Building first system, numerous questions

scotthw
scotthw Registered Users Posts: 5
Hello, and thanks for having me here. I have read a few of the other "My First System" threads and they helped, but did not address all of concerns, so bear with me.

I am building my first solar setup, groping my way through this. This is not for camping, etc, only at home. My initial desire is just to learn and tinker but my ultimate goal is to be able to run my standard size refrigerator off of it in the event of a power outage. I do not know what the surge is but running power is 180 watts. The thing runs roughly half the time (I am guessing, I haven't really measured it, just my feel from living with the noisy thing for years). At this point all I have are the batteries and panels as described below. Basically 228 Ah battery, 2 X 100 watts solar. I realize the capacity I currently have is nowhere near being able to run my fridge 24X7, but that is my goal, and I will add to the bank and panels over time. If I can even run it part of the time and use my 2000 watt inverter generator the rest of the time that would help.

I have attempted to spec out the rest of the system on http://www.solar-electric.com but having a tough time understanding everything and scared of buying the wrong thing and terrified of destroying something/frying myself in the process. I spoke to someone in sales who was very helpful but as soon as I hung up I had more questions and discovered I did not quite understand everything being said to me. I decided rather than wasting any more of their time it would be more fruitful to lay it out here where everyone can ponder what's being said before responding.

The rep convinced me I would be better off with an MPPT controller, which I knew already, just wasn't convinced it would be worth it for what I am trying to do. He explained that the voltage lost with a PWM controller would be diverted and used somehow... I thought I understood on the phone but now drawing a blank. I am currently looking at a Morningstar TriStar 45 Amp MPPT http://www.solar-electric.com/motr45ampmps.html with its meter http://www.solar-electric.com/motrm2dime.html. In addition, I am pondering a Samlex 1,000 Watt 12 Volt Sine Wave Inverter http://www.solar-electric.com/sa1wa12vosiw.html. Other than that I needed to know what cables, connectors, etc I needed to finish fleshing this out.

He said if I use a MPPT controller I did not need to parallel the panels I could serial them together and blah blah connect this to something or other... I went crosseyed. Advice ?

He said I wanted a baby breaker box with 12 AMP input and 50 AMP output. This gets wired how ?

I understand that distance from panels to controller is crucial, the shorter the better especially 12 V vs 24 or 48. I would like to think I would have the panels right next to the controller but its possible I might want/need them some distance, maybe 10 - 20 feet. That's going to be some ginormous cabling isn't it ? Should I get my own bulk cable and add my own connectors ?

How do I ground all of this ?

If I have a breaker box then fuses are moot, correct ?

I can't think of anything else right now, but this alone is enough to spin my synapses into oblivion.

Thanks a million folks!

=====

NorthStar Ultra High Performance Battery SMS-AGM-8DK
BCI Group Number 8D
Height with Terminal 9.6 in
Width 11.0 in
Length 20.8 in
Weight 185 lbs
Terminal Configuration SAE
Pulse Cranking Amps 3,150 A
CA/MCA at 32°F 2,700 A
CCA at 0°F 2,250 A
CCA at -20°F 1,738 A
Reserve Capacity 500 min
Capacity 20 Hour Rate 228 Ah
Capacity 10 Hour Rate 210 Ah
Internal Resistance 1.2 mÙ
Short Circuit Current 7,500 A



Product Description: Two PCS of 100 Watt solar Panel(total 200 Watts)

Renogy 100 Watt Monocrystalline Solar Panel X 2

Key Features

High Modules Conversion Efficiency
Guaranteed Positive Output Tolerance (0-3%)
Delivered ready for connection with cables and connectors
Withstand high wind (2400 Pa) and snow loads (5400 Pa)
Excellent performance in low light environments

Electrical Specifications

Optimum Operating Voltage (Vmp): 18.9 V
Optimum Operating Current (Imp): 5.29 A
Open - Circuit Voltage (Voc): 22.5 V
Short- Circuit Current (Isc): 5,75 A
Maximum Power at STC: 100 W
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 715 VDC
Maximum Series Fuse Rating: 15A

STC: Irradiance 1000 W/m2, module temperature 25°C, AM=1.5;

Mechanical Specifications

Solar Cell: Mono-crystalline 125 x 125 mm (5 inches)
No. of cells: 36 (4 x 9)
Dimensions: 47 x 21.3 x 1.4 in (1195 x 541 x 35 mm)
Weight: 16.5 lbs (7.5 kg)
Front Glass: 3.2 mm (.13 in) tempered glass
Frame: Anodized aluminum alloy
Junction Box: IP65 rated,
Output Cables: 4.0 mm2 (.006 in2), 600mm(23.6inches)
Connectors MC4 Compatible

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Building first system, numerous questions

    Welcome to the forum.

    Okay let's cut to the chase: you're trying to run something that draws 180 Watts for half a day. That's 2,160 Watt hours. So my first advice would be buy a new 'frige 'cause that one is using about double the power a good one will use. Instant savings there.

    Second, that battery you've got is the wrong thing. Notice the utter lack of "Amp hours" in the specifications. Obviously it is not suitable for repeated discharge and recharge cycling. By the number calculated above (2,160 Watt hours) you would need a fairly hefty battery: about 450-480 Amp hours at 24 Volts. Here's a bit of an explanation regarding system Voltages: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

    Third we come to the issue of recharging. Your two 100 Watt panels are "standard" type, meaning they can be used on a battery system with either PWM or MPPT type charge controller. They will not, however, produce enough power. Think of it like this: 200 Watts of panel has to 'harvest' over 2000 Watt hours (the 2,160 Watt hour refrigerator load). It would need 10+ hours of direct sunlight with zero inefficiencies to do so. That's not going to happen.

    If you look at recharging the example 450 Amp hour 24 Volt battery bank you'll find you need 1575 Watts on a PWM controller or 1403 on an MPPT type (you can see the improved efficiency of that controller here).

    To give you some idea, I run my whole cabin and refrigerator from 700 Watts of panel and 232 Amp hours of 24 Volt battery. Your 'frige's excessive use calls for double the system size. Since panels can be bought at about $1 per Watt, the ~700 Watt difference is $700 and that surely ought to buy a new refrigerator that uses less power.

    Other than the horrible disappointment and dreadful realization that what you've got isn't going to work, how are we doing?
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Building first system, numerous questions

    You are going to have to get an ACCURATE measurement of what that fridge is using in order to determine the correct sized battery bank and then the correct size solar array.

    Get a kill-a-watt meter, and run it for a few days to determine your average daily usage. Without this number we would just be guessing.
    Also, if the fridge is old, you will end up spending more money buying excess solar/batteries to produce twice (or more) the amount of power needed to run that old fridge then if you bought a new energy efficient one. Most new ones will use about 1kwh per day. I have seen older ones using 2-5x that amount.

    The panels and battery you have now are not even going to put a dent into what you will ultimately need.
    And if you let us know your location (city), we can determine the average number of "solar hours" per day you will get to help determine the size of the system you will need.

    And realistically, for occasional and rare power outages, you will find that the cost is going to be prohibitive to do solar. A small generator is the way to go. Just throwing numbers out there assuming a new energy efficient fridge consuming 1kwh per day, you'd likely be looking at $3,000-$4000 to put together a system to run a fridge 24x7. And then the cost of replacing the batteries every 3-5 years.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • scotthw
    scotthw Registered Users Posts: 5
    Re: Building first system, numerous questions

    Well I as much as said I knew what I had wouldn't address my goal at this point.

    As for your statement "Notice the utter lack of "Amp hours" in the specifications." then what is this:

    "Capacity 20 Hour Rate 228 Ah" Ah - Amp Hours does it not ?
  • scotthw
    scotthw Registered Users Posts: 5
    Re: Building first system, numerous questions

    "And realistically, for occasional and rare power outages, you will find that the cost is going to be prohibitive to do solar. A small generator is the way to go"

    OK, that makes sense, I guess I will have to live with that (I do have the generator already), so I am just looking to learn and tinker. I do have a kill-a-watt meter which is how I knew the running watts, its just been a while since I ran it, could not find my numbers, will have to set it up again and take note.

    I am in Central Texas btw.

    Thanks
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Building first system, numerous questions
    scotthw wrote: »
    Well I as much as said I knew what I had wouldn't address my goal at this point.

    As for your statement "Notice the utter lack of "Amp hours" in the specifications." then what is this:

    "Capacity 20 Hour Rate 228 Ah" Ah - Amp Hours does it not ?

    So it does. Must have stopped reading when all those automotive specs turned up first. Not a good sign.

    As jcheil said if your usage numbers didn't come off a Kill-A-Watt they aren't accurate. This could be good or bad.

    To analyze your equipment then:
    228 Amp hours @ 12 Volts will give you up to about 1.3 kW hours DC. After inverter consumption and conversion loss that would be less on AC.
    The two 100 Watt panels would provide about 10.5 Amps max using a PWM controller on a 12 Volt system, a charge rate of only 4.6% which is lower than most battery makers recommend. If you could get one more such panel you'd be doing that battery a favour.
    And if you got better numbers for or a more efficient refrigerator that battery could just do it in a pinch.

    Note: 12 Volt systems are less efficient that 24 Volt, and the typical 1kW+ start demand means you need to keep the DC wires between battery and inverter short and fat and in good shape to maximize the power potential. It also means that as the battery is run down the Voltage may be too low to start the 'frige (any 'frige). The current demands are 2X that of a 24 Volt system for the same Wattage, but it can be done.

    BTW with a system this small and the 'standard' panels you already have you would not be better off spending hundreds of dollar on an MPPT charge controller. Sometimes the people at NAWS don't know what they're talking about. Note that I do NOT work for them in any way, and am not out to sell you anything.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Building first system, numerous questions
    BTW with a system this small and the 'standard' panels you already have you would not be better off spending hundreds of dollar on an MPPT charge controller. Sometimes the people at NAWS don't know what they're talking about. Note that I do NOT work for them in any way, and am not out to sell you anything.

    To explain the reasoning using NAWS own prices:

    MPPT version of TriStar 45: $426.25
    PWM version of TriStar 45: $160.00
    PWM controller capable of handling the <15 Amps from two 100 Watt panels: $84 http://www.solar-electric.com/ss-20l.html
    Price difference: 426.25 - 84.00 = $342.25
    What for? You can buy a 140 Watt panel for that (http://www.solar-electric.com/kyocera-kd140gx-lfbs-140-watt-polycrystalline-solar-panel.html) and put it on the same controller. You'll get more power that way than with two 100 Watts on MPPT. Especially in Texas where the temps mean panels run hotter and so have less Voltage overhead to down-convert into current.

    MPPT does not make sense here.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Building first system, numerous questions

    Is this your battery: http://buy.northstarbattery.com/p/sms-agm-8dk-battery

    I sure hope you didn't pay $1,200 for it!
    It says nothing about it being deep cycle, btw. I suspect it's designed for big trucks (if that is the unit).
  • scotthw
    scotthw Registered Users Posts: 5
    Re: Building first system, numerous questions

    I appreciate your honesty, I was sweating the cost but didn't want to shaft myself long term for short term stinginess.

    I will rethink the design RE 12v vs 24v.

    "keep the DC wires between battery and inverter short and fat " As in, 2 gauge ?

    Aside from that do I need a breaker box ?

    What gauge wiring do I need between panels and controller ?

    Thanks
  • scotthw
    scotthw Registered Users Posts: 5
    Re: Building first system, numerous questions
    Is this your battery: http://buy.northstarbattery.com/p/sms-agm-8dk-battery

    I sure hope you didn't pay $1,200 for it!
    It says nothing about it being deep cycle, btw. I suspect it's designed for big trucks (if that is the unit).

    Yes that's it, and Nooo! I did not pay that, about half that. :)

    I had several discussions with the proprietor who did sell some solar components and he assured me it was deep cycle, and the plates are 100% solid lead. I wanted to deal locally for the batteries, hindsight I should have opted for golf cart batteries which I could have gotten locally. Anyway, its a learning curve.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Building first system, numerous questions
    scotthw wrote: »
    I appreciate your honesty, I was sweating the cost but didn't want to shaft myself long term for short term stinginess.

    I will rethink the design RE 12v vs 24v.

    "keep the DC wires between battery and inverter short and fat " As in, 2 gauge ?

    As in 4/0 if you're running 12 Volts. For example if you have a 2kW 12 Volt inverter it can run down to 10.5 Volts at which point it would pull ~200 Amps to supply that 2kW maximum. 2 AWG is good for about 125 Amps continuous (you can find different charts giving different answers for this unfortunately) or 1.2kW's worth at minimum Voltage.
    Aside from that do I need a breaker box ?

    You will have four separate but inter-acting circuits: PV to charge controller, charge controller to battery, battery to inverter, inverter to AC loads. Each of these will have an expected operating Voltage and current maximum. The wire has to be sized accordingly, and appropriate over-current protection provided.

    For examples:

    If you have two PV's in parallel on the input you don't actually need any fuse/breaker there. if you have three or more, then ideally each should have its own according to the Isc rating.

    The charge controller to the battery may be a 20 Amp maximum circuit, wired with at least 12 AWG and possibly larger wire. There should be a fuse or breaker here, and it needs to suit the wire size so that the fuse/breaker goes first should something go wrong.

    The battery to inverter is similar to this, only it will be larger wire and fuse/breaker because this is the heaviest current circuit.

    The inverter may determine what is needed on its output, as some have built-in outlets and some are 'hardwired'.
    What gauge wiring do I need between panels and controller ?

    That depends on the Voltage, current, and distance. First rule: wire sizes have to be able to handle the expected maximum continuous current. With the two panels you have that's <12 Amps which is pretty easy to accommodate. Add in a third panel and the current goes up. Now we get into the Voltage drop question. Longer distance, lower Voltage, higher current = more drop (loss of power).

    Let's say you use the two 100 Watts plus a 140 for a total of just under 18 Amps from the array. Okay, you need at least 12 AWG to handle 18 Amps. Fine. Now let's say it's 20 feet from the array to the controller. You have to deal with 18 Amps @ 12 Volts over 20 feet. Oops. 12 AWG shows up as a 9% V-drop under those conditions. That's about 1 Volt loss, which may make/break charging. Normally we like to keep the drop down around 3% if possible. That would mean at least 8 AWG wire. But it's a bit of a judgement call, as this V-drop occurs at maximum power and minimum Voltage: as the battery charges the Voltage goes up and the current goes down easing the V-drop issue. The important thing is to have enough Voltage at the battery when the Absorb stage begins so that it will manage that stage.

    I suppose that was horribly confusing. If we have a distance we can work out what size is best for this.
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Building first system, numerous questions

    Unless you have SPECIFIC 12v requirements, just go with 24v from the start. You will not regret it.
    I myself wished I had several years ago. You will just end up needing more (solar is addicting) and you will have to scrap all of your 12v stuff when you MUST go to 24v due to your future system size. Been there, done that...twice when I went from 12 to 24 and then 24 to 48 :(

    Also, sometimes, just the additional cost of 4/0 wire vs smaller wire for your battery bank and inverter cables and larger vs smaller wire from the panles to a MMPT controller vs a PWM controller can be the difference between the equipment cost of 12 vs 24 (sometimes).

    And if you can somehow return that battery, you will be happier also. Even at 1/2 price (or even 1/4 the price), it is not a good deal for RE. You will find that it is not going to perform very well since it appears to basically be a starting battery.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html