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preexisting dc wiring and PoE  RSS feed

Posts: 13
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K.... First, my brain hurts!!
My timeline has consisted of doing without for the past ten years. I am now collecting generating capability to apply to the convenience of my off grid living.
The house is wired AC AND DC.
I have four solar panels at 230w each, and four t105 golf cart batteries from Trojan to destroy as per every bit of literature out there that says that's what I'm gonna do!
The charge controller I purchased was for my stream engine, xantrex c40, but I was offered a fantastic deal on new panels that I felt compelled to jump on as a fan of redundancy.one is none, two is one, three is a... For me...
So, I wish to procure a mppt controller for as little expense as possible and seek suggestions. My wire run is less than 75' and existing wire laying about is 1awg.
I am in NW MT and have zero delusions about generating electricity in amounts rated by the watts stated on the labels...radios, laptop and led lights are the targets. 920w available on label I'd be pleased with the bank at a full charge, the laptop battery at a full charge and use of the LED lights in the 16 hours of darkness setting upon us.
Any takers?
Posts: 225
Location: SW Missouri
chicken hugelkultur solar
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I'm not sure anyone will be able to answer you. Your just looking for a charge controller? What's your battery voltage and voltage of the panels. At a 70 foot run I would buy a charge controller like an outback flexmax and run the panels in series as close to 150 v dc that you can. Then your existing 1 awg should work fine.
Eric Tilton
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Hi Eric and thanks for taking the time to reply.
The flexmax would indeed be a boon to my system. However, I would be able to use the $520 it costs in a few other areas to bolster my longer term goals.
What  I'm looking for is a simple and inexpensive, yet functional charging setup to bridge the gap of winter. Certainly not disposable, but for the low consumption I anticipate, something far more economical MUST be available?
The battery in my laptop will last 3-6 hours depending on usage and I would be able to power LED for anything necessary through the dark hours. I can purchase a replacement laptop battery for under $40 and " lump it" if necessary but I'd rather apply that $40 to the mppt controller perform greater feats!
Edit for v
Panels 37.35 voc, 28.78vmp max system voltage dc600v.
Posts: 347
Location: Michigan
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There is no reason to destroy batteries, and with the equipment and usage you are indicating, it is unlikely that you would. The c40 charge control that you have is able to operate at higher string voltages than most pwm types.

If your home run wiring is in fact #1, then two of your modules in series and combined in parallel, and about 56vdc and 16.5A should be .55% loss.

At 34A charging, and C/6 its a good battery charger. As long as you discharge 20 percent or so on average, you are likely to easily charge to full in an average solar day and power daily loads. 1800-2000 watt-hours worst month average though.

All these numbers are rough and fast, there is no sage magic here. Your site and insolation characteristics and deeper loads and system design will yield truer numbers, but... this should work.

The more we know, the better the show!

I used Great Falls as a location. Montana has relatively even and abundant solar resource as long as your actual horizon allows a wide window, mountains and forests are sometimes obstacles or major detractors.

We do what you are proposing and more on about the same pv wattage at Michigan!

Are you buying a new controller or do you need the least expense?

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Posts: 20
Location: Alberta,Canada US Hardy:3b Annual Precipitation: 15" Wind: 62mph Temperature:-45F to 86F
food preservation forest garden hugelkultur
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Hi Eric, give this a try.


I have worked oil & Gas 27 years doing solar  in northern Alberta & British Columbia.

Bob says it like it is. Morning Star  controllers or nothing.
Posts: 111
Location: North central Ontario
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There are cheap basic mppt charger on amazon for a fraction of the cost. Having said that please take every professionals advice I have ever heard and buy quality on the charger. Morningstar outback and midnite solar are all excellent and will bring a smile to your face for a decade or more.  They blow the pants of traditional chargers.  Not on sunny days at noon but of partially cloudy mornings and afternoons where the angle and light are not perfect.  Save the headache and downtime and generating expense down the road.
Best regards, David Baillie
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