Lithium battery charge controller. Li-ion and Li-polymer batteries in our designs

26.06.2023

Engine

Voltage control on each of the cells:
When the voltage on any of the cells exceeds the threshold values, the entire battery is automatically turned off.
Current control:
When the load current exceeds the threshold values, the entire battery is automatically switched off.

Pin Description:
"B-"- total battery minus
"B1"- +3.7V
"B2"- +7.4V
"B3"- +11.1V
"B+"- total battery plus
"P-"- minus load (charger)
"P+"- plus load (charger)
"T"- NTC 10K thermistor output

Controller: S-8254A
Datasheet on S-8254A.

Specifications

Model: 4S-EBD01-4.
Number of series-connected Li-Ion batteries: 4 pcs.
Operating voltages: 11.2V ... 16.8V.
Cell overcharge voltage (VCU): 4.275±0.025V.
Overdischarge voltage (VDD): 2.3±0.1V.
Rated operating current: 3A - 4A.
Threshold current (IEC): 4A - 6A.
Overcharge protection.
Overdischarge protection.
Short circuit protection.
Dimensions, mm: 15 x 46.1 x 2.62.
Weight: 2 gr.

Guarantee

Every item we sell comes with a warranty. We always meet the needs of the client and try to resolve all disputable situations. For more details, you can read the terms of exchange and return in our store at the link.

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

Often there is a designation of the form "xC". This is just a convenient notation for the charge or discharge current of a battery in fractions of its capacity. It is formed from the English word "Capacity" (capacity, capacity).
When talking about charging with a current of 2C, or 0.1C, they usually mean that the current should be (2 × battery capacity) / h or (0.1 × battery capacity) / h, respectively.
For example, a battery with a capacity of 720 mAh, for which the charge current is 0.5C, must be charged with a current of 0.5 × 720mAh / h = 360 mA, this also applies to the discharge.

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 circuit with the application provides a fairly accurate voltage stabilization, which is set by the potentiometer R2.
Current stabilization is not as critical as voltage regulation, so it is enough to stabilize the current using a shunt resistor Rx and an NPN transistor (VT1).

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.

You can solder the LTC4054 charge controller from an old cell phone, for example, Samsung (C100, C110, X100, E700, E800, E820, P100, P510).

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

Here is a simple circuit that lights up an LED when the battery is low and its residual voltage is close to critical.

Rice. 8.

Transistors are any low-power ones. The ignition voltage of the LED is selected by a divider of resistors R2 and R3. It is better to connect the circuit after the protection unit so that the LED does not drain the battery at all.

The nuance of durability

The manufacturer usually claims 300 cycles, but if you charge lithium just 0.1 volts less, up to 4.10 V, then the number of cycles increases to 600 or even more.

Operation and Precautions

It is safe to say that lithium-polymer batteries are the most “gentle” batteries in existence, that is, they require mandatory compliance with a few simple but mandatory rules, due to non-observance of which troubles happen.
1. Charge to a voltage exceeding 4.20 volts per can is not allowed.
2. Do not short circuit the battery.
3. It is not allowed to discharge with currents exceeding the load capacity or heating the battery above 60 ° C. 4. A discharge below a voltage of 3.00 Volts per jar is harmful.
5. Battery heating above 60°C is harmful. 6. Battery depressurization is harmful.
7. Harmful storage in a discharged state.

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.

You can pull out a lot of perfectly working 18650 batteries from an old laptop battery.

Where do I use lithium batteries

I have long converted a screwdriver and an electric screwdriver to lithium. I use these tools on a regular basis. Now even after a year of non-use, they work without recharging!

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

Are on sale. At the same link you will find charging modules and other useful things for DIYers.

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

Honest Sanyo 18650

In modern mobile electronic devices, even those designed to minimize power consumption, the use of non-renewable batteries is becoming a thing of the past. And from an economic point of view, already in a short period of time, the total cost of the required number of disposable batteries will quickly exceed the cost of one battery, and from the point of view of user convenience, it is easier to recharge the battery than to look for where to buy a new battery. Accordingly, battery chargers are becoming a commodity with guaranteed demand. It is not surprising that almost all manufacturers of integrated circuits for power supply devices pay attention to the "charging" direction.

Five years ago, the discussion of microcircuits for charging batteries (Battery Chargers IC) began with a comparison of the main types of batteries - nickel and lithium. But now nickel batteries have practically ceased to be used and most manufacturers of charge microcircuits have either completely stopped producing microcircuits for nickel batteries, or are releasing microcircuits that are invariant to battery technology (the so-called Multi-Chemistry IC). The STMicroelectronics product range currently contains only microcircuits designed to work with lithium batteries.

Let us briefly recall the main features of lithium batteries. Advantages:

High specific electrical capacity. Typical values are 110…160W*h*kg, which is 1.5…2.0 times higher than the analogous parameter for nickel batteries. Accordingly, with equal dimensions, the capacity of a lithium battery is higher.
Low self-discharge: approximately 10% per month. In nickel batteries, this parameter is 20 ... 30%.

There is no "memory effect", making this battery easy to maintain: there is no need to drain the battery to a minimum before recharging.

Disadvantages of lithium batteries:

The need for current and voltage protection. In particular, it is necessary to exclude the possibility of a short circuit of the battery terminals, supplying voltage of reverse polarity, overcharging.
The need for overheating protection: If the battery is heated above a certain temperature, its capacity and service life will be negatively affected.

There are two industrial manufacturing technologies for lithium batteries: lithium-ion (Li-Ion) and lithium-polymer (Li-Pol). However, since the charging algorithms of these batteries are the same, the charge chips do not separate the lithium-ion and lithium-polymer technologies. For this reason, we skip the discussion of the advantages and disadvantages of Li-Ion and Li-Pol batteries, referring to the literature.

Consider the lithium battery charging algorithm shown in Figure 1.

Rice. 1.

The first phase, the so-called pre-charge, is used only when the battery is heavily discharged. If the battery voltage is below 2.8 V, then it should not be immediately charged with the maximum possible current: this will have a very negative effect on the battery life. You must first "recharge" the battery with a small current up to about 3.0 V, and only after that the charge with the maximum current becomes acceptable.

Second phase: charger as a constant current source. At this stage, the maximum current for the given conditions flows through the battery. At the same time, the battery voltage gradually increases until it reaches the limit value equal to 4.2 V. Strictly speaking, upon completion of the second stage, the charge can be stopped, but it should be borne in mind that the battery is currently charged at about 70% of its capacity. Note that in many chargers, the maximum current is not supplied immediately, but gradually increases to a maximum within a few minutes - the Soft Start mechanism is used.

If it is desirable to charge the battery to capacity values close to 100%, then we proceed to the third phase: the charger as a source of constant voltage. At this stage, a constant voltage of 4.2 V is applied to the battery, and the current flowing through the battery decreases from a maximum to a certain predetermined minimum value during charging. At that moment, when the current value decreases to this limit, the battery charge is considered complete and the process ends.

Recall that one of the key parameters of the battery is its capacity (unit of measurement - Ah). So, the typical capacity of a lithium-ion battery of size AAA is 750 ... 1300 mAh. As a derivative of this parameter, the characteristic “current 1C” is used, this is the current value numerically equal to the nominal capacity (in the example given, 750 ... 1300 mA). The value of "current 1C" makes sense only as a definition of the maximum current when charging the battery and the amount of current at which the charge is considered complete. It is generally accepted that the value of the maximum current should not exceed 1 * 1C, and the battery charge can be considered complete when the current decreases to a value of 0.05 ... 0.10 * 1C. But these are the parameters that can be considered optimal for a particular type of battery. In reality, the same charger can work with batteries from different manufacturers and different capacities, while the capacity of a particular battery remains unknown to the charger. Consequently, the charge of a battery of any capacity in the general case will not occur in the optimal mode for the battery, but in the mode preset for the charger.

Let's move on to considering the STMicroelectronics line of charge microcircuits.

Chips STBC08 and STC4054

These microcircuits are fairly simple products for charging lithium batteries. The microcircuits are made in miniature packages of the type and , respectively. This makes it possible to use these components in mobile devices with rather stringent requirements for weight and size characteristics (for example, cell phones, MP3 players). Switching schemes and are shown in Figure 2.

Rice. 2.

Despite the limitations imposed by the minimum number of external pins in packages, microcircuits have a fairly wide functionality:

There is no need for an external MOSFET, blocking diode and current resistor. As follows from Figure 2, the external binding is limited to a filtering capacitor at the input, a programming resistor and two (one for STC4054) indicator LEDs.
The maximum value of the charge current is programmed by the value of the external resistor and can reach a value of 800mA. The fact of the end of the charge is determined at the moment when, in the constant voltage mode, the value of the charging current drops to 0.1 * I BAT, that is, it is also set by the value of the external resistor. The maximum charge current is determined from the ratio:

I BAT = (V PROG / R PROG) * 1000;

where I BAT is the charge current in Amperes, R PROG is the resistance of the resistor in Ohms, V PROG is the voltage at the PROG output, equal to 1.0 Volts.

In the constant voltage mode, a stable voltage of 4.2V is formed at the output with an accuracy of no worse than 1%.
Charging of heavily discharged batteries automatically starts in pre-charge mode. Until the voltage at the battery output reaches 2.9V, the charge is carried out with a weak current of 0.1 * I BAT. Such a method, as already noted, prevents the very likely failure when trying to charge heavily discharged batteries in the usual way. In addition, the value of the starting value of the charging current is forcibly limited, which also increases the service life of the batteries.
The mode of automatic drip charging is implemented - when the battery voltage drops to 4.05V, the charge cycle will be restarted. This allows you to ensure a constant charge of the battery at a level not lower than 80% of its nominal capacity.
Overvoltage and overheating protection. If the input voltage value exceeds a certain limit (in particular, 7.2V) or if the case temperature exceeds 120°C, the charger will turn off, protecting itself and the battery. Of course, low input voltage protection is also implemented - if the input voltage drops below a certain level (U VLO), the charger will also turn off.
The ability to connect LED indicators allows the user to have an idea of the current state of the battery charging process.

L6924D and L6924U Battery Charge Chips

These microcircuits are devices with more features than STBC08 and STC4054. Figure 3 shows typical circuits for switching on microcircuits and .

Rice. 3.

Consider those functional features of microcircuits that relate to setting the parameters of the battery charging process:

1. In both modifications, it is possible to set the maximum duration of the battery charge starting from the moment the transition to the DC stabilization mode (the term "fast charge mode" is also used - Fast charge phase). When switching to this mode, a watchdog timer is started, programmed for a certain duration T PRG by the value of the capacitor connected to the terminal T PRG . If, before this timer expires, the battery charge is not terminated according to the standard algorithm (a decrease in the current flowing through the battery below the I END value), then after the timer expires, charging will be interrupted forcibly. With the help of the same capacitor, the maximum duration of the pre-charge mode is set: it is equal to 1/8 of the duration T PRG . Also, if during this time there was no transition to fast charging mode, the circuit turns off.

2. Pre-charge mode. If for the STBC08 device the current in this mode was set as a value equal to 10% of I BAT, and the switching voltage to DC mode was fixed, then in the L6924U modification this algorithm remained unchanged, but in the L6924D chip both of these parameters are set using external resistors connected to the I PRE and V PRE inputs.

3. The sign of completion of charging in the third phase (constant voltage stabilization mode) in the STBC08 and STC4054 devices was set as a value equal to 10% of I BAT . In L6924 chips, this parameter is programmed with the value of an external resistor connected to the I END pin. In addition, for the L6924D, it is possible to reduce the voltage at the V OUT pin from the generally accepted value of 4.2 V to a value of 4.1 V.

4. The value of the maximum charging current I PRG in these microcircuits is set in the traditional way - by means of the value of the external resistor.

As you can see, in simple “charges” of STBC08 and STC4054, using an external resistor, only one parameter was set - the charging current. All other parameters were either hard-coded or were a function of I BAT . In the L6924 microcircuits, it is possible to fine-tune several more parameters and, in addition, “insurance” is carried out for the maximum duration of the battery charging process.

For both modifications of the L6924, two modes of operation are provided if the input voltage is generated by the mains AC/DC adapter. The first is the standard linear buck output voltage regulator mode. The second is the quasi-impulse controller mode. In the first case, a current can be supplied to the load, the value of which is slightly less than the value of the input current taken from the adapter. In the DC stabilization mode (second phase - Fast charge phase), the difference between the input voltage and the voltage at the "plus" of the battery is dissipated as thermal energy, as a result of which the power dissipation in this charge phase is maximum. When operating in the mode of a switching regulator, a current can be supplied to the load, the value of which is higher than the value of the input current. At the same time, much less energy goes into heat. This, firstly, reduces the temperature inside the case, and secondly, it increases the efficiency of the device. But at the same time, it should be borne in mind that the accuracy of current stabilization in the linear mode is approximately 1%, and in the pulse mode - about 7%.

The operation of the L6924 microcircuits in linear and quasi-pulse modes is illustrated in Figure 4.

Rice. 4.

The L6924U chip, in addition, can work not from a network adapter, but from a USB port. In this case, the L6924U chip implements some technical solutions that can further reduce power dissipation by increasing the charging time.

Chips L6924D and L6924U have an additional input for forced interruption of the charge (that is, load disconnection) SHDN.

In simple charge microcircuits, temperature protection consists in the termination of the charge when the temperature inside the microcircuit case rises to 120 ° C. This, of course, is better than the complete absence of protection, but the value of 120 ° C on the case is more than conditionally related to the temperature of the battery itself. The L6924 products provide the ability to connect a thermistor that is directly related to the battery temperature (resistor RT1 in Figure 3). In this case, it becomes possible to set the temperature range in which the battery charge will become possible. On the one hand, it is not recommended to charge lithium batteries at sub-zero temperatures, and on the other hand, it is also highly undesirable if the battery heats up to more than 50°C during charging. The use of a thermistor makes it possible to charge the battery only under favorable temperature conditions.

Naturally, the additional functionality of the L6924D and L6924U microcircuits not only expands the capabilities of the device being designed, but also leads to an increase in the area on the board, occupied by both the microcircuit package itself and external strapping elements.

STBC21 and STw4102 battery charging chips

This is a further improvement of the L6924 chip. On the one hand, approximately the same functional package is implemented:

Linear and quasi-pulse mode.
The thermistor connected to the battery as a key element of temperature protection.
Ability to set quantitative parameters for all three phases of the charging process.

Some additional features missing from the L6924:

Reverse polarity protection.
Short circuit protection.
A significant difference from the L6924 is the presence of a digital I 2 C interface for setting parameter values and other settings. As a consequence, more precise settings of the charging process become possible. The recommended switching circuit is shown in Figure 5. Obviously, in this case, the question of saving the board area and rigid weight and size characteristics is not worth it. But it is also obvious that the use of this microcircuit in small-sized voice recorders, players and mobile phones of simple models is not expected. Rather, these are batteries for laptops and similar devices, where battery replacement is an infrequent procedure, but also not cheap.

Rice. 5.

5. Camiolo Jean, Scuderi Giuseppe. Reducing the Total No-Load Power Consumption of Battery Chargers and Adapter Applications Polymer// Material from STMicroelectronics. Online placement:

7. STEVAL-ISV012V1: lithium-ion solar battery charger//Material from STMicroelectronics. Online placement: .

Obtaining technical information, ordering samples, delivery - e-mail:

Controllers are useful devices in their own right. And in order to better understand this topic, it is necessary to work with a specific example. Therefore, we will consider the battery charge controller. What does he represent? How is it arranged? What are the job features?

What does a battery charge controller do?

It serves to monitor the recovery of energy losses and spending. First, he is engaged in monitoring the conversion of electrical energy into chemical energy, so that later, if necessary, there is a supply of the required circuits or devices. It is not difficult to make a battery charge controller with your own hands. But it can also be removed from power supplies that have failed.

How the controller works

Of course, there is no universal scheme. But many in their work use two trim resistors that regulate the upper and lower voltage limits. When it goes beyond the specified limits, then the interaction with the relay windings begins, and it turns on. While it is working, the voltage will not fall below a certain, technically predetermined level. Here we should talk about the fact that there is a different range of boundaries. So, for the battery, three, and five, and twelve, and fifteen volts can be installed. Theoretically, everything rests on the hardware implementation. Let's look at how the battery charge controller works in different cases.

What are the types

It should be noted a significant variety that battery charge controllers can boast of. If we talk about their types, let's make a classification depending on the scope:

For renewable energy sources.
For household appliances.
For mobile devices.

Of course, the species themselves are much larger. But since we are considering the battery charge controller from a general point of view, they will suffice for us. If we talk about those that are used for windmills, then in them the upper voltage limit is usually 15 volts, while the lower one is 12 V. In this case, the battery can generate 12 V in the standard mode. The energy source is connected to it using normally closed relay contacts. What happens when the battery voltage exceeds the set 15V? In such cases, the controller closes the relay contacts. As a result, the power source from the battery is switched to the load ballast. It should be noted that it is not particularly popular with solar panels due to certain side effects. But for them they are mandatory. Home appliances and mobile devices have their own characteristics. Moreover, the battery charge controller of the tablet, touch and push-button cell phones are almost identical.

A look into the lithium-ion cell phone battery

If you open any battery, you will notice that a small one is soldered to the terminals of the cell. It is called a protection circuit. The fact is that they require constant monitoring. A typical controller circuit is a miniature board on which a circuit made of SMD components is based. It, in turn, is divided into two microcircuits - one of them is the control one, and the other is the executive one. Let's talk in more detail about the second.

executive scheme

It is based on Usually there are two of them. The microcircuit itself can have 6 or 8 pins. For separate control of the charge and discharge of the battery cell, two field-effect transistors are used, which are located in the same housing. So, one of them can connect or disconnect the load. The second transistor does the same actions, but with a power source (which is the charger). Thanks to this implementation scheme, you can easily influence the operation of the battery. You can use it elsewhere if you wish. But it should be borne in mind that the battery charge controller circuit and it itself can only be applied to devices and elements that have a limited range of operation. We will now discuss these features in more detail.

Overcharge protection

The fact is that if the voltage exceeds 4.2, then overheating and even an explosion may occur. To do this, such elements of microcircuits are selected that will stop charging when this indicator is reached. And usually, until the voltage reaches 4-4.1 V due to use or self-discharge, no further charging will be possible. This is an important function that is assigned to the lithium battery charge controller.

Overdischarge protection

When the voltage reaches critically low values that make the operation of the device problematic (usually in the range of 2.3-2.5V), the corresponding MOSFET transistor turns off, which is responsible for supplying current to the mobile phone. Next, there is a transition to sleep mode with minimal consumption. And there is a rather interesting aspect of the work. So, until the voltage of the battery cell becomes more than 2.9-3.1 V, the mobile device cannot be turned on to work in normal mode. Probably, you might have noticed that when you connect the phone, it shows that it is charging, but does not want to turn on and function in normal mode.

Conclusion

As you can see, the Li-Ion battery charge controller plays an important role in ensuring the longevity of mobile devices and has a positive effect on their service life. Due to the ease of production, they can be found in almost any phone or tablet. If there is a desire to see with your own eyes, and touch the Li-Ion battery charge controller and its contents with your hands, then when parsing it, you should remember that you are working with a chemical element, so you should be careful.

And again a device for do-it-yourselfers.
The module allows you to charge Li-Ion batteries (both protected and unprotected) from the USB port using a miniUSB cable.

The printed circuit board is double-sided fiberglass with metallization, the installation is neat.

Charging was assembled on the basis of a specialized charge controller TP4056.
Real scheme.

On the battery side, the device does not consume anything and can be left permanently connected to the battery. Protection against short circuit at the output - yes (with a current limit of 110mA). There is no battery reverse protection.
The miniUSB power supply is duplicated by nickels on the board.

The device works like this:
When power is connected without a battery, the red LED lights up, and the blue blinks periodically.
When a discharged battery is connected, the red LED goes out and the blue one lights up - the charging process begins. As long as the voltage on the battery is less than 2.9V, the charge current is limited to 90-100mA. With an increase in voltage above 2.9V, the charge current increases sharply to 800mA with a further gradual increase to a nominal value of 1000mA.
When the voltage reaches 4.1V, the charge current begins to gradually decrease, then the voltage stabilizes at the level of 4.2V, and after the charging current decreases to 105mA, the LEDs begin to periodically switch, indicating the end of the charge, while the charge still continues with switching to the blue LED. Switching occurs in accordance with the battery voltage control hysteresis.
The rated charge current is set by a 1.2kΩ resistor. If necessary, the current can be reduced by increasing the resistor value according to the controller specification.
R (kΩ) - I (mA)
10 - 130
5 - 250
4 - 300
3 - 400
2 - 580
1.66 - 690
1.5 - 780
1.33 - 900
1.2 - 1000