Will this setup work?

Discussion in 'Off Grid Living' started by Fury, May 12, 2017.

  1. Fury

    Fury Monkey

    Do you guys mind taking a look at this setup and let me know if it makes sense and is wired correctly?

    Thanks!!! sketch-1494628118802.
  2. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Never EVER, put dis-similar Sized Batteries in Parallel.... That is a recipe for Disaster, and buying New batteries quite often.....
  3. techsar

    techsar Monkey+++

    What BTPost said...and also connect the inverter to your batteries (through a fuse) rather than though the CC output.

    BTW, don't draw down the batteries too much...that 100w panel is going to take a while to recharge them.

    And yes to the CC ground.

    If in doubt, oversize you wiring. Less voltage loss, room for expansion built in, and no unintended "fuses."
    Last edited: May 12, 2017
    chelloveck and sec_monkey like this.
  4. ghrit

    ghrit Bad company Administrator Founding Member

    Even if it were a good idea to have different batteries in the system, that 12 volt batt seems a silly bit of additional storage after the monster 6v units. There's a logical disconnect with that in addition to ruining the cells. Run with the 6s and call it done.
  5. Fury

    Fury Monkey

    Thank you guys for the valuable input. Much appreciated. Of course this is my first system so I know I'm going to make mistakes, just don't want to waste tons of money making those mistakes.
    chelloveck and Yard Dart like this.
  6. Yard Dart

    Yard Dart Vigilant Monkey Moderator

    Welcome to the Monkey Fury!!
    Fury likes this.
  7. Fury

    Fury Monkey

    Ok...let's give this another shot. One additional question: Does the battery negative have to be grounded? sketch-02.

    This system is basically going to be used for some outdoor lighting in my shed (17w AC), some backyard overnight 12v motion sensor light (10w DC) and the occasional using tools out there. The lighting will be very intermittent and the tool usage will be like a weekend type thing. Later down the road I was thinking of burying some lines to run some landscape lighting and probably adding an additional 100w solar panel to get those batteries back to 100% during the day.

    Should I connect the DC light to the CC load or the battery? The CC I was thinking about has a program where you can tell it when to allow power to the light.
    Last edited by a moderator: May 13, 2017
  8. Fury

    Fury Monkey

    After a little more research I came up with this. I still am not sure about the batteries being grounded... Version 0.1.
    Tevin and BTPost like this.
  9. Tevin

    Tevin Monkey+++

    Your system is very similar to mine in that it has a separate DC bypass that can be used even if the inverter is off. Great call! It's more work & planning but adds a lot of versatility.

    I don't understand why you have an earth ground on the solar panel. It won't hurt anything, but it serves no meaningful purpose either.

    Also, the 100 watt solar panel is too small for the batteries. It will take a looooong time to charge those batteries up with that single panel. A rule of thumb is that you should have 1 watt of solar for every amp-hour of battery. That means your 100 watt panel is less than half of what you need. One more 100 watter will get you close; two more would be ideal and give you extra headroom.

    You're on the right track. With a few minor tweaks you'll have an A+ setup.
    Fury and chelloveck like this.
  10. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Better drawing on this one ..
    The inverter your posting on this picture is a POS & will let you down. For the 100W solar panel , pick a SS300 300W unit , 100w panel is what voltage & specs because an MTTP controller is a waste if the 100w panel is a 12V panel , Pick on a Brat from MIdnight . YOU will NEED a SPD for safety of the system & that needs the grounding in the system tie !!
    As posted above , MORE panels & they make many type of 100w type of panels , they are all in different voltages , this is what makes the math work & a great system .
    Fury and chelloveck like this.
  11. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    A 235 AH battery bank, at 12vdc, should have about a 10% charge rate, especially if he wants autonomy and to be able to charge the batteries up in a reasonable amount of time. A single 100 watts panel will have about a 5.0 amp charge rate, in full sun. So, as has been stated, not nearly enough charging for those beefy batteries. Here is an example of the specs of my 100 watts panels:


    So, he should be looking closer to 400 - 500 watts of panels. It's better to have more panels, than less.
  12. Fury

    Fury Monkey

    Ok, so I guess the truth hurts a little. Keep in mind, the reason I went with those batteries is I didn't want to discharge them too much (past 75% full). My setup is strickly for the lighting you see in the picture and occasional AC power tools.

    Thanks for the advice Tevin. Going to get at least 2 panels then to start. I wanted to start somewhere and leave a little room for expansion. The MPPT controller has the ability to handle 4 100 watt panels I think. Also, the manual for the panels said that they need to be grounded. That is the only reason I did that in the diagram.

    Cruisin Sloth, Why would I need that special SPD if I have a fuse between the DC Bus bar and the DC power supply? Thanks for the + on the diagram. I created that other one on my phone while I was on my break at work. Tough to draw on a 5 inch phone!, Ha!

    Another quick question, should I wire the DC bus directly into the Load on the charge controller instead of directly to the batteries? I was thinking I should do that because it will kill the load once the batteries run lower (if I forget to shut them off). The load can handle up to 20amps on the CC I chose so I don't think that will ever be a problem.

    Thank you guys for the help!
  13. ghrit

    ghrit Bad company Administrator Founding Member

    If I understand your question, no, the load should ALWAYS be from the batteries. The controller won't be happy with sudden load changes (like turning off or on an appliance, regardless of wattage) where batteries simply say "meh" and go about the business of dispensing or storing electrons. Your post #8 is correct as drawn.

    Yes, loads CAN be fed from the controller with the batteries at the same terminals, but typically not at all a good idea and will shorten the life of your controller (they are not really designed for surges much greater than the sun coming out from behind the clouds.)

    If you look at the load paths, you'll see different resistances depending on where you are in the circuit. Uv cuss, that means little if anything with AC but with DC you have to now what's going on and where.
    Fury likes this.
  14. oil pan 4

    oil pan 4 Monkey+++

    Cheap MPPT controllers likely do not preform actual MPPT.
    The solar market has been flooded with so much garbage.
    It's gotten to the point they will put anything on a cheap controller to get it to sell.
    Label a charge controller that should be no more than 8 to 10 amps as 20 amp. Take a cheap PWM controller and put a sticker that says MPPT on there.
    Cruisin Sloth likes this.
  15. TnAndy

    TnAndy Senior Member Founding Member

    You get your first lightening hit, and you'll figure out why panels are to be grounded.
    Cruisin Sloth likes this.
  16. Fury

    Fury Monkey

    Thanks ghrit

    Still no answer on grounding the batteries negative terminal?
    Last edited by a moderator: May 14, 2017
  17. Tevin

    Tevin Monkey+++

    To clarify, some controllers have terminals designated to power a load. These terminals are separate from the battery terminals.

    The purpose of these terminals is (usually) so the controller can cut off the power to the load if the battery voltage gets too low.

    Other controllers do not have these separate terminals. You simply connect the controller and load to a battery and go. Whether or not that connection is at the battery terminals themselves or a bus doesn't matter. The two points are electrically identical.

    So the answer to the question "should I wire the DC bus directly into the Load on the charge controller instead of directly to the batteries?" is, it depends on the controller. If you have separate load terminals, use them. If you don't then the decision is made for you.

    As @Fury correctly assumes, you'll have to pay attention to your battery voltage if the controller will not take care of this task.

    I do not agree that the controller will be damaged by load "surges", unless perhaps it was a poorly designed junk controller to begin with. Controllers are not going to pass any more current than is available from the solar panels, in this case about 5-6 amps, nor will they allow themselves to go beyond their rated current limit.

    If your load requirements exceed what can be provided by the controller, the battery will pick up the difference. That is how these systems are supposed to work. When you slap on a sudden large load, the batteries, not the controller, will suffer.
    Fury likes this.
  18. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Well the Kid has a load center as well as the Brat (MIDNITE Products ) buy quality over asian junk .
    I had 3 Reliable inverters as the one you posted in your picture , in six months they killed 2 deep freezers & all 3 are dead , PURE CHINA CRAP & Im was out $$$$$ big time . Now only real low frequency inverters or the cheap MSW for the odd thing.
    If your doing night lighing , using leds , get out of the 12 V thinking & get up to 24 or better 48Vdc ,, Cheaper , harvest more , bought once .
    To ground Panels & the system , MAJOR thought must be considered so no ground loop will develop. I use ONE major ground rod with the 2 ground cable from my - battery's & my controller & my SPD thats one cable , the second grounding cable is from the frames of the panels on the roof . My system is roof to ground 25 feet .
    Fury where are you ? Im PNW , Paul is in Asia , I get the odd thunder storm . Tell us your layout & what you would like to have & build .

  19. Fury

    Fury Monkey

    I'm in rhode island. The plan is to have this setup in/on my shed, which is unfortunately not heated. I realize this means I will need to bring the batteries indoor during the winter. The sun is so low in the winter here that id be lucky to get 2 hours of good light anyways.

    This whole thing started out as a hobby as I'm kinda a nerd who likes to tinker and learn how and why things work. The reason I started with 12v is simple...money. I tried picking out what i thought were decent 12v products. The only thing that isn't 24v capable in my setup is the inverter. It got great reviews and is from a US company. Plus, the 12v led lights are real cheap and only 3 watts at that.

    I really didn't know much about grounding, and even after research, it seems like I still don't! Even professional electricians seem to argue about it, haha.

    I really saw no purpose in grounding batteries. Everything is sure protected so any shorts, if they should occur, should be caught by the fuses/breakers, no?
  20. ghrit

    ghrit Bad company Administrator Founding Member

    Tevin likes this.
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