How tightly entered our lives Li-ion battery s. The fact that they are used in almost all microprocessor electronics is already the norm. So radio amateurs have long adopted them and use them in their homemade products. I contribute to this significant advantages of Li-ion batteries, such as small size, large capacity, big choice executions of various capacities and forms.

The most common battery is 18650, its voltage is 3.7 V. For which I will make a discharge indicator.
Probably, it’s not worth telling how low their discharge is harmful to the crane batteries. And for batteries of all varieties. Proper maintenance of rechargeable batteries will extend their life several times and save you money.

Charging indicator circuit

If you open any cell phone battery, you will find that a small printed circuit board is soldered to the terminals of the battery cell. This is the so-called protection scheme, or Protection IC.

Due to their characteristics, lithium batteries require constant monitoring. Let's take a closer look at how the protection scheme is arranged, and what elements it consists of.

Ordinary charge controller circuit lithium battery is a small board on which is mounted electronic circuit from SMD components. The controller circuit of 1 cell (“bank”) at 3.7V, as a rule, consists of two microcircuits. One microcircuit is a control one, and the other is an executive one - an assembly of two MOSFET transistors.

The photo shows a 3.7V battery charge controller board.

A microcircuit marked DW01-P in a small package is essentially the “brain” of the controller. Here is a typical wiring diagram for this chip. In the diagram, G1 is a cell of a lithium-ion or polymer battery. FET1, FET2 are MOSFET transistors.

Sokolevka, appearance and pin assignment of the DW01-P chip.

MOSFET transistors are not included in the DW01-P chip and are made as a separate chip assembly of 2 MOSFET transistors N-type. The assembly marked 8205 is usually used, and the package can be either 6-pin (SOT-23-6) or 8-pin (TSSOP-8). The assembly can be labeled as TXY8205A, SSF8205, S8205A, etc. You can also find assemblies marked 8814 and similar.

Here is the pinout and composition of the S8205A chip in the TSSOP-8 package.

Two FETs are used to separately control the discharge and charge of the battery cell. For convenience, they are made in one case.

The transistor (FET1) that is connected to the OD pin ( Overdischarge) DW01-P chips, controls the battery discharge - connects / disconnects the load. And the one (FET2) that is connected to the OC pin ( over charge) – connects/disconnects the power supply (charger). Thus, by opening or closing the corresponding transistor, it is possible, for example, to turn off the load (consumer) or stop charging the battery cell.

Let's look at the logic of the control chip and the entire protection circuit as a whole.

Overcharge protection.

As you know, overcharging a lithium battery over 4.2 - 4.3V is fraught with overheating and even an explosion.

If the cell voltage reaches 4.2 - 4.3V ( Overcharge Protection Voltage – VOCCP), then the control chip closes the FET2 transistor, thereby preventing further battery charging. The battery will be disconnected from the power source until the voltage on the cell drops below 4 - 4.1V ( Overcharge Release Voltage – VOCR) due to self-discharge. This is only if there is no load connected to the battery, for example, it is removed from a cell phone.

If the battery is connected to the load, then the FET2 transistor opens again when the cell voltage drops below 4.2V.

Overdischarge Protection.

If the battery voltage drops below 2.3 - 2.5V ( Overcharge Protection Voltage – VODP), then the controller turns off the FET1 MOSFET transistor - it is connected to the DO pin.

There are very interesting condition . Until the voltage on the battery cell exceeds 2.9 - 3.1V ( Overdischarge Release Voltage – VODR), the load will be completely disconnected. The controller terminals will be 0V. Those who are not familiar with the logic of the protective circuit may take this state of affairs for the “death” of the battery. Here is just a small example.

Miniature Li-polymer battery 3.7V from an MP3 player. Composition: control controller - G2NK (series S-8261), assembly of field-effect transistors - KC3J1.

The battery is discharged below 2.5V. The control circuit disconnected it from the load. At the output of the controller 0V.

At the same time, if you measure the voltage on the battery cell, then after the load was turned off, it slightly grew and reached the level of 2.7V.

In order for the controller to reconnect the battery to the “outside world”, that is, to the load, the voltage on the battery cell must be 2.9 - 3.1V ( VODR).

This raises a very reasonable question.

The diagram shows that the drain terminals (Drain) of transistors FET1, FET2 are connected together and are not connected anywhere. How does the current flow through such a circuit when the overdischarge protection is triggered? How can we recharge the “bank” of the battery again so that the controller turns on the discharge transistor again - FET1?

If you rummage through datasheets for Li-ion / polymer protection chips (including DW01-P, G2NK), then you can find out that after the deep discharge protection is triggered, the charge detection circuit is in operation - Charger Detection. That is, when connected charger the circuit will detect that the charger is connected and allow the charging process.

Charging to a level of 3.1V after a deep discharge of a lithium cell can take a very long time - several hours.

To restore a lithium-ion / polymer battery, you can use special tools, for example, the Turnigy Accucell 6 universal charger. I already talked about how to do this here.

It was with this method that I managed to restore a Li-polymer 3.7V battery from an MP3 player. Charging from 2.7V to 4.2V took 554 minutes and 52 seconds, which is more than 9 hours! That's how long a "recovery" charge can last.

Among other things, the functionality of lithium battery protection circuits includes overcurrent protection ( Overcurrent Protection) and short circuit. Overcurrent protection is triggered in the event of a sharp drop in voltage by a certain amount. After that, the microcircuit limits the load current. In the event of a short circuit (short circuit) in the load, the controller completely turns it off until the short circuit is eliminated.

Li-ion battery controller circuit
Scheme of the controller of a lithium-ion battery Device and principle of operation of the protective controller Li-ion / polymer battery If you open any battery from a cell phone, you can

Probably, for most radio amateurs, over the years, a box is put into which they are folded “for later” lithium batteries from the untimely deceased (drowned, fallen from the balcony, gnawed by Druzhok) mobile phones and cameras. They lie in a box and wait in the wings .. And the hour still does not come. The reason is simple - to use battery in the same flashlight you need to do it charge controller, and for some reason they didn’t deliver charging chips at the local radio store .. Yes, a problem.

And what's a poor radio amateur to do? Everything is very simple - you can get by with "pasture" using what is hidden from the eyes of the average user. Namely, the protection board, which is carefully hidden inside each lithium ion or lithium polymer battery. Without it, they are not allowed to use accumulators in household appliances due to the exceptional activity of lithium. If you disassemble battery from mobile phone , we will find such a simple device inside:

That's what it is battery protection board. This board has a two-level comparator chip and field-effect transistor. When the voltage drops to accumulator below 3v or rise above 4.25v this comparator turns off the transistor and isolates battery from the outside world, thereby protecting from damage.

I had an idea to try to use these properties of the protection board to control the process phone battery charging from standard USB ports computer (which has a 500mA current limiter as a bonus). So we get soup from an ax. More precisely, charging “out of nothing”. It remains to somehow display the progress (and completion) of the process to the user charging. Below is scheme this node.

Works very simply. When connected to USB port at charging starts and lights up Light-emitting diode. The charge current is limited by the computer port and resistors on the board. Upon reaching the voltage accumulator 4.25v triggers the comparator of the protection board and breaks the charge circuit. The LED will turn off. In the first charging option, I used the button to start the charging process. But it turned out that a 100nF capacitor was enough for the initial opening field effect transistor. The circuit is very simple and starts working without adjustment.
The board file can be downloaded from the section "File Catalog"

If, while repeating this design, you have any questions or ideas for improving it, write to me online your thoughts on this.

How to charge a lithium ion battery without a controller
How to charge a lithium-ion battery without a controller Probably, for most radio amateurs, over the years, a box is put into which lithium batteries from

If you are interested in how to charge a lithium-ion battery, then you have come to the right place.

Modern mobile devices require offline source nutrition.

And this is true both for “high technologies” like smartphones and laptops, and for more simple devices, say, electric drills or multimeters.

There are many different types of batteries. But for portable equipment, Li-Ion is most often used.

The relative ease of production and low cost led to such a wide distribution.

This was facilitated by excellent performance, plus low self-discharge and a large margin of charge-discharge cycles.

Important! For greater convenience, most of these batteries are equipped with a special control device that prevents the charge from passing critical levels.

During a critical discharge, this circuit simply stops supplying voltage to the device, and during excess acceptable level charge cuts off the incoming current.

At the same time, after reaching the nominal 100%, charging should last another one and a half to two hours.

This is necessary because the actual battery will be 70-80% charged.

When charging from a laptop or desktop computer Please note that the USB port is unable to provide sufficient high voltage, therefore, the process will take more time.

Alternating full and partial (80-90%) charge cycles will extend the life of the device.

Despite such a smart architecture and general unpretentiousness, following some rules for using batteries will help extend their life.

So that the battery of the device does not “suffer”, it is enough to follow simple recommendations.

Rule 1: Don't let your battery drain completely

Lithium-ion batteries of modern designs do not have a “memory effect”. Therefore, it is better to charge them before the moment of complete discharge comes.

Some manufacturers measure the life of their batteries by the number of charge cycles from zero.

The highest quality products can withstand up to 600 such cycles. When charging a battery with 10-20% remaining, the number of cycles increases to 1700.

Rule 2. A complete discharge still needs to be taken every three months.

With unstable and irregular charging, the average statistical marks of the maximum and minimum charges in the previously mentioned controller go astray.

This leads to the fact that the device receives incorrect information about the amount of charge.

Preventive discharge will help prevent this. At full discharge battery, minimum value charge in the control circuit (controller) will be reset.

After that, it is necessary to charge the battery "to the eyeballs", having kept from eight to twelve hours in a state connected to the network.

This will update the maximum value. After such a cycle, the battery will be more stable.

Rule 3. An unused battery must be stored with a small amount of charge

Before storage, it is better to charge the battery by 30-50% and store at a temperature of 15 0 C. In such conditions, the battery can be stored for quite a long time without much damage.

A fully charged battery will lose a significant amount of capacity during storage.

And completely discharged after a long storage, it remains only to give it for processing.

Rule 4. Charging must be done only with original devices

It is noteworthy that the charger itself is built into the design of a mobile device (phone, tablet, etc.).

The external adapter in this case acts as a rectifier and voltage stabilizer.

The use of third-party "charging" can adversely affect their condition.

Rule 5. Overheating is detrimental to Li-Ion batteries

High temperatures have an extremely negative effect on the design of batteries. Low ones are also fatal, but to a much lesser extent.

This must be remembered when using lithium-ion batteries.

The battery must be protected from direct sunlight and used at a distance from heat sources.

The permissible temperature range is between -40 0 C and +50 0 C.

Rule 6

It is not safe to use non-certified chargers. In particular, common Chinese-made "frogs" often ignite during the charging process.

Before using such a universal charger, you should check the maximum allowable values ​​indicated on the packaging.

So, attention must be paid to the maximum capacity.

If the limit is less than the capacity of the battery, then at best it will not fully charge.

When the battery is connected, the corresponding indicator on the frog body should light up.

If this does not happen, then the charge is critically low or the battery is out of order.

When the charger is connected to the network, the connection indicator should light up.

Another diode is responsible for achieving the maximum charge, which is activated in appropriate conditions.

Tips for using Li-ion batteries

How to charge and maintain a lithium-ion battery: 6 simple rules

How to charge and maintain a lithium-ion battery: 6 simple rules
How to charge and maintain a lithium ion battery: 6 simple rules If you are wondering how to charge a lithium ion battery, then you have come to the right place. Modern mobile devices

Everyone knows the advantages of lithium batteries - first of all, this is a high energy density, low weight and the absence of a "memory effect". It is also worth noting that the potential of one lithium battery. (3.6V) is three times that of a single NiCd or NiMH battery (1.2V).

However, lithium batteries have a number of features that do not allow their safe use without special control systems. These systems are called charge and discharge controllers. In today's industry, there are highly integrated microcircuits ready to perform these functions. But, as it turned out, they are not available for mass use. They are not sold in radio parts stores by the piece. They must be ordered from companies specializing in the supply electronic components for enterprises and repair shops. And the minimum lot in this case is from 10 pieces (this is at best).

All this prompted us to develop our controller on discrete elements available in any provincial radio store.

When discharging a lithium battery. you need to control its voltage and current strength in the circuit.

The voltage on a charged lithium battery. is 4.2V, not 3.6V as it says on it. Up to 3.6V, it drops under a load close to the capacity of the battery. Voltage control is not to give the battery. discharge below 3V. This threshold varies within 0.5 V depending on the chemical composition and geometric shape of the battery. Battery discharge. below 3V, leads to irreversible chemical processes inside the battery, which makes it unsuitable for further use.

To control the current strength in the circuit, it is necessary to provide a shutdown mechanism similar to the machine that is in the electrical panel in each apartment. Those. it must protect against short circuits and turn off when a certain current in the circuit is exceeded. In general, the maximum discharge current that a battery can deliver. equal to its capacity. For example, accum. with a capacity of 2A h can safely deliver a current of 2A. Battery work at currents exceeding its capacity, it is possible in short-term modes, or in normal mode, if this is indicated in the documentation by the battery manufacturer. In the event of a short circuit, the lithium battery might explode! Be careful!

More about chemical processes, charge and discharge modes of lithium batteries. can be read here Panasonic Lithium Ion Handbook (in English).

It all started with the fact that the battery in my laptop turned off. The laptop was two years old, from the battery. it almost did not work - it was always connected to the network. As I was later told, this could be the cause of the battery failure. Those. it was not a slow dying battery. with a decrease in capacity, on the contrary, the laptop worked from it for five hours, just one fine day, it did not turn on from the battery and that's it. The battery is no longer detected in Windows, and I concluded that the built-in battery controller burned out. batteries. Having disassembled the battery, we saw 6 elements, combined 2 into 3 cells with a series-parallel connection.

By measuring the voltage on each cell, we made sure that they were charged. This once again confirmed the version of the controller failure. During external inspection of the controller, no visible damage was found. I rejected the idea of ​​\u200b\u200brepairing the controller as difficult (on the forums, people wrote about soldering and programming the controller processor). In general, the complexity of this controller made a strong impression. Who knows what really burned out there?

That's why I ordered new battery, but I decided to do this later. But in vain!

I took care of them two months later. I tore the elements out of the case, disconnected them from the controller, measured the voltage on them and was very surprised - 4 elements were completely discharged! And on the other two, the voltage was about 1V. Apparently the damaged controller completely discharged 2 cells through itself.

According to the instructions, battery. discharged below 3V, it was necessary to charge with a current of 0.1 from the capacity. These 4 elements could not be charged. No tambourine dancing, freezing and thawing, tapping, etc. didn't help. I had to throw them out. This is the deep overdischarge that kills lithium batteries. The remaining two elements were charged successfully.

The elements were labeled Sanyo UR18650FM 2.6AH. It is immediately clear that the capacity of the element is 2.6 Ah and it is produced by the Japanese corporation Sanyo. Searching the corporation's website led us to a document called . Only the letter M at the end is missing. The document turned out to be very interesting. It contained specifications battery with a capacity of 2.5 Ah, the dimensions coincided with ours.

Deciding to use this document as a guide to action, we set about designing our discharge controller.

From the “Discharge rate characteristics” graph (characteristics of the discharge dynamics), it became clear that the element allows a discharge of up to 2.7V and a current of 2C, i.e. double capacity. Accordingly, our element with a capacity of 2.6A h can produce 5.2A.

discharge controller

Having comprehensively analyzed this document and other reference literature, Skvortsov Vladimir Nikolaevich (not to be confused with Starling) created a controller for working with one or two lithium cells. The controller protects the cells from short circuits and overdischarge.

The controller circuit shown in the figure provides load disconnection when the battery voltage drops to 6V (3V for each element). A short circuit is considered a current strength above 4A.

To use a controller with one element (shutdown at 3V), you need to select (increase) the resistor R1 - it is responsible for the response threshold when the voltage drops. You also need to take into account the individual characteristics of the transistor VT1 (tolerance% deviation).

To control the current strength, a resistor R7 is selected. The smaller its value, the more current the controller passes.

As a transistor VT3, you can use any powerful field-effect transistor with a current margin of 3 times the battery capacity, for example 15N03.

The principle and modes of operation of the controller

Power on, normal mode

When a battery of two charged batteries (8.4V) is connected, the VT4 transistor opens. Due to the base current through R4, the voltage at the VT4 emitter becomes about 0.7V. Also, resistor R4 keeps VT2 closed.

When VT4 is opened, a current begins to flow through the R1-R2 divider, which creates a voltage drop across R1, and VT1 opens. The voltage on its drain becomes close to the voltage on the battery. Through the resistor R3, it is fed to the gate VT3 and it opens. In this case, the "-" battery through R7 and open VT3 is connected to the output terminal "-". The controller turned on.

Overdischarge protection

When the battery voltage the battery reaches 6V (3V on each element), the voltage at the R1-R2 divider decreases, the voltage at the VT1 gate also decreases to the closing threshold, VT1 closes. The shutter VT3 is connected through R5 to the "-" battery. batteries, so VT3 also closes. The load is turned off. To bring the controller into the initial state you need to disconnect the load and charge the battery.

When testing assembled circuit you need to connect at least some minimum load to it, for example, LEDs. The protection mechanism works only with the connected load, in addition, the LEDs will clearly indicate the disconnection of the load.

Short circuit protection

The short circuit current is set by R7. The smaller its value, the more current the controller passes. The circuit in Figure 1 uses a 0.1 ohm resistor. With such a resistor, the controller allows current up to 4A, more current is considered a short circuit. When working at high currents, the resistor R7 must be of sufficient power - at least 1W.

When exceeding admissible current, voltage drop at R7 + voltage drop at the source - the drain of VT3 increases to the opening level of VT2. Open VT2 connects the VT3 gate to the "-" battery, VT3 closes. The drain VT3 as well as the base VT4 and the gate VT2 are connected to the “+” of the battery through the load. VT4 closes, the voltage on the divider R1-R2 is about 0, VT1 also closes. The load is turned off. To bring the controller to its original state, you need to disconnect the load.

Printed circuit board

The printed circuit board in Sprint-Layout 4 format can be downloaded in rar, 5Kb.

If you do not have this program, you can download it in rar, 1Mb.

The dimensions of the device (30 x 16mm) were chosen for the possibility of its installation in the end of the battery. batteries.

Device photos

Please note that the base of the transistor VT4 (KT3107) and the gate VT2 (2SK583) are conductors on the reverse side printed circuit board.

Battery preparation

Do not use batteries in the same device different types and stamps. It is better and safer to find identical elements.

When using two elements, you need to balance their initial potential - i.e. they should have the same voltage. To do this, connect their negative poles (minuses) directly, and the positive ones through a 30 Ohm resistor. The power of the resistor is 1 or 2 watts. Then you need to measure the voltage at the terminals of the resistor. If it is more than 10 millivolts, you need to wait. You have to wait about a day. It turns out that a more charged battery is slowly discharged through a resistor to a less charged one. That. voltage equalizes. Balanced elements can be connected directly without a resistor - in series or in parallel.

A little clarification about the serial connection. Factory integrated discharge controllers monitor the voltage on each of the series-connected elements. Our controller only controls the total output voltage. Measurements have shown that when using balanced cells, the voltage difference across the cells is 5 - 8 millivolts. This is perfectly acceptable. Therefore, there is no need to install a separate controller on each element.

charge theory

Factory charge controllers control voltage, current and charge time, select normal or gentle mode. If the voltage on the cell is above 3V, it is charging normally. The charging process in this case goes in 2 stages:
Stage 1 - charging with direct current (Constant current - CC);
Stage 2 - charging with constant voltage (Constant voltage - CV).

The maximum charge current depends on the capacity (C) of the battery, as a rule it is 0.7C or 1.0C. For our cells, the charge current was indicated in the document, and was equal to 0.7C. Charge voltage 4.2V (for one cell).

The power supply for charging one battery must have a voltage of 4.2V and provide a current of 0.7C (where C is the battery capacity, in our case 2.6 0.7 \u003d 1.82A). If the elements are connected in series, then the charge voltage doubles - 8.4V. If in parallel, the current strength doubles 2 0.7C \u003d 1.4C, and the voltage remains 4.2V.

The Charge characteristics graph shows both stages of charging. At the first stage, through the battery. pass a current of 0.7C. The main thing here is not to let the current rise above this value. At the same time, the voltage on the element gradually increases from 3 to 4.2V. This stage is called constant current (CC), which means that while the voltage rises, the current remains constant.

The first stage ends when the voltage on the element reaches 4.2V. This is indicated by the red number 1 on the graph. From this moment, the second stage begins - constant voltage (CV). This means that the voltage remains constant at 4.2V, and the current gradually decreases to a vanishingly small value. The moment of the beginning of the decrease in the current strength is indicated on the graph by the red number 2.

As can be seen from the graph, 80% of the capacity gain falls on the first stage.

Factory controllers consider charging complete when the current drops to a predetermined value - as a rule, this is 0.1C. In our graph, this is 50 milliamps. Also, some factory controllers monitor charging time. If the battery has not been fully charged within a certain time (the current has not dropped to the desired value), the controller also stops charging. The charge time depends on the capacity and charge current, and is indicated in the documentation. For our battery, this is 3 hours at a current strength of 0.7C.

The gentle charge mode is selected by the controller if the voltage on the battery was below 3V. Such an element is considered to be deeply discharged, and it must be charged carefully. In this case, charging starts from the Precharge stage. At this stage, the charge current is set to 0.1 of the capacity (0.1C). With this current, the voltage on the element is slowly raised to 3V. And then everything is as usual.

If you use serviceable elements and do not discharge them below 3V, you can completely get by with improvised means. To do this, you need a power supply with a voltage of 4.2 or 8.4V and current limiting. The end of the charge can be tracked by current strength or not tracked at all, but turn off the power supply after 2 or 3 hours.

In the near future, we will publish ways to refine conventional power supplies to meet the above characteristics.

To be continued…

Development of the device and printed circuit board - Skvortsov Vladimir Nikolaevich
Statement of the problem, submission and design of the material - Ugreninov Vitaly
Tyumen-Kosmopoisk, 2009

Sources used

Mini - USB charging Joint technical group TEGIR. expeditionary energy.

Lithium Ion Handbook Panasonic industrial

UR18650F Specifications SANYO Mobile Energy Company

Lithium ion Battery lineup SANYO Mobile Energy Company

Progress is moving forward, and lithium batteries are increasingly replacing the traditionally used NiCd (nickel cadmium) and NiMh (nickel metal hydride) batteries.
With a comparable weight of one cell, lithium has a large capacity, in addition, the cell voltage is three times higher - 3.6 V per cell, instead of 1.2 V.
The cost of lithium batteries has begun to approach conventional alkaline batteries, the weight and size are much smaller, and besides, they can and should be charged. The manufacturer says 300-600 cycles can withstand.
There are different sizes and choosing the right one is not difficult.
The self-discharge is so low that they lie for years and remain charged, i.e. the device remains operational when it is needed.

"C" stands for Capacity

And you can make yourself a simple or not very simple charger, depending on your experience and capabilities.

Diagram of a simple charger on the LM317

Rice. 5.

The required charging current for a particular lithium-ion (Li-Ion) and lithium-polymer (Li-Pol) battery is selected by changing the resistance Rx.
The resistance Rx approximately corresponds to the following ratio: 0.95/Imax.
The value of the resistor Rx indicated in the diagram corresponds to a current of 200 mA, this is an approximate value, it also depends on the transistor.

It is necessary to provide a radiator depending on the charge current and input voltage.
The input voltage must be at least 3 volts higher than the battery voltage for normal operation of the stabilizer, which for one bank is? 7-9 V.

Diagram of a simple charger on the LTC4054

Rice. 6.

Rice. 7. This small 5-leg chip is labeled "LTH7" or "LTADY"

I will not go into the smallest details of working with the microcircuit, everything is in the datasheet. I will describe only the most necessary features.
Charge current up to 800 mA.
The optimal supply voltage is from 4.3 to 6 Volts.
Charge indication.
Output short circuit protection.
Overheating protection (reduction of charge current at temperatures above 120°).
Does not charge the battery when the voltage on it is below 2.9 V.

The charge current is set by a resistor between the fifth output of the microcircuit and ground according to the formula

I=1000/R,
where I is the charge current in amperes, R is the resistance of the resistor in ohms.

Lithium battery low indicator

Rice. eight.

The nuance of durability

Operation and Precautions

Failure to comply with the first three points leads to a fire, the rest - to a complete or partial loss of capacity.

From the practice of many years of use, I can say that the capacity of the batteries changes little, but the internal resistance increases and the battery starts to work less in time at high consumption currents - it seems that the capacity has fallen.
Therefore, I usually put a larger capacity, which the dimensions of the device allow, and even old cans, which are ten years old, work pretty well.

For not very high currents, old cell batteries are suitable.

Where do I use lithium batteries

I put small batteries in children's toys, watches, etc., where there were 2-3 "tablet" elements from the factory. Where exactly 3V is needed, I add one diode in series and it turns out just right.

I put in LED flashlights.

Instead of the expensive and low-capacity Krona 9V, I installed 2 cans in the tester and forgot all the problems and extra costs.

In general, I put it wherever it turns out, instead of batteries.

Where do I buy lithium and usefulness on the topic

At the expense of capacity, the Chinese usually lie and it is less than written.

Honest Sanyo 18650