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OffGridInTheCity

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Yikes... I did not know the midnites were so crummy... Just thought of another idea... I know you just bought that pallet of used cells but I noticed that you have a ground mount setup. Why not update the panels on the ground mount with some 'newer' ones like 380-420w 72 cell? you might have to buy new/longer rails but it appears you have the ground clearance to get another row also in landscape orientation. Could be a 50% bump from what you have for that one array.
The 16% loss is from the AIMS inverters - not the Midnite Classic Charge Controllers. The Midnites are in the top tier of MPPT efficiency as far as I understand. The existing arrays of 3s5p (285w) are of design to be near the max of the Midnite Classic 150s and the wiring I have in place. I don't believe I have significant loss of the incoming PV power.

Different size panels / wattage is not a clear 'win' (other than space perhaps) in that there would be expense/ripple affects - to physical framework, possibly the wiring, etc.... space is not the main issue. :)

Side note - the picture (12 posts back) shows the size difference between my existing Mono crystalline (black) and the recent Poly crystalline (blue'ish) 'backup generator' panel sizes - they are both 285w. In addition the Poly(s) weight 20lbs more. I never really 'got it' until this week when I see them side by side - its a significant difference.

I'm attracted to SolArks because they 'more' EMP hardened. I'm attracted to MagnaSine because they advertise 96% inverter efficiency. Both systems are a lot more $ than AIMs inverters.
 
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floydR

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check out the specs it is only an 8kw inverter off grid yes 12kw on solar minus what you are charging into batteries other things such as having problems starting high wattage/amperage items while off grid. etc reference
starting around the 3 minute mark he says he shut it down with his air compressor, then a couple seconds later he said is dryer shut it down
The inverter a good one but not for everyone, You essentially lock yourself into a 50amp service Ben also says
Later floyd
 

Solardad

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check out the specs it is only an 8kw inverter off grid yes 12kw on solar minus what you are charging into batteries other things such as having problems starting high wattage/amperage items while off grid. etc reference
starting around the 3 minute mark he says he shut it down with his air compressor, then a couple seconds later he said is dryer shut it down
The inverter a good one but not for everyone, You essentially lock yourself into a 50amp service Ben also says
Later floyd

A good point that most folks over look.
 

dali1972

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I've become a huge fan of 'heat pump' technology as a way to get heat from electricity....
- Hot Water - We have a Rheemes 50gal hybrid (heat pump + regular elements) water heater which is mainstream/good-prices from Home Depot and very efficient in heat pump mode and maxes out at 450w (smaller inverter).
- Forced Air, whole house heat pump - We have a 4ton Lennox heat pump that works down to 30F/-1C with a max draw of 5000w (at 25F) - but typically runs around 3500-4000w while heating 2600sq ft house.
- Mini-splits are cool - I have a 9,000BTU on the trailer and it 'sips' power and is whisper quiet.
- Clothes Dryers - I have read about heat-pump clothes dryers. They max out at only 1,000w instead of the 4,500w of a normal dryer and 'reportedly' use only 1/3 the overall power of a regular dryer.
- Clothes Dryers - I have read about heat-pump clothes dryers. They max out at only 1,000w instead of the 4,500w of a normal dryer and 'reportedly' use only 1/3 the overall power of a regular dryer.

We have a AEG 7000 series heat pump dryer.... and not trying to be sexist, but my wife hates it and constantly complains about it. tumble dryer.jpg

So why is it bad...and why does she hate it so much.... simple, it as you say uses less wattage and the temp is much lower, this means that what would normally have taken 60 mins to dry in the old tumble dryer now takes roughly 3 or 4 times longer. Thus not sure it actually saves a great deal in money, and is certainly a pain, if you need something fast. PS - also bloody expensive to buy in first place...so honest opinion of ours.... DONT...save your money...buy more panels...and buy an ordinary one.
 

dali1972

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- Clothes Dryers - I have read about heat-pump clothes dryers. They max out at only 1,000w instead of the 4,500w of a normal dryer and 'reportedly' use only 1/3 the overall power of a regular dryer.

We have a AEG 7000 series heat pump dryer.... and not trying to be sexist, but my wife hates it and constantly complains about it.View attachment 24053

So why is it bad...and why does she hate it so much.... simple, it as you say uses less wattage and the temp is much lower, this means that what would normally have taken 60 mins to dry in the old tumble dryer now takes roughly 3 or 4 times longer. Thus not sure it actually saves a great deal in money, and is certainly a pain, if you need something fast. PS - also bloody expensive to buy in first place...so honest opinion of ours.... DONT...save your money...buy more panels...and buy an ordinary one.
One more point to add... my wife will only use our tumble dryer if we need to...otherwise its clothes line outside, or radiators. Its a last resort tool...not a goto machine. Thus her issue with the time to dry.
 

OffGridInTheCity

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I'll measure them against a know good panel and see how they actually stack up.
1614561527618.png
38 of 40 panels tested OK....
- Reference panel (new) = tested 34v open circuit and 8a shorted circuit. Vmp spec = 31.3 * 8a = 250w
- Suntech panel (9yrs old) = tested 44v open circuit and 6.9a-7a shorted circuit. Vmp spec = 35.4 * 6.9a = 244w
So I'd say these are at least 90% original spec... the test method is a bit 'loose' is why I'm not claiming 97.6% as numbers show.
Suntech warranty on these panels....
1614561058558.png


Had 2 bad ones.
- Voc = 30v instead of 44v. This is likely a blown diode.
- Panel arrived *shattered*. It was the very last one (bottom of the 2nd pallet). Such a waste, glass all over, and cut my thumb!
1614560649177.png


All in all - I'd say it was a success ordering used panels as I got 38 of 40 that are fine and I think I can fix the 39th one.
 
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Solardad

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Oct 27, 2018
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38 of 40 panels tested OK....
- Reference panel (new) = tested 34v open circuit and 8a shorted circuit. Vmp spec = 31.3 * 8a = 250w
- Suntech panel (9yrs old) = tested 44v open circuit and 6.9a-7a shorted circuit. Vmp spec = 35.4 * 6.9a = 244w
So I'd say these are at least 90% original spec... the test method is a bit 'loose' is why I'm not claiming 97.6% as numbers show.
Suntech warranty on these panels....
View attachment 24060

Had 2 bad ones.
- Voc = 30v instead of 44v. This is likely a blown diode.
- Panel arrived *shattered*. It was the very last one (bottom of the 2nd pallet). Such a waste, glass all over, and cut my thumb!
View attachment 24059

All in all - I'd say it was a success ordering used panels as I got 38 of 40 that are fine and I think I can fix the 39th one.
Thoughts on how you are going to mount these if they are for temporary use?
 

OffGridInTheCity

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Thoughts on how you are going to mount these if they are for temporary use?
I have universal strut, bolts, wire, and connectors stored with the panels - wa la, a 'backup generator' package. The design/plan is to setup them up in the yard and wire them into the existing pv array combiner boxes to take the array from 13kw to 24kw. In winter time, the charge controllers have plenty of extra capacity due to low winter sun and this will get me near 1000kwh/month based on past 2 winters of data.
 
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OffGridInTheCity

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Was successful repairing the panel with bad diodes by installing a new diode box. And here's the final stash/resting place of the 42 * 285w = 12kw 'backup generator'. Phew - a lot of work to drag them under the house. If the worst should happen, I can drag them out into the back yard and have the potential to generate an extra 500kwh/month during the 4 winter months. :)
1617320041989.png
 

Dr. Dickie

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Sep 23, 2020
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Was successful repairing the panel with bad diodes by installing a new diode box. And here's the final stash/resting place of the 42 * 285w = 12kw 'backup generator'. Phew - a lot of work to drag them under the house. If the worst should happen, I can drag them out into the back yard and have the potential to generate an extra 500kwh/month during the 4 winter months. :)
View attachment 24520
WOW. I am jelly!!
Problem I have where I am is, if a storm comes (hurricane), I have to take down all my solar panels and store them inside (at least the shed, if it gets blown away mine won't be the only one). I am seriously sweating a storm coming in the next couple of years until I move.
 
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OffGridInTheCity

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WOW. I am jelly!!
Problem I have where I am is, if a storm comes (hurricane), I have to take down all my solar panels and store them inside (at least the shed, if it gets blown away mine won't be the only one). I am seriously sweating a storm coming in the next couple of years until I move.
Are they attached to the roof? Can a roof attachment be strong enough so that they panels will stay as long as the roof stays on?

I live in a valley with mountains all around.... hurricanes and tornadoes don't form. At worst we could get 80mph winds - but that's nothing compared to what a hurricane can produce.
 

Dr. Dickie

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Are they attached to the roof? Can a roof attachment be strong enough so that they panels will stay as long as the roof stays on?

I live in a valley with mountains all around.... hurricanes and tornadoes don't form. At worst we could get 80mph winds - but that's nothing compared to what a hurricane can produce.
Not on the roof of the house. Some are on the roof of a shed, and they would have come down. My new panels (6) are on a frame that I built in the back yard. It is made from 1.5" galvanized pipe 3 feet down and in 50 lbs of concrete each leg. Then using 12 gauge strut to attach the panels. If we have a serious hurricane, probably won't matter as the sheds will be gone. Where I am, we don't get direct hits though, we can get some close by that might get TS winds--enough to do quite a bit of damage. So I would have to take them down just to be safe.
 

OffGridInTheCity

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Ironridge has design tools - which include ground based mounts. https://base.ironridge.com/gb/projects/new Wind exposure is just one of many inputs - here's an example of max 160mph wind to give an idea:
1620225843781.png


I used this tool to design my ground mount as it seemed pretty sophisticated. You might be able to plugin values and get an actual 'idea' of what your design would withstand wind wise. I suspect the main issue is 'ballast' - e.g. will it pull out of the ground. :)
 
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italianuser

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Feb 25, 2020
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I used this tool to design my ground mount as it seemed pretty sophisticated. You might be able to plugin values and get an actual 'idea' of what your design would withstand wind wise. I suspect the main issue is 'ballast' - e.g. will it pull out of the ground. :)
Wow, nice app, I'll try it tonight. I found my house on the map yee! Map updated to a few years ago I suppose because there's part of the temporary roof we had in those years. You know, I've never been scared so much as with strong wind; a year we had a small tornado over here, 140KM/h wind (86MPH), and we had this 400m2 temporary roof which was mounted on a metal frame made of less-than-1/2" bars. And the night of the tornado I climbed up to see what that racket was and the roof (well, my part of the roof, about 85m2) was waving up and down like a piece of cardboard. The bars fixed on external walls were starting to break out of the bricks so I started reinforcing them with extra bars... real scary, actually terrifying! :eek: after that I saw the roof of the other apartment being ripped of like a tin of sardines.

house_view.jpg

I'm writing from the red dot! LOL
 

OffGridInTheCity

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Reached 1,000 cycles today on my 1st battery! Average DOD 40% within the 3.5v to 4.0v range.

This 1st battery (of 6 in the powerwall) is 14s120p (48v@260ah). It was built with 70% ebike pack cells from BatteryHookup ( LGDAMF11865 ) and 30% from random ebike packs purchased on ebay ( Samsung ICR18650-22P M ). These cells were advertised as 'nearly new or new' (who knows) but definitely higher end on the quality scale.
1621954171619.png


Last touch-up balance of the overall powerwall was 3/24/2021. These 14 packs are not showing any detectable loss and stay balanced with the other 70 packs even though this is the 'larger DOD' period of the year. Spring = 44kwh/day from the 81kwh battery bank = 54% DOD.
1621953480090.png


Only 7,300 more cycles and I'll get my overall solar system investment back :)
 
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OffGridInTheCity

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60days (continuous) on Solar & Discharge Curve Knee...
Just hit 60 days of continuous, whole house operation on Solar! To achieve this, I've had to do a few days (maybe 10 days) of manual intervention with the heat-pump off and delay using the dryer till the sun comes up and a few things like that - but overall its really working to 'power the house'. Couldn't be more excited.

In this process - there have been a few cloudy days, so I've artificially lowered the 'low voltage cuttoff' from its normal 49.5v (3.54v/cell) to 47.0v (3.35v/cell). As you cans see in the post above - the 'normal' max difference between cells is 40-70mv thru the day - but look at this morning. The discharge curve knee / weaker packs are making an appearance:
1622210408827.png

Packs 45(3.30v), 16(3.31v), 44 (3.33v), and 21(3.34v) are showing the discharge curve quite dramatically.... compared to the overall voltage of 3.42v.

I do wonder - does it hurt cells much if they drop into the discharge curve 'cliff' a few times a year?


------------------------------------------
7:15 AM: Cells continuing to drop - Batrium in full alert :). Pack 5 is starting to expose itself. PV is now 800w but still another 30-40 minutes till the PV power takes over completely.
1622211307809.png


------------------------------------------------
8:12 AM: PV has kicked in / battery is charging. Will the packs recover or will I have to do a balance? Should I try to beef up these packs?
1622214843326.png


-------------------------------------------------------------
9:45 AM: Things look 'recovered' - the extreme sag seems gone and things are back within the 40-70mv max difference and the Batrium alert (3.30v low) is gone.
1622220268707.png



This exercise illustrates that the discharge curve 'knee' is not just about overall power - but that vertical line (of the discharge curve) means that pack differences are amplified.. e.g. some packs will drop much lower than others. So in theory you might think you could go to a 42v low (14 * 3.0v/cell) but in practice with many second-hand cell packs its more like 47.6v low (14 * 3.4v) . Also - a BMS is essential!
 
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OffGridInTheCity

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Some interesting 'raw' power numbers - heat and cool average kw/hour for some key months. House is 2600sq ft w/4 Ton very efficient heat-pump running 100% on electricity (secondary fuel disabled).
1626625423429.png


Its the dramatic increase of "Cool" that is kind of setting me back (in my self congratulations) in terms of generating my own power to run my house.

Last year was only 3,421kw/hour * 24 = 82kwh/day. I'm netting around 70kwh/day in this period - so I thought "good enough" I can cut back to make up the difference.

This year, at 114F/46C the power went up to a whopping 6265kw/hour! * 24 = 150kwh/day. This is double what I'm producing! OK, so its just a hot day. But the average for 2021 Cool is much higher this year with July running 4640kw/day * 24 = 111kwh/day. That's pretty hefty and its been at this level for nearly a month now. No way would I stay cool on my own power with a 41kwh/day deficit.

Some Conclusions:
1) Producing your own power is not as easy as it might look based on just 1 year's worth of data
2) My hat's off to the Power Companies - building in capacity to handle surges.
3) Even if not enough - power is good! We only had fans in the earlier parts of my life.
4) More Panels are better!! (There's a vacant lot 2 houses down - my wife will never know where the extra power is coming from :))
1626626740202.png
 
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Cheap 4-life

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Aug 3, 2020
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My vote is for the vacant lot ;)
That’s a lot of power your A/c is using. When my 3.5 ton A/c runs at 3200w for 20hrs out of the day it uses 64kwh a day.
 
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