Hi all. The review is not so much about batteries (which, by the way, came out thanks to Mysku), but about an option for converting a screwdriver. The batteries are of high quality, the capacity matches, their implantation instead of nickel-cadmium ones was successful

Review participants:

LG HE4 High Current Batteries with Gearbest:
The batteries are good, their capacity was checked by a friend using an Opus charger, the capacity is correct. No further special tests were carried out.

Three-channel charger Imax B3:
This is the second attempt to buy such a charger, the first time the order did not arrive, the money was returned. The charger ordered from the seller via the link above has arrived, works, and comes with a 40cm long power cord, in the picture the cord is clearly different. There was no cable for connecting charging anywhere in the kit.

Three 18650 battery holder:
In the seller’s picture, this version of the holder for three 18650s had pins for soldering into a printed circuit board, but a completely different version came to me, not only was it not for printing, but also with soldered collective farm jumpers connecting all three batteries in parallel.

Received a partial refund. I unsoldered the jumpers and used them, although not as originally planned.

Background.
My Interskol DA-12ER-01 screwdriver is almost 10 years old. Most of all he “got it” during renovations in his apartment about 6 years ago, but usually he rested most of the year, worked a little in the summer at the dacha, and did small tasks: crafts, assembling furniture, etc. Problems with batteries began a couple of years ago, one battery stopped holding a charge, the second worked quite normally. I then disassembled the defective battery, identified the two most damaged elements, and tried to replace them with similar ones purchased on eBay. But when I installed new elements, I discovered that the remaining elements, which I considered still alive, were also candidates for the trash bin: under load, the voltage on them changed polarity. There was no point in changing all the elements, so I converted this battery into a kind of adapter for connecting a screwdriver to the car's cigarette lighter.

But I was going to connect it not to the car’s on-board power supply, but to an old 12V 7ah lead battery from a halogen light for a video camera, the socket of which was similar to the socket of a car cigarette lighter. I have had LED lights for video cameras for a long time, powered by lithium batteries, but I still have a 12V battery, so it came in handy for a screwdriver, although it was only used a couple of times. Here is this super mega adapter:

But since the 12V 7AH battery was already more than 8 years old, it stopped holding a charge, it was not possible to restore it, and I was forced to sell it for scrap. So I’ll most likely take apart the “adapter” for the cigarette lighter; I don’t see any point in connecting the “Shurik” to the car.

This summer, the second battery of the screwdriver finally gave up; it began to discharge so quickly that it became impossible to carry out serious work with it. In the spring it still worked somehow, but by autumn a dozen mediocre self-tapping screws on one charge became its limit.

But nevertheless, I think that the screwdriver’s original batteries worked very well - for me they lasted 8 and 10 years, while my friends died in both the 3rd and 5th years, with approximately the same unprofessional mode of use.

Buying even one new nickel-cadmium battery is outlandish; it is 50-60% of the price of a similar screwdriver (yes, they are still sold) with two such batteries included. I also rejected the option of buying an already assembled battery of nickel-cadmium batteries from Ali or Ebay, ready for installation in the case of an obsolete battery: it is cheaper, but the quality of these batteries is questionable, for example, the two elements I bought on Ebay had a decent range in capacity, and how much it will all work out, it is unknown. In addition, I decided to abandon nickel-cadmium completely and irrevocably: from converting a cordless screwdriver to lithium, which I did six months ago, the impressions were the most positive.

In general, of course, my screwdriver is already old and shabby, so I was thinking about buying a new, modern one with a lithium battery to replace it. But the mechanical part is still in perfect order, and modern inexpensive Shuriks have extremely weak mechanics: those that were held in hand had simply indecent play in the cartridge bearing after an indecently short period of time. But there is no point in buying a professional expensive screwdriver; it will lie in the closet for most of the year.

But the most important thing is that my hands were itching to convert the screwdriver for lithium myself. At the same time, there were certain doubts: the cost of the batteries, protection board and charge equalization was close to a simple lithium Shurik from Leroy-Merlin, with a one-year guarantee. But the desire to solder and tinker overcame doubts that they would send the wrong batteries, that something would go wrong, etc.

At first I wanted to do everything according to the classical scheme, that is, take three high-current 18650 batteries, add a 3S protection and charge equalization board to them, and accordingly convert the charger for lithium. But then I decided to make it simpler, and in my opinion, much more convenient.

Based on experience with batteries for video cameras VBG6, F550, F770, etc., where two 18650 batteries are connected in series, I concluded a long time ago that batteries die mainly due to the fact that the charge equalization circuit does not cope with its task. As a result, one battery is constantly overcharged, the second is undercharged, and very soon the battery goes into the trash. Even replacing dead elements with original Sanyo ones, whose parameters are much more stable, did not give the effect as long as we would like, a couple of years and that’s it...

And in a screwdriver the battery will be made of three elements, the current loads are much higher, the imbalance in the capacity of the elements will appear faster, so I very much doubt that the charge equalization/balancing board will help the batteries not die prematurely. Therefore, I decided to abandon charging all batteries at once from one source, in favor of charging each one separately. For a three-channel charger, I decided to take a ready-made, widely known Imax B3; in my opinion, it is in any case more effective than a balancing board, and it is also very compact and lightweight.

I decided to completely abandon the overdischarge/overcharge protection board; there is a battery voltage indicator on the screwdriver; you can use it to determine how discharged the battery is. Well, if one of the three batteries “goes wrong” and suffers along with everyone else (undervoltage protection would have shut down the entire battery long ago)… you know, this is his fate, there is no way to help him, but the battery will not turn off ahead of time.

Figuring that after installing three 18650 cells into the battery case, there would still be quite a lot of free space left in it, I decided to stuff the Imax B3 charger itself there too. In this case, to charge the batteries, it will be enough to simply connect a 220V cord to the screwdriver. And it’s really convenient: no external charges, the screwdriver comes with only a 220V cord, and the cord is universal, even suitable for a receiver/printer/music center.

No sooner said than done. The batteries with GB came to me first, at first I tried to test them myself, placing one at a time in my existing power bank, giving a load of 1A, and calculating the capacity based on the operating time before shutting down. Despite the fact that I recalculated the capacity from a voltage of 5V to a voltage of 3.7V, my results turned out to be very underestimated, about 1.5Ah, so I asked a friend to check these batteries on a full Opus test charge, I don’t remember the model, and he reassured me , the capacity of all batteries turned out to be normal, although not 2.5ah, but 2.3ah, which suited me quite well.

Initially, I wanted to connect the batteries by spot welding, I even bought nickel tape for this, but I never completed the spot welding unit. Therefore, I decided to use a ready-made holder of three 18650 elements, ordered, however, for a completely different craft. It didn’t match the seller’s description, but after a little modification it fit quite well, especially since the batteries fit very tightly in it, the contacts are quite thick and rigid. Even with very dynamic shaking, the batteries did not jump out of the holder.

The very last thing that came to me was the Imax B3 charger. I checked it - it works, then I started the process of converting the screwdriver to lithium.

The original battery was gutted, I soldered the wires to the contact group, secured the battery compartment to the base of the case with screws, and soldered the wires to it. I installed a 10A fuse, but hung it on the terminals: the car holder did not fit into the case. By the way, one of the nickel-cadmium elements supports the contact group; it is just the right length. I drove a screwdriver using lithium batteries and was amazed at how powerfully it now turns.

Next, I installed the Imax B3 charger in the battery cover, and placed a charging connector (not original) on the side wall of the cover. I removed the stands for the indicator LEDs and brought them out into the holes in the case, so that now you can observe the entire charging process through three glowing “eyes”. Naturally, red light means charging, green light means charged.

Next, I connected the charger to the batteries, drove the screwdriver a little, and put it on charge. And here a problem emerged, which I had already read about, and which was, in principle, impossible to avoid. The TP4056 charge controller chips began to heat up wildly. Well, if only they wouldn’t heat up, the charging current (judging by the current-setting resistor with a resistance of 1.8k) is about 600 mA, at the input about 6V. Moreover, I had almost fully charged batteries, the voltage on which during charging was about 4.15 V, while the power dissipated on each microcircuit was about 1.1 W. This is quite enough for three microcircuits on a small board, and even in a closed volume, to actually fry. If the batteries had to be charged from scratch, then even more power would be dissipated on the microcircuits.

So I replaced the current setting resistors, increasing them from 1.8k to 4.7k, thus reducing the charging current to about 270mA. But even so, the microcircuits burned my fingers. Of course, nothing bad happened in this mode, the batteries were charged normally, and the green LEDs lit up almost simultaneously. But still, in extreme heat the charger can overheat; the case was not closed during tests. Well, the charging current is somehow too small.

Therefore, I installed a small radiator on the microcircuits (via nomacon), again changing the current-setting resistors to 2.2k - the charging current is about 500 mA. Having charged in this mode, I did not detect any serious heating of the radiator, and I am sure that even on a hot day, the temperature in the closed battery case will be normal.

The only thing that bothers me is the maximum voltage on the batteries at the end of the charge: 4.20 4.23 4.21V. Isn't that too much? But it is impossible to influence this voltage, except by replacing the microcircuits.

In general, I finally assembled the new battery. Instead of the previous 1.5 AH, it has a capacity of 2.3 AH, and without memory effect. The downside is that you can’t leave it in extreme cold, but no one is forcing you to do that.

Well, I like how the screwdriver works from the new battery.

Now a little about the screwdriver’s native charger:

The charger worked fine for 10 years, despite the fact that it got hot like an iron. Surprisingly, after 10 years the pungent smell of plastic and burnt hetinax has not disappeared from it. Now there is nowhere to use it, so I decided to gut it:

All the products of the Interskol company that I have ever encountered raised great doubts that they were made in our country, as Interskol itself claims. Everything they do is too “Chinese”, including printing, assembly, and exclusively imported components. Also with the charger, there is simply zero “own”. I am familiar with domestic production, both consumer goods and military equipment, and I believe that in this case everything was done “not our way.” I think Interskol was just putting on its own labels.

But since the charger is going to waste, I decided to borrow a contact group from it that was connected to the battery. I disassembled the board and sawed it off, leaving a piece with contacts:

The question is, why? Yes, to be able to connect an external load to the battery instead of a screwdriver. Previously, I had a 12V 7AH battery as a “camping” voltage source, but it died, and it was logical to use a battery for a screwdriver instead. So I made a special adapter from a piece of charger and other materials that came to hand.

The purpose of this adapter with a cigarette lighter plug on the wiring is to power the car's on-board network when removing the starter battery for recharging or replacing with another battery (I have two of them). I really don’t want to restore the settings of the radio and other devices after the power supply is cut off. Plug the plug into the cigarette lighter - and do your job, you can also turn on the dimensions and emergency lights, and all settings will be saved. The only pity is that there are no lamps under the hood... It is not recommended to start the engine with an external battery connected, there is no battery charging current limiter, but if something happens, the 5A fuse in the plug will blow.

There are plans to make the adapter universal to connect different devices, but I didn’t find a suitable connector, I’ll redo it later.

In general, I am satisfied with the modification of the screwdriver. It cost me about 1,100 rubles, plus three evenings after work for the rework. In my opinion, it turned out to be convenient, but, of course, not without its drawbacks. You need to monitor the battery discharge so as not to ruin the batteries, and it is better not to give the converted Shurik into the wrong hands. But I myself still don’t know exactly how a screwdriver will behave when the battery is completely discharged, how much its power will decrease, and what the indicator will show. So you will need to observe the screwdriver while working with it.

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Types, markings and characteristics of lithium-ion batteries 18650

We received quite a lot of questions from readers about 18650 lithium-ion batteries. Therefore, we decided to write a small FAQ on this type of lithium battery. 18650 battery cells are in demand in the modern market. They are used in laptop batteries, various flashlights, power banks, and some types of power tools. In this note, we will consider the main issues that interest people most. Namely, types of 18650 elements, issues related to their labeling, protection, pros, cons and price.

To begin with, it is worth mentioning the main types of 18650 batteries, which differ in cathode material. The properties of batteries such as capacity and maximum permissible discharge current largely depend on this.

LiCoO 2 (lithium─cobalt). These batteries are the most common and have the largest capacity values among models made using Li─Ion technology;
LiMnO 2 or LiMn 2 O 4 or LiNiMnCoO 2 (lithium-manganese group). In terms of their capacity, they are inferior to the first group, but they have a high discharge current (5─7*C);
LiFePO 4 (lithium ferrophosphate). These battery cells are superior to the previous ones in most respects, but inferior in capacity and voltage. They have a service life of up to 1 thousand charge-discharge cycles and charge in less than 1 hour.

Now about 18650 batteries in general. These are cylindrical elements in shape reminiscent of AA (“finger”) and AAA (“pinky”) form factor batteries. But 18650 exceeds them in size. The length is 66.5, diameter ─ 18 millimeters. For comparison, for fingerlings these values are 50 and 14 mm.

The output voltage of the 18650 battery is 3.78 volts. The capacity of the most common batteries is in the range of 2000-3200 mAh. Less common are banks with a capacity of 1000, 1100, 1500 mAh.

18650 batteries are widely used in devices that require large capacity. These are LED lights, laptop batteries, power banks for charging various mobile gadgets, etc.

How to decipher the markings of 18650 batteries?

Let's look at the marking of 18650 lithium-ion cells using the following example: ICR18650-26F M.

The first letter I indicates that the battery is made using lithium-ion technology. The second letter indicates the cathode material. In our case, cobalt. The following options are available:

C ─ cobalt;
M ─ manganese;
F ─ iron phosphate.

Form factor	Explanation
Form factor	Explanation
10440	"pinky"
14500	"finger"
16340	analog CR123
17335
18500	not widely used
18650	elements under consideration
18670, 18700	with protection boards
26650	oversized ferrophosphate batteries manufactured by A123 Systems
32650	have the largest size and weight about 150 grams

And at the end of the marking there is a designation of the capacity. In this example, the capacity is 2600 mAh. But usually the ending of the marking differs greatly depending on the manufacturer. Here, almost everyone can have their own version.

18650 battery protection

According to safety requirements, the voltage of 18650 lithium-ion batteries must be in the range of 2.5-4.2 volts during operation. To meet this requirement, some 18650 batteries are equipped with protection. It is a small printed circuit board.

This board is soldered to the terminals of the element using steel or aluminum tape. As a rule, large manufacturers do not produce such protected elements in mass production. They produce unprotected elements that are used in devices with charge-discharge controllers. An example would be a laptop battery or a screwdriver.

As a rule, protected 18650 lithium-ion cells are made in small batches in China. A protection board is soldered to the unprotected battery, and the entire structure is wrapped in thermal protective film. When purchasing such an element, you need to take into account that its length will be slightly longer (1.5─2 mm).

Protected 18650 batteries are used in all devices that do not have a charge-discharge controller for lithium-ion cells. The most common example of using such elements is LED lights. To prevent the lithium elements in the flashlight from dropping to zero, protection is placed on them.

It is worth considering that installing protection on lithium-ion 18650 increases the length of the element. And when there are several of them, this increase is summed up. As a result, a set of such elements may simply not fit into the flashlight body or interfere with the closing of the lid, which is usually made with a negative contact.

It must be remembered that protecting the 18650 element will not protect the device and batteries from overheating. Its role is to control tension. Many people use 18650 batteries in flashlights without protection. This can be done relatively safely if you have 1 element in the lantern. When several elements are installed, they must be protected.

The task at hand is very simple: to make a battery so that it is quite easy to charge it and replace the elements inside using simple manipulations.

First, let's look at the insides of a regular screwdriver battery. Inside most screwdrivers there are many 1.2 Volt “cans” made using Ni-Cd or Ni-MH technology. There are 12 such cans in the screwdriver on top, i.e. the final battery voltage is approximately 12*1.2=14.4 V. The capacity does not exceed 1.5 A/h. The batteries themselves last quite a long time, but among 12 pieces there are often 1-2 that stop working much earlier than their colleagues. It turns out that after some time the battery dies due to a small part of its insides. There is a recipe: replace the jar that does not work, and leave the rest unchanged. But at the same time, these banks are difficult to find and if you change them, then everything is better. Another plus is that it is very difficult to solder them; you need to have a welding machine. As a result, I came to the following conclusions:

It is necessary to have a larger battery capacity in order to charge less often

The cans were replaced in a couple of minutes

Don't buy a charger

Implementation

Modern battery technology that is used everywhere is Lithium (Li-Ion). It is used in phones, laptops, players, flashlights and much more. An affordable solution is the 18650 battery. If you disassemble a regular laptop battery, you can find them there:

These batteries can be bought or taken from an old laptop. If you buy, I recommend “Sanyo 2400 Ma/h red” based on the price/quality ratio. Keep in mind that they must be unprotected. Otherwise, they will turn off when a 2A current occurs, which often happens in a screwdriver. I recently bought a bunch of them on ebay, unfortunately my seller is no longer available, because... I'm not providing a link.

To make it convenient to change them, we will also need a so-called spring holder for 18650:

Many of these have been seen for regular AA batteries. There are 1-4 batteries. What’s strange is that it’s difficult to find these in a radio store or on the market; it’s easier to order them online on websites with cheap Chinese items using the request “18650 holder”. The cost of the latter is about $1-2.

The last important thing for a homemade battery is smart charging. I had one close by, I highly recommend “Imax B6” or analogues:

Now there are two ways to connect:

1) We simply connect all the batteries in series using holders and connect the terminals of the smart charger to the ends. The advantage of this system is its simplicity. Minus: the jars must be the same, otherwise everything may go bad. The fact is that if the voltage on any 18650 bank drops below 3 volts, then it can soon be thrown away. If your batteries are different, then you will not be able to control this nuance. If something happens to one can, you will need to change everything together, otherwise there will be problems.

Well, what should those who have an old instrument do? Yes, everything is very simple: throw away the Ni-Cd cans and replace them with Li-Ion of the popular 18650 format (the marking indicates a diameter of 18 mm and a length of 65 mm).

What board is needed and what elements are needed to convert a screwdriver to lithium-ion

So, here is my 9.6 V battery with a capacity of 1.3 Ah. At maximum charge level it has a voltage of 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts, a maximum voltage of 4.2. Therefore, to replace the old nickel-cadmium cells with lithium-ion ones, I will need 3 elements, their operating voltage will be 10.8 volts, maximum - 12.6 volts. Exceeding the rated voltage will not harm the motor in any way, it will not burn out, and with a larger difference, there is no need to worry.

Lithium-ion cells, as everyone has long known, categorically do not like overcharging (voltage above 4.2 V) and excessive discharge (below 2.5 V). When the operating range is exceeded in this way, the element degrades very quickly. Therefore, lithium-ion cells are always paired with an electronic board (BMS - Battery Management System), which controls the element and controls both the upper and lower voltage limits. This is a protection board that simply disconnects the can from the electrical circuit when the voltage goes beyond the operating range. Therefore, in addition to the elements themselves, such a BMS board will be required.

Now there are two important points that I unsuccessfully experimented with several times until I came to the right choice. This is the maximum permissible operating current of the Li-Ion elements themselves and the maximum operating current of the BMS board.

In a screwdriver, the operating currents at high loads reach 10-20 A. Therefore, you need to buy elements that are capable of delivering high currents. Personally, I successfully use 30-amp 18650 cells manufactured by Sony VTC4 (capacity 2100 mAh) and 20-amp Sanyo UR18650NSX (capacity 2600 mAh). They work fine in my screwdrivers. But, for example, the Chinese TrustFire 2500 mAh and the Japanese light green Panasonic NCR18650B 3400 mAh are not suitable, they are not designed for such currents. Therefore, there is no need to chase the capacity of the elements - even 2100 mAh is more than enough; The main thing when choosing is not to miscalculate the maximum permissible discharge current.

And in the same way, the BMS board must be designed for high operating currents. I saw on Youtube how people assemble batteries on 5 or 10-amp boards - I don’t know, personally, such boards immediately went into protection when I turned on the screwdriver. In my opinion, this is a waste of money. I will say this, that Makita itself puts 30-amp circuit boards in its batteries. That's why I use 25 amp BMS purchased from Aliexpress. They cost about 6-7 dollars and are searched for “BMS 25A”. Since you need a board for an assembly of 3 elements, you need to look for a board with “3S” in its name.

Another important point: some boards may have different contacts for charging (designated “C”) and load (designated “P”). For example, the board may have three contacts: “P-”, “P+” and “C-”, like on a native Makita lithium-ion board. Such a fee will not suit us. Charging and discharging (charge/discharge) must be carried out through one contact! That is, there should be 2 working contacts on the board: just “plus” and just “minus”. Because our old charger also only has two pins.

In general, as you might have guessed, with my experiments I wasted a lot of money on both the wrong elements and the wrong boards, making all the mistakes that could be made. But I gained invaluable experience.

How to disassemble a screwdriver battery

How to disassemble an old battery? There are batteries where the case halves are attached with screws, but there are also ones with glue. My batteries are just one of the last ones, and for a long time I generally thought that they were impossible to disassemble. It turns out it's possible if you have a hammer.

In general, with the help of intensive blows to the perimeter of the edge of the lower part of the case (a hammer with a nylon head, the battery must be held suspended in your hand), the gluing area is successfully separated. The case is not damaged in any way, I have already disassembled 4 pieces like this.

The part that interests us.

From the old circuit, only contact plates are needed. They are firmly spot welded to the top two elements. You can pick out the weld with a screwdriver or pliers, but you need to pick as carefully as possible so as not to break the plastic.

Everything is almost ready for further work. By the way, I left the standard temperature sensor and circuit breaker, although they are no longer particularly relevant.

But it is very likely that the presence of these elements is necessary for the normal operation of the standard charger. Therefore, I strongly recommend saving them.

Assembling a lithium-ion battery

Here are the new Sanyo UR18650NSX cells (you can find them on Aliexpress using this article number) with a capacity of 2600 mAh. For comparison, the old battery had a capacity of only 1300 mAh, half as much.

You need to solder the wires to the elements. Wires must be taken with a cross-section of at least 0.75 sq. mm, because we will have considerable currents. A wire with this cross-section works normally with currents of more than 20 A at a voltage of 12 V. Lithium-ion cans can be soldered; short-term overheating will not harm them in any way, this has been verified. But you need a good fast-acting flux. I use TAGS glycerin flux. Half a second - and everything is ready.

Solder the other ends of the wires to the board according to the diagram.

I always use even thicker wires of 1.5 sq. mm for the battery contact connectors - because space allows. Before soldering them to the mating contacts, I put a piece of heat-shrink tubing on the board. It is necessary for additional isolation of the board from the battery cells. Otherwise, the sharp solder edges can easily rub or pierce the thin film of the lithium-ion cell and cause a short circuit. You don’t have to use heat shrink, but at least laying something insulating between the board and the elements is absolutely necessary.

Now everything is insulated as it should.

The contact part can be strengthened in the battery case with a couple of drops of super glue.

The battery is ready for assembly.

It’s good when the case is on screws, but this is not my case, so I just glue the halves together again with “Moment”.

The battery is charged using a standard charger. True, the operating algorithm is changing.

I have two chargers: DC9710 and DC1414 T. And they work differently now, so I'll tell you exactly how.

Makita DC9710 charger and lithium-ion battery

Previously, the battery charge was controlled by the device itself. When the full level was reached, it stopped the process and signaled the completion of charging with a green indicator. But now the BMS circuit we installed is responsible for level control and power shutdown. Therefore, when charging is complete, the red LED on the charger will simply turn off.

If you have such an old device, you are in luck. Because everything is simple with him. The diode is on - charging is in progress. Goes off – charging is complete, the battery is fully charged.

Makita DC1414 T charger and lithium-ion battery

There is a small nuance here that you need to know. This charger is newer and is designed to charge a wider range of batteries from 7.2 to 14.4 V. The charging process on it proceeds as usual, the red LED is on:

But when the battery (which in the case of NiMH cells is supposed to have a maximum voltage of 10.8 V) reaches 12 volts (we have Li-Ion cells, for which the maximum total voltage can be 12.6 V), the charger will go crazy. Because he will not understand which battery he is charging: either a 9.6-volt one or a 14.4-volt one. And at this moment, the Makita DC1414 will enter error mode, flashing the red and green LED alternately.

This is fine! Your new battery will still charge - although not completely. The voltage will be approximately 12 volts.

That is, you will miss some part of the capacity with this charger, but it seems to me that this can be survived.

In total, upgrading the battery cost about 1000 rubles. The new Makita PA09 costs twice as much. Moreover, we ended up with twice the capacity, and further repairs (in the event of a short-term failure) will only consist of replacing lithium-ion elements.

Initially, lithium-ion batteries were intended for mobile devices, be it phones, cameras, video cameras, laptops, but in the last decade, the production of lithium batteries has also been launched by most automakers.

Then why assemble it yourself if you can buy a ready-made battery? There are enough reasons:

factory-assembled lithium batteries are unreasonably expensive;
it is very difficult to find a battery of suitable dimensions for a motorcycle or car;
If the assembled battery fits into the installation space with a margin, then it will have a lower capacity.

With your own hands, you can assemble a battery from individual elements, which will be limited only by energy density and price per watt-hour, depending on the type of elements selected:

NiMH- nickel metal hydride;
Li-ion- lithium ion;
Li-pol- lithium polymer;
LiFePO4- lithium iron phosphate;
Lead Acid- lead-acid.

Danger of overcharging lithium cells

Lithium cells must be handled with care because they concentrate a lot of energy into a small area when fully charged. Therefore, protected Li-ion and Li-pol batteries have been on sale for a long time.

Back in 1991, Sony drew attention to the explosion hazard of Li-ion cells. Nowadays, all batteries without exception are wound with a two-layer separator between the plates to eliminate the risk of internal short circuit. All branded batteries are equipped with a field-effect transistor protection board, which turns them off in the following cases:

The battery is excessively discharged - below 2.5 V.
Overcharged - over 4.2 V.
The charging current is too high - more than 1C (C is the battery capacity in Ah).
Short circuit.
The load current is exceeded - more than 5C.
Incorrect polarity when charging.

For additional security, there is a thermal fuse that opens the circuit when the lithium element overheats above 90 °C.

How to find a battery with protection?

Lithium batteries are produced in household and technological versions. Batteries for household use have a durable plastic case and built-in electronic protection. Technological elements intended for industrial use are most often produced in an unframed form and do not have built-in protection.

Protected batteries have the word " protected" in the title, unprotected - " unprotected».
Batteries with protection are 2–3 mm longer than regular ones due to the board, which is installed at the end near the negative pole.
The price of batteries with protection for the same capacity is always higher, because the board with electronic components also costs money.

The positive pole of the battery must be connected to the protective board with a thin plate, otherwise the protection will not work.

When individual elements are connected in series, their voltages are summed, but the capacitance remains the same. Even from the same series, batteries have different characteristics, so they charge at different speeds. For example, when charging to a total voltage of 12.6 V, the element in the middle can overcharge to 4.4 V, which is dangerous due to overheating.

To prevent excessive overcharging of unprotected elements, balancing cables are used that are connected to special chargers, for example: iMAX B6 and Turnigy Accucel-6.

Each Li-ion and Li-pol rechargeable battery for household use has the most advanced surge protection in the form of a voltage control circuit, a field-effect transistor switch and a thermal fuse.

Balancing of the protected elements is not required, since if the voltage on any of them increases to 4.2 V, charging is guaranteed to be interrupted.

When assembling a battery from cells without protection, there is a way out - install one voltage control board for all batteries, for example, connecting them according to the 4S2P circuit - 4 in series, 2 in parallel.

There is also no need to balance parallel connected elements.

When batteries are connected in parallel, their voltage remains the same, and their capacities are summed up.

About the capacity of lithium batteries

Capacity is the ability of a battery to deliver current, measured in milliampere hour (mAh) or ampere hour (Ah). For example, a battery with a capacity of 2 Ah can deliver a current of 2 A for one hour, or 1 A for two hours. But this dependence of the current on the load connection time is not linear - at a certain point in the graph, when the current doubles, the battery operating time decreases fourfold. Therefore, manufacturers always indicate the capacity calculated when the battery is discharged with an excessively low current of 100 mA.

The amount of energy depends on the battery voltage, so nickel metal hydride cells with the same capacity have 3 times less energy intensity than lithium ion ones:

NiMH- 1.2 V * 2.2 Ah = 2.64 watt-hours;
Li-ion- 3.7 V * 2.2 Ah = 8.14 watt-hours.

When searching for and purchasing rechargeable batteries, give preference to well-known companies such as Samsung, Sony, Sanyo, Panasonic. The batteries from these manufacturers have a capacity that most closely matches that indicated on their case. The inscription 2600 mA on Sanyo elements is not much different from their real capacity of 2500–2550 mA. Counterfeits from Chinese manufacturers with a vaunted capacity of 4200 mA do not even reach 1000 mA, but their price is half as much as the Japanese originals.

To assemble a battery from lithium batteries, you can use:

soldering;
junction boxes;
Neodymium magnets;

Soldering during factory assembly is used extremely rarely, since the lithium element is destroyed by heat, losing part of its capacity. On the other hand, at home, soldering will be the optimal way to connect batteries, since even minimal resistance at the contacts will significantly reduce the total voltage at the common terminals. You need to use a powerful 100 W soldering iron and touch the lithium batteries for no more than two seconds.

Powerful rare earth magnets are coated with a layer of nickel or zinc, so their surface does not oxidize. These magnets provide excellent contact between the batteries. If you want to solder wires to a magnet, do not forget about the Curie temperature, above which any magnet becomes a pebble. The approximate permissible temperature for magnets is 300°C.

If you use a box to connect batteries, then a big advantage becomes obvious, since it will be easier to select batteries by voltage or change a damaged element.

Spot welding is the best method for joining lithium cells when assembling laptop batteries.

It is not profitable to buy a ready-made lithium battery for a car or motorcycle when you can assemble it yourself for a lower price. You can save up to $70 if you don't buy a new laptop battery and replace the cells yourself.

It is difficult to judge savings when assembling powerful lithium batteries to power electric vehicles or autonomous power supply systems at home, since in these cases there are additional costs for control and monitoring equipment.