Portable Solar being set up - Please check my plans

[dewey02]

I will be installing a portable solar system and want to check with folks to see if the set up I have planned is correct. While this will be a home-built portable unit, I will be installing an electrical sub-panel inside the trailer (in the pass through) that the panels will connect to.

Our Situation:

We will NOT be installing panels on the roof, just a portable unit. We camp mostly in tree-covered areas. Our electrical use when camping is fairly minimal. I have replaced all lights with LEDs. We do not have (or ever intend to have) a television nor do we plan to use the microwave when boondocking. We do use an iPad, and a laptop that we use which will need to be recharged. We play the radio about 2 hours per day. We have the propane/DC refrigerator, toilet fan, kitchen exhaust fan, and two O2 Cool 12 volt window fans, and of course the water pump, and CO/Propane detector. We do camp when weather gets cold, so we use the propane/DC furnace in the fall.

What I have already purchased and will be using: (we will not revisit this as it is already purchased)

• Two 120 Watt 12 volt semi-flexible solar panels from Solar Blvd. I have built aluminum frames for each of these and they are connected like a solar suitcase. They are 12 volt (Vm 20V; Im 6.0A; Voc 22.8V; Isc 6.65A). I plan to run them parallel to keep voltage at 12 volts. I am using semi-flexible panels because of the great savings in weight vs toting around glass panels of equivalent wattage
• Two Energizer 6 volt golf cart batteries wired in series. 215 amp hours. Connection between the two batteries is 4 AWG wire. I’ve had these for two years now.

I plan to purchase the following from Amazon:

1. 30 ft of 8AWG wire with C4 connectors. Is this an adequate length? And is the gauge large enough? Or can I go with a smaller gauge and save some money? Link Here

2. Renogy CNCT-MC4Y Branch Connectors Solar MC4 Connectors Y connector in Pair MMF+FFM Link here


3. Grape Solar GS-PWM-40BT 40 Amp PWM Solar Charge Controller with Remote Monitoring (I intend to us my Apple iPad’s Bluetooth to access the remote monitoring). I plan to mount the controller in the pass through at the front of the travel trailer. Link here

4. Battery Minder EZ Connector. This will be the plug in to the side of the trailer and will connect/disconnect panel wires from controller. Wire size for this is 12AWG, but I will be only using these wires for very short distance (less than 1 foot).
Link here

5. Two RadioShack Gold-Plated Inline Fuse Holder with 40 amp fuses. Link here



6. Wiring run from Controller to Batteries – need help with gauge here. The run will be approximately 3 feet. What size wire should I be using?

7. Do I need a battery cutoff switch? Between which wires do I install it? What brand/type?

I don’t plan to install an inverter at this time, but will pre-wire the elect. Sub panel for the future.
I would appreciate your critique of the system and suggestions for wiring sizes, improvements, etc. Please avoid the “put it on the roof” and the “semi-flexible panels suck” comments, as those decisions are already made. I have numbered the items that I have not yet purchased, so that you can easily refer to each item. Thank you in advance.

[dewey02]

Thanks red31!

[red31]

http://www.grapesolar.com/docs/GS-PWM-40BT%20manual.pdf

Max Voc 55v, you will be well under that(+/- 22.8v)

Mr Wiz took a cheap tablet and downloaded the app Grape sent, he plugs the tablet into the grape's usb port for power and ends up with a remote display and the added features of the app. One note is the usb follows the load timer, I had mine set for 3 hrs on at dusk and the USB had no power, set to on 24/7 and it had power to charge my phone.

older version at store
https://play.google.com/store/apps/details?id=com.shuorigf&hl=en

[dewey02]

pianotuna wrote:
Hi all,

Some one sent me a private message. There seems to be confusion about what I recommend--so here is a clarification.

Here is what I believe.

For systems under 500 watts it is hard to beat the Grape 40 amp controller. (snip)

Thanks pianotuna. OP here.

Just a follow-up based on a comment a couple of posts back by another poster about PWM controllers frying if getting too much voltage. If I have those solar cynergy semi-flex panels with the following specs (Vm 20V; Im 6.0A; Voc 22.8V; Isc 6.65A), and wire them parallel, will the Grape Solar handle that voltage OK (without "frying") It seems these panels have a somewhat higher voltage than regular panels. Thanks.

[pianotuna]

Hi all,

Some one sent me a private message. There seems to be confusion about what I recommend--so here is a clarification.

Here is what I believe.

For systems under 500 watts it is hard to beat the Grape 40 amp controller.

For larger systems MPPT makes a great deal of sense, and is cheaper per watt.

12 volt panels:

https://www.solarblvd.com/product-category/solar-panels-systems/12-volt-solar-panels/

24 volt panels:

https://www.solarblvd.com/product-category/solar-panels-systems/24-volt-solar-panels/

My system was purchased when panel cost per watt was $5.50 so going MPPT was a no brainer. My input voltage is 33 vdc and charging started at 5:45 a.m. on May 10. It is now 8:20 and charging is 7.5 amps. Load is 2.5 amps so 5 amps @ 14.3 volts are going to the battery bank.

A 1650 watt system with the PT-100 Magnum controller parts cost would be about $1300. In a nominal 12 volt system just the panels would cost that much, then there would be the complication of having 3 grape controllers, and LARGE wire.

My advice in a nutshell? Once you know the size of system, find the cheapest cost per watt to do so. Below 500 watts the Grape controller is darn hard to beat. Above 1000 watts MPPT is cheaper.

[CA_Traveler]

"So if this ever flies, a PWM with max input V of over 55V is what I need. Or go with a cheap mppt. Neither has to be fancy.You need to be very aware of the CC Voc maximum with cold temperatures especially if Ontario implies Canada.

"I posted about my 60 cell on 24-24 stalling out at 30v, which was just ok to meet the 14.8 spec." A successful experiment but CC mfgs recommend 72 cells as there is no head room for 60 cells. A 3 percent wiring loss yields 29.1V which is below the flooded bulk charging voltage.

[pianotuna]

Hi brulaz,

Sorry. You DO want fancy. The Grape 40 amp unit is the KING of pwm controllers with adjustable voltage set points and a battery temperature sensor. It will handle 480 watts of panels. It is readily available (Home Depot) and inexpensive. I think MrWizard is using one.

The cheap MPPT units either are lying (i.e. not MPPT at all), or have an inductance coil that is nearly a joke.

My "real" MPPT started charging at 5:45 a.m. and by 8:20 was doing 7.5 amps @ 14.3 volts. Date is May 10. Location is 50.444593, -104.529741

brulaz wrote:
So if this ever flies, a PWM with max input V of over 55V is what I need. Or go with a cheap mppt. Neither has to be fancy

[BFL13]

That's why I got the Tracer with its 100Voc limit. I wanted to try my 12s in series and the Eco-W can't do that. As it happened the amps with series = amps in parallel so didn't need the Tracer.

I might have got more AH with series in low light, but you can't tell if you do. You don't have the comparable AH number for parallel. Wouldn't be anything worth the bother in our situation. Might be important in another scenario. Not my problem.

I use fat enough wire from panel to controller that I get no loss in amps with 12v PWM so that is extra good with 24v MPPT. Thin wire might be easier to deal with in some rigs, but not an issue in our set-up.

In our trailer, you can store the panels behind the sofa or just lay them on the bed for when on the road.

[brulaz]

BFL13 wrote:
If you go over the controller's Voc input limit, it fries. No margin, no second chances.

You can do 24-24 with a PWM that is 12/24 but of course you cannot do 24-12 unless you have the buck converter MPPT.

I ran my 255w panel 37voc 24-24 with my Solar 30 PWM no problem. Don't know its Voc limit.

My MPPT Eco-Worthy 20 amper has only a 42Voc limit so can't run two 12s in series (newer ones of those have a 50Voc limit)

Not sure where a 32 cell panel stands in terms of meeting charging specs. Not as good as 36. I posted about my 60 cell on 24-24 stalling out at 30v, which was just ok to meet the 14.8 spec.

Thanks.

So if this ever flies, a PWM with max input V of over 55V is what I need. Or go with a cheap mppt. Neither has to be fancy.

And, sorry, I meant 36 cells, not 32.

[BFL13]

If you go over the controller's Voc input limit, it fries. No margin, no second chances.

You can do 24-24 with a PWM that is 12/24 but of course you cannot do 24-12 unless you have the buck converter MPPT.

I ran my 255w panel 37voc 24-24 with my Solar 30 PWM no problem. Don't know its Voc limit.

My MPPT Eco-Worthy 20 amper has only a 42Voc limit so can't run two 12s in series (newer ones of those have a 50Voc limit)

Not sure where a 32 cell panel stands in terms of meeting charging specs. Not as good as 36. I posted about my 60 cell on 24-24 stalling out at 30v, which was just ok to meet the 14.8 spec.

[brulaz]

So you folks have got me thinking again about adding some portable solar to the existing fixed solar.

Curious what happens when the solar panel V exceeds a PWM's max input spec. (on really cold, bright sunny days)? Do they just shut down or blow up ... or? IOW any harm to them?

Looking at two 36 cell panels in series going into a 24V battery bank via PWM. Each panel with Voc of 23.39V @ 25C and maybe 51.5V total at 0C (estimated roughly from that graph posted earlier).

Have seen specs for max solar V of <50V in cheap PWMs and up to 60V in more expensive PWMs.

[landyacht318]

I would pass on the 'Battery Minder EZ Connector.

Those 12v SAE connectors, in my experience heat up greatly and wear out quickly. I used both 10AWG and 18AWG SAE connectors in the past, and had many outright fail and others heat up to the stinky plastic arean at just 20 amps of current. I have removed ALL of them in favor of anderson powerpoles

I'd use anderson 45 amp powerpoles with 10AWG. These are much more reliable and have much less resistance.

Mine regularly pass 40 amps without issue or excessive heating.

The 45's are not so easy to crimp without their special crimper. the 30 amp ones can be crimped with a simple dimple crimper but can only handle 12awg.

[ktmrfs]

DanNJanice wrote:

Lwiddis wrote:
Hey, let's go out for breakfast! Stow your panels. Hey, let's go out to lunch! Stow your panels. Hey, let's go on an afternoon hike! Stow your panels. Hey, let's go out to dinner! Stow your panels. Hey, it's dark.... (Theft) Your choice..stowing or lots of panels on the roof. Very soon the major activity of your day is set up and stowing.

Move, move, move the trailer. Find a sunny spot in the trees. Opps, now it is an hour later no longer sunny , move, move, move the trailer. Maybe park in the open sunshine, opps too hot! Fire up the genny to run the AC. Wait! the animals are in the trailer while we go to lunch, fire up the genny again, so the animals don't overheat.
In all my years of camping, I have never had anything stolen.
Thanks, I will keep my movable panels.

my thoughts and experience exactly. trailer in the best shade, roof panels get what they get, make it up with the portable panels with 150 ft of 10ga cable to get the panels almost anywhere I want in FS campgrounds.

Limit on our stay..... how long it takes for the holding tanks to fill, 2 weeks plus.

[DanNJanice]

Lwiddis wrote:
Hey, let's go out for breakfast! Stow your panels. Hey, let's go out to lunch! Stow your panels. Hey, let's go on an afternoon hike! Stow your panels. Hey, let's go out to dinner! Stow your panels. Hey, it's dark.... (Theft) Your choice..stowing or lots of panels on the roof. Very soon the major activity of your day is set up and stowing.

Move, move, move the trailer. Find a sunny spot in the trees. Opps, now it is an hour later no longer sunny , move, move, move the trailer. Maybe park in the open sunshine, opps too hot! Fire up the genny to run the AC. Wait! the animals are in the trailer while we go to lunch, fire up the genny again, so the animals don't overheat.
In all my years of camping, I have never had anything stolen.
Thanks, I will keep my movable panels.

[BFL13]

red31 wrote:

dewey02 wrote:
They are 12 volt (Vm 20V; Im 6.0A; Voc 22.8V; Isc 6.65A)

I call em 6A panels. it ain't no 7A+ panel.

Just like I call my 3.85A Isc panel a 4A panel. it makes 4A at times! It don't make Isc no more, that would be 50% (C/2) and the batt just can't take that by the time the sun is right.

The OP has 'special' panels, 20v vs my 17v! your 'relationship' is bogus for such panels, and they likely will never make 120 watts!

Right, they are different. 40 cells too.

Since you are the guy who provided that nifty figure 8 Dec chart, I knew you must be correct.

BTW that Dec chart does show the Southern Hemisphere is fatter than the Northern. Our Astro instructor said the Earth is "pear-shaped" which is how that Dec chart goes.