Introduction: 12 Volt Battery Generator

Inexpensive 12 volt back-up battery generator that is not hard to make. It will power what counts if the power goes out! Note:

You must have a working knowledge of electricity and electrical circuits to do this project otherwise you could really hurt yourself.

I've powered space heaters, refrigerators, televisions, fans, washing machines, lights. You name it and this will most likely power it including small ac units. The small mini fridge seen here has been running for 25 hours now with plenty of battery power remaining to run more stuff. You can take this to your remote cabin and be completely off grid. See my other instuctables for the foldable lightweight solar panels that compliment this generator nicely!


1. 60 ft of 3-1/2 in by 1-3/4 in board.

2. Box of wood screws 1-1/2 inches long

3. 1500 watt power inverter (pure sine wave inverter recommended)

4. Solar charge controller

5. Battery meter (I have two on this)

6. Toggle switch

7. DC power outlet

8. Two hinges

9. Two clasps

10 Four battery cables

11. Plenty of wiring and a handful of alligator clamps big enough to clamp to batteries. Also other wire connectors and electrical tape. Amounts will vary depending on how you set it all up.

12. Four heavy duty castor wheels

13. Drill with up to a half inch drill bit. You'll probably want some smaller ones to.

14 Door knob drill kit (2 inch) for the round battery meter. Yours may be a different size?

Step 1: Wood Needed

1. You'll need 60 feet of cheap wood that is 3-1/2 in by 1-3/4 in.

2. Cut 9 pieces 26 inches long

3. Cut 7 pieces 17-1/2 inches long

4. Cut 22 pieces 12 inches long

5. Cut 4 pieces 16 inches long

6. Cut 2 pieces 15 inches long

7. Extra pieces of any kind of wood like (2x4) to brace the batteries inside the box.

Step 2: Constructing the Box

Hopefully this picture explains how the box goes together (at least the end result)

1. Start with building the four sides.

a. connect seven 12 inch boards (no space in between) with a 26 inch top and bottom piece. Center the 26 inch boards which should leave roughly 3/4 of an inch on both ends. Repeat this step again. Use the screws but pre-drill all your holes first.

b. connect 4, 12 inch boards with the 16 inch top and bottom pieces. Repeat this again. Again make sure the top and bottom pieces are centered which will leave you with roughly 3/4 inches on both ends. Remember to pre-drill all your holes first.

c. Connect all four sides now.

2. Use all seven of the 17-1/2 inch boards and screw them in the bottom of the box. Space them out so they go from end to end with no left over space.

3. Use the remaining 5, 26 inch pieces to build the top. Lay them flat with no space in between the boards and screw the two 15 inch pieces down opposite direction on top of the boards.

4. Hinge the top to the box.

5. attach clasps to the front to lock the lid down.

6. Flip the box over and screw the castor wheels to the bottom of the box.

Box is done. (Tires were a later addition).

Step 3: Connect the Power Inverter

1. Chose the exact location where you want your inverter to be and leave enough room to drill holes for the positive and negative cables behind the inverter.

2. Drill two holes behind the inverter using the 1/2 inch drill bit.

3. screw the inverter to the top, connect the cables to the inverter and run the cables down through the two holes.

4. Once batteries are in the box you can connect the cables to the batteries.

Step 4: Connecting the Solar Charge Controller

1. Choose the exact placement of your charge controller and again screw it down and drill holes behind it to run the wires down through the top. When the batteries are in the box, you can connect the battery wires from the charge controller to the batteries.

Step 5: Adding the Battery Meter and Toggle Switch

1. Again, find a good convenient spot to attach the toggle switch, some place close to where the battery meter will be. Drill a small hole next to where the toggle switch will be to run the wires down through.

2. Attach your battery meter where you want and then connect it to the toggle switch and battery. You have to have a basic knowledge of electrical to accomplish this. Mine is set up so that I have to switch on the battery meter to see the battery level. I can turn it off or leave it on.

3. If you use a round battery meter like I have on mine, you'll need to drill a hole with the 2 inch door knob drill bit like I did in order to seat it down nicely in the wood. Looks really cool to do it.

Step 6: Adding the LED Light

This is completely up to you what you use but I recycled some fish tank led lights and an old ipod case to create this light. It's taped to an old GPS suction cup holder with directional capability. It's really bright!

Step 7: Adding the Batteries

I used two MK 74 AH Wheelchair batteries. Found a heck of a deal on Craigs List. Just make sure you use 12 volt deep cycle batteries. There's room for one more in there I think but for now this will do. Connect them in parallel. Attach all your gadgets to the batteries via alligator clamps or how ever you do it.

Brace the batteries in place with extra wood so they don't slide around when you move the box.

I use the homemade solar panels and extension cord you see to charge the generator when I can but I also have a 12 volt battery charger that I use when the sun doesn't shine. The panels I have here equal roughly 100+ watts of charging power on a sunny day. I get about 5-6 amps out of the panels.

I hope you like this instructable. Let me know what you think.

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