Off Grid Power Supply

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About: I'm an inventor / maker / designer based in the Bay Area. My background is in residential architecture, film set design, animatronics, media arts, exhibit design, and electronics. I use digital design and fa...

Intro: Off Grid Power Supply

This project is quiet, indoor friendly alternative to a gas powered generator. If you're charging devices, using lamps, or even running an electric motor for a limited time, this off grid power supply is a great companion for camping or emergency situations.

Step 1: Tools + Materials

Shapeoko XXL by Carbide 3D

    This is a great CNC machine for furniture-sized projects. It's got a 33"(X) x 33"(Y) x 3"(Z) cutting area and it's fully compatible with Fusion's CAM tools. The post processing in Fusion seems to work very well with all the tests I've tried.

    Or Be Your Own CNC...

    If you don't have a CNC router, all you need is a hand drill, a jigsaw with a metal cutting blade, a large format print from a print shop, and some patience. Here's a link to my Digital Fabrication by Hand instructable, showing you how to be your own CNC machine: https://www.instructables.com/id/Digital-Fabrication-By-Hand/

    I'll provide PDF drawings in the next step that you can use as templates to cut out your own parts by hand with a jigsaw.

    3D Printing

    I use a Creality CR-10 for just about everything. It's the best bang for your buck, in my opinion. The trim piece for this project pretty much takes up the whole bed footprint.

    • Use this coupon code at Gearbest to get it for $339: 1111CR10

    3D Print Filament

    • I used Matte Fiber HTPLA from Proto-pasta for this project, but pretty much any filament will work. I like this stuff because the finish looks really good.

    Electronics

    Total: $210 (not counting wood and 3D print filament)

    Hardware

    All of the following hardware can be substituted for smilier hardware available in your location and on your budget, but the CNC files are designed with these parts.

    • 1 1/2" wood screws
    • 1" Ø tubes for cross bars. I used some carbon fiber tubes that I found laying around in the shop, but any PVC tube or wooden dowel will do. These should be cut to 8 5/8" long.

    Materials

    Software

    Fusion 360 is free and it's awesome. I use it for everything I design and fabricate. If you have access to a CNC machine, it's about as good as it gets when it comes to easy and fast CNC programming.

    Student / Educator License (renew free every 3 years)

    Hobbyist / Startup (renew free yearly)

    Step 2: Design + Fabrication

    Just like everything else I make, I designed this project in Fusion 360. I love it because it's so easy to make CAM setups of the things you design, as you'll see in the Fusion archive that's attached here. If you take a look at the parameters list, you'll notice that I'm using a material thickness parameter. This is important because the interlocking parts (held together with screws through pilot holes) can be automatically updated if you're using a different material.

    The STL files are for the end caps that hols the cross bars. The capMid piece is meant to be a connection piece for the side panels, but I ended up not using them because I glued the sides onto the box.

    The DXF files are vector files that can be used for CNC or laser cutting.

    The PDF files are printable files that can be used at templates for hand cutting. They should be printed at 100% on whatever sheet size they'll fit on.

    Layout.PDF is for 1/2" material.

    Face Plate.PDF is for 1/8" material.

    Step 3: Parts Assembly

    The battery and charger fit into slots on the insert piece and are held down with zip ties and screws with washers as seen in the photos. The inverter is fastened with screws through pilot holes in the side of the box.

    The diagrams above show where the parts in the face plate belong. I used power pole connectors to connect all the electronic parts, but you could easily do it all with screw-on wire caps from any hardware store.

    Step 4: Chassis Assembly

    The assembly is basically just a box with X-shaped side pieces. These pieces protrude past the main box and make feet that have carbon fiber cross bars. These bars make good handles for moving the power supply, but the idea is that they also can be used to attach it to a roof rack or something like that.

    I used 2" wood screws to attach the end caps to the X-shaped panels as shown in the diagram. The caps were a bit snug, I would probably make the tolerance bigger for those pieces if I were to do it again.

    Step 5: Go Off the Grid!

    I ran a shop vac off of this power supply for about an hour before the inverted started beeping (warning me that the output was going below 10V). We used it at a cabin in the woods for a weekend charging phones, bluetooth speakers, and fluorescent lamps, and in 48 hours we still had power.

    I'd like to try charging it with solar panels to get a sense of how well it would work with that kind of system. Let me know what you think in the comments!

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      98 Discussions

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      frisbrob

      Tip 8 months ago

      I forgot to finish another thought before I posted my last message. Even if there is no back on this the battery should still be sealed off from the other electronics. As the inverter heats up and the cooling fan comes on it will circulate the gasses through the unit and other electronics. Even people that were just charging the battery in their car in an open garage have had the battery gasses explode, burning the car and the garage down. If you really need to use a lead acid battery it would be better if the battery was separate from the rest of this unit. Just be careful.

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      frisbrob

      Tip 8 months ago

      Just one problem with this, if you are going to have everything all together in this one box you need to do something to separate and seal the battery off from the rest of the components, it also needs to be vented. Even if it is a sealed maintenance free deep cycle battery it will give off corrosive gasses that will destroy your inverter and other electronics, you also have the makings of a bomb, if battery gasses build up in an enclosed space they can explode. Batteries put off a lot more gas while charging. This is why they tell you not to put the inverter in with the batteries in a trailer, camper or RV.

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      refinedwood

      7 months ago on Step 2

      I tried several times to open the "trimNew.stl" file in Utimaker Cura to create gcode for the print but only a few small boxes are shown. Is the file bad or is it me? Thanks!

      5 replies
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      JON-A-TRONrefinedwood

      Reply 7 months ago

      You might be having a problem with units. Small boxes sounds to me like the trim is there, it’s just tiny. Do you get a units option in Cura?

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      JON-A-TRONJON-A-TRON

      Reply 7 months ago

      I think you'll want to scale it up from 1 to 25.4 (25.4 mm in an inch...).

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      refinedwoodJON-A-TRON

      Reply 7 months ago

      It is there as you said but the units are scaled down. X is 9.1584mm, Y is 1.2362mm and Z is 8.6024mm. Should I scale it up to 838.2mm (33") for X? Still, though, the lengths for X and Z while similar aren't the same. I'm a newbie at 3D printing so I'm asking basic questions. Thanks!

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      refinedwoodrefinedwood

      Reply 7 months ago

      I realized that the X value shouldn't be 33". It should be around 7.6". I'm just not sure how much to scale it up.

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      refinedwoodrefinedwood

      Reply 7 months ago

      Cura doesn't seem to have a units option. However, it does have a scale function where a model can either be increased in size by a percentage or X, Y and Z values.

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      ipf_group

      8 months ago on Introduction

      I will make 1 same for myself. Good for use for example when city off electric. Silent and power) nice !

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      gravityisweak

      8 months ago

      I think this would be an amazing system to add solar panels to. With a slight redesign you could probably turn the top surface into a solar panel and incorporate 2 flip-up side panels for a 3 panel top surface while leaving the front open for charging and the handles available for carrying. I'm not 100% certain how the attachment would work with all these other things attached but I think if you ran your solar panels through a charge controller right to the battery terminals, that it would work just fine. In fact that'd be a pretty awesome product that might be worthy of a Kickstarter.

      4 replies
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      JohnC430gravityisweak

      Reply 8 months ago

      this is a standard configuration for an "off grid" system without really being off grid considering that he has an AC-DC converter in it. the only difference is that he made a nice enclosure for it. so why would it be a product "that might be worthy of a Kickstarter"? is it the enclosure that caught your attention?

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      gravityisweakJohnC430

      Reply 8 months ago

      No, I'm talking about a modular portable power system that is DIY from a kit. I like the option of adding a 12v car charging port, or a usb port, or 4. Maybe I want solar panels, or maybe I only want to plug it in to charge. Maybe mine has wheels or a camping lantern built right into the side. If you know that something like that already exists, point me in the right direction.

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      JON-A-TRONgravityisweak

      Reply 8 months ago

      Yeah, I love that idea. I think the design would be a bit different, but it would be good to know what the solar panel options would be and how many you would need to charge the battery in a reasonable amount of time.

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      JohnC430JON-A-TRON

      Reply 8 months ago

      if u use a solar panel you will need a charge controller... this is a DC_DC charger with a MPP (Maximum Power Point) controller to suck out the max power from the solar panel into the battery. so this device goes between your solar panel and the battery. also remember that the panel is a lot bigger than the box that you made. what you made is a battery back up unit with a massive battery and a novel enclosure. you will need a big panel to charge that battery. you have to decide how quickly or slowly you want to charge the battery and buy the panel with that amount of capacity. 35 AH/ 5 hours means 7 amps from the panel for the full day. here is So Cal we have an average of 5.5 hours of sunlight/day.

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      JamesW440

      8 months ago

      What does this do that a portable backup starter system for automobile use doesn't do? I didn't check the actual figures, but what it sounds like is the designer put together standard products into a cute (and well designed) box in order to make use of his toys (kudos for that) but otherwise nothing spectacular nor even special. For about $100 you can go to Walmart or the like and buy a portable car starter. The only thing it is missing is an inverter. Buy a 400 w inverter for $50 and you can mount it inside the original box by pulling the cords out and wiring the inverter into the opening. Along with it you would receive a flashlight and an pretty good air pump to boot. And you would be likely to keep on top of its maintenance because you have it with you in the vehicle all of the time - I would arrange to have it charged from the 12 v of the car.

      Optionally, you could build the pretty (cool) box and install all of the guts out of the automotive backup starter system along with the inverter with a little ingenuity. What do you think about that possibility?

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      gravityisweakJamesW440

      Reply 8 months ago

      I think the main difference would be the size of the battery. You make a good point though, you could purchase one of these backup starter systems, rip out the guts and add a nice big battery and put it into a nice looking box as a nice alternative for having to buy the parts separately. If someone was extra clever they could probably find a way to expand the capacity and keep the form factor of the original. I like it.

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      stdpattern

      8 months ago

      I don't see a free hobbyist / startup option for Fusion 360, am I missing something? I see $40 month/ $300 a year, free 3 year for student, or free 30 day trial.

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      JON-A-TRONstdpattern

      Reply 8 months ago

      Just wait until your 30 day trial is up- you'll see an option to continue for free as a hobbyist / enthusiast / startup (I forget what they're calling it now). You'll be prompted to renew yearly for free.