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Santiago
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Solar 12 v DC regulator question
Off grid 'cabin', use for a couple of weeks at a time then sits empty for a couple of months. Currently runs a 12 volt RV type water pump and a
couple of 4 watt lights. 3-15 watt panels through a very cheap, Chicago Electic (Harbor Frieght) regulator, to charge 1 deep cell battery. All DC.
Nothing needs to be 'on' when cabin is empty.
A few questions for you solar pros:
1. We wish to replace the regulator with an automatic type that will charge the battery when it needs it. We have to manually turn the current
regulator on and monitor the voltage and then turn it off. Sheeesh This is way too much responsibility for us. Recomendations? Keep in mind that we
will want to add a few more lights.
2. Can we wire the lights with romex, 110v boxes, switches etc. under the theory that eventually we will change over to a 110v system? I presume
that the 12v DC system will work with romex, like a #14?
3. When we leave, do we disconnect everything (panels and battery) from the regulator? My buddy (NOT ME!) thinks that solar panels are like teen-age
boys - all that energy they're generating must have regular release or they will explode. I, of course, think this is completely bogus but I have to admit, I tried using that line once or twice myself. With little suscess
as I recall.
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Bob and Susan
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you need a "charge controler"
then just leave it on...
it will "take care" of the energy your panels are producing when you don't need them
personally if the panels are accessible to others they MIGHT
"go missing" when you're gone
I'd lock them up inside and take them out when you arrive
no reason to tempt travelers
i'd wire the place correctly the first time
#14 romex is fine for a small house
use wire caps and correct boxes
if the wire is exposed use condit and watertight boxes
you'll be fine
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Roberto
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What B&S said. Plus, a controller is not a safe way to charge a battery anyway - you can cook your batteries with it if you don't pay attention
because it doesn't taper off the input voltage asthe battery voltage rises. Check your water level in the batteries!
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MrBillM
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Getting Charged Up
In itself, the word "Controller" doesn't mean anything. In many cases, it has simply become a replacement word for "Regulator".
The cheaper Regulators/Controllers/Maintainers (all three words are used here and there) simply "sample" the battery voltage, then continue to charge
at whatever they have available until the battery is at full charge resulting in a battery that tends to be over-charged over longterm light usage
conditions.
For BEST Battery maintenance, you want a Three-Stage Controller such as the Trace C30-C40-C60 or others. Outback is the very BEST, but expensive. I
use two Trace C40s that have been online for almost ten years without issues. The Three-stage will charge the battery array to a (settable) maximum
voltage, maintain it at that voltage for a specified time and then taper off to a "Float" (maintenance) voltage setting, only allowing enough charge
to maintain that float.
That said, I have used the single-stage units in the past and at present to charge small RV battery arrays from one to three 42 watt panels without
any premature battery failures.
Trace C40 3-Stage Charge Controller
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3-stage PWM regulators with field selectable voltage settings. Calibrated scales and test points allow precise adjustment and verification. Electronic
protection for short circuit, overload, overtemp, and reverse polarity. Two stage lightning and surge protection. Equalize mode has manual or
automatic activation (every 30 days). Has diversion control mode for control of wind and hydro sources. Optional backlit LCD meter displays volts,
amps, cumulative amp-hours of array and is mounted on the unit (when ordered together) or remotely with a telephone type cable. Optional remote
temperature compensation probe. Operates as either a charge control, diversion control or a load control. Dim. 9"H x 5"W x 2"D. Wt 4lbs. Limited 2
year warranty.
----------------------------------------------------------------------------------------------------------
Checking current Trace 3-stage offerings: C-12, C-35, C-40, C-60. $110. $119. $159, $199.
[Edited on 11-2-2007 by MrBillM]
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Bob and Susan
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i have a trace c60...
i just got two more outback controlers
they are OUTSTANDING!!!
you get 30% more power out of you solar bank with the outbacks
no more trace controlers
old technology
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MrBillM
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Going Outback
There is NO doubt that the Outback MPPT Controllers are the premier unit in their class with a Theoretical (and practical) charge
advantage over simply increasing the number of panels in the array.
While flawed in not assessing the Exact method by which the Outback produces the added energy, a rough indicator might be:
Trace C60 = $199 Outback MX60 = $500.
60 amp + Max Claim 30 % = 78 amp peak. Addtional Solar panels to accomplish = $1200 +.
Assuming that the claimed 30 % remains steady throughout the input range, any array in the 20 amp and up range would result in a price benefit. At
the margins, of course, longterm endurance would be a question since the Panels might be expected (barring defects) to outlive the controller. Time
will only tell in that respect.
[Edited on 11-2-2007 by MrBillM]
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Russ
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There are lots of sites to look at for your specific needs. Here is one: http://www.gaiam.com/retail/product/53-0115_MSTR
Here in Punta Chivato everyone is pretty much an expert but seldom agree on anything.
My thought would be to look around for a kit. Most good businesses in this area will have a work sheet you can fill out and submit and then they'll
send you a couple of ideas. I'm a believer in using conduit (the gray stuff) and stranded wire. I like to run 3 separate wires (red, green &
black) I understand you'll only need two for the DC system but.... you'll probable want to upgrade to AC at some point and you won't have to pull the
third wires later. I'd stay clear catalogs that sell everything and look at those that sell solar products. Good luck
Bahia Concepcion where life starts...given a chance!
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MrBillM
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12VDC versus 120VAC
Something that should be stressed when discussing wiring is that 12VDC runs require substantially larger guage sizes for equal length runs than do
120VAC. 12V Wiring runs longer than 25 feet or so generally require 8 gauge or larger to avoid excessive voltage drop. 120VAC, on the other hand,
works fine at 100 feet using 14-16 gauge. My personal method when running wiring inside of PVC conduit (sched 40 or 80) is to run multiples of 12 (or
larger) gauge Romex to junction boxes. This gives you the option of combining conductors for 12VDC or separating them later for 120VAC.
The problem with buying so-called kits is that, often, you end up with parts you don't require for your installation and find yourself buying parts
that aren't included. Additionally, vendors offering "Kits" often charge a premium above what the individual parts would cost. Better to educate
yourself and determine what is required for your own installation.
Another excellent supplier of Alternative energy products is:
http://www.backwoodssolar.com
I have purchased thousands of dollars in equipment from them at excellent prices and service with no problems. One thing that does benefit from
"shopping" though are the Solar Panels themselves. You can find a pretty wide variance in price on the same units.
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Roberto
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Quote: | Originally posted by Bob and Susan
i have a trace c60...
i just got two more outback controlers
they are OUTSTANDING!!!
you get 30% more power out of you solar bank with the outbacks
no more trace controlers
old technology |
Sorry, guys, that's just not true at higher ambient temps. I know that's the party line, but I suggest you do more research. The higher the ambient
temperature, the less effective the MPPT controllers are. At Baja temps (except short winter stretches), they are no more effective than a Trace. For
MUCH more money.
Quote: |
Heat is the nemesis of a MPPT controller. As the panels get hot, the MPP voltage droops, and you no longer get great gains in charge current - indeed
on some panels and very hot temperature, I have actually seen a loss of power. However, even in these situations, great gains are made in off-hours
where the temperature is reduced and the sun is not directly on the panels. Overall gain is reduced but is still present. |
Keep in mind that at anything over 20 degrees centigrade (68 degrees Fahrenheit, which is the point where a realistic 30% can be achieved), the gains
start to decrease.
[Edited on 11-2-2007 by Roberto]
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MrBillM
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Outback Efficiency
Roberto is correct regarding the "Heat" factor. However, even if we were to assume a 10-15 % gain averaged during the seasons, the cost versus gain
related to additional solar panels is still valid if we assume a relatively long controller life cycle. The difference of $199 and
$498 is actually less because the Trace Controllers make the Digital Display optional.
A close friend who has worked with Solar for many years now, both in the U.S. and Baja, had such success with the Outbacks that he insisted on
supplying them with any systems he installed, including his own. Thus far, he's encountered no problems.
I don't own any Outback units, BUT if I were installing a new array of any size, I would probably purchase the Outback. The $300
difference between Trace and Outback equates to about three amps of panel purchase.
---------------------------------------------------------------------------------------------------
From Solar-Electric.com:
"Maximum Power Point Tracking - this is electronic tracking, and has nothing to do with moving the panels. Instead, the controller looks at the output
of the panels, and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It
takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern
MPPT's are around 92-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in
summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors."
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hookemup
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Outback makes good products and their service is just outstanding .However the fan is an issue on the MX 60. They do have a free ( so far ) fan
replacement kit that comes with a DVD. We chipped in with others here and bought a spare Mx 60 for the group. They have a new unit FM 80 that mentions
" enhanced cooling " so they hopefully have fixed the problem. Make sure of your source though, as China has a surface to air missle called the FM 80,
not sure about any enhanced cooling
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BigWooo
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Quote: | Originally posted by MrBillM
12V Wiring runs longer than 25 feet or so generally require 8 gauge or larger to avoid excessive voltage drop. |
This is very important. The max distance for 14 guage wire is 22.5 feet with a (12v) 2 amp load. At that distance you will have about a 2% drop in
voltage.
What's more important is, with distances greater than 22.5 feet, or at that distance with a higher load, the wire will begin to heat up due to
resistance. If you overload the wire too much, and it runs unprotected over old dry wood, palapa or some other flammable material, it has the
potential to cause a fire.
Always be sure your wire is sized to the load and that you always have adequate circuit protection: Fuses or Breakers.
edit to add more info.
[Edited on 11-2-2007 by BigWooo]
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Santiago
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Thanks guys - especially the heads up on the wire size - I had forgotten that. I seem to remember a website that had a wire-size-calculator but I
can't find it now - anyone remember it?
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Roberto
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Quote: | Originally posted by MrBillM
You typically get a 20 to 45% power gain in winter and 10-15% in summer |
That is pure, unadulterated, BS (aka - marketing) - EXCEPT in a northern climate, and even there about 50% overstated. And it's not supported by ANY
papers published on the subject. But, if you want to believe that - more power to you.
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Al G
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Santiago... Here is the one I use:
http://www.solar4power.com/solar-power-volt_drop.html
I would not use anything less then 10 Gage Stranded...
I do not use romex solid for anything 12v...also I would run 8 or 6 to a centralized distribution Panel to shorten distances of 10 gage.
DC cost alot and skimping on wire will add to that cost...well since copper has exploded in price...maybe not
I still would use 10 gage (things do change) unless the run was under 10 feet.
Albert G
Remember, if you haven\'t got a smile on your face and laughter in your heart, then you are just a sour old fart!....
The most precious thing we have is life, yet it has absolutely no trade-in value.
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MrBillM
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B.S. ?
Roberto seems to have taken on this subject as a matter of personal honor. Odd.
I'm not making any claims regarding the Outback. Just passing on information. Are the claims hype ? I don't know. It would depend on the voltage
rating of the particular panels used at high temperatures. You could determine that from the Spec sheets. Of course, they may all be lies too.
Maybe they're ALL lying. That WOULD make it hard to design a system, wouldn't it ?
As I stated above, even a 10 % or more average year round would seem to justify the investment in MPPT technology. There are a lot of users (other
than Roberto) who seem to agree. That would seem to include Bob/Susan and Soulpatch. Argue with them if honor demands it. I'm satisfied with the
two Trace C40s (along with three other smaller "primitive" controllers from the Stone Age) that I'm using.
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landyacht318
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45 watts
Quote: | Originally posted by Santiago
Thanks guys - especially the heads up on the wire size - I had forgotten that. I seem to remember a website that had a wire-size-calculator but I
can't find it now - anyone remember it? |
http://www.wind-sun.com/ForumVB/showthread.php?t=29
Since you don't have a great amount of wattage from your harbor freight panels, you won't need a huge expensive top quality MPPT controller able to
handle 50 amps.
That said, any controller will be better than what came with your HF panel kit.
I have been told that the MPPT controllers won't pay for themselves with systems under 300 watts, especially in hotter climates. That didn't stop me
from getting a MPPT Blue Sky 2512i controller, BS IPN pro remote battery monitor powered by a Kyocera 130 watt panel. Apparently having the
appropriate thickness wire is even more important when using MPPT controllers.
My controller says for a maximum 3% voltage drop.
One way lengths between panel and batteries with the controller somewhere inbetween:
6.4 feet 12 awg
10.2 feet 10 awg
16.2 feet 8awg
25.7 feet 6awg
40.8 feet 4awg
Unfortunately I read this little tidbit after I installed 12 awg on my 14 foot one way length, and will no doubt be adding some more copper.
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Bob and Susan
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i'm traveling 20 feet from the combiner boxes
to the controler
with solid copper 10ga with "no problems" yet...
i'll get my camera and take a picture of the inside
of the "dinosaur" trace controler and
the Outback MPPT display controler
the display is WORTH the $200 just to see what you're getting from the panels
the adjustments on the "dino trace" are inside dials which are VERY hard to "dial in"
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Diver
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At 20', 10 ga is rated for 15A @12V.
http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html
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Roberto
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Quote: | Originally posted by MrBillM
Roberto seems to have taken on this subject as a matter of personal honor. Odd.
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Nope - just trying to prevent folks from falling for hype. Not directed at anyone personally.
I know several people who own these controllers in Baja who were sold the same way - the published information by sales people. When they didn't
deliver on that info, I looked into it in detail, as I was going to purchase a couple myself and replace my C60. The best these things can deliver,
and that's only in the coldest parts of the winter, is 5%-10% in Baja. Even BC. The sun is just too strong.
Now, if you have several thousand watts of panels, that is worth it, but for the smaller number that most people install, I don't think so.
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