Author Topic: OFF GRID POWER; various thoughts on...  (Read 468677 times)

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Offline soomb

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Re: OFF GRID POWER; various thoughts on...
« Reply #125 on: February 25, 2009, 11:17:05 AM »
thank you for the excellent explanation.
Live- Phoenix, Relax- Payson

Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #126 on: March 01, 2009, 08:09:05 AM »
I really like the Backwoods Solar catalog.  It's practically an instruction book for getting set up.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #127 on: March 01, 2009, 08:16:32 AM »
They do have good information in it and on their website. I do find their prices just a little higher than some other places like Affordable Solar or TheSolar.biz
Just because something has been done and has not failed, doesn’t mean it is good design.

pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #128 on: March 19, 2009, 04:07:34 AM »
MountainDon,

How frequently do you equalize your batteries?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #129 on: March 19, 2009, 06:22:39 AM »

The goal is to equalize every 30 days. In reality that may turn out to be 45-60 days or so.  d* Keeping a log book, rather then relying on a faulty memory is a good idea. Also logging the specific gravity of each cell may be helpful in tracking changes in performance. (Remember to apply temperature corrections if the temperature of the batteries varies seasonally.)

That's for flooded wet cell batteries. AGM types can be equalized three to four times a year.
Just because something has been done and has not failed, doesn’t mean it is good design.

pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #130 on: March 19, 2009, 06:32:27 AM »
Is it possible to over equalize? What I mean is, can you damage the batteries by equalizing twice per month?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #131 on: March 19, 2009, 06:36:03 AM »
You will just use more water and have to replenish more often. That's for wet cell.
Just because something has been done and has not failed, doesn’t mean it is good design.

pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #132 on: March 19, 2009, 06:39:15 AM »
That's what I was thinking, but someone told me they thought it would damage the plates and equalizing should be done four times per year. I've only had my system since October 2008 so I'm still learning, but it seems that I get a little better performance if I equalize monthly.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #133 on: March 19, 2009, 06:44:41 AM »
... it seems that I get a little better performance if I equalize monthly.

You're onto something...  :D :D

I believe the only way to damage the batteries by equalizing is to initiate the process and then forget about it and run the water down below plate tops. You can do that by overcharging too, or with total neglect.

I believe total neglect is how Glenn got the L16's he's playing with.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #134 on: March 19, 2009, 08:18:37 AM »
I think they failed to equalize often enough and allowed the system to run low for way too long in the winter before kicking the generator in.  Low charge for long periods is conducive to bad sulfation.

I did some serious equalizing yesterday.  I am capable of cooking batteries when I equalize, however most will not be able too and in fact ill have a hard time getting the voltage high enough to do a good job of equalizing.  I believe Don mentioned getting to 32 to 34 volts on a 24v system and many systems cannot get that high.

I use a DC welder on constant current - Variable voltage.  I unhooked the batteries from the system yesterday on the above mentioned set of Trojans I am playing with.  The Xtreme recovery charger is doing the job over a week or two but I think it is better to use for the serious polishing off after a good equalization gives it something to work with.

I first hooked up all eight batts in parallel - 2 sets of 24 volts and I saw that the better set was equalizing but the worse set was not so that told me each string has to be equalized individually.  I hooked the bad set alone and put about 100 to 150 amps to it - slowly raising the voltage for the first half hour or so then raising it to around 32.5 and maintaining that.  As sulfation breaks away from the plates, internal resistance drops and voltage drops across the set.  I monitored it on the voltmeter.  I find that it always seems to drop to around 31.8 or so then slows -likely building a charge in the new found area.  At that point I again up the amps to get the voltage around 32.5.  It is necessary to watch terminal temps doing this also - I overheated one yesterday - didn't destroy it though.

I watched the acid in the cells.  I capped the boiling ones and uncapped the rather dead looking ones.  As each of them started to boil I capped them and continued until all 12 were pretty much boiling acid.  This seems to be an indication of the sulfation being removed.  The acid also turns dark as the sulfation is removed.  It did not seem to be over heating the batteries but they did heat up.  This was done over a period of a couple of hours.  I assume the last ones to boil are not as clean as the first ones and intend to do more after the batteries cool  if the Xtreme Recovery charger does not bring them back.  I will monitor acid SG as that seems to be the best indicator of state of charge and condition. 

The Xtreme Tester - don't know the real name  now - but same company gives a great indication of health also but they must be offline.

As to over equalizing - I think more research is in order.  I have seen old batteries with the plates eaten up - I don't know what the definite cause was.
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pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #135 on: March 19, 2009, 08:30:36 AM »
I can get 31 volts from my panels and I think this is what the charge controller is actually set at, I've thought about opening it up and changing it to 32 volts. I can hear the batteries bubbling so I know they're getting over charged. Do you think this is necessary or is 31 volts enough to break up the deposits? When I charge with the generator I get the full 32 volts.

The strange thing is, and maybe Glenn or Don can fill me in a bit, I have an Outback Inverter with the Mate and my charge controller is a Xantrex. The Xantrex will show battery voltage at 31 while the Outback Mate gives me a voltage of 31.6. Which is more accurate? Does it even matter? I've been considering getting a good battery monitor this summer but then I wonder how necessary that is as well.

Thanks for the information.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #136 on: March 19, 2009, 08:38:58 AM »
I think the higher voltages should only be used for equalizing.  I think that may eat the plates if done all of the time.  I think about 28.5 is about all you want for normal charge.  Don may pop in with that info - I'm about out of time but more research is in order I think.  My cheaper MPPT (BK?) only goes to about 29.5 which I set it at because the batts only get to about 28 something normally.  I don't want it kicking out too soon.

Could be a discrepancy in calibration or a loose connection giving higher resistance raising the reading.

It seems that over the 31.8 is what does the desulfation but that high all of the time could shorten battery life I think.  I think it removes a bit of the surface of one plate.
"Always work from the general to the specific." J. Raabe

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pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #137 on: March 19, 2009, 08:59:16 AM »
It only goes to 31 volts during equalization and in normal charge mode it goes to the bulk charge rate of 29 volts and then drops down to the float stage of 27 volts.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #138 on: March 19, 2009, 09:06:21 AM »
Sounds good.

The solar dealer in Arizona  - 9Lake Powell? - Page? It was over the phone) told me that over 32 volts was necessary to do good on equalizing - My testing seems to confirm that.
"Always work from the general to the specific." J. Raabe

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pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #139 on: March 19, 2009, 09:08:20 AM »
How far over 32 volts? Also is the MPPT worth the money?

Offline Windpower

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Re: OFF GRID POWER; various thoughts on...
« Reply #140 on: March 19, 2009, 12:50:21 PM »
Just got off the phone with the battery place

http://www.staabbattery.com/

Trojan L16 PA C   420 AH for $303

seems like a fair price -- includes delivery locally

so I'll need  8 in series for about 11 KW Hr  of storage (at 50% discharge)

 I'll need at least 2 banks one for the wind generators and one bank for the solar panels (-- I think I will need about 1500 watts of SP) according to this calculator

http://www.wholesalesolar.com/StartHere/OFFGRID/OFFGRIDCalculator.html


unfortunately this is about $5000 in batteries -- ouch

Forget the Rolls -- it would be $10,000 and change, (but they do carry a 10 year warranty)

I think this will be close to optimum -- about 330 KW Hrs per month from both wind and solar


Leaning towards the Xantrex XW4548 inverter

http://www.wholesalesolar.com/products.folder/inverter-folder/xantrexxw4548.html

but I have heard good things about the Outbacks too

I need the high surge to kick start the 3/4 Hp well pump (460 feet deep -- some of the coldest best tasting water ever)

I am thinking that the batteries should get bumped up on priorities -- went to price them at several solar/wind net suppliers and saw a lot of "out of stock" on batteries


Any recomendations on Charge controllers ?

Dave, the battery guy said that the charge controller is critical to battery life in solar applications and is a big reason why many battery manufacturers only give a 1 year warranty on solar apps
Often, our ignorance is not as great as our reluctance to act on what we know.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #141 on: March 19, 2009, 02:31:14 PM »
An MPPT charge controller is a must, not a luxury, in my opinion. Use of an MPPT controller will allow every last watt of power to be wrung from your panels. This becomes even more important the further north you go. No I'll rephrase that; if you are not in AZ or NM you are not making proper use of the power the panels put out if you do not have an MPPT controller. My opinion, but also that of a lot of other folks.

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

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #142 on: March 19, 2009, 03:07:38 PM »
I favor the Outback Flexmate 60 or 80 for a great MPPT charge controller. Someplace else in this thread I believe I addressed my reasons. They are well engineered and solidly built. I believe they are the most programmable of all the units out there.

The Flexmate controllers also connect to the Mate, the Outback remote control panel and programming device. The Mate is also used with the Outback Inverters, so to me it makes a lot of sense to go all Outback. Xantrex probably makes fine equipment too.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #143 on: March 19, 2009, 07:26:43 PM »
Re: the above post. I am enamored with Outback. I'll admit it. Don't let that deter from choosing something else. As I stated someplace previously my criteria for charge controller included the long distance between panels and batteries. Running the panels in series for 72 VDC nominal reduced the cable size saving a bundle of money. That necessitated a charge controller like the Outback. After that choosing an Outback Inverter seemed best because of the ability to use one Mate control panel for both.


The charging and equalization info I go by...
                             one cell             12 VDC      24 VDC         48 VDC
Equalization       2.58 -2.67 (max)    15.5-16.0    31.0-32.0     61.9-64.1

Absorption/Bulk     2.37-2.45 (max)     14.2-14.7    28.4-29.4     56.9-58.8

Float                 2.20-2.23 (max)     13.2-13.4    26.4-26.8     52.8-53.5

The ideal float voltage is the lowest voltage setting that will maintain the battery at full charge. The higher the voltage the more water the cell will consume. The minimum equalization voltage is highly recommended unless it is suspected a sulphation problem exists.

Equalization is required when the cell specific gravities vary from highest to lowest by +/- 0.015 (1.245 - 1.260 at full charge)

The point is to bring the batteries up to the equalization voltage and continue charging for 1-2 hours at a low current, without excessive heat. The final or finishing charging current should be 3-7% (we recommend 5%) of the 20 hr capacity in amps.

If battery temperature exceeds 125ºF the battery should be taken off of charge and allowed to cool before equalization is continued. When two consistent specific gravity readings are taken a half hour apart the battery is equalized. It is recommended to water the battery cells before or half way through the equalization. This is to assure the water is completely mixed into the electrolyte.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #144 on: March 19, 2009, 07:56:53 PM »
How far over 32 volts? Also is the MPPT worth the money?

Looks like Don got some of this same info but I have other stuff too so I will repeat it :)

I just go between 32 and 33 - maybe 32.5 but I use the welder

Some info from Sens charger site

"Q: What does "equalize" charging do, and why is it needed?
 
A: All batteries, even those assembled into unitized blocks, are all built of individual battery cells connected in series to obtain the required DC voltage. Like all manufactured products, there is variation between the capacities of each cell in the battery. As the battery ages this variation increases. Since the battery is a chain of cells that is only as strong as the weakest link some scheme is required to ensure that all cells stay at peak capacity.
 
A scheme called "equalizing" is commonly used in both lead-acid and nickel cadmium batteries. Equalizing temporarily elevates the charging voltage of the entire battery string above the normal "float" voltage. The elevated charging voltage allows all cells, including the weak ones, to accept more current from the charger than they would at float voltage. A consequence of the elevated equalize voltage is that all cells in the battery are overcharged. This is acceptable for short periods provided the battery has sufficient electrolyte.
 
Overcharging greatly increases the rate at which the water in battery electrolyte is electrolyzed into oxygen and hydrogen gas. Since low electrolyte level will permanently damage the battery it is important to limit when, and for how long, the battery is charged at the equalize voltage."
 
This article says 31 to 32 max. for a 24 V system.  Their info seems good and to be safe I would recommend following it.  I have bought from them before - good people.

http://www.thesolar.biz/Battery_charging_article.htm

I do go over the 32 but it drops to the 31.8 pretty fast .  It seems that this is where the action of removing the sulfation takes place.  They say not to overheat the batteries above 125f and to add water as needed - I read that letting them dry out below the plates when equalizing is real bad and will destroy them.

I tested the batteries I equalized this morning with the Xtreme tester and all batteries got a passing grade with some showing good and charge.  Now that they are getting back usable I will spend a bit more time with the equalizing.  I noted that the Sens charger uses Constant voltage DC - that is also a capability of my welder so I may play with that a bit also. -- that will provide a tapering charge as the batteries come up.
"Always work from the general to the specific." J. Raabe

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pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #145 on: March 20, 2009, 03:00:54 AM »
Don and Glenn,

Thanks for all of the information. It looks like I'm right in line with everything you've both recommended, which is nice. I'm happy with the Outback inverter, and the Xantrex charge controller works fine, I'm just thinking an Outback MPPT would give me some extra charging in November and December, which were my worst months so far. Our loads are so minimal, a few hundred watts per day, that I wonder if it’s worth the money. A personal choice, I suppose.

Also your houses are very nice, at some point I'm going to start a thread and explain what I'm considering building.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #146 on: March 20, 2009, 08:40:25 PM »
Our pleasure.

I would think it would take a bigger load to make it pay but if you like quality and tweaking it for the most it may be worth it for the satisfaction.

The panels on it should be matched for best effect but it will also give the best available with what you have if mixed too.

I have one that I checked is  BZ controller but no features - just bulk and float - no equalize.  It does maximize the panel output well though.  I like to equalize manually anyway.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #147 on: March 21, 2009, 12:54:53 PM »
pagancelt, I'm thinking that if during Nov and Dec you were not getting enough power from the PV array, necessitating running the generator for general charging, then an MPPT controller could be a big help. I think you stated someplace you got it operational in October? You might want to hold off until you see what happens over the summer. If you're in VT, like I seem to recall, summer should be much better.

The solution could also be more PV panels. Hard to say for sure. ???
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #148 on: March 21, 2009, 05:46:13 PM »
It also depends on the weather.  If there are lots of storms and little direct sun then you may need the generator no matter what.  Dark cloudy days may only produce a 10th or less power than a sunny day.
"Always work from the general to the specific." J. Raabe

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pagan

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Re: OFF GRID POWER; various thoughts on...
« Reply #149 on: March 23, 2009, 06:22:29 AM »
Central Vermont and it's cloudy through November and December, plus the shortening days. We averaged about 8 to 9 amps per day through those months and now we're averaging 20 to 50 amps per day, depending on state of charge. We're getting to the float stage 4 or 5 times per week so we're easily replacing what we use and this is also showing as fewer amps per day because once we get to float the controller shuts down. We hit float last Saturday by 11 AM so the total for that day was only 18 amps even though it was sunny the whole day. During November and December we never drained the batteries to 50%, I think we drew them down to 80% or so. We ran the generator three times, twice because we were leaving and wanted the batteries at full charge because our place is wood heat and we couldn't find anybody to house sit, and once we did an equalization charge. We'd had the system running for almost 4 months when we equalized and saw an immediate result.

I figure I'll give it another winter before I decide if I want to go with an MPPT or add more panels. Ultimately I want to get to a point where I don't need to use the generator, which might be difficult given my location.

 

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