Author Topic: OFF GRID POWER; various thoughts on...  (Read 519853 times)

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Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1075 on: October 01, 2012, 08:28:16 AM »
So, in your opinion what is the best inverter for 4,000 watts max and general not more than 2,000. Batteries only and genset to charge.  Any real disadvantages to a combination inverter/charger. 12V system.  4 100 AH batteries

Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #1076 on: October 01, 2012, 10:28:23 AM »
There is no best ! Quality is conformance to requirements. So, it depends on quite a few requirements that I may have missed that you have posted. People who do this kind of work all have favorites from experience.

I mainly do offgrid residences and so I would never consider a 12 V inverter/charger for a client. Smaller systems and cabins may be fine for 12V systems. Good Luck!
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1077 on: October 01, 2012, 01:10:36 PM »
....best inverter for 4,000 watts max........  .....Batteries only and genset to charge.  Any real disadvantages to a combination inverter/charger. 12V system.  4 100 AH batteries

Four  100 amp hour batteries and a 4000 watt max inverter output seem to be a mismatch, to me.

I personally really dislike running a generator so genset only seems wrong, to me.  If four 100 amp-hour batteries would truly be sufficient for the use planned, then it would seem that you would not need much in the way of a PV array.A big advantage to me, with PV panels is that the system will run itself and keep the batteries charged when the place is vacant. Ours does that all year round through summer heat and winters freezing months.  Not tp mention no nosiy smelly beast running.

Inverter/charger units simplify things. I can't think of any operational disadvantages, but can think of some pluses.
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Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1078 on: October 01, 2012, 02:37:34 PM »
Well, I did overstate the wattage a bit on the max side..as but as I  said generally no more than 2,000 watts is required. I figured I would oversize the inverter for the future in case I decide to go grid-like as it seems is the case for many on here.  Others of us  do not need all that power and do not miss it.  The  2,000 watts is not continuous. I run my fridge 3 hours a day (300 watts), lights at night for 3 hours (total of 200 watts), which is the standard drill so I have plenty of power from by batteries.  I run a fan once in a while when I am sweaty and the breeze is dead (400 watts) and once in a while heat water for a shower...(1,000 watts for six minutes).

So if I want to do it all and not juggle stuff on and off (which actually is easy enough to do), the 2,000 watts is my number, maybe a bit more. That is why I list that...in reality I could get by on a 1,000 easy.

I run my generator a couple of times a week to pump water to a neighbor and don't want to size up the system just to run the pump 3 hours a week.  As it does that, it charges the batteries and runs my fridge. All getting the most from every gallon of gas.  It is 100 feet from the house in a stone building and the exhaust goes out the back.  Very little noise (the howler monkeys drown it out) and since it is maintained correctly no "dirty exhaust"

So, in spite of what you think it is far from a mismatch.  It is a great little system, Suits me fine, although it may not fit your idea of one.  I simple asked a simple question about thoughts on inverters...you know brand "A" over brand "B" over brand "C"...something which I though people on here with all their experience would be able to answer, but instead I got a lecture about something else.

FYI...mine is an off grid residence. Likely more than the ones you wire up for some of your clients.just not not a heavily wired one.  Big is not better all over.  Does not mean it is not a good fit or set up.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1079 on: October 01, 2012, 03:50:21 PM »

So, in spite of what you think it is far from a mismatch. ...........  ....I simple asked a simple question about thoughts on inverters...you know brand "A" over brand "B" over brand "C"...something which I though people on here with all their experience would be able to answer, but instead I got a lecture about something else.


Without knowing the details about how things are used, and all the rest of it, the mention of 4000 watts of inverter output coupled with 4 x 100 amp-hours of batteries remains a mismatch in my mind. Also, without knowing the level of expertise of the member posing the question, I do not believe it improper to question the match. Perhaps I could have gone into more detail but I thought a short answer was better than no answer. If short answers raise questions, the questions can be dealt with later. IMO.

If the response I gave sounds like a lecture it must be because of the way the recipient received it. It was not delivered as a lecture; it was and is a simple statement of a belief. Until I read the response from you and thought more about who this is, Alex I did not realize it was you, so don't feel picked upon. If the same / similar question comes up again I will respond the same.



Outback.  Xantrex.  Magnum Energy. Take your pick. Some will pick one over the other for a feature that appeals to them. Or as Dave stated because they are familiar with one brand more than another.

Then there's the question of square wave vs sine wave; what does one want or need? That choice can eliminate some brand names.

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1080 on: October 01, 2012, 04:47:36 PM »
Point taken.

Maybe i should have just asked for brands and left out the details, which confused rather than helped.

But now I do have me brands...so all is not lost.

Offline Cowboy Billy

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Re: OFF GRID POWER; various thoughts on...
« Reply #1081 on: October 04, 2012, 06:37:37 AM »
I have been running a Aims 5000 watt 24v power inverter for the last four years. It has been good to us and runs everything we have. Tv, fridge, lights ect. But I strongly suggest fuses on the input and output. The first one we got my brother shorted out the panel and fried it. But we sent it back and they replaced it.

I too suggest that you put a few solar panels on the battery's.  I have two 110watt panels and it really helps out. I am running a 1182 amp hr forklift battery.  And with the panels I run 7-8 days and only have to fire up my generator for 2-4 hrs.

This is the one I have but mine is 24v. I prefer 24v as I can run smaller cables.

http://www.theinverterstore.com/5000-watt-power-inverter.html

Here's my system the power inverter is on the wall and charge controller on the 4x4 post.





I am going to put up more panels as its really nice not to have to fire up the generator.

Billy

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1082 on: October 05, 2012, 04:57:07 PM »
Yeah, I think it's time to try some panels. I have shade and lots of clouds, but hopefully can get 4 hours a day of full sun.   The best place is 120 feet away so I could do 24 volt and run to the house.  But as I observe the sun , looks like  I get 2-3 hours on the roof right above the batteries, so I leave it at 12 volts and keep it simple and cheap and will work on 10 gauge cable for the 15 feet to the charge controller. I still will have to run the genset, but maybe once  a week or less. Investing in three vs. two panels will boost me on the roof location.

My biggest problem now is it takes 3 hours on the genset to get to 85 % capacity from 50% n 400AH batteries and then 4 more to get the other 15% . IOTA says this is the way it is.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1083 on: October 05, 2012, 05:52:37 PM »
Generator powered battery chargers are most efficient at bringing the battery charge up to something like 80 - 85% of capacity. After that they use a lot of fuel to do much less at rebuilding the battery charge. PV modules with an MPPT charge controller perform excellently at charge finishing even later into the day, especially when the PV modules are connected serially.*

With that in mind it is my opinion that when one knows they are going to have to run the generator to recharge the batteries fully, the generator should be run early in the day to build the initial charge through the bulk stage. Then let the solar PV system finish off the charge.

* When the light is failing and the PV module voltage is falling (parallel connected multiple modules) to levels too low to be able to place an effective charge into the batteries, series connected modules will still have a high voltage. The MPPT controller can take that voltage and the available current and manipulate it to produce a voltage just high enough to make a charge go into the battery while it multiplies the current. Selection of the controller must be matched to the maximum possible peak voltage that the serially connected modules could produce.
« Last Edit: October 05, 2012, 07:43:18 PM by MountainDon »
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Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1084 on: October 05, 2012, 07:56:57 PM »
That is what i need. I interpret this to mean I should runs a 24 volt system to the MPPT charge controller and let that charge the 12 V batteries...i am assuming it adjusts to 12 V from the input which is higher automatically.  IF that is the case, then a lot of other times in the day with lower light I will still be charging...even more less genset use.


Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1085 on: October 05, 2012, 08:28:55 PM »
Quote
even more less genset use.

Running an MPPT controller you don't need to think in terms of what volts the modules are running, as long as the Voc of the modules, series connected, is not higher than the maximum input voltage of the charge controller. The rated Voc of the modules is added, then multiplied by 1.25 and then 1.25 again (NEC formula which may be conservative). Although in the tropics that may be over cautious as you are not likely to get lows in the minus 20 or lower range. Anyhow the point is the rated Voc can easily be surpassed on cold/cool days, especially first thing in the coold/cold day as the sun hits the modules. EG: The mathematical Voc of my three modules is 3 x 36.3 = 108.9 volts. In summer I frequently see logged maximum voltages around 120 volts. In winter (below freezing as in -25 or so F) the highest I have seen is 141 volts.

The MPPT controller does a high frequency transformation of the power as it reads the incoming voltage and current and the condition of the batteries. It then adjusts the output to the best voltage and current to charge the batteries. It is sort of like getting something for free, more or less. The MPPT charge controller does do this automatically and continuously. As clouds drift past it changes to output to the optimal.

When the modules are sized correctly for the battery pack and the use and available sunshine a generator is hardly needed.

Outback power has a string sizing tool on their website. Of course it is designed for their equipment, but it may be useful to mess about with as it does have max and min temperature adjustment sliders so you can see how temperature relates. It allows selection of modules and shows the maximum number in series and parallel. Xantrex has one as well.
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Offline hpinson

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Re: OFF GRID POWER; various thoughts on...
« Reply #1086 on: October 06, 2012, 05:17:55 AM »
Changing the topic a bit.  What is a best practice for over-wintering a small solar system that will not be used November - March? Should the PV be disconnected at the breaker from the charge controller/ battery, or is it ok to leave the system charging? I'm also thinking of removing the battery for the winter. Temps can get down to -20.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1087 on: October 06, 2012, 09:39:13 AM »
Here's what we do. Our cabin sits mostly un-used through the winter. Our goal is to snowshoe every other weekend from the time the snow is too deep to be able to drive up. That's usually mid December through to late March or into April. We don't always make it that often but we do make it several times at least. Because of that I wanted to leave the batteries there; I'm not about to snowshoe even one golf cart battery up and back. And I don't like oil lamps for light.

So starting with when we would leave the RV parked there all winter we've left the system active. The RV was only with a small panel good only for floating. Once the cabin PV system was up and running we did the same thing. The hardware is better and there are more batteries. In fall I make certain the batteries are fully charged and the fluid level in each cell is topped up. All DC and AC loads are disconnected (I pull the breakers whenever we leave for home.) The charge controller is left to do its thing. They have never let us down. Each and every time we return to the RV or the cabin the batteries were fully charged and waiting for use. A fully charged battery will not freeze until something like -90 F.

I also leave some partially full jugs of distilled water up there, but have never needed to add any water over the winter. With the system basically not doing much there is very little loss of water. I do top up the levels each spring and fall.

That's my system and it works for me. No guarantees expressed or implied that it will work for anyone else. But if the PV system is built with quality equipment that is installed properly... lightning protection , etc., there is a very good chance that the system will survive the winter. After all, for me at least, I have not had any summer failures either.


If the system has only a battery or two and will not be accessed at all throughout the winter then removing the batteries would be a viable option. However, then you need to keep them floating at home. I would not leave the batteries sitting in the cold without the PV system active. Even the $12 charge controller we used for the RV float worked without any interruptions.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline hpinson

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Re: OFF GRID POWER; various thoughts on...
« Reply #1088 on: October 07, 2012, 05:41:01 AM »
Good information and I'm glad I asked.  What I get from this is there is really no need to removed the battey for winter, just disconnect the load (easily done) and let the charge controller continue to charge and top off the battery.

I had noticed that if I go away for two weeks and have disconnected PV from the charge controller and battery, the battery charge will drop from about 14 volts to 12.6. This is a newish AGM battery, so no water needs to be added.

Quote
A fully charged battery will not freeze until something like -90 F.


I did not know that.  My sense is this small system is built well enough. Grounded, lightning protected (using the Delta protector, which I want to change out with the Midnight Solar at some point). There is one problem that the buried battery box still gets too hot in the summer, and I need to build a little shed over it to keep temps down.  Those high temps are going to shorten the battery life.

Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #1089 on: October 08, 2012, 10:21:48 AM »

 

I did not know that.  My sense is this small system is built well enough. Grounded, lightning protected (using the Delta protector, which I want to change out with the Midnight Solar at some point). There is one problem that the buried battery box still gets too hot in the summer, and I need to build a little shed over it to keep temps down.  Those high temps are going to shorten the battery life.

Keep the Delta and add a midnite SP. They both have their value when it gets nasty !
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Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #1090 on: October 24, 2012, 06:22:29 AM »
"Depending on temperature 11.9 could be classed as dead, as a problem. Also readings taken while in use (charge or discharge) are inaccurate. batteries should be at rest for a few hours before believing what the voltage indicates, in most cases."

Ok Mountain Don...I've been thinking about the above statement, and now I have a question.

A reading during discharge or charge should be considered inaccurate because the batteries are in use....Would it be reasonable to assume that during discharge a battery's reading would be lower than a reading after a few hours "at rest"?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1091 on: October 28, 2012, 12:41:43 PM »
Would it be reasonable to assume that during discharge a battery's reading would be lower than a reading after a few hours "at rest"?

Yes. The heavier the discharge, the greater the potential recovery. Similarly immediately after charging the battery boltage will read higher than it will after a few hours left "at rest" with no loads or further charging.   That is why voltage readings can be a poor guide to the real health of a battery. And that is why anyone with flooded lead acid batteries (gold cart, L16, etc.) should own a battery hydrometer.  (sorry... I "harp" on that a lot I know.)
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Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #1092 on: October 28, 2012, 03:24:30 PM »
"And that is why anyone with flooded lead acid batteries (gold cart, L16, etc.) should own a battery hydrometer.  " I do...

"(sorry... I "harp" on that a lot I know.)" You do...but it is very good advice  ;D.

Figured out that in the winter, with no woodstove, just the furnace, plenty of lights, computer, negligible solar panel action and after 2 loads of laundry, I used 5.34 Kwh in a 24 hour period. (At least that's what the Kill a Watt displayed)  i want to go 3 days without a gen or help from the PV (as in winter).  So after playing with that PV system calculator I came up with 10 L16's or equivalent.  Think I'll have to save some more for that. So, since I have plenty of wood and would much rather sew than work on the computer, 10 L16's might last a little longer than 3 days. (don't worry...I set the calculator for a max 50% discharge...something new I've learned...from others, yet again  :-\)

Offline mfsangel

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Re: OFF GRID POWER; various thoughts on...
« Reply #1093 on: October 31, 2012, 06:02:10 PM »
One other thought...

Not sure if you are looking into it but you might want to get the MPPT style charge controller. I apologize in advance if you are already considering that, I did not read all 44 pages of posts.

In any case, Outback makes an MPPT style charge controller. Basically, they power match your panels to the batteries for maximum output v.s. losing a lot of power due to mismatching or older style charge controllers.

I think the Power Factor is somewhere around a 93-95% efficiency and it matches various voltage output panels to each other as well. I had a system in San Felipe B.C. with a Zantrex controller which is really robust but with additional panels we were not seeing the wattage output as expected. It is not a big issue there due to no additional power needs but I am pretty sure we are losing a large amount of the potential solar output without that style of controller.

Here is a link I found that explains that type of charge controller.

http://www.windsun.com/ChargeControls/MPPT.htm

Cheers,

Roger

Offline davidj

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Re: OFF GRID POWER; various thoughts on...
« Reply #1094 on: November 21, 2012, 07:08:17 AM »
What are the code requirements for cable protection from the combiner box to the panels?  I'm building a pole mount system and I was planning on having the combiner and dc disconnect mounted at chest level on the pole.  Do I need to protect the USE-2 cable to the panels with conduit between the combiner and the panels?  Or should I mount the combiner at the top of the pole where I assume it's okay to have unprotected DC cabling (but where it's harder to access the breakers)?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1095 on: November 21, 2012, 08:52:52 AM »
I am quite certain that the MC cables used to connect cables from the PV panel to the combiner box is sunlight and weather resistant. As long as the cables are fixed in place with zip ties or something similar that should satisfy the NEC and any inspector. Probably a good idea to have provision to lock up the combiner to keep curious fingers away from hot spots. I also used a self velcanizing rubber tape around each MC connection to discourage the curious from unplugging.
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Offline hpinson

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Re: OFF GRID POWER; various thoughts on...
« Reply #1096 on: November 21, 2012, 09:12:31 AM »
What Don describes is exactly what I did-- array out to combiner via zip tied MC4 cables which are rated for outdoor use. The newer combiners have some nice integrated weathertight MC4 socket connectors so tape is not needed.  Plugging them in is easy but unplugging is difficult and can require a special tool. My Midnite Solar combiner is not mounted on the array pole, but on a separate post. Also, a lightning arrestor and a buried ground copper rod both off the combiner are in the mix. The combiner box with breakers is closed with a screw discouraging casual access.  Not planning on inspection though, so I don't really know if this conforms to code or not. It seems safe enough though.

http://www.midnitesolar.com/productPhoto.php?product_ID=278&productCatName=PV Combiners&productCat_ID=9&sortOrder=1

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=23&productCatName=Surge Protection Devices


« Last Edit: November 21, 2012, 09:37:15 AM by hpinson »

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1097 on: March 28, 2013, 12:16:46 PM »
Hey All,

what kind of meters are you using?  Are they worth it?

I have a MorningStar MPPT 60A Controller and often have considered putting in a remote meter so I can see it inside the cabin (the controller is on the porch and out of site).  My neighbor has a meter that gives him a %of charge remaining on the batteries which he finds useful and I wonder if I might also?

So, what are you doing?  Pros Cons?

Thanks!

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1098 on: March 28, 2013, 12:30:28 PM »
By remote meter do you mean,
(a) the optional Morningstar meter, or
(b) a meter like the Bogart Engineering TriMetric?

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1099 on: March 28, 2013, 12:49:14 PM »
By remote meter do you mean,
(a) the optional Morningstar meter, or
(b) a meter like the Bogart Engineering TriMetric?

Either/or -- the  Bogart Engineering TriMetric looks like what I'm thinking I'd like to have though!  More so then the MS model!

 

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