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Small Cabin Forum / Off-Grid Living / Fine tuning your off grid solar
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groingo
Member
# Posted: 1 Feb 2015 11:27
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Well, this has been the first full winter season for the solar and all was well until late November thru December where heavy dark overcast and rain was the norm and so the solar took a pretty good hit which brings us to recharging by generator between times.

The old 10 amp charger did the job but lacked enough punch to get a truly deep charge in the alotted time of 3 hours charge every three days, which could have been run longer but it simply did not provide enough deep charge, every three days whether the charge levels were the same long or short charge....so I began looking at the options, grow the solar capacity to 800 watts which would do it but then would require a major overhaul, bigger batteries with more capacity again big cost, or figure that this only occured over a two month period or 30 hours generator time per month over a two month period....this seemed to be where I should focus so I got an Iota commercial charger that I can program the way I wanted.

Now depending on the battery level I am pushing a conservative 25 amps for the first hour and then it switches to auto mode and tapers power normally over the same three hours this has made a big difference in depth of charge and length of charge duration, now I need to recharge once every 7 days (half the frequency) with little noticeable change in generator fuel consumption per charge for a fraction of what I would have paid otherwise.

The final free bonus paid off by keeping close watch at panel exposure morning to dark which revealed moving the panels just 10 feet to the left from where they were increased exposure by a full hour especially when the sun peeked out.

So in the end, the 400 watts is enough, 235 ah batteries are fine....it's just a matter of fine tuning what you have and sometimes it works.

creeky
Member
# Posted: 1 Feb 2015 12:32
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I hear ya.

a good charger makes a big difference. For me, being able to up the voltage when the batts are cold.

I can usually get away with an hour of charging on the charger in the a.m. and then let the panels take over from there.

for my panels: i've got the second bank 50 feet east of the first set. to beat the shading from the trees. neat to watch. in the earliest a.m. my first panels will start out around 150 watts while the second set is maybe 35. as the tree shade moves: by 9 the second set will be around 400 watts while the first set is 45. by 11 they're both clear and i go into absorb real fast.

next year my fine tuning will be putting the second set of panels in permanently. I'll move them 100 feet east and 30 feet north from the solar shed. this should really help improve that early morning exposure.

Steve_S
Member
# Posted: 1 Feb 2015 13:17
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How much are you running off your system there Groingo ?

We are still planning on 4x 300+/- watt panels for a total of 1200 watts backed with a min of 4 batteries but more than likely 8 (2 banks of 4).

Just waiting on a couple of other quotes to come in but it seems that the use of a SimplePump() solves a few issues we were hung up on this past fall.

Been really looking at various ways to adjust panels for the 4 seasons. Auto-Trackers and such are not a part of the plan, I can adjust them manually... BuildItSolar has some good ideas there and a couple of posting here had some good creative solutions. The tricky part is that the panels will be mounted to a frame on top of a Sea Can.

groingo
Member
# Posted: 1 Feb 2015 14:08 - Edited by: groingo
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Steve:

I use only 180 watts total in 24 hours off my 2 Crown deep cell
batteries, fact is my discharge rate is probably more than my actual use.

The panels do good in bright sky and full sun but with rain, dark clouds and blue sky is where they naturally fall down.

I have poor direct sun exposure to the South due to neighbors trees so split the panel angle to grab more light from directly above during winter months, gives longer charge opportunity.

Can't stress enough, make sure you have plenty of unobstructed South exposure for you panels, without it you are fighting an up hill battle....just makes things more difficult and potentially more expensive.

The key things I have found that work for me is, lots of South exposure, reduce your energy requirement wherever you can and just keep it simple, this is not a plug and play power supply where you can say you have X plus X therefore you need this, it just doesn't work that way, many years of planning showed me that whatever I thought I needed I'd better multiply that by 2 to be safe, but now nearly a season later with variables thrown in like cantankerous batteries, poor quality components etc., (more expensive and especially Made in US don't mean diddly) I have raised the formula to 4 times up from 2....overkill is what solar is all about.

Steve_S
Member
# Posted: 1 Feb 2015 15:16
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Fortunately the location of my Sea Can has excellent South Exposure and clear from East to West... South Facing hill. Attached is a photo showing the 20 footer - the trees are on the north side going over the hill top. Cabin is going West of the Sea Can, Pump House (little bldg. to left) is south of the Sea Can.

Prior to my moving into the temp shelter I'm in now, I was using an average of 10Kwh a day with very outdated and inefficient appliances. Heck the old fridge used 150Kw a month - my new fridge uses 310kwh a YEAR. Everything I have is Low Power - except for my Graphics Workstation which is a seriously HD Computer but used only when & as needed. @ the Cabin, cooking, heating, hot water will be non-electric.

Does not matter where things are made, that's no quality guarantee, the brand name and quality feedback are essential.
SeaCan view with pump house
SeaCan view with pump house


AK Seabee
Member
# Posted: 4 Feb 2015 01:55
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The only shop here in town uses Magnum components. I am looking at the 2800 pure sine wave inverter. Have y'all used it and if so what is your opinion.

MtnDon
Member
# Posted: 4 Feb 2015 10:26
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Magnum is a good brand. That sounds like their MS2812? If you really need 2800 watts you should maybe be considering a 24 volt system, IMO.

creeky
Member
# Posted: 4 Feb 2015 11:01
Reply 


AK I'll second what MtnDon says. 24v is a good idea if you go for a system that big.

I run a good sized system, probably the largest on the site. I started out with a 3kw inverter and then downsized to a smaller 1200/1600w inverter. It runs everything the old inverter does. It is a top of the line unit tho (TBS Inverter) so it has a 20 minute!!! max output of 2500 watts.

The advantage of a smaller inverter. The TBS uses 10 watts on idle. The 3kw inverter used 35. So multiply 25 watts x 24 hrs and you're saving 600 watts a day.

That's a lot of power. More power than Groingo uses in 3 days.

So look carefully at your max loads. It may be you're better off with a smaller inverter. IMHO.

groingo
Member
# Posted: 4 Feb 2015 11:15
Reply 


Don't forget, nearly all power inverters have external shutoff capability so they are not running when you don't want them too and you can save that idle power when not needed.

creeky
Member
# Posted: 4 Feb 2015 12:47
Reply 


good point g:

and some inverters use so little power on idle (like the morningstar sure sine... 55mA self consumption (standby mode)
makes no difference.

MtnDon
Member
# Posted: 4 Feb 2015 14:24 - Edited by: MtnDon
Reply 


The ones I like best have user programmable sleep/search modes, that can be activated by a low wattage LED, like Outback.


But don't forget AK's nearest dealer only carries Magnum. Shipping from the lower 48 can be expensive to AK if that is where he is.

Truecabin
Member
# Posted: 5 Feb 2015 12:33
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Quoting: creeky
to beat the shading from the trees. neat to watch.


i wonder if anybody has ever rigged a solar tracking system to winch a treetop one way then the other

creeky
Member
# Posted: 5 Feb 2015 13:43
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lol. man I like that idea.

ever year about this time I look at my chainsaw. and I look at the "three sisters." and I think .... rrrmmmrrrmmmrrrmmmmmm

Truecabin
Member
# Posted: 6 Feb 2015 03:19
Reply 


i hear ya this year i took pics of the worst offenders and their shadows december 20

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