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Cool Tools: CORDLESS SCREWDRIVER - Review

Scoring

Product Performed to Expectations: 8
Specifications were sufficient to design with: 8
Demo Software was of good quality: 10
Product was easy to use: 10
Support materials were available: 10
The price to performance ratio was good: 10
TotalScore: 56 / 60
  • RoadTest: Cool Tools: CORDLESS SCREWDRIVER
  • Buy Now
  • Evaluation Type: Workshop Tools
  • Was everything in the box required?: Yes
  • What were the biggest problems encountered?: The unit was designed to be sold in the UK so the charger had to be rebuilt for the US electrical system. Unit was not working when received so it had to be fixed.

  • Detailed Review:

    The Duratool 3.6 Volt cordless Screwdriver and 102 Piece Bit set is manufactured in China and sells for less than $30.00. I want to mention this up front so everyone can weigh any criticism that I may make against this tool properly. As an added bonus this is my first Road Test.

     

    The kit arrived in apparently good shape having been shipped the 500 km from Chicago to my front door.

     

     

    From this point on however things got interesting. The first small thing was that the case had been damaged slightly in transit. It was not visible until the wrapping was removed and will not affect operation or the function of the case.

     

     

    When I opened the case everything looked beautiful. The 102 bits and adapters that were included in the kit looked really nice and the arrangement and labeling immediately appealed to my sense of organization. I took the time to pull each bit from its holding spot and examine it. Each bit was labeled which was great for putting them back if more than one gets pulled out at the same time. The metal used to make the tips appeared to be a good grade of hardened steel. The foam of the box held the bits quite snugly so when I returned them to their positions I put them in more loosely so that a pliers would not be need to pull them out the next time they are needed. The adapters in the lower left corner are an extension and a hex to 1/4 square adapter so that the screwdriver can be used with 1/4 sockets. I tried several of the bits into the chuck of the screwdriver and found the retention to be nearly perfect. If the bits were held any more tightly they would not be removable with finger tips. One of my frustrations with tools like this is when the bit pulls out when the tip is being pulled from the screw. This is not likely to be a problem with this unit.

     

     

    I had noticed the next problem immediately but I had busied myself with the tips to give myself time to think. The adapter supplied had a UK style plug not the nice little style that I am used to.

     

     

    While this plug would never work on a regular basis we have our remedies in the shop and really this is what alligator clip jumpers are made for. The jury rigged power to the AC adapter was set up and the unit was on the charger. Unfortunately the manual had indicated that a Red LED charging indicator was suppose to light, but it didn't. The output of the adapter was checked and found to be 5.4 volts with the positive conductor in the center of the plug. While I went and read the Owners Manual I left the screwdriver plugged in.

     

    The owners manual is one of the best written manuals that I have seen for a Chinese manufactured item. I only found a couple mistakes and for the most part it was clear of clumsy wording or bad grammar. The manual was clear that the red light was suppose to light and a second green LED was suppose to signal full charge. The unit had now been on the charger for some time so I returned and checked it out to find there was still no Red LED light and the unit was still dead as a door nail. It was broken and my heart was happy as I like broken things.

     

    The case was opened after finding one addition case screw that was hidden under a black label.

     

    An inspection of the wiring and circuit boards showed no bad connections. The soldering of the surface mount components looked good enough under 7X loupe inspection. The area of the circuit where the battery connections attach to the operation trigger switch had a suspicious white crystallized material that reminded me of alkaline battery leakage. The battery in the unit was however clean with no sign that the leakage may have come from it. You can see the leakage at the left end of the board. I cleaned it off with a small flat screw driver and tooth brush. The circuit traces and solder joints below it all looked good.

     

     

    The next step in the process was to plug in the charger and start tracing voltages. At this point the battery itself had 0.6 volts which is way too low for a Li-ion battery. The power from the adapter was getting all the way to B772 transistor on the right center of the board but its output was comparable to the battery voltage. I once again inspected the circuit, flexed the circuit board and even hit it with a little coolant, all to not effect. Power was removed and I went to work with the analog ohmmeter. I like to use an analog ohmmeter when I am looking for shorts and circuit anomalies as it is much more intuitive than the digital meters. The transistor tested normal and a smaller transistor driving its base 2N7002 turned out to be an N Ch MOSFET which also tested OK. With no problem noted in the ohmmeter survey I went back to powered mode and decided to do an experiment whereby I jumpered across the emitter to collector of the transistor with a 10 Ohm 1/4 watt resistor. I held the resistor in my finger so that any sign of heat would prompt me to break the connection. I held this connection for about 10 seconds and when I looked up again I noticed that the RED charging LED had lit. I was surprised at this and reinspected the board to see what may have caused things to start working again.

     

    My knowledge of the charging circuits of LI-ion batteries is fairly weak so I did what I usually do when I have a question, consult the Oracle of element 14.

     

    Operation of simple Li-ion Battery Charge System

     

    The answers that I received from this post led me to believe that the charging circuit of the screwdriver had interpreted the extremely low voltage of the battery as a don't charge condition. My jumper had put enough charge into the battery to allow the charging circuit to recognize it and go back to work. I also learned that the battery was likely damaged to some extent by having been so thoroughly depleted.

     

    The charger was left on the screwdriver overnight and in the morning the Red LED had extinguished but there was No Green LED as indicated in the instructions. The battery test switch on the screwdriver showed a full charge and so I powered it up for a few seconds and then put it back on the charger. The Red LED came on for 45 seconds and went off. Since things seemed to be working better I decided to not worry about the Green indicator at this time and so I put the unit back together.

     

    My next project was to try to find a charger for the unit that I could plug into a US outlet. I found an old cell phone charger and modified it to fit the jack on the screwdriver. It had an output of 5.08 volts in contrast to the 5.4 volts supplied by the original charger. While my replacement charger would charge the screwdriver for some reason it would never push the internal charge circuit into turning off the Red LED. Back to the drawing board and this time I intend to transfer the UK chargers internals to a housing with a US plug.

     

    Since I am constantly stealing the circuits out of wall warts to use in my projects I had several open cases and the internals transferred very nicely with the strain relief even fitting the new case properly.

     

     

    With the original 5.4 volt supply back doing its job the Red LED once again turned off after a short period.

     

    With the battery fully charged I was finally ready for the acid test. I took a 2 inch sheet rock screw, inserted the proper #2 phillips bit into the Duratool Electric Screwdriver and proceeded to screw that baby an inch and a quarter into a piece of wood. You may be asking why I didn't go all the way. It was my intention but that was as far as the Duratool wanted to go. I checked the battery level indicators and they showed full charge, I tried again and the screw turned another 1/4 turn before stopping the motor. Perhaps it was a bad piece of wood or a mean screw? I took a small $40 Black and Decker similar electric screwdriver and promptly bottomed the screw and backed it out all the way. A second attempt with the Duratool gave the same results. Now a damaged battery can show a full voltage charge to a charge indicator and then show its bad internal resistance as soon as it is loaded up so the problem I am seeing might still be a damaged battery.

     

    I want to note that the trigger mechanism of this screw driver is very nice. It is a normally centered rocker switch so that if it is pulled at its top the driver turns the screw into the material and if the trigger is pulled towards its bottom the rotation is reversed and the screw is extracted from the material. This is an excellent feature and eliminates stopping and flipping a second switch to reverse directions.

     

    At this point however I am satisfied. In the part of the shop where I intend to use the Duratool I seldom have to have that much torque. The quality and selection of the bits are great and the Duratool is probably just as good as my Black and Decker if the battery wasn't compromised.

     

     

    I took a couple points off the rating system at the top of this report since, well, it wasn't perfect and would have been an inconvenience for anyone who didn't like broken things.

     

    I really enjoyed this Road Test. It was my first and it will probably be my last. I had the opportunity to learn more about Li-ion charging and the internals of UK wall warts as well as Chinese electric screwdrivers. I learned about the time and effort that gets put into road tests and it makes me really appreciate the guys on the forum who take on the large complicated equipment and do such a tremendous job.

     

    John


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