Picture of Portable Sun - Rechargeable Work Lamp

Why use a flashlight when you can use a powerful, heavy duty work lamp? Flashlights run out of juice, are under powered, are hard to position and roll away when placed on the floor. How many times have you had to fetch your flashlight from the bottom of your driveway?

This Instructable shows how to build a powerful, rechargeable work lamp. The base is solid and stable since it contains a sealed lead acid battery. Once you position it, this thing stays put. The lamp itself is a car fog lamp so it will illuminate your entire work area. It is brighter than the sun itself!

The work lamp is also packed with a few extra features. It includes a DC/AC Inverter so it can be used as a battery back up. It also has a relay circuit which turns on the lamp in the event of a power failure. Cool to have when the zombies take out the power grid.

This Instructable should be titled “Harbor Freight Hack” since most of the major components come from Harbor Freight. Harbor Freight is a great place to pick up a wide variety of inexpensive tools. http://www.harborfreight.com/ HF is a Maker’s paradise.

Ammo Box - Bunker Hill Security - Item#61451 - Harbor Freight - $6

400 Watt DC/AC Power Inverter Cen-Tech - Item#66814 - Harbor Freight - $30

Automatic Battery Float Charger Cen-Tech - Item#42292 - Harbor Freight - $10

Enercell 12V/5Ah Sealed Lead-Acid Battery - Catalog #: 23-945 - Radio Shack - $30

Genssi LED Off Road Light 4X4 Work Light Waterproof 27W 12V 6000K (60 Deg Flood) - Amazon - $25

DC Power Jack - Catalog #: 274-1583 – Radio Shack - $3.99

DC Power Plug - Catalog #: 274-1573 – Radio Shack - $3.99 (2-Pack)

4 1N4001 diodes – Catalog #: 276-1101 - Radio Shack - $1.49

7812 Voltage Regulator - Catalog #: 276-1771 – Radio Shack - $1.99

100uF Electrolytic Capacitor – Catalog #: 272-1028 - Radio Shack - $1.49

Inline Fuse Holder - Catalog #: 270-1281 – Radio Shack - $3.49

Car Accessory Cigarette Jack – junk box

SPDT Relay - Zettler AZ942-1CT-12DE 16A 250VAC – junk box

SPST Mini Switch – junk box

Female USB connector from old PC backplane card slot – junk box

Nylon web strap with buckle – junk box

PWB Perf Board – junk box

Scrap pegboard

Scrap strips of aluminum sheet

Scrap sheet plastic


Metal Brake Bender
Hole Saw
Heat Gun
Soldering Iron
Tin Snips
Utility Knife
Atomic Powered Ruler

Obaidhanan7 months ago
im using 12v dc battry, with 500w inverter to 220v, when the main power goes down, let me know how to install RELAY, and which type. ... thank you

That sounds like a perfect brand name.... "Portable Sun"d

JKPieGuy1 year ago

I thought I was the only one to use an Ammo Box to house Electronics. Glad I'm not, cause they sure are nifty for Projects.

garagemonkeysan (author)  JKPieGuy1 year ago

Ammo boxes make great cases. : )

They sure do! It's keeping my final project safe from the elements (and scoundrels) when transferring it to and from school. My teacher saw that I was housing my custom PCB's that I had designed, and the ribbon connectors for it inside the container, and mentioned how it was an "Interesting Containment unit". Especially to be brought to school, but I added stickers to the side to make it look less conspicuous.

omni961 year ago

I have something a bit different

Bought a light stand and an E27 socket for the light stand, a diffuser cover for the lamp, and a 12V lamp

I use a 12V battery I once bought, and now it's in my UPS, constantly charging :)

garagemonkeysan (author)  omni961 year ago

Sounds like a great project! : )

w1bmw1 year ago

Just what every vampire hunter needs!

garagemonkeysan (author)  w1bmw1 year ago


baecker031 year ago

might be cheaper, as well as more efficient to DIY with the Led fixture to achieve a minimal input of say 12v. should be lighter using a buck converter and lithium ion batteries.

garagemonkeysan (author)  baecker031 year ago

Good idea. Thanks for the comment! : )

Really great Instgructible and guide. THanks. :)

garagemonkeysan (author)  ColumbusCOOK1 year ago

You are welcome. : )

Kardolf1 year ago

This is a great Instructable. I've got two Kawell Slim 18w Flood Beam units that should work great for this.

garagemonkeysan (author)  Kardolf1 year ago

Great! : )

I just had another thought - you can get cheap UPS's (for PCs etc) that already switch over from mains to backup power automatically - you could fit that into the ammo case, cut the loud annoying buzzer off and use the buzzer voltage to drive your relay for the LED light. Achieve much the same thing, except that you don't need a separate charger and inverter. And if you replace the usually pathetic battery in those cheap UPS's with a larger capacity battery, you might get better run times too.

garagemonkeysan (author)  teddlesruss1 year ago

That's a good idea. Thanks! : )

MrMike1 year ago

Interesting and nicely written.

I see a couple of potential short comings; that 2 Amp LED assembly (27 Watts) on a 5 Amp-Hour battery may last 2 1/2 Hours at best, (perhaps that is enough for you) and the wall charger will supplement a bit if wall AC is available extending the operation, however that 400 Watt inverter (at full load) will draw ~35 Amps, giving you a run time ~ 8 to 12 minutes (again perhaps enough for your needs).

I'd recommend an auxiliary lower power LED set up to extend run time, and add a USB port (with a built in 5 VDC regulator) to charge a cell phone or other device.


PS - lead acid batteries have different 'float charge' needs. That is an AGM, (Absorbed Glass Mat), your 'typical' sealed battery will want to see a lower voltage than a flooded (vented) battery. Check the manufacturer specifications.

garagemonkeysan (author)  MrMike1 year ago

Hey, thanks for doing the analysis. I hadn't thought about running the numbers. I didn't buy the SLA for this particular use. I just had it so I used it. : )

I've run this type of float charger a SLA on another project. No problems. Some motorcycles use SLAs and I know these chargers are designed for motorcycles. But you are correct, check mfg specs.

Thanks again for the comment. : )

sparhawk71 year ago

i've had this in the back of my head fo awhile, glad to see some places to source parts! thanks!

garagemonkeysan (author)  sparhawk71 year ago

You're welcome. : )



How long does the fog light run off the battery before cutting out?

garagemonkeysan (author)  macjedimatt1 year ago

I never have ran it out yet but I've used it for a couple of hours with no problem. Thanks for the comment. : )

J,R,D, Ltd1 year ago

Very nice, looks awesome.

Did you know Tractor Supply Company used to sell a 12v 7.5Ah SLA battery for $20? Would have given you a little more power and saved some money, it is a bit bigger though, the same size as the average UPS battery. Maybe for the next revision.

garagemonkeysan (author)  J,R,D, Ltd1 year ago

Great. Yeah, had limited space for this project. Thanks! : )

muddog151 year ago
From you?
garagemonkeysan (author)  muddog151 year ago

Sorry not for sale. : )

Tanzer261 year ago

I'm wondering why not just a diode in the output of the charger, and power your relay off the charger output. Power goes out and relay kicks out, diode stops the battery powering the relay. I have one of those chargers and I don't think the voltage drop of a diode would affect it charging.

garagemonkeysan (author)  Tanzer261 year ago

Hi Tanzer26 -

Actually, I did try what you suggested. That was plan A. Unfortunately, it didn't work. Had to resort to Plan B, the relay circuit. : )


muddog151 year ago
How much to buy one?