters are huge energy wasters, using more power than an efficient fridge over 24 hours. By all means shut down your inverter when you don't need it.

TellGRBill

Can I connect an automatic LVD/HVD device to the on/off switch.

Are there instructions for doing it?

Maybe even plugging into the Inverter outlet that the remote switch uses?.

littleharbor2

That answer and reasoning why are above my pay grade. While most things are possible, electronically, how to do it is the question.

TellGRBill

Thank you,

Maybe someone else can advise 

TellGRBill

I would like to buy some standby online solar flat fuses.

I have had difficulty finding the fuses without the mounting holders.

Anyone have a good source ?

NANOcontrol

Is that inverter an on/off switch like a slide switch or a momentary push button?  My fridge is wired to turn on the refrigerator when thermostat says too.  It also can be turned on to power other devices manually. Fridge will only come on when it needs to. I do have a LVD and my fridge only turns on in the day when it is sunny and battery voltage is high enough.  I only have a 12V car battery to run everything.  The system is extremely efficient and can run for days with clouds.