Assessing the characteristics of a particular charger is difficult without understanding how an exemplary charge of a li-ion battery should actually proceed. Therefore, before moving directly to the diagrams, let's remember a little theory.

What are lithium batteries?

Depending on what material the positive electrode of a lithium battery is made of, there are several varieties:

• with lithium cobaltate cathode;
• with a cathode based on lithiated iron phosphate;
• based on nickel-cobalt-aluminium;
• based on nickel-cobalt-manganese.

All of these batteries have their own characteristics, but since these nuances are not of fundamental importance for the general consumer, they will not be considered in this article.

Also, all li-ion batteries are produced in various sizes and form factors. They can be either cased (for example, the popular 18650 today) or laminated or prismatic (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, which contain electrodes and electrode mass.

The most common sizes of li-ion batteries are shown in the table below (all of them have a nominal voltage of 3.7 volts):

Designation	Standard size	Similar size
XXYY0, Where XX- indication of diameter in mm, YY- length value in mm, 0 - reflects the design in the form of a cylinder	10180	2/5 AAA
	10220	1/2 AAA (Ø corresponds to AAA, but half the length)
	10280
	10430	AAA
	10440	AAA
	14250	1/2 AA
	14270	Ø AA, length CR2
	14430	Ø 14 mm (same as AA), but shorter length
	14500	AA
	14670
	15266, 15270	CR2
	16340	CR123
	17500	150S/300S
	17670	2xCR123 (or 168S/600S)
	18350
	18490
	18500	2xCR123 (or 150A/300P)
	18650	2xCR123 (or 168A/600P)
	18700
	22650
	25500
	26500	WITH
	26650
	32650
	33600	D
	42120

Internal electrochemical processes proceed in the same way and do not depend on the form factor and design of the battery, so everything said below applies equally to all lithium batteries.

How to properly charge lithium-ion batteries

The most correct way to charge lithium batteries is to charge in two stages. This is the method Sony uses in all of its chargers. Despite a more complex charge controller, this ensures a more complete charge of li-ion batteries without reducing their service life.

Here we are talking about a two-stage charge profile for lithium batteries, abbreviated as CC/CV (constant current, constant voltage). There are also options with pulse and step currents, but they are not discussed in this article. You can read more about charging with pulsed current.

So, let's look at both stages of charging in more detail.

1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).

For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.

To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.

Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the open circuit voltage of the circuit can never exceed 6-7 volts. Otherwise, the protection board may be damaged.

At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.

2. Second charge stage- this is charging the battery with a constant voltage, but a gradually decreasing (falling) current.

At this stage, the charger maintains a voltage of 4.15-4.25 volts on the battery and controls the current value.

As the capacity increases, the charging current will decrease. As soon as its value decreases to 0.05-0.01C, the charging process is considered complete.

An important nuance of the correct charger operation is its complete disconnection from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under high voltage for a long time, which is usually provided by the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, a decrease in its capacity. Long-term stay means tens of hours or more.

During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.

We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.

Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.

At this stage, the charge is provided with a reduced constant current until the battery voltage reaches 2.8 V.

The preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries that have, for example, an internal short circuit between the electrodes. If a large charge current is immediately passed through such a battery, this will inevitably lead to its heating, and then it depends.

Another benefit of precharging is pre-heating the battery, which is important when charging at low ambient temperatures (in an unheated room during the cold season).

Intelligent charging should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion that the battery is faulty.

All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph:

Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.

Let me summarize the above and outline the main points:

1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?

The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.

For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.

2. How long does it take to charge, for example, the same 18650 batteries?

The charging time directly depends on the charging current and is calculated using the formula:

T = C / I charge.

For example, the charging time of our 3400 mAh battery with a current of 1A will be about 3.5 hours.

3. How to properly charge a lithium polymer battery?

All lithium batteries charge the same way. It doesn't matter whether it is lithium polymer or lithium ion. For us, consumers, there is no difference.

What is a protection board?

The protection board (or PCB - power control board) is designed to protect against short circuit, overcharge and overdischarge of the lithium battery. As a rule, overheating protection is also built into the protection modules.

For safety reasons, it is prohibited to use lithium batteries in household appliances unless they have a built-in protection board. That's why all cell phone batteries always have a PCB board. The battery output terminals are located directly on the board:

These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.

Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones:

If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery.

The board increases the length of the battery by 2-3 mm.

Batteries without a PCB module are usually included in batteries that come with their own protection circuits.

Any battery with protection can easily turn into a battery without protection; you just need to gut it.

Today, the maximum capacity of the 18650 battery is 3400 mAh. Batteries with protection must have a corresponding designation on the case ("Protected").

Do not confuse the PCB board with the PCM module (PCM - power charge module). If the former serve only the purpose of protecting the battery, then the latter are designed to control the charging process - they limit the charge current at a given level, control the temperature and, in general, ensure the entire process. The PCM board is what we call a charge controller.

I hope now there are no questions left, how to charge an 18650 battery or any other lithium battery? Then we move on to a small selection of ready-made circuit solutions for chargers (the same charge controllers).

Charging schemes for li-ion batteries

All circuits are suitable for charging any lithium battery; all that remains is to decide on the charging current and the element base.

LM317

Diagram of a simple charger based on the LM317 chip with a charge indicator:

The circuit is the simplest, the whole setup comes down to setting the output voltage to 4.2 volts using trimming resistor R8 (without a connected battery!) and setting the charging current by selecting resistors R4, R6. The power of resistor R1 is at least 1 Watt.

As soon as the LED goes out, the charging process can be considered completed (the charging current will never decrease to zero). It is not recommended to keep the battery on this charge for a long time after it is fully charged.

The lm317 microcircuit is widely used in various voltage and current stabilizers (depending on the connection circuit). It is sold on every corner and costs pennies (you can take 10 pieces for only 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogues of the LM317 chip are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are domestically produced).

The charging current can be increased to 3A if you take LM350 instead of LM317. It will, however, be more expensive - 11 rubles/piece.

The printed circuit board and circuit assembly are shown below:

The old Soviet transistor KT361 can be replaced with a similar pnp transistor (for example, KT3107, KT3108 or bourgeois 2N5086, 2SA733, BC308A). It can be removed altogether if the charge indicator is not needed.

Disadvantage of the circuit: the supply voltage must be in the range of 8-12V. This is due to the fact that for normal operation of the LM317 chip, the difference between the battery voltage and the supply voltage must be at least 4.25 Volts. Thus, it will not be possible to power it from the USB port.

MAX1555 or MAX1551

MAX1551/MAX1555 are specialized chargers for Li+ batteries, capable of operating from USB or from a separate power adapter (for example, a phone charger).

The only difference between these microcircuits is that MAX1555 produces a signal to indicate the charging process, and MAX1551 produces a signal that the power is on. Those. 1555 is still preferable in most cases, so 1551 is now difficult to find on sale.

A detailed description of these microcircuits from the manufacturer is.

The maximum input voltage from the DC adapter is 7 V, when powered by USB - 6 V. When the supply voltage drops to 3.52 V, the microcircuit turns off and charging stops.

The microcircuit itself detects at which input the supply voltage is present and connects to it. If the power is supplied via the USB bus, then the maximum charging current is limited to 100 mA - this allows you to plug the charger into the USB port of any computer without fear of burning the south bridge.

When powered by a separate power supply, the typical charging current is 280 mA.

The chips have built-in overheating protection. But even in this case, the circuit continues to operate, reducing the charge current by 17 mA for each degree above 110 ° C.

There is a pre-charge function (see above): as long as the battery voltage is below 3V, the microcircuit limits the charge current to 40 mA.

The microcircuit has 5 pins. Here is a typical connection diagram:

If there is a guarantee that the voltage at the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the 7805 stabilizer.

The USB charging option can be assembled, for example, on this one.

The microcircuit does not require either external diodes or external transistors. In general, of course, gorgeous little things! Only they are too small and inconvenient to solder. And they are also expensive ().

LP2951

The LP2951 stabilizer is manufactured by National Semiconductors (). It provides the implementation of a built-in current limiting function and allows you to generate a stable charge voltage level for a lithium-ion battery at the output of the circuit.

The charge voltage is 4.08 - 4.26 volts and is set by resistor R3 when the battery is disconnected. The voltage is kept very precisely.

The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (depending on the manufacturer).

Use the diode with a small reverse current. For example, it can be any of the 1N400X series that you can purchase. The diode is used as a blocking diode to prevent reverse current from the battery into the LP2951 chip when the input voltage is turned off.

This charger produces a fairly low charging current, so any 18650 battery can charge overnight.

The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).

MCP73831

The chip allows you to create the right chargers, and it’s also cheaper than the much-hyped MAX1555.

A typical connection diagram is taken from:

An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.

The assembled charger looks like this:

The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.

Here is another version of a printed circuit board with an SMD LED and a micro-USB connector:

LTC4054 (STC4054)

Very simple scheme, great option! Allows charging with current up to 800 mA (see). True, it tends to get very hot, but in this case the built-in overheating protection reduces the current.

The circuit can be significantly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it couldn’t be simpler: a couple of resistors and one condenser):

One of the printed circuit board options is available at . The board is designed for elements of standard size 0805.

I=1000/R. You shouldn’t set a high current right away; first see how hot the microcircuit gets. For my purposes, I took a 2.7 kOhm resistor, and the charge current turned out to be about 360 mA.

It is unlikely that it will be possible to adapt a radiator to this microcircuit, and it is not a fact that it will be effective due to the high thermal resistance of the crystal-case junction. The manufacturer recommends making the heat sink “through the leads” - making the traces as thick as possible and leaving the foil under the chip body. In general, the more “earth” foil left, the better.

By the way, most of the heat is dissipated through the 3rd leg, so you can make this trace very wide and thick (fill it with excess solder).

The LTC4054 chip package may be labeled LTH7 or LTADY.

LTH7 differs from LTADY in that the first can lift a very low battery (on which the voltage is less than 2.9 volts), while the second cannot (you need to swing it separately).

The chip turned out to be very successful, so it has a bunch of analogues: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, 2, HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.

TP4056

The microcircuit is made in a SOP-8 housing (see), it has a metal heat sink on its belly that is not connected to the contacts, which allows for more efficient heat removal. Allows you to charge the battery with a current of up to 1A (the current depends on the current-setting resistor).

The connection diagram requires the bare minimum of hanging elements:

The circuit implements the classical charging process - first charging with a constant current, then with a constant voltage and a falling current. Everything is scientific. If you look at charging step by step, you can distinguish several stages:

1. Monitoring the voltage of the connected battery (this happens all the time).
2. Precharge phase (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm) to a level of 2.9 V.
3. Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
4. When the battery reaches 4.2 V, the voltage on the battery is fixed at this level. A gradual decrease in the charging current begins.
5. When the current reaches 1/10 of the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm), the charger turns off.
6. After charging is complete, the controller continues monitoring the battery voltage (see point 1). The current consumed by the monitoring circuit is 2-3 µA. After the voltage drops to 4.0V, charging starts again. And so on in a circle.

The charge current (in amperes) is calculated by the formula I=1200/R prog. The permissible maximum is 1000 mA.

A real charging test with a 3400 mAh 18650 battery is shown in the graph:

The advantage of the microcircuit is that the charge current is set by just one resistor. Powerful low-resistance resistors are not required. Plus there is an indicator of the charging process, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks every few seconds.

The supply voltage of the circuit should be within 4.5...8 volts. The closer to 4.5V, the better (so the chip heats up less).

The first leg is used to connect a temperature sensor built into the lithium-ion battery (usually the middle terminal of a cell phone battery). If the output voltage is below 45% or above 80% of the supply voltage, charging is suspended. If you don't need temperature control, just plant that foot on the ground.

Attention! This circuit has one significant drawback: the absence of a battery reverse polarity protection circuit. In this case, the controller is guaranteed to burn out due to exceeding the maximum current. In this case, the supply voltage of the circuit directly goes to the battery, which is very dangerous.

The signet is simple and can be done in an hour on your knee. If time is of the essence, you can order ready-made modules. Some manufacturers of ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector).

You can also find ready-made boards with a contact for a temperature sensor. Or even a charging module with several parallel TP4056 microcircuits to increase the charging current and with reverse polarity protection (example).

LTC1734

Also a very simple scheme. The charging current is set by resistor R prog (for example, if you install a 3 kOhm resistor, the current will be 500 mA).

Microcircuits are usually marked on the case: LTRG (they can often be found in old Samsung phones).

Any pnp transistor is suitable, the main thing is that it is designed for a given charging current.

There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown.

The LT1716 comparator in this case can be replaced with a cheap LM358.

TL431 + transistor

It is probably difficult to come up with a circuit using more affordable components. The most difficult thing here is to find the TL431 reference voltage source. But they are so common that they are found almost everywhere (rarely does a power source do without this microcircuit).

Well, the TIP41 transistor can be replaced with any other one with a suitable collector current. Even the old Soviet KT819, KT805 (or less powerful KT815, KT817) will do.

Setting up the circuit comes down to setting the output voltage (without a battery!!!) using a trim resistor at 4.2 volts. Resistor R1 sets the maximum value of the charging current.

This circuit fully implements the two-stage process of charging lithium batteries - first charging with direct current, then moving to the voltage stabilization phase and smoothly reducing the current to almost zero. The only drawback is the poor repeatability of the circuit (it is capricious in setup and demanding on the components used).

MCP73812

There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). Based on it, a very budget charging option is obtained (and inexpensive!). The whole body kit is just one resistor!

By the way, the microcircuit is made in a solder-friendly package - SOT23-5.

The only negative is that it gets very hot and there is no charge indication. It also somehow doesn’t work very reliably if you have a low-power power source (which causes a voltage drop).

In general, if the charge indication is not important for you, and a current of 500 mA suits you, then the MCP73812 is a very good option.

NCP1835

A fully integrated solution is offered - NCP1835B, providing high stability of the charging voltage (4.2 ±0.05 V).

Perhaps the only drawback of this microcircuit is its too miniature size (DFN-10 case, size 3x3 mm). Not everyone can provide high-quality soldering of such miniature elements.

Among the undeniable advantages I would like to note the following:

1. Minimum number of body parts.
2. Possibility of charging a completely discharged battery (precharge current 30 mA);
3. Determining the end of charging.
4. Programmable charging current - up to 1000 mA.
5. Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
6. Protection against long-term charging (by changing the capacitance of the capacitor C t, you can set the maximum charging time from 6.6 to 784 minutes).

The cost of the microcircuit is not exactly cheap, but also not so high (~$1) that you can refuse to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.

A more detailed description is in.

Can I charge a lithium-ion battery without a controller?

Yes, you can. However, this will require close control of the charging current and voltage.

In general, it will not be possible to charge a battery, for example, our 18650, without a charger. You still need to somehow limit the maximum charge current, so at least the most primitive memory will still be required.

The simplest charger for any lithium battery is a resistor connected in series with the battery:

The resistance and power dissipation of the resistor depend on the voltage of the power source that will be used for charging.

As an example, let's calculate a resistor for a 5 Volt power supply. We will charge an 18650 battery with a capacity of 2400 mAh.

So, at the very beginning of charging, the voltage drop across the resistor will be:

U r = 5 - 2.8 = 2.2 Volts

Let's say our 5V power supply is rated for a maximum current of 1A. The circuit will consume the highest current at the very beginning of the charge, when the voltage on the battery is minimal and amounts to 2.7-2.8 Volts.

Attention: these calculations do not take into account the possibility that the battery may be very deeply discharged and the voltage on it may be much lower, even to zero.

Thus, the resistor resistance required to limit the current at the very beginning of the charge at 1 Ampere should be:

R = U / I = 2.2 / 1 = 2.2 Ohm

Resistor power dissipation:

P r = I 2 R = 1*1*2.2 = 2.2 W

At the very end of the battery charge, when the voltage on it approaches 4.2 V, the charge current will be:

I charge = (U ip - 4.2) / R = (5 - 4.2) / 2.2 = 0.3 A

That is, as we see, all values ​​do not go beyond the permissible limits for a given battery: the initial current does not exceed the maximum permissible charging current for a given battery (2.4 A), and the final current exceeds the current at which the battery no longer gains capacity ( 0.24 A).

The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually turn off the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries tolerate even short-term overvoltage very poorly - the electrode masses begin to quickly degrade, which inevitably leads to loss of capacity. At the same time, all the prerequisites for overheating and depressurization are created.

If your battery has a built-in protection board, which was discussed just above, then everything becomes simpler. When a certain voltage is reached on the battery, the board itself will disconnect it from the charger. However, this charging method has significant disadvantages, which we discussed in.

The protection built into the battery will not allow it to be overcharged under any circumstances. All you have to do is control the charge current so that it does not exceed the permissible values ​​for a given battery (protection boards cannot limit the charge current, unfortunately).

Charging using a laboratory power supply

If you have a power supply with current protection (limitation), then you are saved! Such a power source is already a full-fledged charger that implements the correct charge profile, which we wrote about above (CC/CV).

All you need to do to charge li-ion is set the power supply to 4.2 volts and set the desired current limit. And you can connect the battery.

Initially, when the battery is still discharged, the laboratory power supply will operate in current protection mode (i.e., it will stabilize the output current at a given level). Then, when the voltage on the bank rises to the set 4.2V, the power supply will switch to voltage stabilization mode, and the current will begin to drop.

When the current drops to 0.05-0.1C, the battery can be considered fully charged.

As you can see, the laboratory power supply is an almost ideal charger! The only thing it can’t do automatically is make a decision to fully charge the battery and turn off. But this is a small thing that you shouldn’t even pay attention to.

How to charge lithium batteries?

And if we are talking about a disposable battery that is not intended for recharging, then the correct (and only correct) answer to this question is NO.

The fact is that any lithium battery (for example, the common CR2032 in the form of a flat tablet) is characterized by the presence of an internal passivating layer that covers the lithium anode. This layer prevents a chemical reaction between the anode and the electrolyte. And the supply of external current destroys the above protective layer, leading to damage to the battery.

By the way, if we talk about the non-rechargeable CR2032 battery, then the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only its voltage is not 3, but 3.6V.

How to charge lithium batteries (be it a phone battery, 18650 or any other li-ion battery) was discussed at the beginning of the article.

85 kopecks/pcs. Buy MCP73812 65 RUR/pcs. Buy NCP1835 83 RUR/pcs. Buy *All chips with free shipping

Converting a screwdriver battery to lithium cells

Many owners of screwdrivers want to convert their batteries to lithium battery cells. Many articles have been written on this topic and in this material I would like to summarize the information on this issue. First of all, let's look at the arguments in favor of converting a screwdriver to lithium batteries and against it. We will also consider individual aspects of the battery replacement process itself.

First you need to think, do I need this alteration? After all, this will be an outright “homemade” and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let's look at the pros and cons of this procedure. It is possible that after this some of you will decide to abandon the conversion of Ni─Cd to lithium cells.

Pros

Let's start with the advantages:

• The energy density of lithium-ion elements is significantly higher than that of nickel-cadmium elements, which are used by default in screwdrivers. That is, a lithium battery will have less weight than a cadmium battery with the same capacity and output voltage;
• Charging of lithium battery cells occurs much faster than in the case of Ni─Cd. It will take about an hour to charge them safely;
• Lithium-ion batteries do not have a “memory effect”. This means that they do not need to be completely discharged before charging..

Now about the shortcomings and difficulties.

Cons

• Lithium battery cells cannot be charged above 4.2 volts and discharged below 2.7 volts. In real conditions, this interval is even narrower. If you go beyond these limits, the battery can be damaged. Therefore, in addition to the lithium cans themselves, you will need to connect and install a charge-discharge controller in the screwdriver;
• The voltage of one Li─Ion element is 3.6─3.7 volts, and for Ni─Cd and Ni─MH this value is 1.2 volts. That is, problems arise with assembling a battery for screwdrivers with a voltage rating of 12 volts. From three lithium cans connected in series, you can assemble a battery with a nominal value of 11.1 volts. Out of four ─ 14.8, out of five ─ 18.5 volts and so on. Naturally, the voltage limits during charge-discharge will also be different. That is, there may be problems with the compatibility of the converted battery with the screwdriver;
• In most cases, 18650 standard banks are used as lithium cells for conversion. They differ in size from Ni─Cd and Ni─MH cans. In addition, you will need a place for the charge-discharge controller and wires. All this will need to fit into a standard screwdriver battery case. Otherwise, it will be extremely inconvenient for them to work;
• A charger for cadmium batteries may not be suitable for charging the battery after it has been rebuilt. It may be necessary to modify the memory or use universal chargers;
• Lithium batteries lose their functionality at low temperatures. This is critical for those who use a screwdriver outdoors;
• The price of lithium batteries is higher than cadmium batteries.

Replacing batteries in a screwdriver with lithium ones

What do you need to consider before starting work?

You need to decide on the number of elements in the battery, which ultimately decides the voltage value. For three elements the ceiling will be 12.6, and for four ─ 16.8 volts. We are talking about converting widely used batteries with a nominal value of 14.4 volts. It is better to choose 4 elements, since during operation the voltage will drop quite quickly to 14.8. A difference of a few volts will not affect the operation of the screwdriver.

In addition, more lithium cells will give greater capacity. This means more operating time for the screwdriver.

Next, you need to choose the right lithium cells themselves. The form factor without options is 18650. The main thing you need to look at is the discharge current and capacity. According to statistics, during normal operation of a screwdriver, the current consumption is in the range of 5-10 amperes. If you press the start button sharply, the current may jump to 25 amperes for a few seconds. That is, you need to choose lithium ones with a maximum discharge current of 20-30 amperes. Then, with a short-term increase in current to these values, the battery will not be damaged.

The nominal voltage of lithium cells is 3.6-3.7 volts, and the capacity in most cases is 2000-3000 mAh. If the battery case allows, you can take not 4, but 8 cells. Connect them two by two into 4 parallel assemblies, and then connect them in series. As a result, you can increase the battery capacity. But not every case will be able to pack 8 cans of 18650.

And the last preparatory stage is the choice of controller. According to its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to assemble a 14.4 volt battery, then choose a controller with this voltage. The operating discharge current is usually selected to be two times less than the maximum permissible current.

Above, we established that the maximum permissible short-term discharge current for lithium cells is 25-30 amperes. This means that the charge-discharge controller should be designed for 12-15 amperes. Then the protection will operate when the current increases to 25-30 amperes. Don't forget also about the dimensions of the protection board. It, along with the elements, will need to be placed in the battery housing of the screwdriver.

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, most likely I’ll disassemble 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.

I'm planning to buy +57 Add to favorites I liked the review +61 +114

The rapid degradation of batteries in cordless tools is a real scourge. Almost always, the service life of the screwdriver itself exceeds the service life of the Ni-Cd elements and you have to either buy spare batteries or say goodbye to the tool. Today we will talk about the main method of extending the life of a battery.

18650 battery - why is it

Repairing batteries for power tools usually involves restoring the electrolyte of nickel-cadmium “cans” or completely replacing them. The idea of ​​replacing one type of energy element with a more advanced one is quite sensible. This eliminates a wide range of battery tool problems, including heavy weight, low capacity, memory effect and low ability to hold a charge in the cold.

However, why should it be 18650 batteries and not some others? The answer is simple: this is the most common type of battery, with the exception of batteries for mobile phones or other gadgets. The latter can be used, but most of them have a built-in charge controller on board, which is a waste of money.

In addition, the batteries must be high-current, that is, capable of supporting a load of 70-100 W. Batteries for electronic cigarettes made by Samsung or LG are ideal. You shouldn’t take products from an unknown manufacturer: after all, Li-ion is a pretty powerful thing and the poor quality of the energy cell housing can provoke a loss of tightness from overheating with all that it entails. And if there are half a dozen more batteries in the neighborhood, the consequences can be very dire.

You can buy batteries on Aliexpress or other Chinese online stores, where they are quite cheap (200-250 rubles apiece, cheaper in bulk). At the same time, you need to purchase a number of additional gadgets, this is due to the specifics of working with lithium batteries. Well, what are these gadgets and what is the point of using them? We’ll tell you as we describe the modification.

Disassembling the case

The first step is to disassemble the battery case into two halves. The easiest way to do this is if the battery pack is tightened with 4-5 screws: just unscrew them and pull out the upper part.

If the battery case is glued together (Makita, AEG), then the hassle will significantly increase. Place the battery on its side and carefully tap the adhesive seam with a rubber mallet. The blows are precise, not strong, frequent. We evenly tap the joint around the perimeter and try to stretch the halves every 50-100 blows. In 10-15 minutes of such “execution” even the most stubborn corps surrenders.

Next, we throw away unnecessary parts of the contents. The contact block must be carefully torn off from the two upper cans so that two nickel tabs remain on it. Looking ahead, we will say that usually when reworking, a new package of batteries is welded together using resistance welding in the manner of factory ones. This is a cool solution, but not everyone will want or be able to assemble a welding setup. Therefore, leave the length of the strips such that the wires can be secured to it with two small bolts, and the remaining elements will be connected by soldering.

In any convenient part of the case you also need to make a hole for the JST-XH balancing connector. On the outside, use an awl to mark a rectangle 6 mm high and 15 mm wide for a battery voltage of 12 V or 20 mm for a voltage of 18 V. Insert the connector into the hole made and secure it with hot glue or epoxy.

How to place elements

Unlike Ni-Cd or Ni-MH cells, lithium batteries have a higher capacity and voltage, so fewer of them will be included in the battery. The dimensions of the 18650 element are: 65 mm height and 18 mm diameter. Initially, check how many of them will fit in an empty case, and determine the layout, if necessary, cut off interfering stiffeners.

If the battery pack has a protruding top, it will accommodate a couple of cells. It’s convenient to place another one on its side directly under the two vertical ones. The remaining space can accommodate another 5 to 7 batteries. If the battery has a slide-in charging connector, stack the cells across the case in two stacks.

The Li-ion battery voltage is 3.7 V, but under load there is a drawdown of about 10-12%. This means that for a 12 V screwdriver you will need at least 4 batteries, and for 18 V - at least 5 pcs., although it is better to use 6, because a lot is not a little. Don’t worry that the motor will be “scared” by the high voltage and will die for a long time. When sagging under load, the voltage excess will be minimal and quite within operating limits. You need to decide on the number of batteries before you insert the balancing connector into the case, because there should be one more contact in it than there are elements in the series connection.

Now about the capacity. For lithium cells it ranges from 2.5 to 3 A/h, which in itself is not bad. To double the capacity, you will need to double the number of batteries, but it's definitely worth it. The only thing that can stop you in this venture is the size of the battery pack. In any case, remember that the number of elements must be strictly a multiple of 4, 5 or 6, depending on the voltage.

When you have folded the batteries in the desired order, secure them together with electrical tape and ensure that the elements inside the case are completely immobile by filling the remaining space with pieces of polystyrene foam or polyurethane foam. There is no need to leave space for the wires; in extreme cases, during final assembly you will need to make a couple of additional cuts.

Battery connection diagram

To get the coveted 12 or 18 V, the elements must be connected in series. That's it, no tricks, just keep the polarity. The negative of each battery is connected to the positive of the next one, the outer two wires are connected to the terminal block.

If you double the capacity, not individual batteries are connected in series, but assemblies of 2 elements. In each assembly, a positive contact is connected to a positive neighbor, and the situation is similar with negative ones.

To ensure that the jumpers between the batteries do not end up intertwined into an indistinct web, think over the connection diagram in advance. It is most convenient to solder the batteries when they are already wound into a tight bundle; choose the minimum length of the jumpers.

For soldering, the contacts of each battery should be well tinned. First, clean them with a file or fine sandpaper, removing the top nickel layer. Use orthophosphoric acid as a flux; the most common solder is POS-61 with rosin. The soldering iron must be powerful, 60 W, no less. It is strictly forbidden to overheat lithium batteries; contact time with the tip is no more than 2 seconds. Therefore, first we tin, let it cool, then solder.

Also, first tin jumpers from a stranded core of 2.5 mm 2 and supplement them with balancing wires so that there is one wire for each node between parallel-connected batteries or groups. The length of the wires is to reach the balancing connector in the case, the cross-section is about 0.5 mm 2.

When soldering, the tinned wire of the jumper is heated first, then it is brought to the battery contact until the solder melts on it. While cooling, you can press down the joint with a wooden sliver. And don’t skimp on the tin—the connection must be very reliable. Also, do not forget to wash off the remaining flux, otherwise after six months or a year of operation all efforts will go to waste. Wash the intricately shaped positive contact especially carefully; you can use medical alcohol or acetone to wash it off.

If you try to solder the outermost wires of the battery to the nickel contacts of the block, you will most likely damage it hopelessly by overheating the plastic. It is much better to drill two holes with a diameter of 3-4 mm and tighten the cores to the plates with a pair of small screws. Here it is convenient to use strips with double holes, which were massively picked out from old Soviet forks.

Together with the outermost conductors of the battery bundle, screw another couple of balancing wires. The resulting balancing cable must be soldered in a certain order. From the datasheet for the connector, determine its contact, numbered one, and solder the wire from the positive terminal to it. Next, follow the chain of batteries and solder the wires sequentially, one after the other, ending by connecting the last contact to the common negative conductor.

What and how to charge

The peculiarity of charging a bunch of Li-ion batteries is that they need to be charged strictly evenly. Otherwise, one of the elements loses its charge and, due to low voltage, begins to drain the rest, discharging even more. Lithium screwdriver batteries, like laptop batteries, have special charge controllers.

Therefore, your most important and expensive purchase will be a universal charger. It is best if it is something from the SkyRC line - these devices have repeatedly proven that they are worth the money spent. You can take a Chinese fake for 300-600 rubles cheaper, but be sure to have the function of charging Li-ion batteries with several elements. Don’t be upset about the high cost: such a thing should be in the arsenal of every homemade product; it will help restore and properly charge old dead batteries, including lead-acid batteries and Ni-Cd cans recently removed from the battery pack.

To charge a converted battery, you need to convert the standard charger. The task is simple - solder two charging wires to the main terminals, observing the polarity. The balancing connectors are connected with a male-to-male wire, the device is set to the desired mode and a fully automatic charging process is carried out. The main thing in operating such a battery is not to let the cells fall into a deep discharge, but usually the engine noticeably loses power long before such a significant drop in voltage, so you are unlikely to hopelessly kill new batteries.

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.