Building my first Solar System... HELP!

Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
Sorry for the length.

My Vision...
I'm a HAM Radio operator. I'd like to have a Self Contained trailer that I can use to base Emergency Communications out of. Just one of my radios will draw 20 amps when it's transmitting. Each Transmission averages about 1-2 minutes. I have 2 of these radios, along with a couple more that can draw up to 10 amps each. 

Whats been done, so far...
I've installed 3 of 4 109ah 12v Deep Cycle batteries. Changed over to all LEDs inside. I've reworked much of the Trailer's wiring.

The Draw...
Other than the radio equipment, already mentioned, I have a CPAP Machine that draws 3a/h @ 12v. So... 3a/h x 8 hours of sleep = 24ah/night. I figure the H2O Pump (10a/h) & the fridge are negligible. 

My Design thoughts... 
An MPPT Controller
2 (possibly 3) panels.

I've been trying to wrap my skull around all of this but 'tis better to just ask the collective.

Thoughts? Opinions as to what I've done so far and what my next move may be.

TIA,
Scott

Edit: Add Time Sentence for radios.

Comments

  • HorseflyHorsefly Registered Users Posts: 251 ✭✭✭
    edited September 23 #2
    Wow. You didn't say, but I assume your radios are operating on 120VAC. 20A at 120V is 2400W. If you are talking about a 12V system (and assuming an 85% efficiency of your inverter), you will be pulling 2400 / 0.85 / 12 = 235 Amps, and doing that for 1-2 minutes each time. That is a ton of pull.  If your eventual battery bank is 4 of the 109AH batteries in parallel, that's over C/2 of current.  The other guys here are experts, but from my limited knowledge that sounds like too much to ask.

    EDIT: Meant batteries in parallel.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    An h2o pump @10a and fridge are also unlikely to be "negligible". It would help if you could clarify the voltage at which the loads are drawing. Is this entirely 12v, or is there an AC inverter involved?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    edited September 23 #4
    Everything is 12v. Sorry, Gents.

    My Big Radio (12v) has yet to be used in this Rig but I want it to have the capabilities for 2 of them, just in case. It comes with a 20a fuse built into the power cable. 

    The Fridge requires a 12v. "Kicker" to keep the relay/switch for the Propane that actually operates it. As for the Pump, i don't consider it a big draw as it is ran very little.

    My power inverter is only 600w cont. so I'm not planning on doing much in the way of 110v AC. 

    Does his help a Bit?
  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    It helps a lot.

    Drawing 40ish amps from a 3-400ah bank for short periods (1-2 mins) should be fine. The missing piece there is how often (total mins) you'll be doing it.

    Assuming a couple of ~100w 12v nominal panels, you might get something on the order of 6-700 watt hours of power, most of the year, in most locations, with reasonable tilt to sun and no shade, on sunny days. The cpap is 24ah@12v=288wh/day, assuming battery efficiency of 80%, that's 360wh/day. Add the fridge relay, h2o pump, and some lights, there won't be much left for radio time with available pv power.

    Do you have, or can you get, a small generator (eg honda/yamaha inverter type)? Ideally, you would want about 40a charging capacity from the pv, which would be ~800w, which may be difficult in a mobile application. The idea is to bulk charge the batteries for an hour or two in the morning, and let the pv finish charging.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mike95490mike95490 Solar Expert Posts: 7,249 ✭✭✭✭
    >  the fridge are negligible
     Beware the fridge. Usually, the 12V on a 3way fridge, is for an electric heater to replace the propane flame while the vehicle engine is running. Add up the usually thin insulation and you can easily get to more than 500wh daily
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    I assumed it was not a 3way, and the 12v was only for thermostat relay. I agree that a 3way running on 12v can be a surprisingly large load.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,768 admin
    120 VAC Refrigerators also have relatively high starting/surge current. So a 120 Watt (average running wattage) fridge will take >600 Watts to start. To "reliably" run a generic refrigerator needs around a 1,200 to 1,500 Watt AC inverter.

    You need to get a handle on all of your power consumption. A 100 Watt transmitter (taking 200 Watts or ~17 amps @ 12 volts--And the whole issue of radios being spec'ed for 13.8 volts nominal for full rated output and an off grid storage battery system seeing around 11.5 to 15.0 volts, discharging to charging) probably only takes 10 watts (~1 amp @ 12 volts) on receive (wild guess). 5% duty cycle for transmitting--The average overall energy usage (AH/WH per day) is not bad. However, you talked about some other 10 amp loads--If those are 8-24 hour per day, they are not insignificant.

    And will you be using buck/boost for 10.5-15+ volt input to 13.8 volt DC to DC converters for the radios (a bit more losses, and higher average power usage at higher radio bus voltage)?

    Two ways to go here--Design a system for your loads... Or use some part of your system as the limiting factor (i.e., xxx watts of solar panels or yyy AH of battery bank) and then design the balance of system--And see what your available (paper) output power would be.

    end of part 1

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators Posts: 26,768 admin
    Part 2:

    For example, 4x 109 AH @ 12 volts batteries (I would prefer to see you use 6 volt batteries, such as 6 volt @ ~220 AH golf cart deep cycle batteries--I do not "like" too many parallel strings of batteries). Anyway, my quick back of the envelop calculations--Assuming 2 days of "no sun" and 50% maximum discharge (long term deployment suggestions. For weekend/more generator usage, perhaps 1 day storage and 50% maximum discharge would work for you):

    Daily energy usage from batter bank (if 1 day of storage, then 2x AH/WH per day of below):
    • 436 AH * 1/2 days storage * 0.50 max discharge = 109 AH @ 12 volts per day
    • 436 AH * 12 volts * 1/2 days storage * 0.50 max discharge * 0.85 AC inverter eff = 1,112 WH per day
    Then the minimum recommended charging/solar array. 5% can work OK for weekend/summer seasonal usage. 10%+ recommended for full time off grid usage (especially if you have loads during the day when you are charging):
    • 436 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 411 Watt array minimum
    • 436 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 821 Watt array nominal
    • 436 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,888 Watt array "cost effective" maximum
    And there is sizing the system based on where you are located... If you are adding an AC refrigerator, I would be suggesting a 3.3 kWH per day system... But for a small mobile system (limited space/weight carrying capacity)--That is not usually practical. A propane fridge would be highly recommended for a portable unit that will be out in the field for 1-2 weeks at a time (a 20 lb bottle will, typically as I recall, supply around 20-40 days of fuel for RV fridge--Propane stores very well).

    Say you are in Boise Idaho. and you build a rack where you can tilt the array based on season (near flat for summer, towards vertical in winter facing south--don't know when disasters are going to happen):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Boise
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 62° angle from vertical:
    (Optimal summer settings)
    Jan Feb Mar Apr May Jun
    2.83
     
    3.82
     
    5.10
     
    5.88
     
    6.38
     
    6.89
     
    Jul Aug Sep Oct Nov Dec
    7.16
     
    6.83
     
    6.04
     
    4.88
     
    3.11
     
    2.57
     

    Boise
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 32° angle from Vertical:
    (Optimal winter settings)
    Jan Feb Mar Apr May Jun
    3.41
     
    4.25
     
    5.16
     
    5.26
     
    5.17
     
    5.31
     
    Jul Aug Sep Oct Nov Dec
    5.61
     
    5.85
     
    5.89
     
    5.38
     
    3.67
     
    3.17
     
    Lets say you go with the battery bank supplying 1,112 WH per day of energy, and you want to "break even" in winter with 3.17 Hours of sun per day. The minimum array would be:
    • 1,112 WH per day * 1/0.52 off grid AC system eff * 1/3.17 hours of sun (December with tilted array facing south) = 647 Watt array minimum
    And if you used the 10% array, you would harvest in December:
    • 821 Watt array * 0.52 off grid AC system eff * 3.17 hours of sun per day (December) = 1,353 WH per day
    • 821 Watt array * 0.61 DC off grid system eff * 1/13.8 volts nominal * 3.17 hours of sun (Dec) = 115 AH per day @ 12 volts
    The above calculations are a bit on the conservative side (don't know your loads exactly, where/how you will be using the energy, etc.)... But give you an idea of what the basic parameters are. Conservation and a good backup genset (Honda eu1000i or eu2000i + fuel) will help a lot.

    Questions? Answers? Corrections?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    edited September 25 #10
    Ok... most of the stuff mentioned went over this boy's head. Momma did not raise a Math Wizard here. I'll try to expound on what I understand.

    Radios... There is only 1 radio (10amp Max draw) that lives in the trailer. I mostly run him on Medium Power (5amp draw). The other radio(S) would be only under "Extreme" circumstances that may never happen. However, I'd like the capability IF that ever came about. Useage... a vast majority of my radio useage is listening. My small radio "idles" at .5 amp. If the big one is installed, it would be an amp. If I'm deployed, will there be times of heavy Big Radio usage. At that time, I could see the Duty Cycle being as high as .33%-ish transmitting time. 

    Genset... Yes. A generator and battery charger has always been on my radar for the Bulk Power Replacement. The Solar Power System is a back up/ Top Off system to keep the batteries ready.

    The AC/DC/Propane fridge will only be ran on either AC (Shore Power) or Propane. It draws 16amps on D.C. and that is unacceptable at this time. Plus, it running while in tow is also not an option.

    As you can see, a vast majority of the time, it will be just the basics... LED Lighting, the Fridge Relay, some water pump (no shower), my CPAP Machine and the little radio (.5a, idling). I'm looking to make the next step of my goal into a reality. As I can envision this, the next step is to be able to replenish my power while I'm out.

    Thoughts, Opinions, Questions?

    P.S. It's funny that you picked Boise in your example. I'm not far from there.
  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    As a moderator, BB can access info that can sometimes be used to make a reasonable guess on location.

    With a generator (the small inverter types like honda and yamaha are nice), your plan should work fine. The generator gives you to ability to charge if you have heavier load days and/or gloomy weather.

    Like Bill, my preference would be to use 6v golf cart batteries wired as 2 serial strings (4 batteries total) rather than 4x12v in parallel.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,768 admin
    OK... Not much current draw. And, by the way, I like to type 0.5 amps instead of .5 amps -- It is easy to miss the decimal point.

    There are different ways to figure out the "optimum" system for you... If we know your loads, we would start from there. However, your limitations may be battery bank or roof area for the solar panels. And, you may choose to mount them flat to the roof, or pitch them for your location/summer/winter usage.

    For charging, you can run 5% (good minimum for weekend/emergency usage+genset backup) or 10-15% rate of charge on your battery bank (full time off grid/minimal genset+fuel usage).

    Running the fridge from propane is usually the best deal for smaller systems. Wire up a DC line from the tow vehicle to run the 15 amps while moving (may not even be worth it if you are only going a few hundred miles or less). Run the battery bank for 2 hours is only 30 AH out of your (I guess) 436 AH battery bank--Then setup for propane on site (or AC utility if available).

    436 AH @ 12 volts to run a 0.5 amp radio, 1 amps of lighting, and a (for example) 3 amp CPAP machine would look like:
    • 0.5 amp radio * 24 hours = 12 AH
    • 1 amp lighting * 12 hours = 12 AH
    • 3 amp (@12v) CPAP * 8 hours = 24 AH
    • 5 amp radio * 0.33 duty cycle * 24 hours = 39.6 AH
    ===============================================
    87.6 AH per day
    87.6 AH * 13.8 volts nominal = 1,209 Watt*Hours per day

    And 1/4 of your bank AH capacity is ~109 AH... So, you could run the above a bit more than 2 days straight just from the battery bank.

    If you want to run 110% from solar with a tilted (worst case December), you would break even with:
    • 1,208 Watt DC loads * 1/0.61 DC solar system eff * 1/3.17 hours of sun (December) = 625 Watt array (break even December)
    And if you only wanted panels mounted flat to the trailer (Boise ID):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Boise
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a horizontal surface:
    Jan Feb Mar Apr May Jun
    1.72
     
    2.66
     
    4.07
     
    5.38
     
    6.36
     
    7.24
     
    Jul Aug Sep Oct Nov Dec
    7.37
     
    6.44
     
    4.99
     
    3.43
     
    1.97
     
    1.49
     
    You can see that mounting the panels flat will really kill your December output:
    • 1,208 Watt DC loads * 1/0.61 DC solar system eff * 1/1.49 hours of sun = 1,329 Watt array Flat December Array
    So... That gives you an idea of the upper end of what you could want from solar with my estimated loads... However, you could also design for floating the system (parked, no AC power)--For that, I would suggest a 2% rate of charge (minimum). Such an array would look like:
    • 436 AH battery bank * 14.5 volts charging * 1/0.77 panel+controller derating * 0.02 rate of charge = 164 Watt array minimum float charging
    And, for example, if you are deploying spring/summer for tornado and/or fire seasons--That give you more sun, and more solar power. If you are deploying for winter/spring rains/snows/floods--Different seasons, different sun.

    I am sorry to keep throwing math at your questions--But it is a good place to start. Can you tell me more about your loads/deployment/what you are looking for (i.e., hardly any genset use, or short term deployment+10 gallons of gas will keep the batteries charged with an eu200i for 5-10 days is "good enough"). How much room on trailer roof? Will you tilt panels? Are you looking to minimize cash outlay? Will you have AC power for float charging the battery bank? etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    edited September 26 #13
    Our last deployment was for the Solar Eclipse. We had a starting battery voltage level of 12.7. We were released 3 days later with an ending voltage of 12.2v. Looking over BB's "Guesstimate" of equipment (lights, radio, etc...) was pretty darn close. As a test, I did not hook to shore power to see what the system would do. Now, mind you, I only have 3 of the proposed 4 - 109Ah 12v. Deep Cycle Batts. currently in the system.

    Deployment... An actual "On Site" deployment, I would think is... about 7 days. At that time, I'd need to dump my tanks, get fresh water, food, propane, etc... I will not hesitate to use the Genset or, if available, Shore Power to stay operational. The Solar Power Panels are there to do their thing while I am shut down. As for mounting, currently I have not really considered tilting them so I'm looking at a flat mount. Not saying it is not out of the question due to this still being in the planning stages. Yes, money IS a factor. Lol...

    The useable area on on the roof of the trailer is about... 7.5' wide and about 10' long. Give or take. 

    I will I'll try to get an actual amperage draw on the current systems (i.e... Lights, H2O pump, Little Radio, etc...) here in the next few days. Tomorrow (Tues.) & Wednesday are super busy.

    Thank you for the Help. I appreciate your putting up me.
  • BB.BB. Super Moderators Posts: 26,768 admin
    You are very welcome Scott.

    Mounting the solar panels is a "big thing". They need to withstand the winds when driving, and tilt (if you want them to).

    In winter (November through February), you are loosing a fair amount of "hours of sun" with the panels flat on the roof. If you do not plan on traveling in the winter (or do the snow-bird thing and head south)--Flat panels are not as big of draw back (play with the solar electricity hand book, and see where and how tilts affect your hours of sun). More or less, 4 hours of sun is pretty good, and less than 3 hours of sun is not great for solar.

    http://www.solarelectricityhandbook.com/solar-irradiance.html

    For the number of panels, just sq ft wise (using random, less expensive, solar panels):
    SolarWorld SW-285 Mono All Black

    Pmax: 285 Watts
    Voc: 39.2 Volts
    Vmp: 32.0 Volts
    Isc: 9.52 Amps
    Imp: 9.0 Amps
    Silicon type: Monocrystalline
    Efficiency: 17%

    Amphenol UTX locking connectors
    Weight: 39.7 Pounds
    Dimensions: 65.95" x 39.4" x 1.30"

    And your trailer is:

    7.5 feet = 90 inches

    10 feet = 120 inches

    At best you can fit ~3-4 of these "full size" panels. That is ~855 to 1,140 Watts of solar panels.

    Just to give you a feel--To supply ~1,208 Watt*Hours per day

    • 1,208 Watt DC loads * 1/0.61 DC solar system eff * 1/1.49 hours of sun = 1,329 Watt array Flat December Array
    • 1,208 Watt DC loads * 1/0.61 DC solar system eff * 1/3.17 hours of sun = 625 Watt array 32 degrees from vertical (or 58 degrees from horizontal) December Array

    Only you can make the decision on what will work best for you (I can only give you the "numbers"). If you will be using the system a lot in winter, a tilted array gives you about 2x the daily power vs flat to the top of trailer. Of course, you can install more solar panels, or even use more genset fuel (a Honda eu2000i generates about 3,300 Watt*Hours per gallon of gasoline--loaded with 400 watts or more of loads). Or, 1 gallon of fuel (charging your batteries, no sun) supplies about 2-3 days of usage. Solar panels (and tilting framework)--They cost significantly more than a few gallons of gasoline (if you are not in the field that many days in the winter in the far north).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    edited September 26 #15
    Around the Southern Idaho area, we do not have much in the way of "Natural Disasters".

    Spring Flooding is our major concern. We had about 20" of snow (at 1 time) last winter, however that was extremely abnormal. Once the flooding started, some areas were inaccessible till the middle of summer.

    My normal deployment is providing communications for local events... Jet Boat Races (Salmon River) in April, Road Rallies in the mountains, assisting with local Bike Races, etc... I think of these as kinda like Practice Runs to help us keep our skills sharp.

    My main goal is preparedness in case something were to happen. Look at California... IF there were to be another large quake, I'm only a state away. I could come down and help provide "Emergency Communications". The power, cell phones, etc... all will be out. The only communications happening are gonna be by radio.  The Amateur Radio community already has the capabilities to pass "Traffic" (think messages) to each other and help get or direct emergency services to those who need it, pass word to friends/families in other states concerning personal welfare, etc...

    The possibilities are endless. This is why I'm putting this trailer together. 


    Ok... another question. Why the 6v Golf Cart Batteries (in series) VS the regular 12v. Deep Cycle?
  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    6v golf cart batteries have more amp-hours per battery than 12v typically do. 2x6v in series will provide ~220ah@12v. 2 such strings in parallel about 440ah@12v. They are also typically "true" deep cycle, designed for slow but relatively deep discharge (fewer, thicker plates)

    A 12v battery may be a deep cycle, but are often a sort of hybrid "marine deep cycle" (more thinner plates) that's a comprimise between high output and deep discharge. If the battery has a CCA rating, it probably isn't a "true" deep cycle design.

    A reasonable sized 12v might be ~100ah, so you'd need 4 in parallel to get roughly the same capacity. More than 2 parallel connections gets trickier in terms of keeping batteries balanced in charge/discharging.

    A single string of larger 6v batteries might arguably be better than golf carts, but an L16 size 6v (~370ah) is about 150lbs and harder to find. Golf carts are reasonably easy to handle, and widely available.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,768 admin
    Yes, a few of us here are HAMs too.

    I am more trying to get your desires regarding the system design. Batteries are quiet and, relatively fuel/energy efficient with variable loads (low average current, high&short peak current).

    Downside is batteries age (golf cart batteries last around 3-5 years, whether used or not). Plus you have maintenance (4x12 volt batteries = 24 cells to check; 4x7 volt batteries = 12 cells to check, and golf cart batteries tend to be cheaper).

    Gensets, pretty much only age/require fuel when running. But can suck fuel just to supply a small amount of energy (less than 400 watt load 2-3 gallons per day and 1 oil change for an eu2000i Honda). $1,000 for generator, 2,000-6,000 hours of life of taken care of [200 hours a year, 10-30 year life].

    Solar panels last 20+ years easily (good glass faced panels that don't get rocks or heavy hail). But they only produce power when the sun shines. Cloudy weather, shade (trees, buildings, even power line shadows kill output) and winter in the far north... That is why we have gensets and a good a.c. battery charger:

    http://www.xantrex.com/power-products/battery-chargers/truecharge-2-2.aspx

    With solar and energy demands of anywhere&anytime, you already have the gensets and, maybe a small battery bank. Adding solar can help, but it is not the only Answer.

    Some RVers have eu2000i's converted to propane (runs cleaner, and gets rid puff fuel storage issues.

    Many times, it is difficult to justify a large solar power system that only runs a few weeks per year. Unless it makes sense to you.

    Anyway, my 2 cents worth of thoughts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    Bill, thanks. Yes, ultimately this trailer will only see about a month use out of the whole year, unless something out of the ordinary happens. 

    I truly appreciate the questions. Not only do they give you the information in order to suggest possibilities but they also give me food for thought. 

    When looking at Panel Specs, what are the more important ones to look at and what do they mean? Ie... PMax, Voc, Isc...
  • BB.BB. Super Moderators Posts: 26,768 admin
    edited September 28 #19
    More or less, don't worry about the exact hardware just yet.

    Panels cost around $1 to $2 per watt. Smaller panels cost more (less than 175 watt) and larger panels cost less (more than 200 watt).

    However the small panels use less expensive PWM charge controllers. And larger panels generally need more expensive MPPT type controllers. (Small systems tend towards PWM controllers and larger systems towards MPPT controllers and larger panels). Many times for mid size systems, the costs pretty close in the end.

    Get an idea of what you need, then we will walk through a couple paper designs before buying the hardware.

    A small solar+battery system (300 watt loads or less) , plus a few lights. And the gensets for times when more power is needed (1,500 watts+). The two work well together.

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    Ok... by what I understand, I need to know my Watt Hours/Day. So.. I am basing my calculations on a "Worst Case Scenario" while still being realistic in my power consumption and getting 8 hours of down time (eating, sleep, etc...) 

    436AH @ 12v. ...
    • 5 amp radio (mid power) * 12 hours = 60 AH
    • 1 amp lighting * 12 hours = 12 AH
    • 3 amp (@12v) CPAP * 8 hours = 24 AH
    • 20 amp radio (Full power) * 0.33 duty cycle * 12 hours = 79.2 AH
    ===============================================
    175.2 AH per day
    175.2 AH * 13.8 volts nominal = 2,417.76 Watt*Hours per  

    Being new to this, 2,418 WH/D seems like a LOT! I honestly do not think this will ever happen, however... it IS a "Worst Case Scenario". 

    Now, that being said, I can see a "Normal" camping style (No Shore Power, Water or Sewer hookups) deployment looking like this...

    436AH @ 12v. ...
    • 5 amp radio (mid power) * 8 hours = 40 AH
    • 1 amp lighting * 12 hours = 12 AH
    • 3 amp (@12v) CPAP * 8 hours = 24 AH
    ===============================================
    76 AH per day
    76 AH * 13.8 volts nominal = 1,049 Watt*Hours per day

    What else am I missing?


  • BB.BB. Super Moderators Posts: 26,768 admin
    I would suggest checking your radio current draw on receive. A modern radio may be closer to 0.5 amps vs 5.0 amps on receive (a huge power savings).

    And antennas (good whip+ground plane vs directional antenna, good coax cable, low loss, good matching, etc) can dramatically increase your your defective radiated power, and reduce your transmitter power/energy usage (VHF vs shortwave frequencies, etc. all matter).

    6db = 2x power (or 1/2 power) usage or 1 S-meter unit. Antennas+cables+matching can easily save you a bunch of battery power.

    You van design system for low power operation (battery + solar), and use the eu1000i type genset with 1.5 gallons per hour (12 hour day with 400 watt average load). Or 10 gallons per week (emergency). 2x 5 gallon gas cans.

    How many 6 volt@200 AH batteries (for example) can you fit/want to buy? That is a good start.

    2x golf cart batteries gives you 200 AH @ 12 volts. 50% discharge is 100 AH usable between charges (down to 20% can work fine if you recharge right away with genset (160 AH usable). Cheap batteries, replace for $100 each after emergency (if you kill bank). Cheap and reliable power.

    2 to 4 golf cart batteries should be good for your needs. Plus genset and a.c. battery charger.

    You have the radios? Measure the operating current. Especially during standby.

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    edited September 28 #22
    Bill, the radio pulls 5 amps on medium power while transmitting according to the manual.

     I'm basing that specific listing/figure off of our last deployment for a Road Rally up in the mountains.  I was having trouble hitting the repeater with my HT from my assigned position. I remedied this by just hitting my trailer (half mile away) and allowed the Kenwood TM-V71a (Dual Band Mobile) to do its thing in Cross Band. I ran the HT side on 440 low power and the Repeater side on 2 meters med. power. Worked like a charm. As mentioned, I can see this being more the normal type of deployment.

     To give you a bit more info on the installation... I have two antenna capabilities on the trailer for the V71a. The first is a Diamond NMO mounted on the trailer. If I need more, I can flip an antenna switch and send the signal to a 25' Telescoping Mast with a 4' Dual Band Vertical on top and pop it up on High power. IF my HF radio was ever needed, I can hang a G5RV off of the mast with a tuner in line.

    Beings that I just bought the 3 12v. Deep Cycle Batts, back in June, I'm in no hurry to switch over to the 6v. just yet. That may be for next year or a couple of years down the road. But for fun, I have enough space for 4 of them. 

    Scott

  • BB.BB. Super Moderators Posts: 26,768 admin
    300 ah @ 12 volts it is. Still a good size bank. A 10% rate of charge would be:
    • 300 ah * 14.5 volt charging * 1/0.77 panel+controller derating  * 0.10 rate of charge = 565 watt nominated array
    Are you happy with that? Will its be flat or tilted to sun (in winter)?

    What questions do you have?

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    I'm still planning on adding 1 more 12v. 109Ah batt for a total of 4. And for now, the panels would be mounted flat. Beings I haven't started to assemble this system, apart from the batts, anything can still be done.
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    At this point, I think we've worked out my requirements. It's time to put pencil to paper and start looking at equipment, 
    or have I missed something?

    To be fair, I'll probably have to purchase this 1 piece at a time. The Tooth Fairy is fair but not overly generous. Lol...
  • BB.BB. Super Moderators Posts: 26,768 admin
    I think you have the basics (panels, batteries, loads) documented--And the limitations (solar array size, battery bank size/weight).

    Just remember to keep the battery bank floating (ac power+float charger). If the batteries are allowed to sit for days/weeks under charged, or months of no-charging, they will sulfate and die.

    Plan for the ultimate configuration. Do not buy something "on sale" that does not fit into your long term plans (unless you have made the decision for short term vs long term). Many times, it is very difficult to mix and match differing equipment into one unified system without wasting money on those issues (i.e., small charge controller now, add panels, then need new charge controller. Or too large of AC inverter for what is starting out as a small system, etc.)..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tabbycattabbycat Solar Expert Posts: 40 ✭✭
    Given the 109 AH battery rating I am guessing these are WalMart batteries. They give ratings in Peukert capacity which is that a draw of one amp will last 109 hours. It is not a 20 hour rating.
  • Scott_WaldyScott_Waldy Registered Users Posts: 11 ✭✭
    You are correct. It is a Walmart battery. I'm guessing I have A LOT MORE to learn as I too think of the draw as I have 109 hours worth. 
  • tabbycattabbycat Solar Expert Posts: 40 ✭✭
    The Peukert equation will let you know how long your batteries will last at any amp draw. Time (hours) = Peukert capacity (109)/ (I (amps) ^ n). A guesstimate for n is 1.3 for flooded; 1.15 hybrid; and 1.1 AGM.

    I have these batteries. Using 1.15 I came up with an amp draw of 4.4 amps will last 20 hours. You really only want to run for 10 hours to avoid an early death for your batteries. Thanks.
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