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48 Volt system

Discussion in 'Off Grid Living' started by rsbhunter, Feb 13, 2012.

  1. rsbhunter

    rsbhunter Monkey+

    I am once again thinking about going to a 48 V system,going into an outback charge controller. I can go to 3600 watts on panel out put, i now have 2350 watts, and might add 2 more before i even mount the panels,is there a bad to going to 48V. ? Everything i read says i can use smaller gauge wire, i'll have more capacity to add panels....There is almost always a good/bad balance....what is the bad? Thanks again, to all of you, my system is actually coming together!!!!!! rsbhunter
  2. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Going to 48 volt would be nice in a lot of ways, but, you really want a min of 2 battery banks, and that would mean 16+ batteries. That way, should one battery fail, you can disconnect that entire bank, buy a new battery to replace the lost one, or just run on a single bank from there. Ask TnAndy about the wiring and also the charge controller settings.
    hank2222 and rsbhunter like this.
  3. rsbhunter

    rsbhunter Monkey+

    2 battery banks

    That make sense, and with what i save on not having to buy a second controller ($600.00) i will put towards the second battery bank....None of this is cheap, and i've accepted that now, so , you just suck it up and do it the right way the first time....i've done it twice too many times because i thought i was saving $$$$$...not that i have the $$$ , but , thats why i am still at the J.O.B.....rsbhunter
  4. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Nobody ever said, "Prep'en was cheap"... just like nobody ever said, "Life was Fair"... In the end you get what you pay for, so how much is Off-Grid Power worth to you, and does it make sense to invest in it, as opposed to other Preps? That is the question... .... YMMV....
  5. TnAndy

    TnAndy Senior Member Founding Member

    When you go from 12v to 24v, your wiring needs and fusing cuts in half....and when you from 24 to 48, it cuts in half again......and your entire system efficiency goes up as you increase voltage. I did a 24v system, out of pure ignorance at the time. Had I known I was going to increase my system from the original 2.1kw to 5.95kw, I SURE would have gone 48v.

    I don't guess I'll every go back at this point, but IF I had it to do over, 48v it would be.

    And you're right....you can save one charge controller at nearly 600 bucks. Actually, I'd step on up to the FM80, and that way you'd have room to double your system size down the road IF you wanted, and the difference in cost is only about 100 bucks between the 60 and 80.
    hank2222 and rsbhunter like this.
  6. rsbhunter

    rsbhunter Monkey+


    Yeah, i was thinking about going to the FM80, it's like $70.00, maybe $80.00 bucks higher, and i don't "think" i would ever outgrow it with the system...unless i install that electrically heated hot tub!!!! (ONLY KIDDING) But i honestly feel that it would save grief down the road if i go that route.....Now, to get batteries, inverter, cables, build the cabin, buy the water tank(s)...etc, etc.....But again, i really want to thanks you guys, i know that trying to pound this stuff into our heads (newbies) is probably a major headache, but it does sink in, and will be passed on once we are smart enough to do so....rsbhunter
  7. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    I want to reserve the right to come "visit" and crituque your system when all is done and working well. LOL
    hank2222 and rsbhunter like this.
  8. rsbhunter

    rsbhunter Monkey+

    critique system

    Heck, i was hoping it would be sooner than that!!!!!!rsbhunter
    Nadja likes this.
  9. farmboyJD

    farmboyJD Monkey+

    nadja's visit

    He'll wait until you get the hot tub installed.
    Nadja and weegrannymush like this.
  10. rsbhunter

    rsbhunter Monkey+

    hot tubs finished

    FarmboyJD....are you implying that Nadja is like a blister......only shows up after the hard work is done????:D (only kidding) I KNOW that he has done his fair share and more in the "hard work" dept. Anybody over the age of 40 (and some younger) can probably remember what hard work is......Then you get smart enough to avoid it like the plague!!!!!!!! Then, old age sets in (me) and you start thinking, build a cabin, set up a solar system, put in water tanks, clear trees, SURE i can do that.....I wanta rub ben gay all over my body just thinking about it!!!!!rsbhunter
  11. jasonl6

    jasonl6 Monkey+

    So if someone has a 24 or 48 volt system and wants to run 12v appliances and lighting how does that work? I am looking at running a wind/water setup at a remote location with a 24v military generator running on natural gas for backup. All my stuff will be 12v (lighting, air pumps, water pumps and refrigerator). How do i use my 24v system as a 12v?

  12. TnAndy

    TnAndy Senior Member Founding Member


    You're gonna have a battery bank anyway. Here's a mini version of it to keep the explanation simple.....two 12v batteries.

    Wired for 24v input, you run the positive of the source input (solar/hydro/generator) to one positive of the battery. On the same battery, you run from the negative to the positive of the other battery. The negative of the second battery back to the source completes your 24v circuit. The batteries are wired in series.

    For 12v, you take leads off the pos/neg of the SAME battery, along with leads off the pos/neg of the second battery, (parallel legs) so you draw EQUALLY off both batteries, and run those leads to a distribution box ( Like say a 60amp SquareD QO series box.....rated for up to 48v DC as well as AC ), then on to your lights/whatever.

    BUT depending on the distance those uses are located FROM the battery bank, you might well find it's better to invert AT the battery bank to 120vAC, and run "normal" stuff. The voltage drops using 12v can be pretty serious real quick if you get into any distance at all....like even 50'.
  13. CATO

    CATO Monkey+++

    You need, in your case, a 24v inverter.

    hank2222 likes this.
  14. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Why would he need a 24v interter ? He needs to run 12v which is dc and an inverter would be giving he 110 ac. He does not need an inverter to do this at all.
  15. TnAndy

    TnAndy Senior Member Founding Member

    The above assumes my last statement, that one would invert DC to AC then USE IT as AC power.

    But what he was asking was how to use 12v DC directly off a 24v DC system.

    The system loss for inverting from DC to AC and then back to DC ( which your diagram doesn't show ) would be ridiculous.
    hank2222 and Nadja like this.
  16. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Farmer, don't tell him. I will be working on picking out the hot tub I want him to install. LOL
  17. BTPost

    BTPost Old Fart Snow Monkey Moderator

    If you have no reason to use AC in your location, AND all your loads are 12 Vdc, then you would stay with a 12 Vdc Buss and Battery Bank. this will limit you to a maximum of about 1.5Kw of Total Loads, as the current used would make I2R losses unacceptable, above that level.

    However, should you need a bigger system to run your outfit, AND just have a few smaller 12Vdc loads, THEN what you would need is a DC/DC Switching Power Converter that has an input of 24-48 Vdc and a Regulated Output of 12-14 Vdc. These come in various sizes from 6 Amps clear up to 35 Amps.
    I have one of these down at my Beach Cabin, as part of that Power System. the Main Battery is a pair of 8D CAT batteries in series for 24 Vdc. I have a Trace 2624SB Inverter/charger and a 3Kw Onan Diesel Genset. Then to power the Cabin's 12 Vdc Buss I have a pair of L16s in series. A Numar 35 Amp 24/12 Dc/Dc Switching Power Converter, running at 13.4 VDC output to keep the L16's charged. The 12 Vdc Buss runs the 12Vdc side of the Fridge, the Comm Shack, and four 12 Vdc Emergency LED Lights.

    Using such a system keeps both Dc Systems, charged and operating without compromising the Battery Bank integrity. .... YMMV....
    hank2222 and TnAndy like this.
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