Batteries and accumulators
When powering radio equipment from batteries and accumulators, it is useful to know the common schemes for connecting batteries and accumulators. The fact is that each type of battery has a permissible discharge current.
Discharge current - the most optimal value of the current that is consumed from the battery. If you consume a current from a battery that exceeds the discharge current, then this battery will not last for a long time, it will not be able to fully give up its rated power.
You probably noticed that for electromechanical watches, “finger” (AA format) or “little finger” (AAA format) batteries are used, and for a portable lamp lamp, larger batteries (format R14 or R20), which are capable of delivering significant current and have a large capacitance. Battery size matters!
Sometimes it is necessary to provide battery power to an instrument that draws significant current, but standard batteries (for example, R20, R14) cannot provide the required current, it is higher than the discharge current for them. What to do in this case?
The answer is simple!
It is necessary to take several batteries of the same type and connect them to the battery.
So, for example, if it is necessary to provide a significant current for the device, a parallel connection of batteries is used. In this case, the total voltage of the composite battery will be equal to the voltage of one battery, and the discharge current will be as many times greater than the number of batteries used.
The figure shows a composite battery of three 1.5 volt batteries G1, G2, G3. If we take into account that the average value of the discharge current for 1 AA battery is 7-7.5 mA (with a load resistance of 200 Ohms), then the discharge current of the composite battery will be 3 * 7.5 = 22.5 mA. So, you have to take the quantity.
It happens that it is necessary to provide a voltage of 4.5 - 6 volts using 1.5 volt batteries. In this case, you need to connect the batteries in series, as in the figure.
The discharge current of such a composite battery will be the value for one cell, and the total voltage will be equal to the sum of the voltages of the three batteries. For three elements of the AA format (“finger-type”), the discharge current will be 7-7.5 mA (with a load resistance of 200 Ohms), and the total voltage will be 4.5 Volts.
When working with mobile home devices or a special tool with a built-in power source, it is often necessary to solder a wire to the battery.
Before embarking on this seemingly simple procedure, you should carefully prepare, which guarantees 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 the stripping of the battery terminal, to which it is supposed to solder the connecting wire. 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 the power supplies (finger or other type - it does not matter) are subject to oxidation and are constantly covered with plaque that interferes with soldering.
For their stripping and subsequent isolation from the air, you will need:
- sandpaper;
- medical scalpel or well-honed knife;
- fusible solder and flux neutral additive;
- not very "powerful" soldering iron (no more than 25 watts).
After all these components are prepared, it is necessary to perform the following operations. Firstly, you need to carefully clean the place of the intended soldering, using first a scalpel or knife, and then a fine emery cloth (it will provide a better removal of the oxide film from the contact area).
In parallel with this, the bare part of the soldered wire should be subjected to the same stripping.
Immediately after preparation, you should proceed to the protective treatment of the terminals of a finger-type or any other battery.
Flux processing
To prevent subsequent oxidation of the contact, the battery surface cleaned of plaque should be immediately treated with a flux mixture made on the basis of ordinary rosin.
If, for example, there are no greasy stains from oils on the contacts of the phone’s battery, just wipe them with a soft flannel soaked in ammonia.
After that, it will be necessary, after warming up the soldering iron well, to solder the contact zone with a few quick touches. On this preparation for soldering can be considered complete.
soldering process
After each of the connected parts is cleaned and processed with flux, they proceed to the direct soldering of the wire with the contact area of the battery.
For 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 fusible composition, and for its good spreading, use a rosin-based flux.
The final soldering procedure should take no more than 3 seconds. This applies to any type of batteries (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 thoroughly damaged. The possibility of its complete destruction (rupture) during the soldering process is not excluded.
When considering how to solder a wire and a battery, it should be noted that this situation is much more common than it seems. First of all, this concerns a special construction tool (if necessary, soldering screwdriver batteries, for example).
It is not uncommon for the built-in power supply of the tool used to be completely destroyed for some reason, and there is nothing to replace this screwdriver with. In this situation, the conductors feeding 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 in production, spot welding is used for batteries. But not everyone has an apparatus for this type of connection, while a soldering iron is a more common device. Therefore, at home, soldering comes to the rescue.
Everyone knows that a lithium polymer battery cannot be overheated, soldered with an ordinary soldering iron. But what to do if you still need to connect two batteries. This will be discussed in the article.
When I was building the Cessna, site users advised me to buy at least two batteries so that I would not have to go out into the field to fly for a few minutes.
Two of these batteries have been ordered. .jpg)
Battery Turnigy 1300mAh 3S 20C Lipo Pack
Product http://www.site/product/9272/
One of them categorically did not want to take a charge. It immediately gave a break error, then during charging. I soon discovered that inside it the contacts were shorting out. And so he began to fly with one battery.
Here are the hands to disassemble it. After removing the outer wrapper, it was found that the iron plate between the first and second jar was torn and the contact was provided only due to the "tightness" in this place.
When he started poking around and completely came off. 
But everyone knows that LiPo batteries cannot be overheated over 60 degrees Celsius. Regular solder melts at about 200 degrees Celsius. Moreover, the solder practically does not stick to this plate from the liposhka - it means that you will have to tinker for a long time. As luck would have it, only a couple of millimeters of this plate remained on one can.
Then I remembered the Rose alloy. Its melting point is only 95 degrees Celsius. Those. it can be melted even in boiling water. 
There was no adjustable soldering iron at hand, I had to solder with the usual ones. The temperature was regulated by "undocking" from the soldering iron socket. Rosin melts at about 70 degrees, so ten seconds after heating to melt the rosin, you can safely turn off the soldering iron.
I pre-clamped with steel wire all three "antennae" that needed to be soldered together (two of the neighboring lipos, the third with a white wire for the balancing connector) and proceeded to soldering. This wire helped me very well later - as I wrote earlier, native plates repel the alloy very diligently, at first the solder stuck just to this wire, and then slowly moved to the plates. 
At the same time, the remaining wires can be clamped with an elastic band, otherwise they interfere very much with this "jewelry work". 
After soldering, I cut off the excess steel wire, took care of the insulation and reassembled everything. In the end, I wrapped everything with ordinary electrical tape. Now she is white. 
Ran 5 charge/discharge cycles. The charge shows normal.
Tomorrow I'm going to test on the Cessna.
I also want to add that the disassembly and soldering of LiPo batteries are associated with a great risk to health and this article is by no means a guide to action!
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To assemble the simplest battery-powered circuit, we have to resort to various tricks so that the wires fit snugly against the poles of the battery itself. Someone manages with electrical tape and adhesive tape, someone comes 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 it turns out to be loose, and the device works intermittently. To avoid this, it's best to just solder the wires to the poles. In our article, we will tell you how to solder the wires to the battery so that the contact is perfect.
The simplest device example
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 hundred, we wind a copper wire around it in dense rows. We isolate the turns from above with electrical tape. The electromagnet is ready. Now it remains only to power the device from the battery.
Of course, you can simply press on the wire at each end of the battery, and the device will already start working. But it's inconvenient to use. Therefore, it is best to ensure that the wires are in constant contact with the power source. This can be done by adding an ordinary switch (tumbler) to the network and soldering the wires to the battery poles directly. The device will become more reliable, it will be more convenient to use it, and if it is not needed, you can always turn it off by opening the circuit with a 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 needed for soldering
In order to carry out reliable soldering of wires to the battery poles, you need the necessary set of tools. Since soldering a wire to a battery is a more difficult task than just 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:
- Ordinary household hand soldering iron. They will solder the wires to the poles of the battery.
- Sandpaper or a file to clean the soldering iron tip from slag and soot.
- Sharp knife. We will strip the wires with them if they are braided.
- Flux or rosin. Which flux for soldering is suitable in this case? We won’t break our heads here, let’s take a simple soldering acid, it is sold in any store selling radio products. Well, rosin, although it often differs in color and shade, is always the same in properties.
- Flux brush.
- Solder. It can be purchased at the same place where the flux is.
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 act according to the following instructions:
Everything, the wires are qualitatively soldered to the battery.
Solder the wires to the crown
How to solder a wire to a Krona battery? Here, soldering is carried out in almost the same way as in the case of a conventional battery. The only difference is that in the Krona 9V battery, plus and minus are located side by side on one upper side of the battery. The nuances are as follows:
- In the case of flux, we treat the Krona contacts with acid from opposite sides. There we will solder the wires.
- In the case of rosin, it will be necessary to tin the Krona contacts, and also from opposite sides. Why opposite? Because in this case, the risk of a short circuit between the wires is practically reduced to zero.
- The Krona 9V battery has contacts (poles) that are very inconvenient for soldering. At the top, they open in breadth, and therefore for high-quality tinning and soldering on the side of such a contact, it is necessary that the tip of the soldering iron be narrower or pointed.
In general, the whole process is similar to the previous one. We process 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. Process completed.
Batteries square 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 wiring 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, after picking up the tin with a soldering iron, soldering.
Batteries type "accumulator"
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 pole contacts of the container. The material of the battery-accumulators consists of alloys that can be soldered even worse than ordinary lithium ones. But if you are very impatient, then soldering is carried out, as in the case of a conventional 1.5 V battery, just use flux, not rosin. Plus, soldering should be done as quickly as possible, keeping the soldering iron touching 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 the flux. It will provide soldering 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 fumes released during soldering are very harmful, so it is not recommended to inhale them, and after the procedure you should wash your hands thoroughly.