To assemble a simple battery-powered circuit, we have to resort to various tricks to ensure that the wires fit tightly to the poles of the battery itself. Some people make do with electrical tape and adhesive tape, others come up with various kinds of clamping devices. But the contact in this case will be imperfect, which ultimately affects the performance of the assembled circuit. Often the contact disappears or becomes loose, and the device works intermittently. To avoid this, it is best to simply solder the wires to the poles. In our article we will tell you how to solder wires to a battery so that the contact is perfect.
The simplest battery-powered device is an ordinary electromagnet. Using his example, we will check the performance of our student soldering. We take an ordinary nail, for example a weave, and wrap copper wire around it in dense rows. We insulate the turns on top with electrical tape. The electromagnet is ready. Now all that remains is to power the device from the battery.
Of course, you can simply press the wires at each end of the battery, and the device will start working. But it is inconvenient to use. Therefore, it is best to ensure constant contact of the wires with the power source. This can be done by adding an ordinary switch (toggle switch) to the network and soldering the wires directly to the battery poles. The device will become more reliable, it will be more convenient to use, and if it is not needed, you can always turn it off by opening the circuit using the switch so that the battery does not run out. But how to solder the wires to the battery so that they do not fall off after five minutes of using the device?
In order to reliably solder wires to the battery poles, you need the necessary set of tools. Since soldering a wire to a battery is a more complicated task than simply soldering a pair of copper wires together, we will do everything exactly with the instructions below. In the meantime, let's prepare everything you need:
So, how to solder wires to a 1.5V battery? This task is not difficult if everything you need is already at hand. We proceed according to the following instructions:
That's it, the wires are properly soldered to the battery.
How to solder a wire to a Krona battery? Here, soldering is carried out almost in the same way as in the case of a conventional battery. The only difference is that in the Krona battery the 9V plus and minus are located side by side on one top side of the battery. The nuances are as follows:
In general, the whole process is similar to the previous one. We treat the contacts and edges of the wires with acid (or tin in the case of rosin), press the wires to the contacts, take a little solder with a soldering iron and solder them. The process is complete.
It is even easier to solder wires to such batteries. They have flat, folding contacts that can be easily tinned. And soldering to them is easier and faster. The main thing is not to move the wires during the soldering process. Otherwise they will simply come off.
Here you can not hold the wire at all, but wrap it around the plane of the contact strip. And then, having collected tin with a soldering iron, carry out soldering.
It is better not to solder batteries, but to make a special container for them, in which the contacts of the elements will be in close contact with the polar contacts of the container. The material of the batteries consists of alloys that are even worse for soldering than conventional lithium ones. But if you really need it, then soldering is carried out as in the case of a regular 1.5 V battery, just use flux and not rosin. Plus, soldering should be done as quickly as possible, keeping the contact of the soldering iron to the poles to a minimum, since such batteries are afraid of overheating.
Of the two options - rosin or flux - it is better to choose flux. It will provide the soldering with greater durability and reliability. Such soldering will not fall off even if the device is used very often. The only caveat is that the acid vapors released during soldering are very harmful, so it is not recommended to inhale them, and after the procedure you should wash your hands thoroughly.
Restoring a disassembled battery only makes sense if you managed to carefully disassemble the old laptop battery without damaging the controller board or causing a short circuit and correctly disconnect the assembly of elements (from maximum plus to minus). However, the battery controller did not fail or become blocked. Yes, you can buy a new controller or find a programmer and program to unlock the controller, but this is not justified for a single battery repair!
The first thing to do is to find new workable elements, which we will install in the battery case. Look at the brand of old cells and find their characteristics on the Internet: type of chemistry, voltage, charge and discharge currents, capacity.
For example, my Toshiba laptop is equipped with six Panasonic NCR18650 elements; in any search engine you can find a pdf file with the characteristics of these elements.
Where can I get the elements?
You can choose good elements from old ones - “recycled” use, you can buy new elements in your city, order from foreign stores or auctions such as eBay or Aliexpress. However, I took a third route: I bought and disassembled Xiaomi 10000 mobile chargers into elements.
Many insist that a battery can only be assembled from cells using resistance welding, as is done in production. Soldering the battery will damage it or shorten its service life. I can say that if this assembly is not used in extreme conditions, then you can get by with proper soldering.
Of course, it will take more time, but a resistance welding machine will not be needed.
For proper soldering you will need:
The quality of any soldering depends entirely on the correct tinning of the surfaces being soldered. And the most important thing in soldering batteries is not to overheat them!
Therefore, you need to be well prepared:
Now you can start:
The photo shows a tinned cell from an old battery. With soldered wire. 
Important!!! You cannot tin the battery for more than 2 seconds; if you did not manage to tin it in 2 seconds, then put the element aside and try again only after it has cooled down.
Important!!! Do not inhale fumes when soldering; acid and its vapors are harmful to health.
Important!!! When the battery is tinned, it is necessary to remove the remaining soldering acid, for example, with a cotton swab moistened with alcohol, or at least vodka.
The safest soldering option is soldering batteries with already welded petals. How to solder a 18650 battery with petals? It is necessary to tin the very edge of the petal, preventing the element itself from heating.
And this is a new battery with a contact welded petal from a mobile charger. 
When all the elements are tinned, you need to check the equality of the voltage on them; if the voltages differ by more than a few hundredths of a volt, then you should equalize the voltages using a special charger, or by connecting the batteries in parallel.
Attention!!! When connecting elements in parallel with different degrees of charge and, accordingly, different voltages, enormous currents can flow, since the currents are limited only by the scanty internal resistance of the batteries and the resistance of the circuit wires.
To limit the current, a resistor must be connected to the battery circuit. The resistor resistance value should not be lower than dU/Imax, that is, we divide the voltage difference across the battery elements by the maximum permissible battery charge/discharge current.
We connect the batteries and the resistor according to the diagram above and wait until the voltage across the resistor becomes less than a hundredth of a volt.
When the voltage on all elements is balanced, you can proceed to assembling them into a battery; the easiest way to connect new elements is to use old connecting bars, but if they are damaged during disassembly, you will have to look for copper foil 100-200 microns thick.
The first time I was too lazy to look for foil and I used a regular stranded wire with a cross-section of 1.5 sq. mm, for which I later paid: the assembly barely fit into the battery case, and the battery barely fit into the laptop.
When assembling elements into a battery, you need to adhere to the original battery layout, and it is better to leave the arrangement of the elements as in the original battery.
When assembling a battery of six elements, I first combined all the elements in pairs: the minuses of the two elements together and the pluses also together. Then I connected three pairs in series.
Now that the assembly of elements is ready, you need to connect the controller to it.
Important!!! The controller is connected in the reverse order, that is, we start with the wires with the lowest potential and move upward: 0 V and 3.6 V, only then 7.2 V and finally 10.8 V.
Now all that remains is to carefully assemble the battery for testing. Without sealing the battery case, I connected it to the laptop and pressed the power button, but the laptop did not turn on and realized that when I disconnected the old battery assembly, the controller went into transport mode and disconnected the battery. I connected the mains power to the laptop, the laptop started up and saw a restored battery!
When working with mobile household devices or special tools with a built-in power source, there is often a need to solder a wire to the battery.
Before you begin this seemingly simple procedure, you should carefully prepare, which will guarantee that you will receive a reliable and high-quality connection at the end of the work.
Both the alkaline or lithium battery itself and the connecting conductor soldered to it need preparation.
These procedures also include the preparation of the necessary consumables, including such important components as solder, rosin and flux mixture.
The most difficult and crucial moment of the upcoming work is stripping the battery terminal to which the connecting wire is supposed to be soldered. This procedure may seem simple only to those who have never tried to do this.
The problem in this case is that the aluminum contacts of power supplies (finger or other type - it doesn’t matter) are susceptible to oxidation and are constantly covered with a coating that interferes with soldering.
To clean them and subsequently isolate them from air you will need:
After all the specified components are prepared, the following operations must be performed. First, you need to carefully clean the area of the intended soldering, using first a scalpel or knife, and then fine emery cloth (this will ensure better removal of the oxide film from the contact area).
At the same time, the bare part of the soldered wire should undergo the same stripping.
Immediately after preparation, you should proceed to protective treatment of the terminals of a finger-type or any other battery.
To prevent subsequent oxidation of the contact, the surface of the battery, cleared of plaque, should be immediately treated with a flux mixture made from ordinary rosin.
If, for example, there are no greasy stains from oils on the phone battery contacts, simply wipe them with a soft flannel soaked in ammonia.
After this, you will need to warm up the soldering iron well and solder the contact area with a few quick touches. At this point, preparation for soldering can be considered complete.
After each of the connected parts has been cleaned and treated with flux, they proceed to directly soldering the wires to the contact area of the battery.
To carry out this final procedure, you can use the same 25-watt soldering iron that was used to prepare the battery terminals from NI or CD.
As a solder, you should choose a low-melting composition, and for good spreading, use a rosin-based flux.
The final soldering procedure should take no more than 3 seconds. This applies to any type of battery (both NI and CD).
The most important thing is to prevent overheating of the terminal part of the element, as a result of which it can be seriously damaged. The possibility of its complete destruction (rupture) during the soldering process cannot be ruled out.
When considering how to solder a wire and a battery, it should be noted that this situation occurs much more often than it seems. First of all, this applies to special construction tools (if it is necessary to solder screwdriver batteries, for example).
There are often cases when the built-in power supply of the tool used is completely destroyed for some reason, and there is nothing to replace this screwdriver with. In this situation, the conductors powering the device are soldered to a spare battery designed for the same voltage.
The considered technique can be used when you just need to solder two batteries together.
It should be noted that instead of soldering, spot welding is used in production for batteries. But not everyone has a device for this type of connection, while a soldering iron is a more common device. That’s why soldering comes to the rescue at home.
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