Replacing Batteries In A Screwdriver With Lithium 18650

Replacing Batteries In A Screwdriver With Lithium 18650

Lithium-ion batteries are rightfully considered the best power sources for modern gadgets and power tools. They provide increased power, have a large capacity, which ensures long-term autonomous operation of certain devices. That is why many screwdriver owners are trying to install Li-ion batteries instead of cadmium or metal hydride. Is it possible to do this without harming the instrument? It is in this matter that we will understand below.

Advantages and disadvantages of replacing batteries

If you have an expensive Bosch screwdriver or a powerful Japanese Makita, you should think carefully before performing such a replacement. Despite all the advantages of Li-ion power sources, there is a risk of failure of both the battery itself and the power tool. Therefore, for starters, you need to look at the pros and cons that replacement will entail.

As mentioned above, lithium-ion banks operate much longer in offline mode than the rest. In addition, they have several additional benefits:

  1. Fast charge. If the Ni-Cd battery needs to be charged for about 7 hours, then only 60 minutes will be enough for Li-ion.
  2. High energy density provides low battery weight, which will increase the usability of a screwdriver.
  3. Due to the lack of a memory effect, Li-ion batteries can be charged without the need for a complete discharge.
  4. lithium-ion batteries provide more powerful screwdriver performance.
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In addition to the undeniable advantages, there are also a number of disadvantages of remaking a screwdriver for lithium-ion batteries:

  • possible compatibility problems associated with the fact that the voltage of lithium power supplies is three times higher than the same indicator for cadmium and metal hydride batteries (3.6 vs 1.2 V).
  • The need to install a controller that will monitor the level of charge. This step cannot be avoided, since Li-ion power sources cannot be discharged below 2.7 V and charged over 4.2 V.
  • The size of the 18650 batteries is larger than that of cadmium cells. Therefore, they may simply not fit in the battery pack.
  • The high price of lithium-ion cans.
  • The need to use a 18 V PSU instead of a 12 V power supply
  • Unstable operation at low air temperature. If you expect to use a screwdriver on the street in the winter, serious problems with autonomous operation can arise.

Video: Replacing Batteries In A Screwdriver With Lithium 18650


You made a firm decision, and no arguments against can not stop you? Then you can start the replacement, which is carried out in several stages.

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Workflow for installing lithium batteries in a screwdriver

First, we take apart the battery pack, remove the cadmium batteries from it, and ruthlessly bite them off the connector. In addition, we remove the temperature sensor, which is designed to protect the cans from overheating. Next, the replacement of cadmium batteries in a screwdriver with lithium power supplies is performed as follows:

  1. We select a controller that will automatically cut off the current supply when the voltage reaches 4.2 V. Or signal the need for charging if it drops to 2.7 V. Buy a controller with a thermocouple, which will additionally eliminate the risk of overheating.
  2. Consistently connect the batteries to each other.
  3. We connect the controller to the resulting assembly and connect the balancing points to a special connector.
  4. Solder the positive and negative output.
  5. We put the batteries in the battery pack.

As you can see, the procedure is quite simple and in the presence of experience takes no more than 1-2 hours. If you first decided to delve into modern electronics, then the following tips on connecting batteries to each other are very useful:

  • Assembly is made using thin metal strips. Without further ado, you can simply cut them out of a regular tin can.
  • The surface of the connection strip and battery is treated with alcohol to ensure good contact in the future.
  • The connection of the cans with a metal strip is carried out by resistance welding. The thing is that Li-ion batteries can inadequately respond to prolonged heat exposure with a soldering iron and simply explode. In contact welding, heating lasts only a few seconds, so such problems are completely eliminated.
  • So that the plate does not fall off from the slightest mechanical impact, several point connections are required.
  • The welding pulse must be set in such a way as to prevent overheating of the batteries.
  • The resulting kit must be firmly connected with electrical tape or tape.
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Finally, do not forget about the strict observance of the polarity of the interconnected batteries. Errors are unlikely to cause an emergency, but the assembly will definitely not be charged.