newbie with off-grid questions

truck2fftruck2ff Registered Users Posts: 5
Great site with tons of info. Wish I had found this a little sooner.:roll: I'm in the process of installing a small off-grid system at my home and I wondered if anyone here would be willing to give me a second opinion or comments on the equipment I've planned so far and any problems with what I want to do. I hope it's not too long but I'll try to give as much info as possible for you all to digest and pick apart.

My goal for the system initially was to run a small DC fridge (sundanzer 5.8 cf), some LED DC lighting, and occasional DC charging of cellphones batteries etc. The only DC load that would be constant would be the fridge. I have a son with diabetes and wanted another backup to the small propane RV fridge I jerry rigged for his insulin during a long term power outage, but I plan to use it for day to day storage also. That's how this whole thing started.

My AC loads are minimal, two circuits basically one in the garage for small AC appliances and AC chargers for battery powered tools and one to the house to run the small blower fan on my woodstove insert and maybe a lamp with a CFL.

I worked with a company called backwoods solar for most of the equipment on the recommendation of a friend who has a similar system at a hunting cabin and spoke highly of them so that's where I started.

Equipment list so far: (12 volt system)

(2) Kyocera 135w solar modules w/universal rack @ roof
Simple Combiner Box at attic
Tristar-45 charge controller w/ remote metering kit
60 A bayonet fuse and holder between charge controller and batteries
(4) 6V trojan t-105's (or could I get by with two?)
Truesine 300 Inverter
100amp fuse and holder between batteries and inverter.
Square D (QO series) panel for the two AC circuits (niether circuit would be in use at same time.)
#2 inverter cables and battery cables
Home-built Plywood battery box with passive venting to outside. (Still wondering if this works without a fan)
Sundanzer 165 DC chest refrigerator
Some DC LED rope lights and one strip light to mount over equipment mounting board.

That's about it. I live in Central IL, the batteries and equipment will be in an attached garage about 15 feet from a closet with a NG furnace and Hot Water Htr.
Temps in garage never fall below about 40 deg. F, but approach 90 in the heat of summer.

I have the panels and mounts on the roof, wire pulled to the combiner box but not terminated . Wire pulled from Combiner Box to Equipment mounting panel and all of the equipment mounted to a 3/4 " pc of plywood near my battery box location. I have a friend that's a journeyman electrician that's offered to help with the terminations and equipment, but admitts that he hasn't done much with solar, but has a couple of guys in his shop that have some experience with grid-tied systems that we might be able to tap with questions.

Any glaring problems? Suggestions ?

Comments

  • SevenSeven Solar Expert Posts: 292 ✭✭✭✭✭✭
    Re: newbie with off-grid questions

    If you are running 4x6v batteries in a 12v system that will double the Amp hour of your batteries. I don't think that your two panels will have enough for the charging of the batteries if they are constantly being pulled down by the fridge.
    What is the exact draw of that fridge?

    IIRC passive venting of your battery box would only happen if there was a lower intake and the vent was at the top and the batteries could heat the surrounding air enough to make the hotter air rise. The intake would have to be external also.

    Guys will be here shortly with much better answers than I am able to give.
  • truck2fftruck2ff Registered Users Posts: 5
    Re: newbie with off-grid questions

    Thanks- After reading some other comments here I wondered about the number of batteries. Backwoodssolar's info on the sundanzer fridge indicates 240 watt/hours on a 90 degree F day, and that would probably be my worst case.

    The 4 t-105's would be 450 amp/hrs at 12 volt correct.

    As far as the battery box goes can I bring my inverter cables and other DC/out wires into the lower part of the box? There would be area around the wires for vent air to enter the box down low. Then run a hotwater htr vent out of the top of the box through the wall of the garage to the exterior?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: newbie with off-grid questions

    Welcome to the forum.

    Avoiding the usual first question of "why are you doing this?" ... :p

    The first problem I see is that four T105's aren't going to recharge well off 270 Watts of panel. Configured for 12 Volts, that's 450 Amp hours of battery. Ideally they'd want at least 22.5 Amps of current (minimum 5% of Amp hours recommended) which would mean about 400 Watts of panel. Your two Kyocera's will produce something like 14 Amps, just barely enough for one set of the 225 Amp hour batteries. The Tristar 45 Amp controller is much larger than necessary with those panels.

    Do you need all those batteries? To answer that you're going to have to get at least a rough estimate of daily power consumption. One set @ 50% DOD would give you 100 Amp hours or so to work with. That's 1200 Watt hours a day, strictly DC speaking. Twice as much battery equals twice as many Watt hours - and then you're in the neigbourhood of the mount of power I use per day to run the whole cabin.

    Also, you're guessing at fuse sizes. Don't. Get the actual configuration worked out then determine the proper size fuses for the equipment selected. Morningstar makes a very nice 300 Watt pure sine inverter, btw: http://www.solar-electric.com/mosu300wasiw.html There are others which will fit the bill too, but several people here have used these with great success.
  • BB.BB. Super Moderators Posts: 26,837 admin
    Re: newbie with off-grid questions

    In general, I don't see any issues--all good product and should operate (in your solar conditions) well, on average in support of the refrigerator... The AC circuit breaker box is overkill for a 300/600 watt inverter--but will not hurt anything.

    You need to pick the amount of AH/WH per day you want to supply/use for sizing the battery bank.

    Your fridge is rated for ~14 AH/12 volts at 90F as a refrigerator. Lets pick 20 AH per day and 12 volt bank. A battery can be sized for 1-3 days of no-sun... Lets pick 2 days:
    • 20 AH * 2 days * 1/0.50 maximum discharge = 80 AH bank minimum
    And the batteries should be charged by a range of ~5-13% of AH capacity. Pick 10% for a good sized solar array:
    • 80 AH * 14.5 volts charging * 1/0.77 system derating * 0.10 rate of charge = 151 Watts Nominal
    For a 2x 225 AH @ 12 AH battery bank and a 270 Watt panel, the charging rate is:
    • 270 watts * 0.77 derating / (14.5 volts * 225 AH) = 0.06 = 6%
    I would not use a larger battery bank unless you add more panels... And even your system as designed could easily use upwards of 2x the number of panels you have today... Your choice. Start small and grow later (more panels and more batteries as you need). It is difficult to grow systems by more than 2x without stripping out most of the old system (typically move to higher voltage battery bank with larger systems needs new inverter).

    And, you should plan for bad weather... Backup AC battery charger that you can plug into your wall and/or backup battery bank.

    A 20 Amp charger would work well and you could use a small Honda eu1000i (~$750 off the web delivered). A small genset will be much more fuel efficient--much easier to store enough fuel for emergencies (or siphon your car).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • truck2fftruck2ff Registered Users Posts: 5
    Re: newbie with off-grid questions
    BB. wrote: »
    In general, I don't see any issues--all good product and should operate (in your solar conditions) well, on average in support of the refrigerator... The AC circuit breaker box is overkill for a 300/600 watt inverter--but will not hurt anything.

    You need to pick the amount of AH/WH per day you want to supply/use for sizing the battery bank.

    Your fridge is rated for ~14 AH/12 volts at 90F as a refrigerator. Lets pick 20 AH per day and 12 volt bank. A battery can be sized for 1-3 days of no-sun... Lets pick 2 days:
    • 20 AH * 2 days * 1/0.50 maximum discharge = 80 AH bank minimum
    And the batteries should be charged by a range of ~5-13% of AH capacity. Pick 10% for a good sized solar array:
    • 80 AH * 14.5 volts charging * 1/0.77 system derating * 0.10 rate of charge = 151 Watts Nominal
    For a 2x 225 AH @ 12 AH battery bank and a 270 Watt panel, the charging rate is:
    • 270 watts * 0.77 derating / (14.5 volts * 225 AH) = 0.06 = 6%
    I would not use a larger battery bank unless you add more panels... And even your system as designed could easily use upwards of 2x the number of panels you have today... Your choice. Start small and grow later (more panels and more batteries as you need). It is difficult to grow systems by more than 2x without stripping out most of the old system (typically move to higher voltage battery bank with larger systems needs new inverter).

    And, you should plan for bad weather... Backup AC battery charger that you can plug into your wall and/or backup battery bank.

    A 20 Amp charger would work well and you could use a small Honda eu1000i (~$750 off the web delivered). A small genset will be much more fuel efficient--much easier to store enough fuel for emergencies (or siphon your car).

    -Bill

    Bill- Thanks for the input. Looks like I can save some money on batteries.;) My buddy had the panel and breakers so we decided to use it for the AC stuff and I figured If I every moved up to a larger mod-sine wave inverrter and a bigger system it would still work.

    I have a small gas generator. Any suggestions on a resonable AC charger that would work well with AC house current or off of the generator?
  • truck2fftruck2ff Registered Users Posts: 5
    Re: newbie with off-grid questions
    Welcome to the forum.

    Avoiding the usual first question of "why are you doing this?" ... :p

    The first problem I see is that four T105's aren't going to recharge well off 270 Watts of panel. Configured for 12 Volts, that's 450 Amp hours of battery. Ideally they'd want at least 22.5 Amps of current (minimum 5% of Amp hours recommended) which would mean about 400 Watts of panel. Your two Kyocera's will produce something like 14 Amps, just barely enough for one set of the 225 Amp hour batteries. The Tristar 45 Amp controller is much larger than necessary with those panels.

    Do you need all those batteries? To answer that you're going to have to get at least a rough estimate of daily power consumption. One set @ 50% DOD would give you 100 Amp hours or so to work with. That's 1200 Watt hours a day, strictly DC speaking. Twice as much battery equals twice as many Watt hours - and then you're in the neigbourhood of the mount of power I use per day to run the whole cabin.

    Also, you're guessing at fuse sizes. Don't. Get the actual configuration worked out then determine the proper size fuses for the equipment selected. Morningstar makes a very nice 300 Watt pure sine inverter, btw: http://www.solar-electric.com/mosu300wasiw.html There are others which will fit the bill too, but several people here have used these with great success.

    CC- I know, I know....My buddy that was on the roof in the wind storm helpoing me mount the rack and modules asked the same question.;)

    Why would they (backwoods solar) suggest the fuse sizes at the charge controller and inverter if they knew what I was buying?

    Will the Tri-Star still work ok even though it's oversized for the bank of 2 batteries it sounds like I'll be using? The fridge has an inline 15A fuse wired into the cord. I'd planned to wire a DC duplex near the fridge for it and maybe some other small DC appliance later, but I have no other real plans for that receptacle right now.

    I purchased the Morningstar and it seemed like it got pretty good reviews. I wanted to be able to charge some battery powered tools, but there are problems with Modified-sine wave inverters and some battery powered equipment, correct?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: newbie with off-grid questions

    I was speaking "generically", as your first post didn't indicate the Morningstar. It does recommend a 100 Amp fuse, due to its high 600 Watt surge rating. It also has switchable Low Voltage Disconnect. You might prefer the 11.5 Volt setting over the 10.5.

    The 45 Amp Tristar will still work, it's just overkill for a set of panels that will put out <20 Amps. It will allow for future expansion, of course, if that is your goal.
  • BB.BB. Super Moderators Posts: 26,837 admin
    Re: newbie with off-grid questions

    Just remember the fusing is there to protect the wire (not the devices). If you have a 100 amp fuse, you need wiring that can carry 100 amps.

    The PWM TS 45 is a good controller and will work fine for you.

    You can look at the whole MPPT controller world--But that is only useful (cost effective) for larger arrays and/or if you have a long wire run from the solar array to the controller/battery bank.

    All About Charge Controllers
    Read this page about power tracking controllers

    Look at getting a remote battery temperature and the TS family has a nice Remote Battery Voltage Sensor connection too (nice if you have a bit long controller to battery bank cable run).

    Regarding inverters... If you can justify TSW (at least for your smaller loads)--I would do it for off-grid reliable power.

    All About Inverters
    Choosing an inverter for water pumping

    Roughly 80% of the stuff will work fine on MSW (may be less efficient). And 10% will not (overheat, pop internal components, etc.).

    Your job is to figure out which device$ are in which camp.

    Small wall wart transformers, many types of electronic power supplies, some motors (typically heavily loaded motors), timers, and some refrigerators do not like MSW. It is difficult to tell.

    What DC Power Supply... Short answer:

    Iota DLS-15: 12 Volt 15 Amp Battery Charger + Honda eu1000i
    Iota DLS-45 12 volt 45 amp regulated battery charger + Honda eu2000i (I think is OK)

    The IQ4--perhaps if you leave plugged in to AC Mains all the time... Otherwise, just use the jumper on the supply and set to "high voltage" when running from genset and save the money (jumper out = float voltage for long term standby).

    Long Answer ;):

    Question about battery charger selection with EU2000 generator

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • truck2fftruck2ff Registered Users Posts: 5
    Re: newbie with off-grid questions

    Wow, thanks guys! I'll try to catch up here. Posted this morning while finishing up some paperwork here at work and just got back from a fire call that kept us out of the enginehouse for a several hours.

    Lets see...Bill first : Understood on the wire size. 2/0 on the inverter cables and battery. #6 from the combiner box to the charge controller then #6 from controller to batteries. #10 from the batteries to the DC fridge.

    The charge controller and metering kit came with the remote battery temp sensor I'll research it a little more with the other paperwork for the controller.

    I'll probably stick with the TSW inverter for now.

    I'll look into the charger you indicated.

    CC- Thanks and I guess it would be nice to be able to expand the system at a later date even if the controller is overkill for what I have right now.

    Thanks alot guys. I'll take a better look at the threads you linked and hopefully be able to be a little more specific with the questions I have in the future.

    Truck
  • PhotowhitPhotowhit Solar Expert Posts: 4,254 ✭✭✭✭
    Re: newbie with off-grid questions

    If your sticking with 2 panels you don't need a combiner box, just get MC4 2 to 1 connector.

    http://www.solar-electric.com/mumc4colam.html
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
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