I have often found myself looking for a portable power supply that
- Can last a long time
- Can support a versatile range of accessories
- Doesn't require lots of additional cabling/batteries
I also happen to carry several power tools in my van that all run on the same battery system, as such I have now ended up with 12 batteries and 6 chargers. It was then that I had an idea to create a 12V accessory socket attachment to fit to my battery set. I mean I always have multiples with me, I always have them charged and they hold a pretty big charge.
WARNING: This project involves the following things that can hurt you: knives, drills, electricity, heat (soldering iron), etc. Please be careful(I wasn't at one point but you'll see that later.
Step 1: What You Will Need
- A power tool battery (obviously), I use Metabo tools and the batteries slot on, this makes mounting pretty easy, other batteries use a stalk, this would require a little more planning and design but would still work.
- A voltage regulator, I used an Orion DC/DC switchmode power supply, it takes in 18-35V DC and outputs 12V DC, the beauty of DC-DC is there are fewer losses than converting to AC, get one here
- A rocker switch
- A 12V accessory socket, I used an illuminated one to show when the power was on, get one here
- A project box, I like the aluminum ones, I got this in Maplin Electronics in their closing down sale but you can find one here
- Finally, a parts bin was salvaged from my workshop wall and sacrificed to the project gods.
I also used some solder, 1.5sq wire various crimp connectors, and some Gorilla glue.
All in it cost me about €80.
Step 2: Replace the Base
The project box for this project is made from aluminum and as we plan to protrude the electrodes for the battery through the case, this poses the issue of shorting the battery and potentially causing an explosion.
One side of the box slides out, I found that my parts storage bins are almost exactly as thick as the aluminum base and slid into place quite nicely.
I simply laid the lid on the base of the parts box and cut around it with a knife, the edges got a little cleanup with the drum sander on my Dremel.
Step 3: Prep the Power Supply
The power supply as it came was too large to fit inside my box so I removed the covers.
PLEASE PLEASE do not power up the power sully without the cover on, you may get a shock and the regulator gets very hot.
I removed the innards and glued them to the base, I also fitted a couple of little spacers underneath to make it sit level.
I kept the casing as it indicates which terminals are positive, negative and which are inputs and outputs, note the negative is common to both the input and output.
Step 4: Give It Switch
I wanted to put a switch on the device, that way I could leave it on a battery when not in use and not worry about the regulator self-discharging the battery.
I drilled out the case with a step drill and inserted the switch, I then soldered tail wires to the switch.
*Ultimately it turned out the switch was faulty and never turned on so it was by-passed later on, I now have to remove the unit from the battery when not in use.
Step 5: Mount the Outlet
I again used the step drill to drill for the accessory socket, it needed to be opened to 32mm and this is quite a catch on the small end plate from the box, it slipped from the vise and hit my hand twice so BE CAREFUL.
To fit the socket, I needed to remove the illuminated collar and slot that in first, the socket then slid in and clicked into place.
The light for the illumination ring was wired back to meet with the terminal connections on the socket. The positive (+) is the middle terminal and connects to the tip of the plug, the negative (-) goes to the shield.
Step 6: Add Battery Connectors
There needs to be a way to get power from the battery to the regulator.
On the power tools, this is a straight metal terminal that slides into the battery.The batteries are clearly marked for the function of each terminal (Metabo batteries have 6 terminals, we only need 2 and they are the outside terminals).
To achieve the connection, I cut 2 small slots in the bae corresponding to the locations of the battery terminals. I then pushed some square eye crimp terminals through and glued them in place.
Step 7: Quick Test
I connected everything up and connected on the battery (I know I said don't do this and its where I found out how hot the regulator gets!)
It also showed up the faulty switch so I cut the wires and by-passed it.
Step 8: Close It Up
I cleaned up all of the wirings and then fitted the base and the ends.
Everything screwed into place with the screws provided with the box.
Step 9: Add Mounting Strips
The box sits happily on top of the battery but it it got bumped it may fall off.
Call back the parts bin, the top of the boxes have a handy profile that fits into the mounting slots on the batteries.
I cut them from the bin with a knife, mounted the supply on top of the battery and pushed the strips in place, they were then glued in with hot glue.
Once the glue was set it was time for a quick test with the beacon from my van,
I can also run USB devices using the 12V -> USB adapter I use in the van, making it the mother of all USB power banks!
There are tonnes of 12 accessories you can now run wherever you want be it a job site, camping or during a power outage and it's small enough to drop into my toolbox.
What would you power with this?