Introduction: Jobsite Hotbox

About: Contractor by day, handy crafting putz by night

Being a contractor once the deep freeze comes to MN is not an easy change of season.

Besides pulling out all of the cold weather gear, boots, thermals, insulated bibs etc.... We also have to prepare all of our tools. One tool that gets most of the use is the cordless drill/impact. New Lithium Ion batteries do NOT like cold weather just like the person using them doesn't. So drills keeping their charge while outside is a challenge. And getting them to recharge is more of a challenge.

Normal cold weather (or hot weather also) when a battery dies, you place it on the charger and the red light flashes indication battery temperature is not good for charging. Summertime it's usually overheated, which can be cooled off easy before charging. But in winter it is a much harder ordeal to warm them up enough to charge.

Well With my Jobsite *Hotbox* it makes it easier on the batteries to start charging. And also keeps cell phones warm, caulking tubes too.

Step 1: Materials and Tools

First thing you need to find is an old cooler that you don't mind putting holes into.

Also you will need:

  1. Magnetic engine block heater (if local stores don't have them, Google search comes up with a bunch)
  2. Power strip
  3. Metal plate ( I used a mending plate ) can find these by joist hangers in big box stores
  4. 2x2 piece of wood long enough for two pieces the width of metal plate
  5. few screws ( length depends on lid thickness) and some fender washers


  1. Drill
  2. Reciprocating saw or dremel tool

Step 2: Metal Plate Location

First take your metal plate and place it on the lid in the best position possible for mounting. For me it was center, it had a little circle indent which worked great. every cooler is different. If need be, one of the sides of the cooler could work also, but then you loose space for tools.

Once the corners of plate are marked, measure and place a piece of 2x2 in the best location. Try to keep it as flat as possible. Doesn't need to be perfect, just flat for the metal to be attached to it. I made sure that holes on the plate would line up close to center of the 2x2's. I then marked the corners of the 2x2 on the lid for reference for drilling locations.

Step 3: Drilling the Lid and Mounting the Plate

Once you have your 2x2 location marked out find appropriate drill bit for the size screws you are using and drill 4 holes through the plastic lid. make sure you stay at least an inch, maybe more in from the ends of the 2x2's so they do not split when driving the screws into it.

Using a fender washer (the wider washer with smaller hole) mount the wood pieces with a screw that is long enough to go through the lid, but not stick out through the 2x2 on the underside. Don't over tighten the screws, the fender washer will help distribute the pressure and make it so the screw won't pop all the way through the lid.

Next after the 2x2's are mounted, using about a 1/2" screw, attach the metal plate to the wood pieces. Best to use 4 screws, one close to each corner.

Step 4: Power Strip

Lay your power strip into the cooler approximately where you'd like it to sit. Drape the cord over the corner you want to go to the power source and mark a line on each side of it. Using a saw or dremel, cut this channel out making sure you go deep enough so that the lid will go on all the way. another option is to drill a hole through the side of the cooler, but to fit a plug it'd be a pretty big heat escape if you didn't seal it up well.

Step 5: Plug and Go

Attach the magnet heater to the metal plate, plug it into power strip and turn everything on to test it out. If you don't feel heat, double check a fuse or circuit breaker on the power strip.

Plug in your chargers and you are set for 6 months of winter work ( and yes winter is 6 months in MN )

The other picture is my old box I built out of plywood and 1-1/2" rigid foam. It was getting too small for everything I needed to keep warm.

This box also helps with caulking tubes, cell phones (their batteries hate cold too) And can help keep morning coffee at least drinkable for a bit too !!

Hope you like, any questions leave a comment

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