What battery for a screwdriver is better to choose

The cordless screwdriver is an incredibly convenient and popular tool. Its ability to operate independently from the power grid makes it highly mobile and enables users to complete tasks in hard-to-reach locations. However, despite its many advantages, the rechargeable battery is the vulnerable component of the screwdriver. Therefore, it is crucial to have a solid understanding of the various types of batteries available, their distinctions, and the advantages and disadvantages associated with each type, when selecting a power tool.

Varieties of batteries for a screwdriver

• nickel-cadmium (NiCd);
• nickel-metal hydride (NiMH);
• lithium-ion (Li-Ion).

Nickel-cadmium batteries

This type of battery is one of the most commonly used, even though they have been around for over 100 years. NiCd batteries are known for their good capacity and affordable price.

NiCd batteries offer the following benefits:

1. Durability. When used correctly, these batteries can last for 8-10 years.
2. Ability to operate at low temperatures. The battery’s charge doesn’t significantly decrease, allowing for outdoor use in winter.
3. High level of reliability and ability to withstand various working conditions.
4. The battery can handle a thousand charge-discharge cycles.
5. The battery can be stored for long periods of time in a discharged state.

Due to the fact that NiCd batteries do not have a fear of being completely discharged, you are able to continue using the tool until it completely stops functioning, which means the battery is deeply discharged. It is only at this point that you can safely recharge it without worrying about the battery’s capacity decreasing.

However, there are drawbacks to nickel-cadmium batteries. The toxic nature of the battery’s internal components creates challenges when it comes to disposal.

For environmental reasons, the use of nickel-cadmium batteries is prohibited in certain European countries.

NiMH rechargeable batteries

NiMH batteries were designed to address the drawbacks of nickel-cadmium batteries. Some notable advantages of NiMH batteries are:

• They have a compact and lightweight design;
• They have low toxicity levels;
• They exhibit a weak "memory effect";
• They boast high capacity characteristics;
• They are resistant to physical damage;
• They can endure a larger number of charge-discharge cycles (up to 1500).

On the other hand, NiMH batteries have their share of disadvantages:

• They are not suitable for use in negative ambient temperatures;
• They tend to discharge quickly;
• They have a shorter lifespan when compared to NiCd batteries;
• They are relatively expensive;
• They require a long time to charge;
• They cannot withstand deep discharge cycles.

Therefore, despite being created as a rival to NiCd batteries, NiMH batteries are considerably less efficient than their counterparts.

Li-Ion batteries

When it comes to batteries, Li-Ion batteries stand out from the rest. One of the major advantages of lithium-ion batteries is that they do not suffer from the "memory effect" that other types of batteries do. Additionally, Li-Ion batteries can be recharged at any point of discharge without worrying about losing capacity. Even at low battery charge levels, Li-Ion batteries do not lose power. Furthermore, these batteries have an impressive lifespan of 5-8 years and are known for their low self-discharge rate. Another advantage of Li-Ion batteries is that they require minimal charging time. Moreover, they do not contain any toxic elements, making them an environmentally-friendly choice. Lastly, despite their small size, Li-Ion batteries pack a powerful punch.

The downsides of lithium-ion batteries include:

• Being sensitive to shocks, which can cause them to explode when subjected to strong impacts;
• Being intolerant to complete discharge and overcharging, leading to battery failure;
• Discharging rapidly at low temperatures;
• Having a high price;
• Having a shorter service life compared to nickel-cadmium batteries.

It is challenging to determine definitively which battery is superior. It primarily depends on the intended purpose of the screwdriver. For home use, where the tool is infrequently used with long breaks in between, it is advisable to choose a tool with a nickel-cadmium battery.

This can be explained by the fact that when stored for extended periods without recharging, the NiCd battery retains its properties, provided it is discharged completely.

How you can replace the "original" battery in your screwdriver

If your screwdriver batteries have reached the end of their lifespan, it’s simple to replace them. Battery interchangeability exists, meaning that you can find batteries from the PowerPlant brand that are compatible with most popular power tool brands. These batteries are significantly cheaper than the original ones and function effectively.

If you’re not interested in this alternative, you have the option to replace the power cells in the device with new ones. To accomplish this, you’ll need to dismantle the battery pack and remove its constituent elements.

Replacing the batteries with similar ones

There are screws on certain blocks that need to be unscrewed, but the majority of battery packs do not have self-tapping screws due to being glued together. To open a block of this kind, it is necessary to delicately insert a screwdriver into the area where the glue is located (indicated by an arrow in the photo) and apply slight pressure to separate the case walls. The same procedure should be repeated along the entire periphery.

Once you have opened the device, the batteries will become visible.

In order to proceed, it is important to examine the markings on the cells, record them, and select matching replacements from an online retailer. Once you have acquired the new batteries, it is necessary to solder them and reinstall them into the case. Soldering the batteries requires a soldering iron, flux (either alcohol on rosin or soldering acid), and tin. Several important details should be considered during the soldering process:

1. It is crucial to solder quickly to prevent the battery from overheating and potentially becoming damaged.
2. When making connections, it is imperative to use the "native" plates that were desoldered from the old batteries, as they possess the appropriate cross-section and resistance.
3. Once all the cells are connected, it is important to ensure that the potentials on all the batteries are equalized, as they may be different initially.
4. To achieve this, perform a charge-discharge cycle: connect the charger to the battery overnight, then allow it to cool down for a day. Then, measure the output voltage on each cell individually. If everything is working properly, all batteries should have a similar voltage reading, within a 1.3V range.
5. Next, it is necessary to discharge the battery by inserting it into the screwdriver and loading the screwdriver to its maximum capacity. It is important to avoid overheating the tool’s motor during this process. Afterwards, give the battery a short break.
6. Repeat the full charge and full discharge procedure two more times to ensure optimal battery performance.

Replacement with lithium batteries

Replacing NiCd cells with Li-Ion cells is a straightforward process. As we learned in school, when batteries are connected in series, their voltage levels add together. For instance, if your screwdriver runs on a 14.4 V battery, it can be substituted with four 3.3 V lithium-ion batteries. This total voltage will be sufficient since lithium batteries experience minimal voltage drop when starting the device.

It is advisable to purchase batteries from reputable manufacturers, such as Sistem A123. This company offers a LiFePO4 battery with a capacity of 2400 mAh, which is sufficient for the proper functioning of your screwdriver. If you choose to buy batteries online, you can get them at a cheaper price – around 900 rubles for a pack of 3.

When making battery purchases, it is important to check if there are copper strips on the battery contacts. Having these strips makes the soldering process much easier.

Additionally, it is recommended to use soldering acid instead of alcohol flux. This will help minimize the risk of overheating the batteries. It is also important to have a soldering iron with a power of 65 W.

If you want to learn more about the process of replacing batteries with lithium batteries, you can watch this informative video.

Charger for a screwdriver battery with your own hands

If your screwdriver charger is not functioning properly or if you have modified the tool’s battery by replacing NiCd batteries with Li-Ion cells, you will need to purchase a new charger. The diagram below depicts a charger that can deliver a charging current suitable for any type of battery.

This current generator is based on transistor VT2 and is powered by a rectifier bridge. To achieve the necessary output voltage, a step-down transformer is connected to the bridge. It is important to use a transformer with sufficient capacity to prevent overheating and ensure continuous operation without burning out. The output voltage from the transformer should not exceed 27 V.

Resistor R1 is responsible for regulating the charging current (the screwdriver battery should be connected). It is important for the charging current to remain constant throughout the entire process. Resistor R3 is used to limit the maximum current. The LED VD6 will be illuminated during the charging process and will start to fade as the process nears completion until it goes out completely.

Accuracy and control of the temperature and voltage are crucial for ensuring optimal performance of lithium-ion batteries.

All the components of the electronic circuit are mounted on a printed circuit board (PCB) made of textolite, which is coated with a layer of copper foil. The diodes mentioned in the circuit can be substituted with diodes sourced from old radio equipment, such as KD202 or D242. It is important to arrange the components on the PCB in a manner that avoids any overlaps. While a high component density is not necessary, it is recommended to leave a 3-5 mm gap between them to simplify the soldering process. Additionally, it is essential to secure the transistor on a heatsink with a minimum area of 20-50 cm².

To enclose the circuit, you will need to create a case that matches the size of the PCB (plastic can be used), and a glue gun can be utilized for this purpose. The complete list of required radio parts is presented in the table below.

If you follow this diagram and put together the charger, you will have a trustworthy, straightforward, and cost-effective tool for your screwdriver.