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Old 01-02-2011, 10:01 PM   #15
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Thanks for the reply.

I did see in your blog the thing about the fused AC disconnect. I'm kind of wondering about using a bussmann switched marine breaker, though. It appears to be pretty compact and rugged. I was also kicking around a stud post single pole fuse holder.

The Trimetric 2025 suggestion has me convinced. I'll get one.

You also convinced me to go parallel with the panels.
Quote:
10 gauge is fine for the panel feeds as long as they are individual, or two in series.
So if I go two in parallel, how to I go bigger with MC4 connectors? I don't seem to find them in bigger gauge? So is the only option then to run feeds to from each panel to the junction box and not use multibranch connectors?

I will for sure fuse the volt sense wires. Good tip on using leftover temp sense wire. I think I have a spool of 18/2 around too, and the converter will take up to 16 ga for the volt sensor.

Also, thanks for the suggestion to shop around on the panels. The 135's are the biggest UPS will ground ship so I'll have to do some math to figure out where I'd get the most watts for the buck with shipping.
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Old 01-03-2011, 12:21 PM   #16
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You will not find larger gauge MC cables. There are parallel connectors available, but you should not parallel panels unless the run is very short. These are intended to be used for short runs on home & commercial arrays, between the panels and the combiner boxes with distribution circuit breakers. They are now a code requirement. I would like somebody to explain to me how requiring a special connector that somebody is making a profit on is "Life Safety", which is the name of the building code. The code is full of things that some salesman thought were good ideas. Maybe we should change the name to the "Seems Like Good Idea Code". There is that old building design engineer attitude of mine again!

You need to fuse both the PV input & battery output (two fuses or circuit breakers).
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Old 01-03-2011, 04:05 PM   #17
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I see. Though the run will be very short, I'll go ahead and wire each panel to the junction box separately.

To clarify on the conduit, I don't plan to run it clear to the controller, just down the corner of the closet (maybe painted tan to match) to keep things clean looking.
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Old 01-04-2011, 05:53 AM   #18
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Another option you have (your choice) is to drop the #4 gauge cable running from your roof down through the rear of your coach. In our '01 HR Endeavor, I drilled a small hole in the end cap, dropped the 'jumper cable' wire down through the read and right into the compartment that holds our inverter and solar charge controller. This compartment on our coach is the last one on the curbside and it is right next to the battery compartment.

Doing this was actually easier and had a shorter wire run than trying to go down the refrigerator vent. We also used the MC4 connectors to run from the panels to the junction box on the roof. Please note that if you cut the MC4 connector off of your solar panel....you just voided the warranty on the panels. This was pointed out very specifically in the paperwork for our Evergreen panels.

After using the MC4's plus the 4 gauge wire, we still have 22 volts at the fuse panel that is in front of the solar controller.

Once you have your panels on the roof....remember to treat them like a live wire as the MC4 connectors will have power to them. We wrapped ours in electrical tape until we were ready to make the final connection.
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Old 01-04-2011, 01:15 PM   #19
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RV Electrical Guide

Quote:
Originally Posted by Bob/Becky D - VA View Post
I have found that Jack Mayer's site has provided the most comprehensive discussion of determining solar requirements, discussion of various components, and installation procedures.

RV Electrical

Bob
I just want to say that I had not looked at Jack's site for years. So much for my thinking that I should get my book written so I could make some money from it. He has written it and it is free. It is a great source of good information, but written from a different perspective than mine.

Jack & I had our discussions early on and I get the feeling that he doesn't appreciate my brutal assessment of the state of the RV Solar industry. Notice that he never once mentions me or my blog. However, I see that he says much the same things, just more nicely. I originally tried to use the same tone as his and it failed when people would not believe me. I have been on my mission to make solar power work for longer than most of the RV'ers you see on here and I got mad early on after being taken advantage of by more than one of those dealers that I complain about.

The only issues I would take with Jack's recommendations is that they are made by a guy with a lot more money to spend than I have. At the beginning of my RV Battery Charging puzzle I say that it is aimed at the budget minded RV'er, something that most people ignore. Just take a look at his rig compared to mine and you will understand what I am saying. He ignores the lower priced Morningstar charge controllers that all have built in temperature compensation and are real bargains. This is because he believes the MPPT boost marketing claims. He jumped from a non working Heliotrope RV30 all the way to a big MPPT controller in one leap, when he bought a brand new custom built rig, while I have never been able to spend the money. I found that just by going from the old Heliotrope to a real three stage controller (first Trace C series & then Morningstar Tristar), these big controllers that were designed for off grid houses put a lot more into the batteries than even the small MPPT units. The small MPPT controllers are not worth what they cost. Go big or don't do it and spend the money on more panels instead. The $250 difference between a Tristar PWM and any good, big MPPT controller will pay for another solar panel if you do some serious shopping on line and that panel will work even on cloudy days, when the MPPT does not.

Jack also seems to think that the inverter charger combination units are everybody's solution, while I realize that not everyone can afford one or needs it. I love the Magnum inverter chargers, but I don't need one and don't own one. I am installing another Samlex PSE modified wave inverter in an old motor home right now and hooking it up to the whole electrical panel with a 30 amp automatic transfer switch. This inverter is a good one with soft start technology and it will run the microwave and it will work when the system goes over 15V on cold days. This will cost less than $600 including cables & labor, while a Magnum 2000 watt inverter charger that I installed a few days ago in a big diesel pusher was $1300 including the remote, no cables & no labor. Yes, the charger in the Magnum is a lot better than the old converter in the motor home, but this guy has a working solar system, a limited income and rarely needs back up charging, so it is serves his needs. One size does not fit all.

Jack also parrots the common belief that solar systems rarely charge batteries all the way up, while I have a long list of friends who can tell you that is not true.

My message here is that you don't need to be rich to use solar power, even though that seems to be the general consensus. You just need to do it correctly. Jack's guide will help you to do it right.

One of these days I will have to change my signature, because we are working on getting our home in Montana built and then we won't be full time boondockers. I cannot wait until I will have a 1200 watt solar system where I can do real world comparison testing between a Tristar 45 PWM and a Tristar 45 MPPT. A couple of industry professionals who don't want to be named have admitted to me that the MPPT story is mostly hype. Some day I intend to prove it.
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Old 01-04-2011, 01:27 PM   #20
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Spurs,

Thanks for the tip, but going down the back won't work. The rig is a 40' 5th wheel toyhauler with separate garage. The fridge is at the rear of the living quarters, curb side, and the battery box is curb side front.

Looking at it, if I drop through the closet at the front driver's side, I'll drop into the area behind the water heater.

There is an outside hatch that gives access to the back of the water heater, outside shower, and the back of the power distribution box. This is right below the closet.

I should be able to snake across the rig there (under the stairs) as the battery cables do, and come out at a hatch on the underside (between the frame and exterior wall) where the battery cables also come out.

It will take a little more fiddling than going down the fridge vent, but it will give me a lot shorter run and would have the cables well protected.

I'm not sure where to stick the charge controller, though. I could go along side the curb side landing jack, which is right next to the battery compartment, but also right next to the propane tanks.

Alternately I could go in the generator compartment (no gen) but that would add 4' of run to the batteries.

I'm thinking there might be room in the space above the hatch where the battery cables come out but there might not be enough free space for it to get cooling air. I'll have to pull that apart and look.
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Old 01-04-2011, 05:45 PM   #21
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There is a fairly complete YouTube MPPT vs PWM demonstration YouTube - MPPT vs PWM Solar charger performance - Part 1
And yes I will be interested in what you come up with same manufacturer controllers.
One other factor I would like to see looked at as a variable is the high voltage panel vs low voltage when used with an MPPT and throw in shading...
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Old 01-05-2011, 05:51 PM   #22
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From what I've learned so far, there isn't much doubt that MPPT generates more amps of charge, especially when battery voltage is low, and the panel voltage is high (Lots of sun, low temp).

The point HandyBob made for me is to question whether spending the $ for MPPT is where you get the most bang for the buck in improving system performance.

The difference between a Tristar 45 amp PWM controller VS the same controller with MPPT is $270.

I'd like to see a comparison between systems with the PWM and the MPPT charge controllers, but not with the same solar panels. Test them with the PWM running panels worth $270 more than the panels hooked to the MPPT.

That would be the comparison I think might be most telling.

Direct comparisons are pretty tough, though. I was looking at a pair of 220 watt panels, and found 36 v panels at about $200 cheaper than 17 v-max power panels in that power range. Of course the 36v's would require a MPPT controller, and would offset all but $70 in the difference in the price of the MPPT controller. Still, that is a comparison of brand panels vs house branded...
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Old 01-06-2011, 08:18 AM   #23
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Well, after doing a bunch of number crunching this is a list of stuff I'm thinking of ordering. I'll run a 2 pole safety disconnect switch or a pull out AC fused disconnect.

Roughly $2000 including shipping, for 440 watts with MPPT, battery meter, and pretty decent wire.

What do you guys think?


Panels:

Sun Solar Panel 220 Watt 29.38 Volt SUN-FTS220PC $349.80ea (2) $699.60. Shipping $229 Need also 2 10ga w/Solarlok connectors


Other stuff:

Morningstar TriStar 45 amp MPPT solar charge controller $428.40

Unirac RV Flush Mounting Feet (4) for PV Panels $20.00x3 $60.00

Trimetric TM-2025A Battery Monitor System TM-2025-RV RV Version $152.00

Deltec 500 amp, 50 millivolt current shunt $27.00

Morningstar TriStar PWM & MPPT RM-2 Remote Digital Meter $126.68

2-Wire (twisted single-pair) Tray Cable #16 AWG shielded $9.00

4-Wire (twisted two-pair) Tray Cable #16 AWG shielded $15.60

Welding Cable, #4 AWG $1.45 $72.50

Welding Cable #2 AWG $2.39 $71.70

#4 x 3/8" stud ring connectors, bare $0.60 $6.00

#2 x 3/8" stud ring connector tinned copper $0.70 $14.00

Hammer Crimp Tool for Large Terminal Lugs $27.50

Outback Power TBB-X InsulatedTerminal Bus Bars Black $16.15

Outback Power TBB-X InsulatedTerminal Bus Bars White $16.15


Subtotal: $1,042.68
Shipping: $40.30
Total: $1,082.98
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Old 01-06-2011, 09:02 AM   #24
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JeffinTD

I don't see any proactive alarm capabilities
Check out the Morningstar RD-1 it's a really nice fully programmable device and will easily interface with your system
Well worth the $100 or so that it costs - mine is programmed to light LEDs and drive a sonalert - to indicate low/high battery voltages on both battery banks as well as over temperature conditions

I went with the Morningstar MPPT-60 because it offered an Ethernet interface and like the MPPT-45. Internally they are constructed of parallel lower current "controllers" the 45 has two 22.5amp controllers while the MPPT-60 has three 20amp. When the extra power is not needed the unsed ones are shut off increasing the efficiently
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Old 01-06-2011, 09:28 AM   #25
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I'm stumped on the welding cable. Are you running off the solar panels or just charging the batteries? A 220 watt 12volt solar panel will only put out 18 amps. 220 watt 36volt will only put out 6 amps. Am I missing something?
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Old 01-06-2011, 09:46 AM   #26
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The RD-1 looks interesting. I don't know if I will go with that, at least at this stage. If I were going to run a generator on auto-start it would sure make sense.


Yeah, I know the #4 cable is overkill, considering both panels together would only be around 16 amp at short circuit current. With the size of those panels I'm going to end up with a pretty long run, as I'm going to have to place them towards the rear over the garage section to find space that won't be shaded by antennas and other stuff. The battery compartment is up at the front.

I'm shooting for absolute minimum loss, and price wise it wasn't that much more to bump up wire gauge. Also welding cable is really flexible and easy to work with.

Still too much overkill?
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Old 01-06-2011, 11:37 AM   #27
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Watch for the jacket on welding cable. You need to have outdoor cable if its in the sun. #10 is what I'd run. good for 30 amps #12 =20 amps

I run a #2 on my 25KW generator. that's 125 amps
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Old 01-06-2011, 12:23 PM   #28
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Yeah, the welding cable will just go from buss bars in the watertight box over to the fridge vent (or out the bottom through the roof, haven't decided) but if it does run across the roof to the vent it will be in conduit.

Loosing part of a volt in 110v ac would make no difference at all, but I'm thinking in LV solar...
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