Introduction: Portable 120v Backup Power


  • One 120v Receptacle
  • Two USB Ports, 2.1A and 1A
  • Inverter On/Off Switch
  • Integrated Charger
  • Rugged and Portable Case

Bill of Materials (Price - Source):

  • 150 W Inverter (~$20 - Amazon)
  • 12v 20Ah SLA Battery (~$40 - Amazon)
  • 12v 2A Black and Decker Charger (~$18 - Amazon)
  • Rugged Case Apache 2800 (~$30 - Harbor Freight)
  • 1 Switch
  • some wire heat shrink

Durable Tools

  • wire stripper
  • some crimp connections
  • a drill with bits
  • a file
  • screwdriver
  • happiness

Step 1: Fitment: Place Things Where You Want Them to Go.

For mine, I placed the heavy battery middle, center and on the floor of the case, with the handle up. The charger fit on one side and the inverter on the top of the other side. Cables should be shielded from the terminals to prevent a short and a fuse should always be used between the batter and ANY appliances.

Warning: It is not advised to charge a lead acid battery in an enclosed space, whether sealed or not, so I left the top area open, drilled air holes on one end, and put the inverter, with fan, on the other side so there could be some cross ventilation.

Step 2: Wiring

Disconnect the positive lead when working with the wires, especially when cutting and splicing. Double check your work and measure twice so you only cut once.

I wired the negatives from the battery, charger, and the inverter all together. None through a switch, but I did provide negative to the switch to power the small indicator light.

I wired the charger and battery positive together with a 20A fuse proximal to the battery. Then I provided one positive lead to the switch to be received by the inverter when the switch is on.

Tripple check your work, make sure all wires (if they are not the ones provided) are of proper gauge for the application using the power calculations.

Step 3: Aesthetically Modify

I wanted the charger cable to be coming out of the box, so I made a hole and sliced the wire through. I put some air holes near there as well.

I wanted the 120v Receptacle to also be accessible from the outside so I outlined the faceplate, drilled and filed away to my desired shape.

I wanted the switch to be accessible from the outside so I drilled for that as well. The case came with pick-apart, square foam, so I filled the side spaces so the battery would not swing back and fourth.

Step 4: Test

Do not take this camping, or expect to rely on it in an emergency unless you have properly tested it. I ran some lights off it for an extended period of time and was pleasantly surprised by its performance.

I will say this though. A crappy power inverter from Amazon in a previous model would lower the AC voltage to ~90v when the battery was low, instead of cutting off automatically. This was bad as it ruined one of my nice LED lights, so do not be cheap in purchasing a power inverter. Look for one with a low voltage cutoff.

Next, I hope to complete a lithium version of this but until that, happy building!