Battery design of the battery tool

All the battery packs that are used to power a hand-held power tool are arranged in approximately the same way. Inside the block there are several standard elements — the so-called "cans". For example, in lithium-ion batteries, "banks" of the 18650 standard with a nominal voltage of 3.6 V and high current output are used as cells, and in nickel-cadmium batteries, 1.2 V cells are used.

The design of a modern battery for a rechargeable tool.

By changing the number of cells and the way they are connected to each other (in series or in parallel), you can get batteries with different characteristics. They will differ in operating voltage (in fact, blocks with a voltage from 10.8 V to 24 V are used) and capacity (batteries of hand-held power tools have a capacity from 1 Ah to 12 Ah). Some manufacturers (for example, DeWalt) even produce convertible battery systems, in which the order of connection of the "cans" through the terminals automatically changes depending on which instrument the battery is connected to: 18-volt or 54-volt.

Methods of connecting "cans" in batteries using the example of DeWalt Flexvolt batteries.

The relationship between the voltage and the power of the screwdriver: is there or not?

It is known from the course of electrical engineering that the power of an electric motor is directly proportional to the voltage that is applied to the windings. From this we can conclude that the more volts in the battery, the more powerful the screwdriver. Is it true? There is a whole gulf between bare theory and practice. In fact, the power of the battery tool is also affected:

  • discharge current — cheap high–current "banks" give up to 15 A, and the current output of the elements that make up the batteries of high-quality screwdrivers reaches 25 – 30 amperes, necessary to tighten the screw until it stops or tear off the stuck nut;
  • the design of the gearbox — the gear ratio of the gear mechanism and the strength of the gears that are inside it determine whether the tool will be able to develop a large torque and cope with tasks that require significant effort.;
  • engine quality — good motors that can withstand high currents and loads without damage are much more expensive than simple electric motors from cheap screwdrivers;
  • electronics settings — the control electronics board, which regulates the current output, protects the motor from overloads and prevents excessive heating of the battery cells, imposes restrictions on the capabilities of the tool.
Cordless screwdrivers with batteries up to 12V

Considering the above, it is easy to conclude that the voltage of the battery pack is far from the only factor affecting the output power of the power tool. Therefore, it often happens that a "branded" 12-volt screwdriver in fact turns out to be much more powerful and useful in operation than a cheap 18-volt "Chinese".

The Makita DF330DWE screwdriver and its Chinese clone are identical in voltage and design, but differ significantly in price and characteristics.

Classes of screwdrivers by battery voltage

After a short excursion into the design of batteries and the basics of electrical engineering, it's time to consider battery screwdrivers in more detail. They are equipped with batteries with voltage:

  • 10.8 V (12 V) — a tool of this class is compact in size and light in weight due to small batteries. It is used mainly for installation and assembly work;
  • 14.4 B is an intermediate class that occupies a place between a compact tool and high—performance models. Only a few manufacturers produce such screwdrivers;
  • 18 V (20 V) is the most popular segment, there is a huge selection of models with different parameters and characteristics. Screwdrivers of this class are in the greatest demand, because they are more versatile than others;
  • 24 V — models with battery packs of this voltage are still few, despite the fact that the increased voltage allows you to improve the characteristics of the tool.

Separately, it is worth mentioning the difference in voltage measurement methods. Japanese and European manufacturers, guided by the rules of the EPTA (European Power Tools Association), indicate the rated voltage, and American manufacturers indicate the full charge voltage. Therefore, the same instrument in Europe is labeled "10.8 V", and overseas — "12 V". The same applies to screwdrivers with 18 V and 20 V batteries — this is a tool of the same class, just the voltage is measured in different ways.

Cordless screwdrivers with batteries up to 18-20 V

The effect of battery voltage on other characteristics of the screwdriver

All parameters of the battery tool are "linked" to each other. The greater the voltage and capacity of the battery, the greater its weight and size. For example, the battery of a 10.8-volt screwdriver can consist of only three lithium-ion "cans" of 3.6 V each, and for an 18-volt battery they need at least five (in fact, there are usually more "cans" inside the battery to increase its capacity). In addition, increased voltage requires a more powerful electric motor and a more massive gearbox, and this also leads to an increase in the weight and size of the tool. Therefore, to work in a confined space or overhead, it is worth buying a screwdriver with a 10.8 V battery, because it will be more compact and lightweight. And 18-volt models are better taken by those who have enough space in the workplace to use a larger tool.

The difference in size between Bosch 18-volt batteries with a capacity of 4 Ah, 8 Ah and 12 Ah.

There are other nuances that should be taken into account when choosing a screwdriver. For example, the design of the engine is of great importance. Modern tools with brushless motors, even at a voltage of 10.8 V, have more power and torque than many 18-volt models with conventional collector motors, thanks to reduced power consumption and less friction and heating losses.

Compatibility of batteries with other types of tools

The cost of the battery (especially when it comes to high-capacity battery packs) often reaches half the price of the tool itself. Therefore, you should immediately think about how to choose a screwdriver in such a way as to save on batteries later.

Fortunately, power tool manufacturers have already taken care of this. Many of them build a whole "ecosystem" of different types of tools around one type of battery. That is, the same battery can fit a screwdriver, drill, grinder, electric jigsaw, renovator and other devices. Some companies even produce powerful punchers, concrete cutters, lawn mowers and electric bicycles powered by one, two or three standard batteries from a screwdriver. At Milwaukee, for example, the "ecosystem" of an 18-volt instrument consists of more than 200 models.

More than 200 models of Milwaukee tools and garden equipment can be powered by the same 18 V battery.

Conclusions

It is impossible to unequivocally answer the question of which screwdriver is better: 12 V, 18 V or 24 V. Each of them is a kind of compromise between power, operating time on a single charge, size and weight. Although 18-volt models are the most popular, it does not always make sense to overpay for them. It is better to choose a tool based on what kind of work you will do with it. A screwdriver is your main assistant, and you work all day long? In this case, it is worth buying a high-quality 18-volt model with a capacious battery and a spare battery. Do you use a screwdriver as an auxiliary tool for individual operations that do not require special power? Then an inexpensive 12-volt device from some low-cost brand will be just right.