Need help on a few things for off grid solar setup

Vic

Yes,  Bill,  the Vmp that justinlee noted is what I found a couple of days ago for the AP-130 PVs.

Justin,  that cable in the link that you provided,  appears to be SAE gauged wire (a bit smaller than the standard that most of us use in Solar systems  --  AWG.   Also,  that cable is rated at only 60 degrees C,  you will probably want to use cable that has a 90 - 105 C Rating.   And,  generally you would want to enclose the cable run from your Combiner box,  If it is exposed to the elements,  in conduit,   Standard building wire is fine for this THHN,  THWN-2 etc).   BUT  Building wire must not be exposed to sun.   So,  you may want some USE-2 or RHW cables between the PVs and a junction box,  as those cables will stand exposure,  and so on ...   there are a number of fine details that should be carefully considered,  as you design and build your system   ...

Also,  AIMs has worked fairly hard to earn a fairly POOR reputation for quality,  reliability and performance for their Inverteers  and to a certain extent their Charge Controllers,   from reports here and elsewhere (IMO).

Not to be TOO nit-piking,     Vic

justinlee

I'm dying here trying to learn and piece together this system...VIc if it were your system what charge controller would you be looking for and what inverter

Vic

Justin,

We all need to make tradeoffs,  and most of us cannot make systems that are the picture of perfection.   AND,  we all are learning as we go along ...

We have followed this discussion,   but it is not exactly clear just what you are trying to do.

So this is an off-grid system,  and you own  16 ea AP-130 PVs and two Sharp 230 w PVs,  and believe that you have your 48 volt battery bank,  IIRC.

The Inverter and the Charge Controller (CC) are very,  very important components.   Sizing the inverter for your current needs,  perhaps with a bit of reserve,  but  inexpensive inverters are often disappointments.  Some of the fine details in the Specifications on these two items  can make a large difference in the performance of the system.  AIMs inverters have seemed to by fairly unreliable,   and have other issues,  as have been reported here.

Normally,  systems are designed from knowing the loads that the system needs to supply,  and also knowing what time of day that the loads occur,   as well as what are the peak demands on the system (like well pumps,  A/C,  etc).

What loads does this system need to supply,   for how long does these loads need to be supplied,   and what is the peak amount of power that this system needs to provide??

Sorry to beating you up a bit.  Thanks,  Vic

justinlee

I understand it is all about mathematics of usage vs Supply versus sustainability. I understand It can get fairly complex in order to assure that you have an almost uninterruptible power supply... I guess this is the difference in somebody setting your system up for you and you paying ten's of thousands of dollars or you doing it yourself in having to learn the ropes ...or it may end up costing you on an expensive mistake or you just being sorely disappointed with the system that you built. I want neither of those I want to be able to do it myself and do it fairly economical but most importantly I want something that will last for the time and the money I'm investing... So with that being said it is a 16 by 40 lofted cabin sitting in the shade 90% of the day. The insulation is going to be the best I can afford. You are correct on the AP panels being 16 of them they're located 55 feet away from the cabin where the charge controller will be located. I will be running a 8000 BTU AC about 5 hours today in the summer of course. Refrigerator is about 700 watts and it will be running 5 to 6 hours a day and it will be moved into a shed outside to keep the heat from . Dispersing in the house.... The well pump is 96 Watts at a half hour a day.... The lights I have no idea now because they are going to be changed to 120 volts LEDs since I am not going to run 12 volt in the cabin now... The other few miscellaneous things would be microwave 1200 watts and 150 watt television about 3 hours a day a CPAP machine 8 hours a day ssatellite dish receiver ...I have no idea on the Watts of the receiver but it will also run around 3 to 4 hours a day along with the TV and a phone charger hour or two a day. This will eventually be a full-time living off the grid. I have not purchased the battery bank yet until I am 100% sure of what I'm putting together and I do believe at this point it will be around 8 6 volt 225 amp lead acid. I do know I made a decision to run 48 volt system for the most efficiency. What I am trying to buy now to match these things would be the inverter the charge controller the wiring the combiner Box some fuses exedra. And this is pretty much where I stand at this point

justinlee

morning star is an option im looking at for charge controler....the mppt 45...and i may buy the external monitor...it runs around 368,00 ....plus 89.00 for the monitor....the inverter i still have no idea now i have heard the reviews on the aims...i think i may need a 3000 watt....just incase...but the 2000 watt aims with a 6000 surge for 20 seconds seemed resonable on size.. before i learned they had problems.....so now iam looking for a reasonable inverter and where to buy the right pv to charge controler  8 awg wire

Vic

Hi Justin,

First,  it is good that you are asking questions before you have acquired too many hardware items,  this  is a very good thing.

Taking a few more weeks to design a system that will meet your needs,  is a very good use of time (obvious,  isn't it?).

Couple things,  Believe,  that the 700 watts for the refer may be a Typo,  or an error.  Hope that the running power is more like 100 -  120 watts at 120 VAC.

That 8K BTU  A/C  I s a bit large,  and you might need to moderate its use,  especially when the power will need to come from batteries to limit the discharge of the batteries.  The power needed to run this A/C  will depend,  somewhat on the ambient temperatures,  but this could need about  6 - 8 amps at 120 VAC.

Also  the CPAP machine power consumption is an unknown.

Many Satellite receivers (especially ones with the DVR)  consume considerable power 24/7,  even when not in use,  perhaps to about 800 - 1,000 Watt Hours per day.

If you have a Kil-A-Watt meter (measures power usage of 120 VAC items)  please measure the demand of that Satellite RX,  the CPAP,  and other items.

Regarding inverters,  Stand by or Tare power is a very important spec for inverters.  This is the power need to just run the inverter,  with no loads.   Many inexpensive inverters can have horrible Tare losses and sometimes this is not specified,  or speced bin a misleading way.

The Morningstar CCs are solid and efficient,  BUT,  they are a NO FRILLS inverter.  No meter,  No Auxiliary outputs,  basically NOTHING but a CC.  Everything else in an option.  Efficiency is important,  but you may not yet know what additional functions in a CC that you might need.

More Later,   Thanks for your patience.     Vic

justinlee

Can i get an opinion please http://www.invertersupply.com/index.php?main_page=product_info&products_id=2886&cPath=0_493&gclid=CjwKEAjwxoG5BRCC7ezlzNmR8HUSJAAre36jcQ3Q83uQwI3riyqfWDPxKwxpaJ-uSBW_QMKa3qjROxoC1YDw_wcB

justinlee

specs say it shuts down @42 low.....and 61.2 high....will the battery's get sufficient charge under the 61.2.....cold sunny days with high voltages effect this with my ap 130 panels?   thanks

Vic

justinlee said:

specs say it shuts down @42 low.....and 61.2 high....will the battery's get sufficient charge under the 61.2.....cold sunny days with high voltages effect this with my ap 130 panels?   thanks

This is a very good question ...   You would really WANT an inverter/charger that has a programmable Low Voltage Disconnect (LVD)  and  a HVD that is at least 64 V,  and,  better yet,  up to about 66 V,  for cold or old batteries that need an EQ

BUT this places one in the higher tier of Inverter/chargers.

My opinions,    Vic

justinlee

thanks..i will keep looking ...but I did purchase the morningstar TS mppt 45 with the  TS digital meter today....so I will be working with this CC  on the system

Photowhit

justinlee said:

specs say it shuts down @42 low.....and 61.2 high....will the battery's get sufficient charge under the 61.2.....cold sunny days with high voltages effect this with my ap 130 panels?   thanks

Your charge controller will limit the voltage going into the battery, 61 volts should be fine, though might effect equalizing voltages, but it's close. (It's in that minimum range I suggested earlier. But the spec sheet says voltage range 42-60 and over voltage protection at 61.2, love to know what is in between! I think equalizing for 48 volts is between 60.8 and 62volts)

It's nice that it can be hardwired.

mike95490

What will your cold weather charging voltage be?  EQ voltage ?  

justinlee

can i get an opinion on this wire...thanks http://www.savegreenmoney.com/product-p/10-0008.htm?gclid=Cj0KEQjwjIy5BRClh8m_9Zu64d8BEiQAtZsQfyMLEL6n_qNgzX6DuaIbuNMYyyj1w0Mm5-_oUsFPTh4aAm848P8HAQ

justinlee

or this wire here...said rated for direct burial ...what does that mean http://www.wireandcabletogo.com/8-AWG-Solar-PV-Photvoltaic-UL4703-Wire.html?gclid=Cj0KEQjwjIy5BRClh8m_9Zu64d8BEiQAtZsQf7x0DYp97Nro9BAsHZztjcYU1wYJKm5_zl5izFvEUTcaAtHa8P8HAQ

justinlee

sorry for the three post in a row...but are any of these two wires sufficient for my 55 foot run from the panels to the CC

vtmaps

justinlee said:

sorry for the three post in a row...but are any of these two wires sufficient for my 55 foot run from the panels to the CC

justinlee, this thread is three pages and many subjects long.  I've lost track of your proposed system... please post a summary with your panels, combiner, controller, battery voltage, etc.

--vtMaps

justinlee

I'm sorry it's so long....I definitely needed help. 2080 Watts at 48 volts at 27 amps I don't have a combiner box yet but cc is Morningstar mppt 45

vtmaps

justinlee said:

I'm sorry it's so long....I definitely needed help. 2080 Watts at 48 volts at 27 amps I don't have a combiner box yet but cc is Morningstar mppt 45

What is the Vmp of each string of panels?  And what is the 27 amps?   --vtMaps

Vic

Hi vt...

I am not Justin,  but he does have 16 ea AP-130 PVs,  and has been going with a 48 V system (was considering GC-2 batteries.  So that could be four strings of four PVs,  depending on things   ...

Justin,  please slow down a bit.   The exact items that you will need to connect the hardware items together  will depend on exactly what items you will need,  and just where all of these elements are located.

Doing a paper design of what you NEED in order for this system to do what it must do  is where you are now.  Buying more things right now can lead to making a number of costly mistakes.

Later,   Vic

vtmaps

Thanks, Vic.

Assuming Vmp = 18 and Imp = 7.2, a 55 ft run of 8 gauge copper will have a round trip voltage drop of 2.82%.  At full nameplate power there will be a 58.5 watt cable loss. 

Bottom line: 8 gauge is OK for the run.  

--vtMaps

justinlee

18.9 vmp

Vic

Justin,

There are a number of variables in how one may want/need to connect the PVs to the Combiner and CC.

Would guess that those AP-130 PV modules have a real Junction Box on their rear,  that could allow one to run normal Building wire,  like THHN (available at Big Box stores),  all the way from the PVs, Combiner right to the CC's input breaker,  in conduit.   Normally,  one would use a short  piece of liquid tight Flex conduit to a weatherproof junction box,  and from that box you could use PVC conduit to the Combiner,  etc.   This could mean that you might not need any cable that is rated for Exposure (like the PV cable in your post above).

And,  those of us that are at a distance cannot know all  of the variables in your site,  and just what might be the best approach for your situation ...

FWIW,   Vic

Vic

Justin,

Here is a high quality PV Combiner:
http://www.solar-electric.com/installation-parts-and-equipment/midnite/pvarco/mnpv6.html

These Combiners use breakers like these:
http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/stfubr1/mnepv.html

The size of the PV breakers in the Combiner will depend on the Isc rating of the PVs,  or perhaps the Maximum Fuse Size specified for the AP-130s  --  the Fuse size may not be noted on the sticker on the back of the PVs,  as they are probably about 15,  or so years old,  and this was not as common to see when those PVs were made.

One slight disadvantage of using somewhat small PVs,  is that there are more connections and racks per watt of PV power produced.  The above Combiner does not have very much room to add more PVs later  --  only two more strings.   So,  you might want to build your system from the start by making it easy to expand later ...

Vic

justinlee

If I went ahead and went with the 6 awg wire for the 55 foot run would it help on the percentage voltage drops?...or just not enough to make a difference?...thanks

BB.

Can you repeat your planned system configuration?

Array Wattage
Panel Vmp / Imp
Type of solar charge controller (PWM/MPPT)
Battery Bank voltage

In general, for a 55 foot run, I would be suggesting putting panels in series for a higher Vmp-array and a MPPT charge controller.

-Bill

justinlee

16 12volt ap-130 panels wired in 4 strings of 48
Vmp 18.9 V
Imp 6.9 A
Voc 24.6 V
Isc 7.6 A
Series Fuse: 15 Amps
Bypass Diode: 8 Amps
 morningstar mppt-45

batterys one string 48 volts @225 ah
 55 foot run to CC
so my question ....(8awg being sufficient with less than 3% drop) ....but what would be the benifit of going to 6 awg
thanks

BB.

OK, first thing is use MorningStar's string calculator (they do not AP/All Power panels listed) but for your configuration, 4xseries by 4xparallel panel configuration is fine.

So--That would be 4x18.9 volts Vmp = 75.6 volts Vmp-array
And 4x 6.9 amps Imp = 27.6 amps Imp-array

Using a string calculator 8 awg:
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=75.6&phase=dc&noofconductor=1&distance=55&distanceunit=feet&amperes=27.6&x=52&y=11

Voltage drop: 1.91
Voltage drop percentage: 2.53%
Voltage at the end: 73.69

Same thing at 6 AWG:

Voltage drop: 1.20
Voltage drop percentage: 1.59%
Voltage at the end: 74.4

You will save some power losses:

P=V*I
(75.6v-73.69v) * 27.6 amps = 53 Watts lost (8 awg)
(75.6v-74.4v) * 27.6 amps = 33 Watts lost (6 awg)

The operating voltage at the charge controller is fine with either cable diameter. 20 Watts drop difference is hardly worth worrying about.

Are you planning on adding more panels to the array sometime in the future (save pulling new/more cables)?

Charging a 255 AH @ 48 volt battery bank at 5% to 13% rate of charge:

• 225 AH * 59 volts charging * 1/0.77 panel+controller drating * 0.05 rate of charge = 862 Watt array minimum
  
• 225 AH * 59 volts charging * 1/0.77 panel+controller drating * 0.10 rate of charge = 1,724 Watt array nominal
  
• 225 AH * 59 volts charging * 1/0.77 panel+controller drating * 0.13 rate of charge = 2,241 Watt array "cost effective" Maximum
  

And your array is:

• 16 * 130 Watts = 2,080 Watt array
  

So, your present array is a nice match to your bank. And no other combination of this panels will run the 45 amp MPPT controller at any more power "optimally". So--If you wanted a larger array, you would probably want a larger MPPT controller, or run a second set of cables from the array to the battery shed with a second MPPT controller.

If you are planning on running a second controller someday... Then you may want to pull two sets of cables. And/or bury a much larger diameter conduit (easier pull) and leave a pull cord.

Do you see adding a second string to your battery bank or using large AH batteries in the future?

-Bill

justinlee

yes..will eventually get to 4000 watts 2 strings

vtmaps

BB. said:

Using a string calculator 8 awg:

Voltage drop: 1.91

Voltage drop percentage: 2.53%
Voltage at the end: 73.69

Same thing at 6 AWG:

Voltage drop: 1.20
Voltage drop percentage: 1.59%
Voltage at the end: 74.4

You will save some power losses:

P=V*I
(75.6v-73.69v) * 27.6 amps = 53 Watts lost (8 awg)
(75.6v-74.4v) * 27.6 amps = 33 Watts lost (6 awg)

Something to consider:  The voltage drop percentage does not change with the power being transmitted.

Power loss, on the other hand, goes as the square of the power being transmitted in the cable.  Solar panels, because they get hot in the sun, rarely put out their rated power.  Therefore the power loss will rarely be as great as Bill calculated.

At half power, for example, the power loss with 8 gauge cable will be one fourth of 53 watts.

--vtMaps

justinlee

so i guess looking into the future.....if i ran 6 awg now.......changed the charge controller to 60 + amp...doubled the array....too 4160 watts 54 amps @48 volts....would that 6 awg be enough making it a wise decision to run bigger wire now?