Proposed System....what do you think?

anadiner

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Compasses don't point north. They align with the Earth's magnetic field, save for any local magnetic fields which may overwhelm that. Depending where you are magnetic north can be quite some azimuth angle away from true north.
I dont remember exactly. It was a plastic cheapo compass and think did have arrow pointing to N.

All I know is if South is what I think South is here then thats not gonna work
 

wattmatters

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It was a plastic cheapo compass and think did have arrow pointing to N.
Compasses whether cheap or expensive don't point North. Indeed there are places at higher latitudes where the needle on a compass, despite saying N will actually point to the South.
 

pollenface

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I use google earth to look over my house to find a couple of things I can use as a "true north" reference.

Eg. a line drawn from the corner of the shed to a tree stump, then you can put a magnetic compass over that to get an "offset" measurement
 
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pda1

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I talked with the electrical inspector and told him plainly about what I want(ed) to do.

He said, in brief, as follows;

- any equipment that isn't UL approved/listed will prevent my entire off-grid system from being accepted.
- all batteries require venting and LiFePo batteries will require venting UNLESS the LiFePo battery has manufacturer documentation which says UL approved for non-venting. So, DIY homemade LiFePo batteries aren't permissible.

There are UL listed MPPT controllers but at this point, sadly, I'm going to re-think this venture. Cost is a factor as well. I've figured it would cost a minimum of $2,000 in additional equipment and material just to get everything running.

In my area there are no electricians who, 1) know anything about off-grid systems 2) know how to wire one up.

There is a very small consolation- in the event of a fire caused by the off-grid system the insurance company would want to see permits and electrical underwriter documentation. Without them I can be assured they'd pay nothing.

But I must remember that my original intent was just to have 2 panels to run a well pump.
 

pda1

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I use google earth to look over my house to find a couple of things I can use as a "true north" reference.

Eg. a line drawn from the corner of the shed to a tree stump, then you can put a magnetic compass over that to get an "offset" measurement
True North is easy to determine;

Put a stick in the ground and make a mark where the tip of the shadow falls.
2, 3 or 4 hours later make another mark where the tip of the shadow falls.

The line between the two points indicates East and West. 90° to that line, and with the Sun to your back, is True North in Northern latitudes. In Southern latitudes you'll have the Sun in your face.
 

wattmatters

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True North is easy to determine;

Put a stick in the ground and make a mark where the tip of the shadow falls.
2, 3 or 4 hours later make another mark where the tip of the shadow falls.

The line between the two points indicates East and West. 90° to that line, and with the Sun to your back, is True North in Northern latitudes. In Southern latitudes you'll have the Sun in your face.
This will give you an approximate North. To get true North you need to choose your marking times with care - they need to be same number of hours before and after solar noon, and also the shadows need to be cast onto flat ground, or ground with a slope that is all facing true North (or true South).

That's because the tip of any shadow doesn't move in a straight line west to east but it follows a curved path with some north-south motion as well.

Here's a quick video showing how a shadow tip moves at different times of year (this is southern hemisphere). True north is upwards.

The three examples shows shadow tracings for June (our Winter), March and January (our Summer). Note how the shadow tip shows not only side to side motion (West to East), but also moves in a North and South direction. This means just choosing two shadow tip points a few hours apart makes that line not true East-West but with a slight North-South displacement as well. Unless that is the times of those shadow tips are taken at times equally spaced either side of solar noon.
 

pda1

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Well, best method is to use Pub. No. 249 for your latitude, LHA (Local Hour Angle) and declination of the Sun. Wait until MP (Meridian Passage) of the Sun when LHA is 0° With a stick in the ground the shadow of the Sun will then be pointing True North and South.

It's simple....like radar.
 

pda1

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Alright....a new plan.

4- 250w (38 Voc 9 Isc) panels in series or parallel.....doesn't need to be decided just yet. The system will charge a 24 battery(s)

Back to the ol' battery and MPPT selection.

I'm tending to stay away from LiFePo. Why? Scared of 'em- fires, exploding, too sensitive (temperature wise), initially expensive and too many extra electronics to control them (BMS). It's understood that a lot of battery problems are caused by the installer and end user but I don't want to be an experimenter or sorts.

I'm giving consideration to FLA deep cycle golf cart batteries. Still want to have 100AH usable for a good amount of time.

Can you give a recommendation for a FLA battery that would satisfy these requirements?

The MPPT? Well, probably something that would either handle 38 x 4= 152v and 9a .....or some perhaps a 2s2p (hope I using the correct nomenclature) for 76v and 18a.

Thanks, men.

Peter
 

HRTKD

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The Victron 100/50 MPPT would work well if you configured the panels in 2s2p.

Trojan makes a very good 6v GC battery. I used those before I went LiFePO4. Shop around for a good deal. I went to an actual golf cart shop and saved at least $20 per battery.

I don't like the maintenance requirement of flooded lead acid batteries. If I had to go back to lead acid, I would look hard at AGM.
 

pda1

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Thanks for the recommendations.

Will consider AGM also.

A lot of my concerns about fire and explosions would be mitigated if the batteries, inverter and MPPT (everything) was stored outside. The problem for the batteries is that it sometimes (but not often) gets down to about 10° F here in the Winter. I'm sure I'd feel really safe if they were stored in a 1" thick steel vented box. There are plenty of photos of batteries and controllers mounted on...wood! That is not safe or smart. Even using some Hardi-backer board would be helpful.
 

DerpsyDoodler

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Thanks for the recommendations.

Will consider AGM also.

A lot of my concerns about fire and explosions would be mitigated if the batteries, inverter and MPPT (everything) was stored outside. The problem for the batteries is that it sometimes (but not often) gets down to about 10° F here in the Winter. I'm sure I'd feel really safe if they were stored in a 1" thick steel vented box. There are plenty of photos of batteries and controllers mounted on...wood! That is not safe or smart. Even using some Hardi-backer board would be helpful.
You can get deep cycle agms from costco. (just an fyi so you can explore all your options).
 
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