Cordless/Corded Drill

This instructable may seem a little counter-intuitive, why would you take a cordless drill and put a cord on it?

Well I bought this ROK 14.4V cordless drill to use as a cheap screw gun about a year ago (I use my good 18V cordless to drill the holes). The drill came with 2 batteries and I have obviously favored one as it now only holds a charge for about 10 mins. The drill cost about 70 euro and I do like using it as its well balanced, however, I could not track down a replacement and a local tool center quoted 110 euro to rebuild so it would be cheaper to buy a new drill.

I have seen some tutorials on fully converting to corded but I still have one good battery and I also have a good corded drill so I came up with this. I use a mains voltage to DC converter and adapt the failed battery housing to supply the drill from the mains and I can still swap to the battery and go cordless when needed.

WARNING!!!!

THIS INSTRUCTABLE DEALS WITH MAINS AC POWER, THERE IS A RISK OF SHOCK RESULTING IN INJURY OR DEATH. PLEASE ONLY FOLLOW THESE INSTRUCTIONS IF YOU ARE COMPETITENT TO DO SO. ALSO THIS INSTRUCTABLE DEALS WITH MODIFICATION OF A POWER TOOL, THIS MAY RESULT IN DAMAGE TO THE TOOL AND WILL VOID ANY WARRANTY YOU MAY HAVE.

For this instructable I used:

• Cordless drill with dead battery
• 230AC -> 24DC power supply (10A)
• 2 pole MCB (6A)
• gG fuse holder and fuse (6A)
• Fibox enclosure
• DIN rail
• 16mm cable glands x3
• 4m 3 core 1.5mm sq cable
• Assorted ferrals and barrel crimps

As I said earlier, the drill is 14.4V. After measurement, I found that the drill draws 6A at full speed and no load.

This results in 14.4V x 6A = 86.4W

I had a spare 24V 10A power supply, using the adjustment I could dial this down to 22V, not really caring about the drill that much and knowing that they are usually fairly tolerant I tried it and there was no excessive heat or burning of the motor. I did not test the drill running continuously, this is used as a screw gun and is used in short bursts, there is no hammer action so I do not use with masonry. If you plan on running continuously then you need to better match the power supply to the drill.

The resultant current requirement is 86.4W/22V = 3.92A

I started by fitting 2 cable glands on the side of the box.

I cut and mounted some DIN rail inside and mounted the 6A MCB, power supply, and the fuse holder.

I wired the 230V AC supply through the MCB for mains protection and to provide isolation if needed.

From the 24V output, I wired the + though the fuse. In an ideal world, I would have used red/black 2 core for the DC, but all I had to hand was regular 3 core.

I started by removing the casing of the battery.

I noted that the battery holder retains the spring on the battery pack clip so I needed to keep that.

I removed the lithium cells and disposed of them in my companies battery recycling.

Be careful not to short batteries when removing them, wrap the terminals with tape before disposing to prevent fire risk.

The + and - terminals are clearly identified on the battery casing.

I drilled out the case and fitted a gland, then ran the cable through and connected on using barrel crimps.

I then tightened the gland and closed up the battery.

I happened to have a nice clear cover already fitted with a warning label to isolate the supply before opening the box.

I inserted a 6A fuse into the holder and closed it up, then put the lid in place.

Check out the video to see the drill in action.

I can now swap between mains and battery in a matter of second.

The drill is portable when required and when I'm near a mains outlet I never need to worry about running out of battery!