Power supply to run cordless drill

It is a waste of money buying those very cheap Made-in-China dry cells and batteries as they don't last as long as the branded cells. I have  used those AA dry cells in clocks . And they last for a short period. The power level in them drained out very quickly. They are cheap but I have to buy more of them. So now I avoid buying the cheap cells .

-If you have to replace your car battery do not throw away the old one as it still retains a charge that is sufficient to operate a 12 volt fluorescent light ,12volt pcb drill and even a simple house alarm. The battery can be connected to a trickle charger to maintain a reasonable electrical charge. A plug in 12volt dc converter can be used as a trickle charger. The old battery is not totally dead yetbut in it there isn't enough power to turn the starter.

Cordless drills are designed to work at different dc voltages depending on the models. They are powered by batteries supplying  9, 12, 14 , 18 and 24 volts dc. There are also drill  that work on 5 volts supply but they are only commonly  used for  light duty power screwdrivers,

Two commonly used drills are those powered by either 9 volt or 12 volt rechargeable batteries. The battery do not last the whole life of a drill. Once it cannot be recharged anymore it has to be replaced. A replacement battery is not cheap. It can cost more than than a new drill with one or two batteries. If the drill is an inexpensive nonbranded model it is unreasonable to buy a new battery.

I never had an expensive cordless drill in my workshop. The first cordless drill I had was ,made in China . It served me for a few months before the motor went dead. Then a friend gave me a cheap drill without the battery. I made a power supply for it and  used it for  driving screws into wood . A variable speed electric drill would not drive screws  as efficiently as a cordless drill with many torque settings.

The donated drill used a 12vdc supply. Initially I used a 12v car battery as the power supply . The car battery did not store enough power to start my car but it had more than enough juice to drive the drill as the drill will work with lower current. To make sure the car battery survive I connected it to a trickle charger when it was not used as a power supply.. But no battery could last forever. Eventually it conked out and I had to get power from a power supply. source.

I had a few step down transformers salvaged from other dead electronic equipment. I constructed simple dc  power  supplies using these transformers. I found that those with current output of 1000mA was too weak to  drive the drill motor. The power supplies with 1500 mA and above were ok . But those with 2000mA and above were good. Actually I could buy a suitable power supply but I had limited cash to spend. All my power supplies were unregulated. I found that the drills could run on half wave dc without problem . As I had no transformers with center tap secondary winding I used  bridge rectifiers sometimes to get  soother outputs.

Cordless PS

Power supply circuits for cordless drill.  

To make a 12vdc power supply the step down transformer should have at least 18v or 15v output as two  rectifiers will consumed about two volts.

Some drills used 9.5V batteries. I did not have any 9.5 V dc power supply I used the 12vdc supply to operate the drill which I had. I connected two In4007 rectifiers in series with the output to reduce the voltage to about 10 volts. It did not overheat as the drill  was normally on for brief periods . I only used all the "cordless drill" for driving screws .

This ps could not drive a 12v or a 9V drill. I use. The PS looked battered because I used an old casing.

This is a 9vdc power supply.

Here is a 12vdc power supply circuit. 
I used a transformer from an old radio set. A new transformer was expensive. Printer power supplies could not be used as their current output is low.

Another drill power supply circuit


This is the first drill which I still use . It is now more than three years old . It is still working well.

The output leads were connected to the battery terminals inside the drill body. The positive wire was connected to the positive terminal.

To secure the leads I packed styro foam  into the  battery compartment. I cut the foam slightly larger than the battery compartment and pressed it into the battery space.

A 14V drill. . I made another power supply for this 14v drill . I found that this drill could operate on 12v but it became less powerful.



Instead of opening the drill casing to connect the leads I used the two cells from this old drill. The battery had spring contacts stil attached to them. I sooldered the leads to the contact springs and pushed the assembly back into the battery compartment. This was much easier than soldering to the contacts inside the drill.

The disadvantage of operating a cordless drill with a power supply is that the drill is no longer cordless. The advantage is that you can continue using the drill at the workbench.

Go back to Listing 

Woodwork    Electronics    My Blog    Plus    About me