OFF GRID POWER; various thoughts on...

[glenn kangiser]

That drawing is a beauty, Don.  I like it.

I use black for all of my DC grounds because I am used to automotive DC having a black ground and all other colors are hot.  Just easy for me to remember - maybe not right.

[TheWire]

I'm looking at getting 4 40 watt PV panels from Sunelec specs are below and wiring them in series to a MPPT charge controller.  Any thoughts as to these panels in this application, dealing with Sunelec or the quality of their products?

Thank you.

Model     SUN-40
Power (W)    40 Watts
Open Circuit Voltage (V)    21.90 Voc
Short Circuit Current (A)    2.54 Isc
Maximum Power Voltage (V)    17.50 Vmp
Maximum Power Current (A)    2.28 Imp
Dimensions    22" x 21 1/4" x 1 3/8"

$120/ea

[OlJarhead]

I'm looking at getting 4 40 watt PV panels from Sunelec specs are below and wiring them in series to a MPPT charge controller.  Any thoughts as to these panels in this application, dealing with Sunelec or the quality of their products?

Thank you.

Model     SUN-40
Power (W)    40 Watts
Open Circuit Voltage (V)    21.90 Voc
Short Circuit Current (A)    2.54 Isc
Maximum Power Voltage (V)    17.50 Vmp
Maximum Power Current (A)    2.28 Imp
Dimensions    22" x 21 1/4" x 1 3/8"

$120/ea

They've done me well but for the $440 why not buy a 200 watt panel?  I bought 3 205 watt panels for $364ea a month ago.

[TheWire]

OlJarHead,

Do you have the SUN-40's?  I'm curious if these are a quality or low end panel.

As far as going with 4 small panels instead of single large panel,  my challenge is mounting them.  My cabin is in a wooded area and I expect I'm going to have to get creative with placing the panels to avoid shade.  The small panels give me more mounting options and using 4 wired in series allows me to go 48V to my charge controller to cut down on the size of the wire.

[MountainDon]

I am a believer in series wiring to raise the voltage and reduce the necessary wire gauge. When sizing things though, remember to use the Voc (open circuit voltage, the highest voltage the panel would be likely to put out) and then muliply that by 1.25 and 1.25 a second time. Use that figure as the maximum peak spike voltage you would likely encounter in the coldest of weather and size everything to be able to handle that voltage. Those multiplication factors will pretty much ensure nothing will blow.

There is a handy tool at Outback Power that is a great help sizing arrays when using the Outback charge controllers. It has high and low temperature adjusters.    http://outbackpower.com/resources/string_sizing_tool/    I believe Xantrex has one for their equipment as well.   

[MountainDon]

Also not illustrated is the single connection from the neutral (white, Glenn   ) and the ground within the 120 VAC service panel.   If I was doing it over, or with more time available, I would have placed units in better positions to eliminate or reduce wire crossing in the diagram.


As far as what's hot, positive, neutral or negative, as long as one's system is not going to be inspected by a code nazi all that matters is not confusing oneself. My head seems happy to use white as neutral and negative within the confines of a non mobile unit (cabin, house...)  It would be nice if there were distinctive colors used to tell AC wiring from DC wiring.  So I label a lot of stuff that in my younger days I would not bother with.

[glenn kangiser]

I use white for neutral on A/C, Don.  Seems I saw something about black for negative on DC systems once so have always done that - but as you said - if nobody is looking then lack of confusion is important  too.   Dave may jump in here and tell me I am all wrong though and I'd say listen to him - not to me.

[MountainDon]

Just keep the emergency disconnect tool handy in case of confusion. 



FYI, for those who are looking to pass inspections, the NEC does state white is to be used for neutral and negatives.



BTW, I also keep a jug of a baking soda solution handy in the battery chamber as well as a dry box. I haven't figured out what to do when winter temperatures arrive though. Last winter I placed the solution in a couple half filled plastic jugs. It did freeze at one point. Perhaps a more concentrated solution would have a lower freeze point. Some research and experimentation may be called for.

[glenn kangiser]

... I do that also - or mix it once in a while for cleanup and I try to be sure I do not confuse it with rain water or distilled water for filling the batteries if I set it down....

A magic marker helps.

[OlJarhead]

OlJarHead,

Do you have the SUN-40's?  I'm curious if these are a quality or low end panel.

As far as going with 4 small panels instead of single large panel,  my challenge is mounting them.  My cabin is in a wooded area and I expect I'm going to have to get creative with placing the panels to avoid shade.  The small panels give me more mounting options and using 4 wired in series allows me to go 48V to my charge controller to cut down on the size of the wire.

Actually mine is a Sun 205 watt panel (or is it evergreen?  have to go check now)....but I have 3 of them   I got them from sunelec for my system...I was just thinking that one panel would be easier to mount and provides more power for less money (mine was $1.82/watt).  Something to consider.

[TheWire]

Don,

I'm trying to decide on a MPPT charge controller for 48V PV array charging a 12V battery bank.  I'm looking at 200watts of PV panels wired in series for 48V.  I think I have it narrowed down to the:

Outback FM 60 $525 + $30 battery temp sensor
BZ Products MPPT250HV $120 + $30 case
Morningstar TriStar TS-MPPT-45 $415 + $80 display + $30 battery temp sensor

The BZ Products is by far the cheapest but has no data logging or other enhanced features. 

I have a question about the Outback, does it completely power off when the PVs are in the dark or does it stay running off battery power?

Any other thoughts from anyone on my charge controller options would be appreciated.

Thank you.

[glenn kangiser]

I am sure the controllers will have a very minor draw when powered down so that they will know when to wake up.  They need a little power to know when to work for you.

http://www.oynot.com/files/flexmax-product_catalog.pdf

Found it - standby - less than one watt.  It will gain you much more than it uses on standby.

Here is the way I see it, Jerry.

If you want the cheapest with no equalization or other bells and whistles the BZ will work.

If you like gadgets, equalize and other capabilities then it is one of the more expensive ones - both are good.

If you plan to expand the bigger ones have room but you need to be able to get and use the same panels.  If not planning to expand, you have one of the best but a lot of wasted capacity.

The BZ is not highly rated but most of them work and are guaranteed.  I have had one failure out of three and did not try for warranty although they are supposed to take care of it.  I jumpered around it but may have to change it when I hook up the new panels.  $14 return shipping for repair plus sending it in.

[Tickhill]

This may be an advertising scheme but I looked at sunelec.com today and the price glenn and I gave for our panels have gone up a .10 cents since yesterday and they are saying "PV Industry Shortage is Happening Now!"
I wish I had done like glenn and went ahead and got 3 more.
Just thought I would put that out there that there may be something to this and that $$ may start on the way back up.

[Tickhill]

I meant to say .10 cents a watt increase....

[OlJarhead]

This may be an advertising scheme but I looked at sunelec.com today and the price glenn and I gave for our panels have gone up a .10 cents since yesterday and they are saying "PV Industry Shortage is Happening Now!"
I wish I had done like glenn and went ahead and got 3 more.
Just thought I would put that out there that there may be something to this and that $$ may start on the way back up.

I'd call it inflation -- I've seen it in many places and with Uncle Sam printing money like rain falling from the sky it's only a matter of time...

[glenn kangiser]

I heard it may go up - quite a few solar projects going on.

[TheWire]

Anyone have any experience with Rasmond solar panels?  http://ramsond.com/solarprod.php
They sell on their site, Amazon & Ebay.  The Ebay auction prices are competitive with Sun Elec.
I'm looking at their 80W Mono-Crystalline.

I really had to look at our property to find a spot that wasn't shaded by trees.  I also didn't want to take down a lot of trees to gain solar exposure.  Finally found a spot that should be good for 6-8 hours of full sun a day.  Its the corner of the cabin.  I'm looking at installing about a 16' pole that will get the panels above the eve of the cabin.  I would attach the pole to a base on the ground and midway with a heavy bracket attached under the cabin's eve.  Anyone know of any information on sizing a post with a certain square feet of PV panels mounted on it?

[glenn kangiser]

A standard wall  three inch or 4 inch should work braced as you mentioned.  Guys could be added to the top if in doubt.  Trees you mention nearby should kill most of the low level wind.

There are lots of different voltages on different panels so if you are adding to your sun-elec panels you should get the same ones  to keep your charge controller working most efficiently for all - otherwise you will be working at the most efficient level of an innefficient mix.  If all from the new source then no problem.  I haven't heard of them but that doesn't mean anything - - check their specs and compare them to sun - also check the vendor and see if it looks like they may be around for warranty.

[Dave Sparks]

Thanks OJ - I was thinking Phoenix would be the one with their stuff together.  I think I have it handled now.

These folks are as bad as it gets!  But, there prices are usually the best!  I said that 15 years ago BTW.
It usually helps if  you spend 15 minutes each day thinking happy thoughts about Sunelec! Well it might help, OK, it has the potential to help.

When GEL's first came out and now the AGM's it was 2 X the price for 1/2 the cycles, 1/2 the capacity and unknown lifespans over 5 years.

That never bothered me as I would pass it on to the customer ( But I always talk them out of it!) What really would bother me is losing one of the best tools in my box, the specific gravity measurement! Now that would really be a loss living offgrid!

[MountainDon]

Don,
I have a question about the Outback, does it completely power off when the PVs are in the dark or does it stay running off battery power?

The Outback FM60 has some very small power draw even when it's not charging the batteries. For one thing, the display indicates that it in silent or sleep mode. That costs something in power use, but is negligible as far as I am concerned. It's nothing to be concerned about. Even a brand new lead-acid battery sitting there doing nothing likely has more loss due to self discharge than what the FM60 draws.

FWIW, I have the FM60 charge controller plus the VFX3524M Outback inverter/charger plus the Outback Mate and Hub 4 and two battery temperature sensors. (see note below) When we leave the cabin for a few days I pull the breaker disconnect between the batteries and the inverter. I do that just because I feel more comfortable knowing all the AC power to the cabin and outbuildings is completely off. As an experiment I have also left the system sit there for two weeks with the inverter still powered and in its normal standby mode. I can not discern any difference in power use between leaving the inverter disconnected or in standby.

(note below)  I have two battery temperature sensors, one connected to the FM60 and one connected to the VFX3524M. It is possible to have only one temperature sensor in the system when an Outback Hub and mate are used. However Outback told me that IF I depowered the inverter/charger I needed to have a temperature sensor connected to the FM60 inorder to have the FM60 read the battery temperature. IF I left the inverter/charger powered up, even in standby, I could use just one temperature sensor connected through the Hub and it would supply data to both the FM60 and/or the inverter/charger as required. If that's not clear don't worry about it unless you have an Outback Inverter/charger as well as an Outback Charge Controller.

[MountainDon]

Outback FM 60 $525 + $30 battery temp sensor
BZ Products MPPT250HV $120 + $30 case
Morningstar TriStar TS-MPPT-45 $415 + $80 display + $30 battery temp sensor

Thank you.

I think the BZ is great for those who are needing to stick within a tighter budget. My opinion on the Morningstar is "why bother with it when you consider the price is close to the Outback?" I'm sure it's good but I like having the system all Outback.

[MountainDon]

 Anyone know of any information on sizing a post with a certain square feet of PV panels mounted on it?

UniRac has information on pole sizing, depth, etc available n their website. I believe it is in their downloadable catalog pages for their pole mount racks. Of course their info is centered around using their mount kits. Their info takes wind loads into account on various combinations of panel sizes and numbers of panels. They supply the required depth and concrete volume for a safe installation.

[MountainDon]

What really would bother me is losing one of the best tools in my box, the specific gravity measurement! Now that would really be a loss living offgrid!

Absolutely!!!!!!!!

[Tickhill]

OK, here is the Visio produced wiring diagram. Thanks very much to Tickhill for his fine rendition of my pencil sketch - MD

[MountainDon]

That's pretty much got it.  

Thanks very much for the great work.