Cordless drill

A **cordless drill**  or **battery drill** is a portable power tool that operates on rechargeable batteries, usually **lithium-ion** technology. Its cordless design allows great freedom of movement, making it ideal for DIY, carpentry, assembly and professional use on construction sites.

## Features

- It works without a cable, powered by a rechargeable battery.
- Allows drilling, screwing and has percussion in some models
- Includes automatic or manual chuck.
- It has multiple torque positions.
- They usually incorporate an LED light, charge indicator and carrying case.

## Type according voltage

Cordless drills are classified by battery voltage, which determines their power and autonomy.

### 10–12V

Compact, lightweight models suitable for household or precision tasks.

- **Bosch PS31 10-12V **
- **Bosch GSR 12V-15**
- **Makita DF331DSAE**
- **Black+Decker BDCHD12S1**

### 14.4V

Balance between power and size. Still present in mid-ranges.

- **Bosch GSR 1440-LI**
- **Makita HP347D**
- **Makita DF347DWE**
- **Makita BL1430B** (compatible battery)

### 18–21 V

Professional range. High power for demanding jobs.

- **Bosch GSR 1800-LI**
- **Bosch GSB 18V-21**
- **Makita DHP453RFE**
- **DeWalt DCD776C3-QW**
- **Einhell TE-CD 18 Li-i**
- **Worx WX375 20V**

### 28V

Less common models aimed at industrial or high-performance tasks.

- Some Milwaukee and DeWalt models in industrial ranges.

## Technical comparison between models

They started out as low-power electric screwdrivers, but today they fill a very wide range.
|Brand|Model|Volts|Engine|Max. torque|Max RPM|Percussion|Drill chuck|Drilling capacity (Wood / Metal / Bricks)|
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|Bosch|GSB 18V-55|18V|Brushless|55 Nm|1,800|Yes|13 mm|35mm / 13mm / 13mm|
|Bosch|GSR 18V-110 C|18V|Brushless|110 Nm|2,100|No|13 mm|82mm / 13mm / —|
|Bosch|GSR 1800-LI|18V|With brushes|34 Nm|1,300|No|10mm|29mm / 10mm / —|
|Bosch|PS31|12V|With brushes|30 Nm|1,300|No|10mm|19mm / 10mm / —|
|Makita|DHP453RFE|18V|With brushes|42 Nm|1,300|Yes|13 mm|36mm / 13mm / 13mm|
|Makita|DF331DSAE|12V|With brushes|30 Nm|1,700|No|10mm|21mm / 10mm / —|
|Makita|HP347D|14.4V|With brushes|34 Nm|1,400|Yes|10mm|25mm / 10mm / 10mm|
|DeWalt|DCD796D2|18V|Brushless|70 Nm|2,000|Yes|13 mm|38mm / 13mm / 13mm|
|DeWalt|DCD710D2|10.8V|With brushes|24 Nm|1,500|No|10mm|20mm / 10mm / —|
|Einhell|TE-CD 18 Li-i|18V|Brushless|60 Nm|1,800|Yes|13 mm|38mm / 13mm / 13mm|
|Worx|WX375|20V|Brushless|60 Nm|1,600|Yes|13 mm|40mm / 13mm / 13mm|

## Battery pack technology

Battery packs require battery balancing, which is a technique that maximizes a battery's ability to have all of its energy available for use and increases battery longevity.  The battery regulator is typically a device built into the battery pack that performs battery balancing.  Most modern cordless drills use lithium-ion batteries that offer:

- Greater energy density.
- Less weight.
- Absence of memory defect.
- Fast charging and extended battery life.

|Manufacturer|Model|Voltage|Capacity (Ah)|BMS type|Observations|
| --- | --- | --- | --- | --- | --- |
|Bosch|PBA 12V 2.5Ah|12V|2.5|External|Home use, Power for All system|
|Bosch|GBA 18V 5.0Ah|18V|5.0|Internal|Professional, CoolPack technology|
|Bosch|ProCORE 18V 8.0Ah|18V|8.0|Internal|High energy density, intelligent BMS|
|Makita|BL1021B|12V|2.0|External|CXT series, compact|
|Makita|BL1850B|18V|5.0|Internal|LXT series, with load indicator|
|Makita|BL4040|40V|4.0|Internal|XGT series, digital battery-machine communication|
|DeWalt|DCB124|12V|3.0|External|XR Compact, light professional use|
|DeWalt|DCB184|18V|5.0|Internal|XR Li-Ion, compatible with the entire 18V range|
|DeWalt|DCB546|18V / 54V|6.0|Internal|FLEXVOLT, dual voltage, smart BMS|

## Internal architecture of battery packs

The nominal voltage of a battery pack is determined by the number of 3.7V cell subgroups connected in series. Each subgroup can consist of one or more cells in parallel, which increases the capacity (Ah) of the pack
|Rated voltage|No. of 3.7V subgroups in series|Example of models|BMS|Comment|
| --- | --- | --- | --- | --- |
|3.7V|1|USB Power Banks|Not required|The cells are in parallel; a 3.7 V → 5 V DC-DC converter is used|
|10.8–12V|3|Black&Decker BL1510, Makita BL1013, Bosch BAT411 (PS31)|External|2 intermediate sockets for BMS on the charger|
|14.4–16V|4|Makita BL1415G|External|3 intermediate sockets; BMS usually in the charger|
|18–21 V|5|Makita BL1850B, Bosch SM31 (GSR 1800-LI)|Internal|4 intermediate sockets; with integrated BMS|
The presence of intermediate taps in the pack connection allows the BMS (internal or located in the charger) to monitor and balance the state of charge of each group of cells. This balance is essential in series configurations, since the cells do not automatically balance as they do in parallel. Some low-cost designs use diodes to limit the imbalance between cells, although this technique offers limited protection and can reduce the useful life of the set.

## Power packs => % charge vs. Volts

|Loading|3.7V pack|10.1 V pack|14.8V pack|18V pack|21 V-pack|
| --- | --- | --- | --- | --- | --- |
|100%|4.2V|12.6V|16.8V|21.0V|25.2V|
|75%|3.9V|11.7V|15.6V|19.5V|23.1V|
|50%|3.7V|10.8V|14.4V|18.0V|21.0V|
|25%|3.5V|10.0V|13.2V|16.5V|18.9V|

## Applications

- Furniture assembly.
- Installation of shelves, curtains, supports.
- Drilling in wood, metal, plastic and masonry (models with percussion).

## Security

- Ergonomic and non-slip handle.
- Overload and overheating protection.
- Electronic brake on some models.
- LED light for dark areas.

## Bibliography

- Bell, Brian. Farm Machinery. Old Pond Books, 2010-02-12. .
- Peterson, Chris. Black & Decker Readymade Home Furniture: Easy Building Projects Made from Off-the-Shelf Items. Cool Springs Press, 2018-12-25. .