Electric screwdrivers, drills are of two types: working from a mains power source and from a battery. Both types have advantages and disadvantages. To use a network screwdriver, you have to pull the cable to the place of work, which is not always convenient and sometimes very dangerous (for example, if you have to work at a considerable height). For the battery type, the main drawback is frequent restoration of the screwdriver battery.
Device network screwdriver.
Why the battery does not hold charge
At first glance it may seem that this inconvenience is not so significant - it is enough to buy a new battery for the screwdriver, replace the shrunk with it and continue to use the tool further. But the snag is that almost every model, not to mention the trademarks, has its own battery, and the tool will not work with other brands. Yes, and the cost of the battery in different models of the screwdriver ranges from 60 to 70% of the initial cost of the tool. If we consider that the battery life even with extremely proper operation and storage is no more than 3-4 years, and in fact no more than 2 years, then such a replacement will cost the owner a considerable penny.
Different brands of screwdrivers use different types of batteries. Battery can be:
- nickel cadmium;
- nickel metal hydride;
- lithium-ion, or colloquially lithium.
Scheme of the device cordless screwdriver.
The loss of capacity of the screwdriver's battery is an inevitable process, regardless of the type of battery, and it can only be slowed down, but not avoided. It depends on the number of charges used and how the instrument is stored. Simply put, the more intensively the screwdriver is used, the faster its rechargeable battery sits down. But even in rarely used tools, the battery spontaneously reduces its capacity (especially if the owner keeps it discharged), decreasing every month (depending on the type of battery) by 3-4% of its original capacity.
The direct cause of the loss of battery capacity is oxidation inside the battery cell, which is scientifically called suphalting. If the battery is disassembled, a yellow-white powder can be seen on the surface of the elements damaged by sulfation. It is clear that such elements cannot work normally.
Determining whether a battery is losing capacity or not can be done without disassembling it, especially since most modern batteries for screwdrivers are considered as non-separable units. For such a test, even special devices are not needed, simply lay your hand on the battery while charging and hold it a little. If the battery is in good condition, it heats up to about 30 ° C, and the hand will hardly feel such heating, but if the battery capacity has decreased, the heating will be stronger - 50-60 ° C, and the hand will easily feel it.Back to table of contents
What is a "memory charge"
Diagram of the device lithium-ion battery for the screwdriver.
The main thing you need to pay attention to when buying a screwdriver is the voltage and capacity of its battery. For most of these tools, the capacity does not exceed 2.7A / h. Such tools are charged from a normal household network with a voltage of 220V, for which a charger is included with the instrument. The voltage range in different models ranges from 6 to 22 V. A fully discharged battery takes time to charge an average of 5-6 hours.
According to their power screwdrivers can be divided into professional, semi-professional and domestic. The most powerful and durable - professional, but they are also the most expensive. And the most popular (they are the cheapest) - household, equipped mainly with one or two nickel-cadmium batteries.
The main problem of these batteries is the so-called memory effect of their charge. For semi-professional tools, equipped mainly with nickel-metal hydride batteries, this problem is not so acute, and for professional tools with lithium-ion batteries, this problem practically does not arise.
The “memory effect” occurs when the capacity that is not completely discharged is not charged again, but is not fully charged again. In this case, the battery simply ceases to “understand” how full its charge is. If the reason for the drop in battery power in this, then eliminate it is relatively simple. First you need to disassemble the battery pack, detect undercharged cells in it and “overclock” them - charge them with more current than they should according to the instructions, then fully discharge and recharge them again, but not at full capacity. If the electrolyte from the battery does not evaporate, then the chances of successful restoration of the screwdriver battery in this case are very decent.Back to table of contents
Preparing for recovery operation
Screwdriver battery connection diagram.
Before you restore the battery, you need at least within the school curriculum to figure out what electricity is and how it works in batteries.
Also to perform the recovery will need tools and materials:
- soldering iron;
- tin with the addition of low-corrosion flux.
To restore the lost battery power of the screwdriver, you need to have on hand another, "donor", battery.
Therefore, it is best when buying a tool to choose a model that comes with a second rechargeable battery.
Although if there is no second “native” battery, you can use the old battery from another screwdriver, if the batteries of both tools are of the same type. The internal structure of nickel-cadmium batteries is made using a single technology, therefore it allows changing some internal elements.
Before restoring the battery of the screwdriver, you first need to charge both batteries to the maximum, keeping the tools on charge for at least 6 hours each. Then, disconnecting from charging, disconnect the recoverable battery from the instrument and carefully remove the plastic cover from it. No company has provided tools for such an operation, so you have to act with what you have at hand: a wide screwdriver or a knife with a strong, solid blade.
The composition of the battery.
It is necessary to perform this operation with extreme caution and care so as not to damage the cover and, if possible, to keep its clamps intact. Although the latter is rarely possible, and later, when reassembling the block, the lid has to be fixed with glue “Moment”, “Secunda” or others like them.
Nickel-cadmium batteries consist of individual elements - "cans", each of which has a nominal voltage of 1.2 V and an energy capacity of 1200-1500 mA / h. The total power of the battery provides a different number of cells inside the battery. So, in the battery with a capacity of 9.6 V there will be 8 “cans”, 12 V -10, 14.4 V - 12, etc.
Contrary to the popular opinion of the ignorant inhabitants, the battery is very rarely discharged to zero, and the loss of its power provoke individual damaged cells. It is this circumstance that allows restoring "dead" batteries.Back to table of contents
The order of recovery steps
To identify damaged elements, it is best to use a tester, checking with it all the "banks" in the recoverable battery. In working cans, the voltage will approach the nominal value of 1.2 V. In the case of inoperative elements, this indicator will approach zero. Defective jars must be marked with a marker in order to replace them later.
Then the same procedure must be done with the battery "donor". The only thing that there is no need to check all the "banks", it is enough to find the necessary to replace the number of working elements, which also need to be marked with a marker.
Battery screwdriver disassembled.
After that, from the recoverable battery, you need to remove the damaged elements, and from the "donor" - the necessary number of workers, soldering them into the first battery in place of the damaged ones. Soldering needs to be done carefully, it is imperative for this work to use tin with low corrosion flux. The assembly welded together is inserted into the battery case.
And the final touch in restoring battery health is the operation of charge equalization, a kind of "grinding" of elements from two sets. It is performed simply: first, the assembled battery must be charged to the eyeballs, and then completely discharge.
On charging, the battery needs to be kept for 10-12 hours, not 5-6, as usual, and after charging you need to wait 1-2 hours before turning on the battery for discharging. If you turn it on immediately, the soldered “banks” heated during charging will heat up even more and may fall off. You need to discharge the charged battery completely, keeping the tool turned on until it refuses to work. Performing such an operation 3-4 times, you completely erase the old "battery memory".
Properly restored battery with proper care and operation will be able to last long enough. You should not worry if its power drops noticeably on the first day of work. This feature is inherent in almost all nickel-cadmium batteries - on the first day of work, a sharp, up to 10%, loss of charge, but later these losses will be only 2-3% per month.
So if you need to restore the battery of the screwdriver, then arm yourself with the necessary knowledge and tools, and - good luck!