Typical set-up for a 48V cabin

Texas Wellman
Texas Wellman Solar Expert Posts: 153 ✭✭
I'm looking at installing a 48V system for an off-grid cabin about 600 sf. Not looking to live there full time. I want to be able to run a fridge and some simple things like a tv.

I can do all the wiring and electrical. Grid power is not available at this location. My budget is about $15-20K.

What I'm looking for is some typical set-ups etc.

Thanks.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Typical set-up for a 48V cabin

    Well typically you start by figuring out how much power you need to supply. The size of the cabin has nothing to do with this, but your desire for a refrigerator and TV sure does.

    If you can measure what you want to use first, or something comparable to it, you'll be much happier with the results. My refrigerator, for example, uses about 1200 Watt hours per day. Some use more, some use less, and much depends on the climate and how often you open the door.

    A TV is another matter because the usage will be inconsistent. You may not use it at all one day, and then when it rains sit around and watch all day (a worst-case scenario). So the question arises; what do you do when you run out of power? The answer is: generator. That will save a fortune on the system, especially for an occasional use cabin.

    I probably would not go 48 Volts because you probably do not need that much Watts or stored Watt hours. Again we're talking occasional use so keeping the investment down is a priority, no?

    Look at what you can do on a single set of batteries for 24 Volts:
    220 Amp hours, 50% DOD (again; occasional use compromise) = about 2.4 kW hours AC. That's 2X the 'frige alone rating, and does not include power available direct from panels during daylight which can improve efficiency. You can even nudge this up a bit with some East Penn PS2200's at 232 Amp hours. Roughly $1,000 (check local prices).

    You won't need a big inverter either. You could go non-charger type and 2kW for about $1,000 with a stand-alone Iota charger. Or you could go whole-hog Outback for double the money.

    PV you're looking at roughly 700 - 800 Watts minimum on an MPPT charger. These days that's about $1,000 too.

    So really for <$5,000 you can have a pretty good occasional use system. If you want more power you can just up-size everything. For your budget you could get a seriously powerful system. But is it necessary?
  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    Re: Typical set-up for a 48V cabin

    There will be a generator incorporated into the design (small one). I'm not opposed to going 24V but I thought there was a better market for 48V off-grid appliances. Or would it be better to invert the power back to 110?

    I do not want to run everything all of the time. I want to be able to have a refrigerator stay cold all the time and then do things like watch tv (when there is enough power) or turn on a few lights. Not looking to have "like grid power" availability.

    Educate me.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Typical set-up for a 48V cabin

    The only reason I can think of that would push you to 48V is having to run a deep well pump or A/C for many hours, otherwise you should be fine with 24 V based on those minimal loads. The major cost will be the batt bank, 2 X a 24V ... which will far outweigh the cost of a bit more copper to go 24V.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Typical set-up for a 48V cabin

    Well you'll save a bundle avoiding DC appliances and lights. The off-the-shelf AC stuff is pretty efficient these days and makes the wiring much simpler. You can run 120 VAC further on smaller wire with less loss than any lower Voltage for the same amount of power. The conversion efficiency and tare loss of the inverter is negligible.

    I run the whole cabin off a 24 Volt system with 700 Watts of panel, 232 Amp hours of battery, and a Honda EU2000i for when the sun doesn't co-operate. This includes a standard 16 cu. ft. refrigerator, the computer/internet/phone set-up (via satellite), any lights needed at night, water and septic pump, and occasional microwave zap. Load management goes a long ways towards making things efficient.

    For example if you use the 'standard' end-to-end formula on my system you get:
    700 Watts * 5 hours equivalent good sun * 0.52 over-all efficiency = 1820 Watt hours AC.
    But in reality I use around 2400 Watt hours AC. One advantage comes from the 3200' elevation which allows my array & controller to operate at 82% instead of the typical 77%. The rest comes from timing loads to make best use of power the panels are capable of but will otherwise not produce once the batteries are full.

    In your case get out the Kill-A-Watt meter and measure your TV viewing and refrigerator consumption. It doesn't matter if these aren't what you'll use at the cabin; you just need an approximation.

    When you go up to 48 Volts there are extra costs involved: more batteries to get a 48 Volt system (eight 6 Volt units instead of four) which is necessary whether or not you need the stored power (10.5 kW hours vs. 5.2 kW hours using GC2's). More expensive circuit breakers to interrupt the Voltage (all over-current protection and disconnects have to be able to handle >60 Volts). Inverters for 48 Volt systems tend to start out at large and expensive: Magnum 4.4 kW @ $2,200, Outback 3.0 kW @ $2,000, Conext 4.5 kW @ $2,400. You don't need that big of an inverter to run what amounts to a single outlet (1800 Watts).

    So the only caution is: what about expansion? Is there the possibility you may want more power in the future?

    And then look at the 'single charge controller' limit based on 80 Amps output @ system Voltage:
    800 Amp hours @ 24 Volts is 9.6 kW hours. Although this is quite a large battery bank, it is possible. That's the same as 400 Amp hours on 48 Volts (about two parallel strings of GC2's). Quite a bit of power either way.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Typical set-up for a 48V cabin

    I am a big fan of running most of your stuff at 120 (or 230) VAC from an inverter... If sized correctly, you run the inverter at ~85% efficiency (get a 1.18x larger array and battery bank to make up for losses) and go forward.

    It is difficult to send 12 (or even 24/48 volts) very far--especially for larger loads. You can send around 1,200 watts a 100 feet on a simple 14 AWG extension cord at 120 VAC (with ~3.8 volts drop).

    A 24 volt system with 1,200 watts or 50 amps, you have about 2 volts headroom. 6 AWG cable will give you around 40 feet at 1.9 volt drop (and if you have surge current--you would need ~3 AWG heavier cable or ~3 awg or heavier, to maintain the ~2 volt maximum drop).

    The difficulty is finding an AC inverter that will match your loads... As you go higher in battery bank voltage, the majority of the AC inverters get larger minimum ratings (and their losses can be 20-40 watts just "turned on"--A lot for a small system).

    It really does come back to loads... If you go with a used RV propane refrigerator (usually pretty easy to justify fuel costs for weekend/seasonal use)--You could probably drop to a 12 volt battery bank and a very nice 300 Watt TSW inverter (with remote on/off, search mode to save power) to power your random small loads (and a 12 VDC water pump if needed). Use a "cheap" genset to run power tools when needed/backup power (get a Honda eu2000i if you want a very nice/quiet genset that will recharge your batteries in bad weather).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Typical set-up for a 48V cabin

    There's not much left for me to add to the other comments. Use the lowest voltage system that is practical.

    Many off-grid systems have a single load that defines the system... for many folks it is a deep well pump. In your case it looks like the fridge might be it... except for the fridge, you could get by with a 12 volt morningstar inverter.

    If you really have no plans to expand the system, consider a DC fridge. Yes they are expensive, and I wouldn't recommend it if you have a large inverter for other reasons... but if the only reason to have a large inverter is the fridge, it might make sense to look at DC fridges.

    One other thing... the Iota chargers are cheap and rugged, but have huge startup surges and low power factor. This may be a problem if you try to power one with a small generator.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    Re: Typical set-up for a 48V cabin

    Our host offers a variety of preconfigured kits. Have you looked at them to see if any would meet your requirements?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Typical set-up for a 48V cabin

    My two cents... Before looking at any kits (including our host's)--Try to work out the power needs first--Then see what fits those needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Typical set-up for a 48V cabin
    BB. wrote: »
    My two cents... Before looking at any kits (including our host's)--Try to work out the power needs first--Then see what fits those needs.

    -Bill

    Absolutely. Otherwise you're 'buying blind' whether your buying a kit or individual pieces.
  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    Re: Typical set-up for a 48V cabin

    I don't have any "loads". I was looking for typical set-ups and what was possible. I'm in the design phase.

    Thanks for the answer.
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Typical set-up for a 48V cabin
    I don't have any "loads". I was looking for typical set-ups and what was possible. I'm in the design phase.
    Thanks for the answer.

    Well, you kinda need to know what your "expected" loads are in order to design a system to be able to supply it.
    For example, if you need a truck, you would have to determine if you need a 3/4 ton, 1 ton or 2 ton BEFORE you buy it. Otherwise you will buy more truck than needed, or not enough truck. And it costs more to convert (if even possible) a 3/4 ton truck to a 2 ton truck than it would have to just buy it outright.

    If you can list the items you expect to run, we could likely give you a "guess" on their consumption based on the fact that many of us likely run one of those ourselves.
    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
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    Re: Typical set-up for a 48V cabin
    I don't have any "loads". I was looking for typical set-ups and what was possible. I'm in the design phase.

    Thanks for the answer.

    Here is the wind/sun packaged systems link. As others have asked you have to be able to know if you will condition air, pump water, and if you will expand. If you plan to leave the reefer running unattended the use of propane or DC becomes a piece of mind issue if solar weather could cause spoilage in the refrigeration.
    Thanks again for the help you have lent here with your pumping expertise!

    http://www.solar-electric.com/ofsokiforho.html
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Typical set-up for a 48V cabin
    • 1,000 WH per day (1 kWH per day)-- Nice cabin power. Lights, laptop, radio, charging cell phone/hand tools, 12/24 volt water pump
    • 3,300 WH per day (3.3 kWH per day/100 kWH per month)-- Add a refrigerator, washing machine, well pump (and lots of conservation)--Good sized DIY system
    • 10,000 WH per day -- Full off grid home (propane/other heating/cooking fuels)--System is getting pretty large/expensive. Possibly run a small mini-split in sunny weather.
    • 33,000 WH per day -- Typical North American home's average power usage (1,000 kWH per month)
    • 100,000 WH per day -- Living with A/C+electric heat/cooking/hot water in in Texas/Florida/etc.

    The first system can run 12 volt battery bank The 3.3 kWH system 24 to 48 volts. Anything more should be a 48 volt system.

    How much do you want to spend? Is this full time or seasonal use? For most people, the dividing line between a "small" and "larger/more expensive system" is a full size refrigerator (and/or sometimes deep well pump).

    More or less--Just as a starting point, figure ~$10 per Watt*Hour system installation cost (i.e., 1,000 WH per day would cost a bit less than $10,000 installed). Smaller systems will be more $$$/Watt and larger systems will cost slightly less (but you may have to pay for installation of a larger system--Can be pretty daunting if you never have done electrical/DC power systems before for a first time install).

    Again, not trying to give you an accurate quote--Just some rough numbers you can aim for. As always, do a couple of full paper designs before you purchase any hardware. If you are going to be building--A generator (or two, one small Honda eu2000i and a large "noise maker" when needed to run large tools) plus perhaps a small (1 kWH per day) PV system (for night lights, radio/laptop, etc.) will do well for you.

    Electric energy use is highly personal--What works well for me may not for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • cupcake
    cupcake Solar Expert Posts: 254 ✭✭✭
    Re: Typical set-up for a 48V cabin
    I'm looking at installing a 48V system for an off-grid cabin about 600 sf. Not looking to live there full time. I want to be able to run a fridge and some simple things like a tv.

    I can do all the wiring and electrical. Grid power is not available at this location. My budget is about $15-20K.

    What I'm looking for is some typical set-ups etc.

    Thanks.



    I am in a 12v cabin... everything is inverted to AC current and runs all the typical household stuff... There is a refridgerator running constantly.. 5 sealed 12v batteries in parrallel and 2 (for now) 280w pannels... the panels are in the desert, so its constant sun...


    No TV, I have not owned one since 1999....

    I use the moringstar mppt 60 controller and a samlex 2000w inverter hardwired to the AC stuff...

    basically you balance what you bring in versus your usage... makes you conscientious over every electrical device....

    many setups work - what ive found is that its a balance between what you get and what your lifestyle demands....

    Some people "need" 90" televisions, air conditioners, jumbo refrigerators, PlayStation 13, landscape lighting, and 67 kitchen lights to be 'happy'...

    --cake
    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    Re: Typical set-up for a 48V cabin

    Thanks, this is the type of info I was looking for. I'm thinking the 3300 WH per day would serve me well.

    The well will have it's own solar set-up. I just finished installing one similar that pumps 5,000-7,000 gallons per day running two 190-watt panels.
    BB. wrote: »
    • 1,000 WH per day (1 kWH per day)-- Nice cabin power. Lights, laptop, radio, charging cell phone/hand tools, 12/24 volt water pump
    • 3,300 WH per day (3.3 kWH per day/100 kWH per month)-- Add a refrigerator, washing machine, well pump (and lots of conservation)--Good sized DIY system
    • 10,000 WH per day -- Full off grid home (propane/other heating/cooking fuels)--System is getting pretty large/expensive. Possibly run a small mini-split in sunny weather.
    • 33,000 WH per day -- Typical North American home's average power usage (1,000 kWH per month)
    • 100,000 WH per day -- Living with A/C+electric heat/cooking/hot water in in Texas/Florida/etc.

    The first system can run 12 volt battery bank The 3.3 kWH system 24 to 48 volts. Anything more should be a 48 volt system.

    How much do you want to spend? Is this full time or seasonal use? For most people, the dividing line between a "small" and "larger/more expensive system" is a full size refrigerator (and/or sometimes deep well pump).

    More or less--Just as a starting point, figure ~$10 per Watt*Hour system installation cost (i.e., 1,000 WH per day would cost a bit less than $10,000 installed). Smaller systems will be more $$$/Watt and larger systems will cost slightly less (but you may have to pay for installation of a larger system--Can be pretty daunting if you never have done electrical/DC power systems before for a first time install).

    Again, not trying to give you an accurate quote--Just some rough numbers you can aim for. As always, do a couple of full paper designs before you purchase any hardware. If you are going to be building--A generator (or two, one small Honda eu2000i and a large "noise maker" when needed to run large tools) plus perhaps a small (1 kWH per day) PV system (for night lights, radio/laptop, etc.) will do well for you.

    Electric energy use is highly personal--What works well for me may not for you.

    -Bill
  • TucsonAZ
    TucsonAZ Solar Expert Posts: 139 ✭✭
    Re: Typical set-up for a 48V cabin

    Conservation is a HUGE part of solar so make sure you work out maximizing efficiency. If you need a fridge for example, consider using a chest freezer conversion instead, if you need a fridge and freezer, two chest freezers would still use less power than a normal home fridge/freezer combo. A 3.6cf converted chest freezer to run as a fridge should use about 300-400 watts per day with light use (opening/closing), a normal house fridge will use 5-10x that.
  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    Re: Typical set-up for a 48V cabin

    I wonder if something like this http://kingtecsolar.com/products/solarpoweredairconditioner-k25cj-4/ wouldn't work well with that 3.3 KWH system? I'm surprised that we haven't seen any posts or other info about it since it came out about two years ago.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Typical set-up for a 48V cabin
    I wonder if something like this http://kingtecsolar.com/products/solarpoweredairconditioner-k25cj-4/ wouldn't work well with that 3.3 KWH system? I'm surprised that we haven't seen any posts or other info about it since it came out about two years ago.

    There's a whole thread on that here: http://forum.solar-electric.com/showthread.php?17347-The-Kingtec-K25Z-4-Solar-Air-Conditioner

    BTW, you're guessing 3.3 kW hour will do. If you guess wrong, it won't. You really need firmer basis for system sizing then Bill's estimates and your estimations. Try to approximate the conditions at home and measure the power usage. Then try to keep the Mrs. from adding more and more electric gadgets to overtax the system. :p
  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    Re: Typical set-up for a 48V cabin

    Yes, I was on that thread, but we haven't heard anything of the unit since the thread was posted. I did note that they now make one that does not have the battery/charge controller, much more suitable for someone with an existing system. It would probably be in-line with a mini-split cost-wise.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    Re: Typical set-up for a 48V cabin
    Yes, I was on that thread, but we haven't heard anything of the unit since the thread was posted. I did note that they now make one that does not have the battery/charge controller, much more suitable for someone with an existing system. It would probably be in-line with a mini-split cost-wise.

    I looked at the window unit they made and it was loud. The cost/energy use just did not compete with a 25+ SEER mini-split. The final decision for my customer was that the unit could not run with small amounts of power. The beauty of a quality inverter based mini split is you can set the room differential to 2 degrees and a 12K BTU will consume 300 to 400 watts or so. On a cloudy day this can be a great piece of mind thing off of the grid.

    If you need cooling in Texas you better size your battery right and have the arrays set for long solar days. The other way of coarse is a generator.

    I would say the reason you have not heard much about this is because the mini split is just better, even with the DC to AC and AC back to DC loss offgrid.

    King does now make a mini - split and that might have some promise if the price and energy use were good.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Typical set-up for a 48V cabin
    Yes, I was on that thread, but we haven't heard anything of the unit since the thread was posted. I did note that they now make one that does not have the battery/charge controller, much more suitable for someone with an existing system. It would probably be in-line with a mini-split cost-wise.
    Before you decide on a Mini Split find out where the nearest servicing dealer is. The closest Dealer to me is 200 miles a service call + mileage and time is out of the question, no one else will touch them.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    Re: Typical set-up for a 48V cabin
    Before you decide on a Mini Split find out where the nearest servicing dealer is. The closest Dealer to me is 200 miles a service call + mileage and time is out of the question, no one else will touch them.

    Definitely need an HVAC tech do the first run if you want the 5 year warranty and 7 years compressor. I do have quite a few folks who have installed them who are so remote they just roll the dice. They are easy to install, bleed the line set, and turn it on. The LG 9000 BTU would work well in his cabin and at 28 SEER you could run it on flashlight batteries ;)
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Typical set-up for a 48V cabin
    ... The LG 9000 BTU would work well in his cabin and at 28 SEER you could run it on flashlight batteries ;)
    Well, Lithium flashlight batteries anyway. The Tesla car runs on about 7000 "flashlight batteries", the 18650 size.
    SMA SB 3000, old BP panels.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    Re: Typical set-up for a 48V cabin
    inetdog wrote: »
    Well, Lithium flashlight batteries anyway. The Tesla car runs on about 7000 "flashlight batteries", the 18650 size.

    Nice ! Better do the lease on this one!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net