How to solder batteries from a battery. Ultra-low-cost spot welding of lithium batteries at home

There comes a time in the life of every “radio killer” when you need to weld together several lithium batteries- either when repairing a laptop battery that has died from age, or when assembling power for another craft project. Soldering "lithium" with a 60-watt soldering iron is inconvenient and scary - you will overheat a little - and you have a smoke grenade in your hands, which is useless to extinguish with water.

Collective experience offers two options - either go to the trash heap in search of an old microwave, tear it apart and get a transformer, or spend a lot of money.

For the sake of several welds a year, I didn’t want to look for a transformer, saw it and rewind it. I wanted to find an ultra-cheap and ultra-simple way to weld batteries using electric current.

Powerful low voltage source direct current, accessible to everyone - this is an ordinary used one. Car battery. I'm willing to bet that you already have it somewhere in your pantry or that your neighbor has it.

I'll give you a hint - The best way getting an old battery for free is

wait for frost. Approach the poor guy whose car won’t start - he will soon run to the store for a fresh new battery, and give the old one to you for nothing. In the cold, an old lead battery may not work well, but after charging the house in a warm place it will reach its full capacity.

The problem is that ordinary automotive relays 12 volts are designed for a maximum of 100 amperes, and short circuit currents during welding are many times higher. There is a risk that the relay armature will simply weld. And then, in the vastness of Aliexpress, I came across motorcycle starter relays. I thought that if these relays can withstand the starter current, many thousands of times, then they will be suitable for my purposes. What finally convinced me was this video, where the author tests a similar relay:

My relay was purchased for 253 rubles and reached Moscow in less than 20 days. Relay characteristics from the seller's website:

• Designed for motorcycles with 110 or 125 cc engine
• Rated current - 100 amperes for up to 30 seconds
• Winding excitation current - 3 amperes
• Rated for 50 thousand cycles
• Weight - 156 grams

I was pleased with the quality of the unit - two copper-plated contacts were installed threaded connections, all wires are filled with compound for water resistance.

On a quick fix I assembled a “test stand” and closed the relay contacts manually. The wire was single-core, with a cross-section of 4 squares, and the stripped ends were fixed with a terminal block. To be on the safe side, I equipped one of the terminals to the battery with a “safety loop” - if the relay armature decided to burn out and cause a short circuit, I would have time to pull the terminal from the battery using this rope:

Tests have shown that the machine performs well. The anchor knocks very loudly, and the electrodes give clear flashes; the relay does not burn out. In order not to waste a nickel strip and not to practice on dangerous lithium, I tormented the blade of a stationery knife. In the photo you see several high-quality points and several overexposed ones:

Overexposed dots are also visible on the underside of the blade:

First he piled up simple diagram on a powerful transistor, but quickly remembered that the solenoid in the relay wants to consume as much as 3 amperes. I rummaged around in the box and found a replacement transistor MOSFET IRF3205 and sketched out a simple circuit with it:

First, we try the circuit on foil (with joyful clicks it burns holes right through several layers), then we take out nickel tape from the stash for connection battery assemblies. We briefly press the button, we get a loud flash, and examine the burnt hole. The notebook was also damaged - not only the nickel was burned through, but also a couple of sheets underneath it :)

Even a tape welded at two points cannot be separated by hand.

Obviously, the scheme works, it’s a matter of fine-tuning the “shutter speed and exposure”. If you believe the experiments with the oscilloscope of the same friend from YouTube, from whom I spied the idea with the starter relay, then it takes about 21ms to break the armature - from this time we will dance.

YouTube user AvE tests the firing rate of the starter relay in comparison with the SSR Fotek on an oscilloscope

• Arduino itself - Nano, ProMini or Pro Micro will do,
• Sharp PC817 optocoupler with a 220 Ohm current-limiting resistor - to galvanically isolate the Arduino and the relay,
• Voltage step-down module, for example XM1584, to turn 12 volts from the battery into Arduino-safe 5 volts
• We will also need 1K and 10K resistors, a 10K potentiometer, some kind of diode and any buzzer.
• And finally, we will need nickel tape, which is used to weld batteries.

We upload some simple code to Arduino:

Const int buttonPin = 11; // Shutter button const int ledPin = 12; // Pin with signal LED const int triggerPin = 10; // MOSFET with relay const int buzzerPin = 9; // Tweeter const int analogPin = A3; // Variable resistor 10K for setting the pulse length // Declare variables: int WeldingNow = LOW; int buttonState; int lastButtonState = LOW; unsigned long lastDebounceTime = 0; unsigned long debounceDelay = 50; // minimum time in ms that must be waited before triggering. Made to prevent false alarms when the release button contacts bounce int sensorValue = 0; // read the value set on the potentiometer into this variable... int weldingTime = 0; // ...and based on it we set the delay void setup() ( pinMode(analogPin, INPUT); pinMode(buttonPin, INPUT); pinMode(ledPin, OUTPUT); pinMode(triggerPin, OUTPUT); pinMode(buzzerPin, OUTPUT) ; digitalWrite(ledPin, LOW); digitalWrite(buzzerPin, LOW); void loop() ( sensorValue = analogRead(analogPin); // read the value set on the potentiometer weldingTime = map(sensorValue, 0, 1023, 15, 255); // convert it to milliseconds in the range from 15 to 255 Serial.print("Analog pot reads = "); "\t so we will weld for = "); Serial.print(weldingTime); welding: int reading = digitalRead(buttonPin); if (reading != lastButtonState) ( lastDebounceTime = millis(); ) if ((millis() - lastDebounceTime) > debounceDelay) ( if (reading != buttonState) ( buttonState = reading;<= 3) { playTone(1915, 150); // другие ноты на выбор: 1915, 1700, 1519, 1432, 1275, 1136, 1014, 956 delay(500); cnt++; } playTone(956, 300); delay(1); // И сразу после последнего писка приоткрываем MOSFET на нужное количество миллисекунд: digitalWrite(ledPin, HIGH); digitalWrite(triggerPin, HIGH); delay(weldingTime); digitalWrite(triggerPin, LOW); digitalWrite(ledPin, LOW); Serial.println("== Welding ended! =="); delay(1000); // И всё по-новой: WeldingNow = LOW; } else { digitalWrite(ledPin, LOW); digitalWrite(triggerPin, LOW); digitalWrite(buzzerPin, LOW); } lastButtonState = reading; } // В эту функцию вынесен код, обслуживающий пищалку: void playTone(int tone, int duration) { digitalWrite(ledPin, HIGH); for (long i = 0; i < duration * 1000L; i += tone * 2) { digitalWrite(buzzerPin, HIGH); delayMicroseconds(tone); digitalWrite(buzzerPin, LOW); delayMicroseconds(tone); } digitalWrite(ledPin, LOW); }
if (buttonState == HIGH) ( WeldingNow = !WeldingNow; ) ) ) // If the command is received, then we start: if (WeldingNow == HIGH) ( Serial.println("== Welding starts now! =="); delay (1000); // We output three short and one long beeps to the speaker: int cnt = 1; while (cnt

Then we connect to the Arduino using the Serial monitor and turn the potentiometer to set the length of the welding pulse. I empirically selected a length of 25 milliseconds, but in your case the delay may be different.

As a result, we have a simple, unsophisticated welding installation that is easy to disassemble:

A few important words about safety precautions:

• When welding, microscopic splashes of metal may fly to the sides. Don’t show off, wear safety glasses, they cost three kopecks.
• Despite the power, the relay can theoretically “burn out” - the relay armature will melt to the point of contact and will not be able to return back. You will get a short circuit and rapid heating of the wires. Think in advance about how you will pull off the terminal from the battery in such a situation.
• You can get different degrees of welding depending on the battery charge. To avoid surprises, set the welding pulse length on a fully charged battery.
• Think in advance what you will do if you make a hole in the 18650 lithium battery - how you will grab the hot element and where you will throw it to burn out. Most likely, this will not happen to you, but with video It is better to familiarize yourself with the consequences of spontaneous combustion 18650 in advance. At a minimum, have a metal bucket with a lid ready.
• Monitor the charge of your car battery, do not allow it to be severely discharged (below 11 volts). This is not good for the battery, and it won’t help your neighbor who urgently needs to “light up” his car in winter.

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:

• sandpaper;
• medical scalpel or well-sharpened knife;
• low-melting solder and neutral flux additive;
• not a very “powerful” soldering iron (no more than 25 watts).

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.

Flux processing

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, just 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.

Soldering process

After each of the parts to be connected 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.

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 example of a device

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?

Tools and consumables required for soldering

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 according to the instructions below. In the meantime, let's prepare everything you need:

1. An ordinary household hand-held soldering iron. We will use it to solder the wires to the poles of the battery.
2. Sandpaper or file to clean the soldering iron tip from slag and carbon deposits.
3. Sharp knife. We will use it to strip wires if they are braided.
4. Flux or rosin. What soldering flux is suitable in this case? Let’s not rack our brains here, let’s take simple soldering acid, it is sold in any store that sells radio products. Well, rosin, although it often differs in color and shade, is always the same in properties.
5. Brush for applying flux.
6. Solder. It can be purchased in the same place as flux.

Solder the wires to a regular battery

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.

Solder the wires to the crown

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:

1. In the case of flux, we treat the Krona contacts on opposite sides with acid. There we will solder the wires.
2. In the case of rosin, you will need to tin the Krona contacts, also on opposite sides. Why from the opposite ones? Because in this case the risk of a short circuit between the wires is practically reduced to zero.
3. The Krona 9V battery has contacts (poles) that are very inconvenient for soldering. At the top they open wider, and therefore for high-quality tinning and soldering from the side of such a contact, it is necessary for the soldering iron tip to be narrower or pointed.

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.

Quad batteries 4.5 V

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.

Rechargeable batteries

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.

Conclusion

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.