Greetings from new user (pics inside)

[_OS_]

Hello everybody,

OS from Norway here. Last year we inherited a 40 year old cabin from my father in law and we are in the process of upgrading. First thing we installed was a small scale solar electric system.

Here is a picture of the 80W BP Solar panel on the wall of the tool shed:

http://lh5.ggpht.com/osaether/SIB_K-rdA5I/AAAAAAAAAC0/a6ntkWup_1M/s800/solar.jpg

The "technical room" with Victron Energy 1200VA inverter, Trimetric 2020 battery monitor, 2x Concorde Sun Xtender PVX-2580L batteries, cheap solar controller (I will replace the solar controller with a SunSaver MPPT soon) and 2kW generator.

http://lh3.ggpht.com/osaether/SIB_JpUwysI/AAAAAAAAACk/Zf4W9_2XAks/s800/battery1.jpg

The cabin:

http://lh5.ggpht.com/osaether/SIB_LjvmmSI/AAAAAAAAAC8/BHpvIZ9cFWg/s800/cabin.jpg


Best Regards,
OS

[mike95490]

That 80W panel is not going to do much except to trickle charge the batteries. You will be getting the bulk of the recharging from the generator.

[_OS_]

That 80W panel is not going to do much except to trickle charge the batteries. You will be getting the bulk of the recharging from the generator.

I have used the system for about a year now without using the generator. We use the cabin only every three weekends or so and use the power only for TV and lights.

That said I am considering buying one more panel or sell this one and buy a larger one. My dealer has a Kyocera 85W panel on sale now but I am not sure if I can use it together with the 80W BP Solar panel I have.

Regards,
OS

[icarus]

It is a simple matter of "doing the math" Add up all the expected loads (amp/hrs) (Kw/hrs) over some sample time frame. Since you use the cabin only every few weekends, your charging system could be a bit smaller than average, though your batteries might be larger. Factor in charging/inverter efficiencies etc, and average expected sun, plus some reserve, and that will give you a base line number. If you are only using the cabin as seldom as you do, I would think that you could draw down the batteries to ~50% without worrying about it. Down only 20-25% would be better.

Remember that when you have 24/7 power available, loads will increase with time. Consider those numbers as well.

One thing I have noticed on this site, is that people on this site bring their own experience to the forum. As such, few have lived in primitive cabins for very long. Most tend to live in more substantial houses, with the corresponding (though low by average) loads. So when one suggests that "you won't be able to do much with X watts of panel or battery" that may not relate to your situation very well.

We lived for years with no power, drawing water from the lake with buckets, using Kerosene lamps etc. Our first solar installation was one ~60 watt panel, coupled to 2 t-105 golf cart batteries. I built this system to power the fridge ignitor, one reading light, and the radio. It worked famously, and we got 12 years out of the original batteries. As time went on, we realized the luxury of having 24/7 power. Inverter, CFLs, laptop charger, internet modem, water pump etc. We upgraded our system for all those things, and it feels like we live in a "real house". Even at that, we still only run ~200 watts of panel. Tiny by most comparisons.

So do the math, plan to expand, and avoid the "ready, fire, aim" syndrome

Good luck,

Tony

[Bad Apple]

The first thing I noticed about the first picture is that you've got a huge shadow that either just cleared the panel or is about to obscure it, and judging by the shadow the panel is casting, you're very near solar noon. You're losing ALOT of your potential. As soon as that shadow hits one of the columns of cells, output drops to nil until it clears the opposite column. Can you relocate it to a more suitable spot? If so, you may not need the second panel.




That said I am considering buying one more panel or sell this one and buy a larger one. My dealer has a Kyocera 85W panel on sale now but I am not sure if I can use it together with the 80W BP Solar panel I have.

OS

You can determine how well mismatched panels wired parallel will work together by multiplying the lowest Vmp of each panel by the Imp of each panel and add the result together, for example, if the BP 80 watt panel (using easy math and standard test conditions):

Vmp = 20 and Imp = 4 then 20v X 4A = 80watts

and the Kyocera specs are:

Vmp = 17 and Imp = 5 then 17v X 5A = 85watts

What happens is that the 17v Kyocera will drag the 20v BP down to 17v and power will be:

(17v X 4A) + (17v X 5A) = 153 watts.

You lose 12 watts on the BP panel.

Cheers,

Bad Apple

[niel]

i agree you will need more to properly charge those batteries. i see they are sealed and as such they may be gels or agms. should they be agms they would lose their power less quickly and charge more efficiently, but in a case like yours you should not be below 3% of your battery capacity for a charge rate, which i estimate your batteries to be around 400ah. .03x400=12 amps for a 3% charge rate. normally most will have a charge rate between 5% and 13%, but situations like yours that can build the power up over a longer period of time can go slightly lower. too low though won't work as it begins to act more like a maintenance or float type charge and not allowing much in the way of a bulk charge to them. a rough extimate of your present charge rate with estimated capacities is 4 amps/ 400ah = 1% rate of charge. that is good for float charging.
my advice is keep the pv you presently have and add around another 8 amps or so of pv to it. something like this may work out, http://store.solar-electric.com/kyso130wa12v.html , otherwise you will need to add 2 pvs in keeping with using a non-mppt type controller.
speaking of controllers i don't know what you are using for one and what its limits are so you may need to consider if another controller is needed to accomodate the extra pvs. if you need another controller then consider an mppt type and some of them do have the ability for voltage downconversion in the case of using 24v pvs into a 12v battery system. that woud leave you with a 12v stragler if another isn't placed in series with it of the same current rating to make it 24v, but 24v pv systems and mppt may be projecting too far with possibilities for you.

edit to add: after looking at the pics more closely and reading between the pics. (hitting head)
1> good catch BA on the shadowing as this will lessen the available charge time he is capable of. some tree trimming is in order.
2> i see the batteries are the big concordes and these are 255ah each so 3% of 510ah is 15.3 amps minimumly needed and more would be better due to shading and available sunshine in your area. the sunsaver mppt is a good choice and get the bts for it.
edit to add: if you think you may get more pv than the max of the sunsaver you have 2 options: 1 get more than 1 of them or 2 get a larger rated controller that is mppt like the xw60 or the mx60.

[_OS_]

Hi all and thanks for the feedback.

The shadow in the first picture is from a big pine tree that I am considering cutting the top of (about 4 feet is enough).

The batteries are Concorde and are specified for at most 1% self discharge per month which is one of the reasons I bought them. I have done the math but I might be missing something here. My calculations: 1% of 510Ah is 5.1Ah per month and roughly 0.2Ah per day. Even in the darkest months of the year (November to January) my current panel delivers more than that. Also in these months we do not use the cabin.

I will visit my cabin the coming weekend and will report back. When I left last week the Trimetric showed a capacity of 94% left in the batteries and it was at mid day last Friday charging at 4.5A. We have had mostly sunny days since that.

Here is the expected power from an 80W panel in my part of our country. These numbers are an average collected by a research institute over several years and places:

80W panel: Jan:49Ah, Feb:117Ah, Mar:173Ah, Apr:227Ah, May:246Ah, Jun:205Ah, Jul:171Ah, Aug:163Ah. Sep:125Ah, Oct:91, Nov:31Ah, Dec:33Ah

Regards,
Ole

[mike95490]

I will visit my cabin the coming weekend and will report back. When I left last week the Trimetric showed a capacity of 94% left in the batteries and it was at mid day last Friday charging at 4.5A. We have had mostly sunny days since that

Lets hope the batteries are full - that's a LOT of battery to charge from a small panel.



Here is the expected power from an 80W panel in my part of our country. These numbers are an average collected by a research institute over several years and places:


But that cannot take into account your trees and roofline that shades your panel. One small area of shade can shut down a panels production.

[_OS_]

Lets hope the batteries are full - that's a LOT of battery to charge from a small panel.


But that cannot take into account your trees and roofline that shades your panel. One small area of shade can shut down a panels production.

That is correct, the numbers are taken in open land without anything shading for the sun.

I will move the panel a few cm down and cut the top of the tree. And as I said in another thread buy one more panel.

Regards,
Ole

[nigtomdaw]

Thanks for taking time to send in pictures, always good to see other peoples set ups, the more the better IMHO.

[_OS_]

This weekend I visited my cabin again. The Trimetric battery monitor showed 100% charged and that it occurred 3 days ago so my panel is charging fine for my use.

The plan this weekend was to install a stove and a fridge, both propane-driven. I hope it is ok to post a few off-topic pictures.

I began to remove the pine panel on the wall behind where I want to place the stove and fridge. My idea was to get more space in front of the two. This is what I found behind the panels:

http://lh6.ggpht.com/osaether/SIB_NJMtOvI/AAAAAAAAADM/LsrB7K_b3XI/s800/wall.jpg

The 45 degree beam looked like it's vital for the strength of the cabin. It’s time to call my father in law (which is not easy since the cabin is so far out in the woods that I have no mobile phone coverage). I have to wait until the day after so I fired up the old stove outside. This is at 8:30 in the afternoon and you can see the sun is still shining:

http://lh4.ggpht.com/osaether/SIB_MfkiWII/AAAAAAAAADE/GKU_-92CRek/s800/outside.jpg


I called my in-law and he believed it was ok to remove it:

http://lh6.ggpht.com/osaether/SIB_Nr2HlWI/AAAAAAAAADU/l9q0hUD9cGQ/s800/saw.jpg


The final result after adding a few smaller "beams" and reinstalling the pine panels on the other side:

http://lh5.ggpht.com/osaether/SIB_OXarZwI/AAAAAAAAADc/1MgIaJcjDBM/s800/stove.jpg

Thanks for reading!

Regards,
Ole

[mike95490]

The 45 degree beam looked like it's vital for the strength of the cabin.

I think you were right, and whomever thought it was OK to remove, was WRONG. It was a lot of trouble to add it in the original construction, if it was not really needed.

That (was) a brace to keep the entire structure from leaning to the side. When it's wood, it functions in both Compression and Tension. Now that's it's gone, you should use a pair of steel cables, in an X configuration, to prevent leaning either direction.


more info:
http://www.contractorreferral.com/glossary/index.php?letter=W&limit_index=300
Wind Brace. A diagonal structural member whose function is to stabilize a frame against lateral forces.

http://www.answers.com/topic/diagonal-brace-1

http://nisee.berkeley.edu/elibrary/getpkg?id=GoddenD50-69
Unavoidable in this solution is the appearance of the heavy X-bracing crossing window areas.

[BB.]

You would really need to look/inspect the overall cabin structure to determine if that cross member adds to the overall rigidity of the Cabin or not...

If you want to return the shear resistance to that wall... You could pull the paneling (I assume that this is not plywood vernier), and add a 1/2" or 3/4" piece or two of plywood underneath with lots of nails (http://www.mcvicker.com/vwall/page014.htm) (and you can even put glue under the framing/plywood connection). (I know you are metric--but I don't know standard metric plywood definitions...). And add the paneling back on top for looks.

Even though, adding this structure back in won't necessarly help overall... This is only adding shear strength in one axis (left-right). It does not help in the other (front-rear) unless there is already some other buried structure elsewhere.

You can add shear walls (nailed plywood) for roughly 1/4 the total exterior wall length in each wall section and that will do a pretty good job of wind/earthquake proofing a wooden structure. (plywood can be added to the exterior or interior wall and repaneled/covered after it is done).

I notice that the interior shot of the walls where the battery system is--there appears to be no diagonal bracing or plywood shear wall. The shear component resistance of the exterior planks is not great--so the walls could "rack" (think of a rectangle becoming a parallelogram if you anchor the base and push sideways on the top) if exposed to wind/quakes.

But I would guess that this is overkill for a small cabin in the woods of Norway. It appears that you may not even have a solid foundation (concrete wall/footings buried below the frost line). Building could be knocked off foundation if subjected to a strong lateral force--regardless of internal bracing.

If you are concerned--perhaps you can invite a structural engineer or builder up for a nice weekend visit to "consult".

You have such a nice looking interior--I would be a bit more concerned about staining behind/above the propane fridge/stove with soot/combustion by-products/food/grease against "raw wood" or even issues with fire... Perhaps some sheet metal, tile, or "sheetrock" (or whatever you use there for fire proofing) around/under the fridge/stove area would take care of two problems at once (ease of cleaning and fire resistance).

-Bill

[_OS_]

Thanks for the answers! It was my father in-law that built this cabin and he believed I could remove the beam but after reading your posts I am not so sure but maybe this additional information can "help me": One thing that is not shown in the picture is that the 45 degree beam is also nailed to a vertical beam behind the first panel to the right of the opening I made. Also the wall I modified is an extra wall inside the cabin made there to make a division between the kitchen and the living room. It is only about six feet from the main wall which I believe also have cross braces. Please see the picture below that is taken from another angle (pardon the mess :-)

Bill: you write "If you want to return the shear resistance to that wall..." Do you mean to add a new "beam" and put the old paneling back in place?

The cabin stands on concrete feats that extend about five feet down in the ground.

The battery system is in the tool shed (behind the open door in the first picture with the solar panel on the wall) which is of a much "cheaper" structure. I guess that is why there are no "cross bars".

http://lh3.ggpht.com/osaether/SIB_PSGpeXI/AAAAAAAAADk/KfMki0cbR2k/s800/kitchen.jpg

[westbranch]

Ole, hilsen fra Canada,...

I concur with the others about the purpose for the diagonal 2"x4" or what ever the metric equivalent is.

Its purpose was lateral strength, but I am suspicious as to the reason it was installed away from the outside wall.
Normally it would have started at the lower 'plate' (above the floor) and proceeded up to the 'plate' at the top of the wall thus forming a double triangle within the wall panel... very stable in one direction.

Is there another angle brace on the opposite side of the house? If so that is the other half of 2 triangles for lateral stability...

Nice (modern) Hytte.

Ha det

Eric

[BB.]

Bill: you write "If you want to return the shear resistance to that wall..." Do you mean to add a new "beam" and put the old paneling back in place?

_OS_

What I was trying to say was you can replace what the "beam" was doing by removing the paneling, nailing up plywood sheet(s) in the wall section, and then put the paneling back on top of the plywood sheet(s) to make it look nice again.

The plywood, with lots of nails into the "2x4" (2"x4" US term for standard structural lumber) underneath will make the wall very strong against the top shifting sideways with respect to the base/bottom of the wall. It will make the ceiling of your kitchen much "stiffer" to "left and right" movement. If the ceiling is strong and well attached to the roof--then the whole center of the building will be stiffer and better able to resist "left to right" forces. This one wall, however, only provides "shear" (left-right) strength (in one direction). If you have weakness in the other direction--other walls/structure would have to be worked on too.

Of course, how much this will help (or is needed) depends a lot on your foundation ties (in the US, and especially in earthquake country like California--we have to bolt the base of the home to the foundation so that the home is not thrown off of the foundation--in areas with strong winds (tornadoes/hurricanes), the foundation ties for newer buildings are carried up through the side walls and into the ceiling/rafter/roof area to prevent the sides and the roof from being blown off...

Much of this is "newer" building code requirements based on natural disasters (and large fires) that have happened in the 20th century.

Since your's is a single story "home/cabin"--these are generally much safer in earthquakes because there is very little weight up high (like a 2nd and 3rd story).

If you want to see what a weak 1st story (ground floor) looks like in a multistory building--look up "Soft Story".

Here is a link with some pictures (http://www.earthquakecountry.info/daretoprepare/building/softstories.html) of a Soft Story and explanations. You can see the upper structure came though pretty much OK--only the first floor with the poor bracing was flattened.

And a nice page with links (http://www.daretoprepare.org/secure_your_building.html) that describes other common structural issues in earthquake country.

I will leave it to use to figure if quakes are an issue where you live or vacation (www.jordskjelv.no (http://www.jordskjelv.no/) in Norwegian). I would be (somewhat) more concerned about the foundation than this one interior wall (from what little I can see).

Still looks like a lovely place to spend some quality time! I would not loose sleep over this one cross brace.

-Bill

[niel]

os,
i concur with the father-in-law that it doesn't matter. i say this because it has a breakfast nook above it. the real supports will be in either wall to the sides of the nook. if in doubt, you can diagonally put a smaller board like the back planks or metal bracing placed diagonally as has already been suggested. i think for a floor to ceiling wall i would've been more concerned of taking a diagonal out.
i like that pine and is there a finish on the would out of curiousity as it all looks like it was built yesterday?

[icarus]

This is a classic "let in brace" to resist lateral loads and wracking of the wall. You can replicate it's function by using a piece of plywood to carry the lateral load, or even another cross brace. In small wood frame construction the same general lateral brace can be achieved by 1 4x8 panel on the corners and every 20' (I don't really remember) of wall. You can also achieve the same stability with the rigidity of the floor or roof diaphram above. In a small cabin, I don't think I would worry about it. The house is not going to fall down without it, but it may start do wrack out of plumb (slowly) depending on the loading (wind, snow etc) I used to work for a bush camp that had ~50 simple frame buildings, all sided with shiplap siding. No diagonal, no plywood, no ridged roof deck. Over 100 years we had several buildings significantly out of plumb, but none that was un safe. We rewracked some just with a come a long and a chain.

Not something I would worry about,

Tony

[_OS_]

os,
i concur with the father-in-law that it doesn't matter. i say this because it has a breakfast nook above it. the real supports will be in either wall to the sides of the nook. if in doubt, you can diagonally put a smaller board like the back planks or metal bracing placed diagonally as has already been suggested. i think for a floor to ceiling wall i would've been more concerned of taking a diagonal out.
i like that pine and is there a finish on the would out of curiousity as it all looks like it was built yesterday?

Hi Niel,

The pine panels are of a very common type used here in Norway. There is no special finish and they are not painted. The cabin was built in 1969-71 and the walls have not been treated since then.

The only wood my father in-law bought back then was the pine panels and the panels on the floor. Everything else, the beams and the planks on the outside walls he sawed himself at a local sawmill!

Ole

[niel]

very nice os. pine here seems to dull after so many years, but yours has the look of having been done very recently.:D
btw, sorry about the wrong spelling of wood, but it was prnounced the same.:cry:

[icarus]

Upon second look at the pics, I took a bit more look at the fridge. Be carfeful if you are going to push the fridge back tight into the nook. Make sure that it has free air over the coils. Propane fridges work because of natural convection drawing air up from the bottom, passing it over the coils, and releasing the heat into the air. If you block the top exit path you will reduce the efficiency of the fridge, and risk damaging the cooling unit due to overheating. The Dometic site shows a number of baffling (no pun intended) schemes to help with venting. You can also add fans to assist with air movement, but then you have to add in the parasitic energy costs,

Tony

[mike95490]

From the photos, I can't tell what the original configuration of the cabin was. Was that diagonal beam in a whole wall, or was there a "pass thru" window in the wall beforehand ?

Really, a person skilled in structural work should look at it.

Generally, wood is not installed unless is serves a purpose.

[_OS_]

Thanks for all the replies!

I am going on holiday tomorrow and will shut down the server while I am gone so the pictures in the thread above will not display.

EDIT: I just found out about google photos and have embedded them in the posts above. I do not know if this will work out but you can view the whole album here:
http://picasaweb.google.com/osaether/Cabin

There you will also find a map so you can see where my cabin is. I have also included a couple of pictures of Muskoxes that live not far from my cabin (http://en.wikipedia.org/wiki/Muskox)

Ole

[_OS_]

Drove to my cabin this afternoon (3 hours roundtrip) and installed the SunSaver controller. It was late when I installed it but the Trimetric showed +0.1A. I sold my old controller for a little bit more than I gave for the SunSaver!

http://lh3.ggpht.com/osaether/SJ9V_w_ALhI/AAAAAAAAAJ8/HRyMDEOkmS0/s800/mppt1.jpg

And I know the cables from/between my batteries are too long and I have ordered new, shorter #00 cables.

http://lh3.ggpht.com/osaether/SJ9WA8J8eGI/AAAAAAAAAKE/fc7vfEEuix4/s800/mppt2.jpg

Sorry about the bug on top of the controller (I hope the MPPT firmware is bugfree)!

Ole

[niel]

the cc looks good there.
i guess with that dead bug there that mppt now may have to stand for Multi Purpose Pest Terminators:p:D.

[_OS_]

Cleaned up the wiring a bit last weekend:

http://lh6.ggpht.com/osaether/SKhlJpkbXzI/AAAAAAAAAMA/mRHqL5HxuQ4/s800/mppt4.jpg

http://lh4.ggpht.com/osaether/SKhjsD9LkyI/AAAAAAAAALc/ovsMQi2vK3I/s800/mppt3.jpg

[_OS_]

Hello everybody! It's been a while since posting here but here comes a short status report.

I visited my cabin this weekend for the first time in three months. I was very curious of the charge state of the batteries since the SunSaver MPPT draws 50mA 24hrs a day compared to my old controller that used zero at night and only a few mA when the sun was shining.

I came up Saturday at noon after 30 min cross-country skiing from where I parked the car. The sun was shining and the temperature -10 C (14F). Here is a picture I took on the way:

http://lh5.ggpht.com/_plELtD-q2SU/SYXJL1iEFCI/AAAAAAAAARY/KmeYAlYuQAs/s800/snow.jpg

There was less snow than last year but it took me two hours this morning to remove most of the snow from the roof. Before:

http://lh5.ggpht.com/_plELtD-q2SU/SYXHjO0bCAI/AAAAAAAAAQw/5zk1KVV3mgA/s800/hytta0.jpg

After:

http://lh3.ggpht.com/_plELtD-q2SU/SYXHjuS3KyI/AAAAAAAAAQ4/skH4pQSpG_s/s800/hytta1.jpg

The Trimetric battery monitor showed a charge state of 93% which means that the system has lost 42Ah since my previous visit 90 days ago. In a similar "experiment" last year the battery was full.

I have e-mailed Morningstar about the current consumption of 35mA and they said it is the same day and night. Probably because the firmware needs to keep track of the amp hour used. Since I do not use the 12V outputs when I am not in my cabin I am thinking about adding a relay that shuts down the SunSaver at night. The relay and control circuit must use significantly less than the SunSaver for this to be of any help. Any ideas?

OS

[mike95490]

Too bad we can't see a photo of the Solar Panel. Was it completely buried in snow? I can't see how a small drain of 35mA (24 hrs= .84 AH) is not replenished even with a little sunlight. 42Ah / .84 = 50 days of no charge.

Did you make a battery voltage check ?

What are the chances the Trimetric looses it calib at very low currents ?

[Solar Guppy]

The Charger Controller is using about 11 watt/hours a day .. That's not your issue

Either your panels a buried in snow or you have other loads ... even sun one day a week with your system would keep the battery's fully charge

Also the Trimetric is not very precise especially at low currents and has only fixed programed values to determine the charge efficiency of the battery, which changes with age and temperature. Its OK for a general state of charge, but 7% difference is 2-3X lower than what in best conditions it can estimate for the battery SOC

[_OS_]

Thanks for the reply. My panel is not covered in snow but keep in mind that at this time of year we only have a couple of hours sun each day and the sun is very low in the sky and there are quite a few pine trees making shadows.

[_OS_]

Please see my reply to mike.

[icarus]

Find your phantom load.

On another note. I designed my system specifically so that some of the panels are mounted vertically on the wall, so that when I go away for extended periods in the winter, there is almost no chance for them to be covered with snow. While they are not at the optimal angle fro harvest, the fact that they get some sun, keeps the batteries at float while I am away.

I have the panels mounted on hinges, so I can adjust to the proper angle when I am home.

Tony

PS. Your bush looks alot like mine! http://www.wind-sun.com/ForumVB/showthread.php?t=4368 Go to posts # 1&2

[_OS_]

Please remember that my cabin is at aprox 62.5N which is more than 1 degree further north than Anchorage, Alaska.

[_OS_]

Hi Tony,

I have checked and double checked and there is no phantom load. The only devices connected to the batteries while I am away are the Trimetric and the SunSaver. That said I have no trouble understanding the 42Ah loss. It was expected because there is almost no sun at this time of year. What I am considering is to use another controller in the darkest months, November-January and use the SunSaver in the other months.

I am also considering buying one more panel of the same type because they have them on sale now. With another panel I am sure the batteries will be fully charged during these months.

My panel is mounted almost vertically during winter and is is not covered with snow at any time.

Very nice place you have there! Do you have any pictures of your solar electric system?

Ole

[Solar Guppy]

The Trimetric is a load ... I would power off that as its serves no purpose when your not there. If your curious at the battery SOC, use a DVM for the one or two visits in the winter

[_OS_]

Thanks, I will consider that. The trimetric uses 16mA when the display is off. It also measure it's own consumption so the figures I read should be approx correct. I have e-mailed Bogart about what accuracy to expect for such long periods and small currents.

[mike95490]

Would it be acceptable to bypass the CC in the winter, and wire panels directly to the battery ? (blocking diode needed) 1 hour of weak sun per day, can't overcharge too much

[_OS_]

Hi Mike, that is a good idea that I will consider!

[icarus]

On sober second thoughts, I'm not sure I would worry about the recorded ~40ah " missing from the battery. I would rely more on the voltage and the SG of the cells. I know that the Tri-metric can be a bit quirky when you are dealing with small loads both on the charge as well as the discharge side. If after a number of months you are that close I wouldn't worry about it. Turning off the meter will save a tiny little bit, as well as the controller. Depending on how often you get there in the winter 63N isn't going to give you long enough days, coupled with cold batteries so that I wouldn't worry about over charging them. On the other hand, if you can't get back until sometime in March, that same 63N coupled with cold temps, and reflection off the snow you might risk over charging. Just the meter alone would account for ~50ah over 90 days.

If it were me, I would kill the Trimetric, check the panel output the next time you are there with a DVM or the Trimetric, check the SC relative to what the meter says,,, and then figure out what to worry about.

Adding a second panel is never a bad idea IMHO!


Tony

PS Your days must be getting noticeably longer. Our day is almost 3 hours longer

[icarus]

One more note,

Going back to your earlier post #7, you provide calcs from your panel in November, December and January, total ~113 ah total!

Add the meter draw of ~75 ah for the 90 days, plus the controller draw of ~82 ah for a total of 157 ah. Given that you might have gotten ~113. 113-157=44! Pretty close to what your meter reveals.

Clearly 1 more panel or killing the meter or the controller would be a good idea in the winter while you are away.

Tony

[_OS_]

I have today made up my mind and purchase one more 80W BP Solar panel. It is more expensive than many other brands available here but then I will get two identical panels.

So now the question arises whether to wire in series or parallel? The SunSaver MPPT can handle both. Accordning to the efficiency graph in the data sheet of the SS it is better to wire them in parallel. I e-mailed Morningstar tech support about this and got this answer:


Hello Ole,

Yes, a parallel, 12V nominal/17Vmp, solar panel configuration will provide the best efficiency for charging a 12V nominal battery configuration.

This in addition to that I have fairly short cable run to the controller calls for a parallel connection. The batteries can be very cold compared to the panels and that calls for a series connection but I guess this is why Vmp is 17.x Volts on most panels in the first place. They are made to handle this temperature difference.

I hope I can wire them together at the panel end and use the same cable run to my controller.

Any comments on this?

Thanks!

Ole

[icarus]

Wiring the panels to feed the same home run is fine, as long as the wire size is adequate. I wired mine using Anderson polarized connectors so that I can move the panels around as I need. One set of mine move through out the year. I also agree that parallel would be the way to go.

Tony

[Brock]

Are you sure you have the Trimetric set correctly? I don't remember what the default is on the %, but it is user adjustable. I would be willing to bet the battery is full and the meter has wandered off over time. Is it set to auto reset on a full charge? Did the bank come up to full charge while you were there?

[icarus]

Brock,

Remember Ole is North of 62N. Makes for VERY short days in Nov, Dec, Jan, even it it is clear.

Tony

[_OS_]

Yes, I am pretty sure is set correctly. I charged for 4 hours before I left in November and then reset the Trimetric to 100%. And as Tony said there is very little sun here at this time of year so the 42Ah loss was as expected.

[_OS_]

The new 80W panel arrived last week and I "transported" it to my cabin last weekend. I had to go cross-country skiing for about an hour with the panel mounted on a ski pulk. The temperature was about -10C (14F) and heavy wind so I did not even try to mount it. I have to move my other panel a bit to the right as well to make room for the new panel (see pic above). I will return as soon as the temperature rises a bit and mount it. I ordered a adjustable mounting bracket for the new panel of the same type that I have on my existing. This bracket has positions for winter, all-year and summer.

I have also ordered the Sunsaver MPPT Remote Display from Maverick solar. Hopefully this will arrive in time for my next visit (I was a bit worried about this order since Maverick did not respond to many of my e-mails).

Ole

PS: The Trimetric showed 100% this time and days since charged 1.1.

[niel]

ole,
can we see new pics when you are done?

[_OS_]

Yes I will take more pictures when I am done.

[_OS_]

I visited my cabin again last week. It was cold and the sun was shining from a clear sky. The Trimetric showed a charge current of 6.3A! This is the highest current I have seen in my system (still only one 80W panel). I guess this is the result of the MPPT controller working. With my old controller I got a little bit over 5A on days like these.

I regret that I ordered the Morningstar remote display now that I have my wireless remote display almost up and running. I will drive to my cabin again tomorrow afternoon and test it.

It is still too much snow and too cold to install the new 80W panel. Last week it when I was there the temp was -11C in the morning and +3C mid day.

OS

[mike95490]

I visited my cabin again last week. It was cold and the sun was shining from a clear sky. The Trimetric showed a charge current of 6.3A!

If there are no loads, where is the current going ? Boiling batteries ? Or was that a peak charge current reading ? What's your water usage in the batteries ?

[niel]

my thought too, how is that much power being used with no loads on to allow the controller to send that much to the battery?:confused: a few ma from meters or the controller even ongoing will not result in the necessity of full bore mppt bulk recharge action unless the site went without sun for awhile. please clarify the circumstances.

[_OS_]

If there are no loads, where is the current going ? Boiling batteries ? Or was that a peak charge current reading ? What's your water usage in the batteries ?

This was a peak reading at about 1PM and the batteries where 80% full at the time. I have two Concorde 305Ah (100 hour rating) AGM batteries and use no water.

Do you mean this is an error? What's wrong with charging these big batteries with 6A? I often use my Victron charger to charge them at 50A and there are still much to go on according to Concorde.

OS

[BB.]

I think the other believed you went to your cabin and immediately checked the charge controller (without using any other power)--and found it charging with (its) maximum current. Their worry is that the charge controller may be pumping maximum charge current into the batteries and charging them over >100% capacity--and damaging the battery bank.

I believe you put a load on the battery (over night use--or there was no charging for several months and the batteries where down to 80% state of charge?) and you saw your maximum current from the charge controller going into the partially discharged batteries..

They just wanted to make sure that the charge controller was behaving properly and the batteries really need the maximum charge rate from the controller.

-Bill

[_OS_]

Hi Bill,

Thanks for the reply. Yes I was discharging the batteries down to about 75% the weekend before.

The reason I wrote the message abobve was to telle you that I am glad the MPPT is working and putting more amp hours into my batteries than the cheap CC I used to have before.

OS

[niel]

thanks for the clarification as we were starting to worry. glad it's working good for you.:D

[mike95490]

Right, I was not ware you had consumed any power, and that when you hiked in, you saw it at >6A.
Mike

[_OS_]

I and my family spent the Easter Holiday in the mountains and I finally managed to mount the new 80W panel. The panel (BP Solar 380J) has the same electrical specifications as my old one (BP Solar 380S) but came with a junction box instead of pre-wired connections. As you can see in the picture they are not completely level but I will fix that when the snow is gone.

The first sunny day after I mounted them my SunSaver MPPT charged at 11.6A peak at 1PM and a total of 30Ah that day! Battery charge state around 60%

http://lh3.ggpht.com/_plELtD-q2SU/SeNV9YC-X3I/AAAAAAAAAW8/b44LjyVXP-E/2xbp80.jpg

[niel]

"Battery charge state around 60%"

ole,
does this mean you went from 25% soc to 60% soc? i interpreted the 25% from your statement of "Yes I was discharging the batteries down to about 75% the weekend before." and i am not sure i am interpreting you right.
remember these both mean a dead battery-100% dod, 0% soc
and these both mean a full battery-0% dod, 100% soc

in any case i'm glad to see you getting a higher charge into the batteries.

[_OS_]

Hi Neil,

The reason I wrote that was to let you know that my batteries was not fully charged.

When we arrived last Monday my batteries where fully charged and the Trimetric showed 100%. After two days I installed the new panel and the morning after the Trimetric showed 60%. This was a sunny day and at five in the afternoon the same day the Trimetric showed 65%. I have a 600Ah bank which means that the panels have charged 30Ah that day.

When I wrote 75% above I meant SOC.

This said I have never discharged my batteries more than 50%.

Ole

[dwh]

Ole,

Forget the solar for a moment - I just wanted to say; That is one nice cabin. And the woods around it are beautiful. I wish I had one just like it. :D

[_OS_]

Ole,

Forget the solar for a moment - I just wanted to say; That is one nice cabin. And the woods around it are beautiful. I wish I had one just like it. :D

Yes it is nice but there is so much work to be done such that my kids can bring their friends with them; there is no water, no shower and the t**let is in the tool shed.

It was built by my father-in-law in 1970. He did not have much money then and made most of the woodwork himself.

Please note that the solar panels are mounted on the tool shed. Picture of the cabin at the beginning of this thread.

[icarus]

Ole,

600 ah battery with only 11 amps of charge capacity is a bit light. I understand you only draw on the weekends,,, and have the week to recharge,, but going forward,, more panels might be welcome.

Tony

[mike95490]

He's just doubled the array size, but sure, more power is always nice to have.

[icarus]

I realize that he has doubled his PV,,, but even with the doubling he is still at the very low end of the range.

Tony

[_OS_]

Hi Tony,

Yes I know I am on the low end of the range but I also have a generator that I can connect to the Victron inverter. The Victron inverter has a built in 50A charger.

I have only charged the batteries twice so far using the generator (last fall and a right after I bought the system in 2007). I guess this will change soon because I am installing a water system (a water tank that I fill up manually, with a pressure triggered, 130W pump and propane water heater). I will also install a digital TV decoder so my kids can watch TV.

Ole

[icarus]

Ole,

Youare discovering the slippery slope of loads! Water pump,, TV, satellite dish,,Internet dish/modem. You are where I was 10 years ago. Keep resisting the urge for more loads,,,,, betcha can't!

Good luck,, sounds like you have a nice spot. Are you just about through your ice season? We have had warm days,,, +15c with overnight lows ~-5. All the snow is off the ice,,, and the bush is getting bare here and there. I suspect our ice will be out in about another 3 weeks or so.

Tony

[dagr51]

Is your water tank underground? Mounted on a platform or some other way to take advantage of gravity? How large? How do you hump water in to your cabin? Lots of questions, but you have gotten my attention!

[_OS_]

Is your water tank underground? Mounted on a platform or some other way to take advantage of gravity? How large? How do you hump water in to your cabin? Lots of questions, but you have gotten my attention!

Hi,

Please remember that my cabin is in Norway not far from the Arctic Circle.

My water tank is 80 liters and sits on the floor inside the cabin and I have to carry the water in buckets from a near by river and poor into the tank. The law in my country allow me to do this without any wastewater treatment. If I run the water through a pipe from outside the cabin to the inside I have to install a large and expensive wastewater treatment system.

Ole

[dagr51]

Got it. Thanks for the update!

[_OS_]

Ole,

Youare discovering the slippery slope of loads! Water pump,, TV, satellite dish,,Internet dish/modem. You are where I was 10 years ago. Keep resisting the urge for more loads,,,,, betcha can't!

Good luck,, sounds like you have a nice spot. Are you just about through your ice season? We have had warm days,,, +15c with overnight lows ~-5. All the snow is off the ice,,, and the bush is getting bare here and there. I suspect our ice will be out in about another 3 weeks or so.

Tony

Yes I am discovering the slippery slope of loads. At the same time I have also made up my mind to run a 12V cable from the tool shed to the cabin for lighting during night time. This way I can turn off the inverter and save a few Ah. I have also, as I wrote in another thread, ordered a SureSine inverter that has much lower no-load self consumption. I will use relays in the tool shed and a switch in my cabin to switch between the two (during my search for relays to use I discovered that this was not as easy as I thought. More on that later).

The temperatures you have are almost identical to the temperatures over here now. In the city, where we live the snow is almost gone.

Ole

[solarnewbie]

Hi OS,

I'm curious about your earlier specs ( 1 80w bp panel and two 350A batteries)
What did you use on those in terms of TV and Lights and for how long?

[BB.]

SolarNewbie,

You can very roughly size an Off-Grid solar systems AC (120/230 VAC) output by:


Number of "Full Sun" hours per day... 5-6+ hours per day in summer (equivalent to "noontime sun").
Size of Panel in Watts (assume ~82% of factory rating)
Assume flooded cell storage battery (80% efficient) and reasonably efficient AC inverter (85% efficient)
Derating factor of 52% (or 0.52) from above
Assume fixed mounted (not tracking array) tilted at the angle of your latitude.

Assuming you are in a very sunny area and get 6 hours of sun per day (UAE?)

80 watt panels * 6 hours sun per day * 52% = 240 Watt*Hours per day

If you have a 50 watt TV running 2 hours and a 13 watt CFL lamp for 4 hours:

100 Watt*Hours = 50 watts * 2 hours (TV)
52 Watt*Hours = 13 watts * 4 hours (CFL Lamp)
=================================
152 Watt*Hours of daily load

So, an 80 watt panel could easily supply the above load (240WH of energy vs 152 WH of load)...

If you are making an off-grid system for daily use (vs an emergency backup power which may have fewer batteries)--we usually use the rule of thumb for 3 days of no sun plus a maximum of 50% discharge... Or the battery would be sized:

3 days of no load * 1/50% = 6x your daily operating load.

To figure out 350AH x 2 of 12 volt batteries and how much recommended load:

350 AH * 2 batteries in parallel * 12 volts / 6 battery sizing factor = 1,500 Watt*Hours of useful storage...

In this example, with my above example load of ~152 Watt*Hours per day, such a battery bank would supply:

1,500 Watt*Hours / 152 Watt*Hours per day = 9.9 days of "no sun" storage...

Now, we would recommend that your batteries be charged at 5%-13% of the batteries 20 Hour AH rating...

350 AH * 2 * 12 volts * 5% = 420 watts of solar panels
350 AH * 2 * 12 volts * 13% = 1,092 watts of solar panels

If you don't have enough solar panels, then normally we would expect that a generator would need to be used once in a while to recharge your battery bank (typically, run the genset when the batteries fall below 75% state of charge).

Anyway--you really need to understand your loads/needs and how much sun you have available in your area (by season, if it matters). Then we can help size your system to your needs.

-Bill

[_OS_]

Hi OS,

I'm curious about your earlier specs ( 1 80w bp panel and two 350A batteries)
What did you use on those in terms of TV and Lights and for how long?

We are usually not using the system for more than three days at a time with an average draw of around 50Ah per day.

OS