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Solar powered Desktop PSU — Parallax Forums

Solar powered Desktop PSU

eagletalontimeagletalontim Posts: 1,399
edited 2014-10-26 18:24 in General Discussion
Hello all once again! I found this and am wondering if this would be enough to power my computer in my shed :

http://www.mini-box.com/M4-ATX?sc=8&category=981

I really don't know what the minimum wattage needed would be, but the power supply in the computer is rated at 305W. That could be one more thing pulled off the grid :) I doubt this computer pulls a solid 305W all the time so I should probably figure how many amps it draws while in use and when not in use. 250W = 20.8A which is quite a large load IMO.

Comments

  • evanhevanh Posts: 15,921
    edited 2014-10-26 14:26
    I'm a big fan of PV panels but, be wary, shade a single solar cell on the panel and an entire chain of cells collapses. This generally has a huge impact on power output. So, presuming brownouts are an issue, throw in a battery and it's charger on top of that power supply. Basically, similar to a fully online UPS.
  • xanaduxanadu Posts: 3,347
    edited 2014-10-26 14:35
    What's inside your computer?

    If you have one hard drive and integrated graphics I think it would be more than enough.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2014-10-26 15:03
    The computer is an old Dell Optiplex that I upgraded the motherboard on to handle a better processor. It has one hard drive and it does use the integrated video card. About the only thing I use it for is to browse the web researching things I am tinkering with in my shed or listening to music while in my shed. I also have a DVR system running on the computer, but I hardly ever use it anymore. I may eventually, but it is not necessary.

    After running the Kill A Watt meter on it for a bit, I found that running idle, it draws around 72 to 75 Watts and the highest I could get it to was 120W by opening a bunch of browser windows and streaming music. I also plan on converting my speakers to run from the battery bank and the wireless router (I use as a bridge) to run from it as well.
  • evanhevanh Posts: 15,921
    edited 2014-10-26 15:39
    Cool, you've obviously got a decent sized off-grid setup already. What is its wattage may I ask?

    Your readings sound nominal and clearly don't even come close to the 250W. In reality, even a regular dedicated GPU gaming rig is topping out at 250W. Only the over the top rigs need more. That said, individual voltage rails can sag before reaching the full overall rating, so some overrating is wise.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2014-10-26 15:56
    Well, that is the thing... I only have about 480 watts of solar panels minus real world conditions and the charge controller. The solar panels are running on a solar tracking setup being controlled with a Prop. I ran a 10A load for 9 hours and the batteries were still topped off at the end of the day. I really need to invest in some more panels and batteries, but the budget does not allow for that at the moment.

    The more stuff I can get off the grid, the more I can save in the long run so I need to maximize the amount of items that can feasibly run from the current setup I have. If I do it wisely, I am not dumping excess power to nothing like I am now. My batteries stay fully topped off all day and all night. I know as soon as I add a decent load, the batteries will drain quickly as I am just using 3 car batteries at the moment. I don't care about the batteries so if they Smile out, so be it.

    The listed PSU has the ability to shut down the computer when the input voltage drops below a specified amount. This can be useful since I do run this computer 24/7 which is a waste of power.... If I use it only while I am in the shed, I could save about $3 to $4 a month. If I switch it to solar, I would save about $5 a month.

    I really don't know the limit of my solar setup now since all I have running from it is a small computer fan that kicks on when the shed temperature is below the thermostat and the solar heater gets to 140 degrees, and the circuit that kicks on my shed lights with motion. A total draw of about 1A max. On one car battery, it was able to run for over 30 days without a charge.
  • evanhevanh Posts: 15,921
    edited 2014-10-26 16:39
    Lol, I'd forgotten all about that tracker. You must have got it operating reliably. :) You're all set for running the PC then.

    Looking to the future - I hate lead-acids, the whole boost cycle thing is so messy and they're totally out performed these days - If you ever want to spend money on the batteries I suggest looking for the best float charged only setup. There is more of these tech batteries coming on to the market now but, sadly, the chargers are not keeping up. Forward looking companies that make the end equipment are forced to either remove the boost circuit, undocumented, from existing chargers or design their own charger.

    EDIT: PS: The boost function is often in the firmware on new chargers so getting rid of it isn't as simple as removing a component from the PCB. Software lock-ins can stab you in the back in more than one way.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2014-10-26 17:23
    I am actually using a cheap eBay pwm solar charger. Less than optimal, but it fit the budget. I just don't have enough electronic knowledge to make my own mppt charge controller so I gave up on that project...
  • evanhevanh Posts: 15,921
    edited 2014-10-26 18:24
    Yeah, no worries. MPPT only makes a difference if the batteries are not being fully charged each day. I was more focused on the battery tech. The chargers all assume one is using lead-acid batteries so are going to perform a boost cycle either way. So, using off-the shelf chargers, one is always locked into using lead-acids. :(
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