Simple Battery Charger ICs for Any Chemistry
It is common for many battery-powered devices to require a wide variety of charging sources, battery chemistries, voltages, and currents. For example, industrial, high end, feature-rich consumer, medical, and automotive battery charger circuits demand higher voltages and currents as newer large-battery packs are emerging for all types of battery chemistries. Furthermore, solar panels with wide-ranging power levels are being used to power a variety of innovative systems containing rechargeable sealed lead acid (SLA) and lithium-based batteries. Examples include crosswalk marker lights, portable speaker systems, trash compactors, and even marine buoy lights. over, some lead acid (LA) batteries found in solar applications are deep cycle batteries capable of surviving prolonged, repeated charge cycles, in addition to deep discharges. A good example of this is in deep sea marine buoys, where a 10-year deployment life is a prerequisite. Another example is off-grid (that is, disconnected from the electric utility company) renewable energy systems such as solar or wind power generation, where system up-time is paramount due to proximity access difficulties.
Even in nonsolar applications, recent market trends imply a renewed interest in high capacity SLA battery cells. Automotive, or starting, SLA cells are inexpensive from a cost/power output perspective and can deliver high pulse currents for short durations, making them an excellent choice for automotive and other vehicle starter applications. Embedded automotive applications have input voltages 30 V, with some even higher. Consider a GPS location system used as an antitheft deterrent; a linear charger with the typical 12 V input stepping down to 2-in-series Li-Ion battery (7.4 V typical) and needing protection to much higher voltages, could be valuable for this application. Deep cycle LA batteries are another technology popular in industrial applications. They have thicker plates than automotive batteries and are designed to be discharged to as low as 20% of their total capacity. They are normally used where power is required over a longer time constant such as fork lifts and golf carts. Nevertheless, like their Li-Ion counterpart, LA batteries are sensitive to overcharging, so careful treatment during the charging cycle is very important.
Current integrated circuit (IC)-based solutions cover just a fraction of the many possible combinations of input voltage, charge voltage, and charge current. A cumbersome combination of ICs and discrete components has routinely been used to cover most of the remaining, more difficult combinations and topologies. That wasn’t until, in 2011, when Analog Devices addressed and simplified this market application space with its popular 2-chip charging solution consisting of the LTC4000 battery charging controller IC mated with a compatible, externally compensated dc-to-dc converter.
Switching vs. Linear Chargers
Traditional linear topology battery charger ICs were often valued for their compact footprints, simplicity, and low cost. However, drawbacks of these linear chargers include a limited input and battery voltage range, higher relative current consumption, excessive power dissipation, limited charge termination algorithms, and lower relative efficiency (efficiency ~ [VOUT/VIN] × 100%). On the other hand, switch-mode battery chargers are also popular choices due to their flexible topology, multichemistry charging, high charging efficiencies (which minimize heat to enable fast charge times), and wide operating voltage ranges. Nevertheless, some of the drawbacks of switching chargers include relatively high cost, more complicated inductor-based designs, potential noise generation, and larger footprint solutions. Modern LA, wireless power, energy harvesting, solar charging, remote sensor, and embedded automotive applications have been routinely powered by high voltage linear battery chargers for the reasons stated above. However, an opportunity exists for a more modern switch-mode charger that negates the associated drawbacks.
An Uncomplicated Buck Battery Charger
Some of the tougher challenges a designer faces at the outset of a charging solution are the wide range of input sources combined with a wide range of possible batteries, the high capacity of the batteries needing to be charged, and a high input voltage.
Input sources are as wide as they are variable, but some of the more complicated ones that deal with battery charging systems are: high powered wall adapters with voltages spanning from 5 V to 19 V and beyond, rectified 24 V ac systems, high impedance solar panels, car, and heavy truck/Humvee batteries. Therefore, it follows that the combination of battery chemistries possible in these systems—lithium-based (Li-Ion, Li-Polymer, lithium-iron phosphate (LiFePO4)) and LA-based—increases the permutations even more, thus making the design even more daunting.
What is a battery charging circuit?
A battery charger circuit is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it. The charging protocol is determined by the size and type of the charged battery. Some battery types can be recharged by connecting to a constant voltage or constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle or may have a timer to cut off the charging current at a set time. Other battery types are unable to withstand prolonged high-rate overcharging; the charger may include temperature or voltage sensing circuits as well as a microprocessor controller to adjust the charging current and cut off at the end of the charge cycle. A trickle charger provides a relatively small amount of current, only enough to counteract the self-discharge of a battery that is idle for a long time. Slow battery chargers can take several hours to charge; high-rate chargers can restore most capacity in minutes or less than an hour, but they usually require battery monitoring to avoid overcharging. For public use, electric vehicles require high-rate chargers; the installation of such chargers, as well as distribution support for them, is a concern in the proposed adoption of electric vehicles.
What are the 3 stages of battery charging?
Three-stage battery chargers are commonly referred to as Smart chargers. They are high-quality chargers and are popular for charging lithium batteries. Ideally, however, all battery types should be charged with three-stage chargers, this three-stage charging process keeps the battery healthy.
Before getting into three-stage battery charger circuits, we must understand more about multi-stage battery chargers and why they are used.
Lithium batteries have 3 stages of charging, usually divided into these three stages:
- Constant Current Pre-charge Mode
- Constant Current Regulation Mode
- Constant Voltage Regulation Mode
Sounds similar to a Lead-acid battery? Something different. That’s why we need to buy a new charger for lithium batteries. over, what exactly is “quick charge” and how can it make your battery be charged faster?
The battery charging circuit process consists of 3 stages. There are explained in detail below.
Constant Current (CC) Charging
CC charging is a simple method that uses a small constant current to charge the battery during the whole charging process. CC charging stops when a predefined value is reached. This method is widely used for charging NiCd or NiMH batteries, as well as Li-ion batteries. The charging current rate is the most important factor, and it can significantly influence the battery’s behavior. For this reason, the main challenge of CC charging is setting a suitable charging current value that will satisfy both charging time and capacity utilization. A high charging current provides a quick charge but also significantly affects the battery’s aging process. A low charging current provides high capacity utilization but also produces a very slow charge, which is inconvenient for EV applications.
Constant-Voltage (CV) Charging
Another method is CV charging, which regulates a predefined constant voltage to charge batteries. Its main advantage is that it circumvents overvoltages and irreversible side reactions, thus prolonging battery life. Since the voltage is constant, the charging current decreases as the battery charges. A high current value is required to provide a constant terminal voltage at an early stage of the charging process. A high charging current from 15 percent to 80 percent SOC provides fast charging, but the high current stresses the battery and can cause battery lattice collapse and pole breaking. The most difficult aspect of CV charging is determining an appropriate voltage value that balances charging speed, electrolyte decomposition, and capacity utilization. In general, the CV charging method is effective for quick charging, but it depletes the capacity of the battery. The negative effect is caused by an increased charging current at a low battery SOC (at the beginning of the charging process), where the current value is significantly higher than the nominal battery current. The high battery current causes the battery lattice frame to collapse and contributes to the pulverization of the active battery pole substance.
Constant-Current-Constant-Voltage (CC-CV) Charging
A CC-CV charging method is a hybrid approach that combines the two previously mentioned charging methods. It uses CC charging in the first charging stage, and when the voltage reaches the maximum safe threshold value, the charging process shifts to the CV charging method. The charging process is complete when the current levels off or when full battery capacity is reached. The charging time is mainly defined by the constant current value (CCmode), while the capacity utilization is predominantly influenced by the constant voltage value (CV mode).
Fundamentals Charging Parameters
Li-ion batteries follow a relatively common charging profile, described in greater detail below. Note that if a charger IC provides configurability, the designer may be able to set their thresholds for these phases. These configurable thresholds are highly beneficial, considering that most battery manufacturers specify certain thresholds for different maximum charge current levels. Configurability can provide an added layer of safety by protecting the battery from over-voltage and over-temperature conditions and overloads, which could permanently damage the battery or degrade its capacity.
Trickle charge
Generally, the trickle charge phase is only used when the battery voltage is below a very low level (about 2.1V). In this state, the battery pack’s internal protection IC may have previously disconnected the battery due to it being deeply discharged, or if an over-current event occurred. The charger IC sources a small current (typically 50mA) to charge the capacitance of the battery pack, which triggers the protection IC to reconnect the battery by closing its FETs. Although trickle charging usually lasts for a matter of seconds, the charger IC should integrate a timer that stops charging if the battery pack is not reconnected within a certain amount of time, as this indicates that the battery has been damaged.
Pre-charge
Once the battery pack has been re-connected or is in a discharged state, pre-charging begins. During pre-charge, the charger starts to safely charge the depleted battery with a low current level that is typically C / 10 (where C is the capacity (in mAh)). As a result of pre-charge, the battery voltage slowly rises. The purpose of pre-charge is to safely charge the battery at a low current. This prevents damage to the cell until its voltage reaches a higher level.
Constant current (CC) charge
Constant current (CC) charge is also considered fast charging, which is described in greater detail below. CC charging starts afterpre-charge, once the battery has reached about 3V per cell. In the CC charge phase, it is safe for the battery to handle higher charge currents between 0.5C and 3C. CC charging continues until the battery voltage has reached the “full” or floating voltage level, at which point, the constant voltage phase begins.
Constant voltage (CV) charge
The constant voltage (CV) threshold for Lithium cells is usually between 4.1V and 4.5V per cell. The charger IC monitors the battery voltage during CC charging. Once the battery reaches the CV threshold, the charger
transitions from CC to CV regulation. CV charging is implemented because the external battery pack voltage seen by the charger IC exceeds the actual battery cell voltage in the pack. This is due to the internal cell resistance, PCB resistance, and the equivalent series resistance (ESR) from the protection of FET and cell. To guarantee safe operation, the charger IC must not allow the battery voltage to exceed its maximum floating voltage.
Charge termination
The charger IC determines when to terminate the charge cycle based on the current going into the battery dropping below a set threshold (about C / 10) during the CV phase. At this point, the battery is considered fully charged and charging is completed. If charge termination is disabled in the charger IC, the charge current will naturally decay to 0mA, but this is rarely done in practice. This is because the amount of charge going into the battery exponentially decreases during CV charging (since the cell voltage is increasing like a large capacitor), and it would take a significantly longer time to recharge the battery with a very little increase in capacity.
Why are CC and CV important?
CC-CV charging was initially used to charge lead-acid batteries and, later, to charge Li-ion batteries. Li-ion batteries require a much longer CC mode. The CC-CV charging method is more efficient than either the CC or CV methods individually, and as such, it is used as the reference for comparison with the latest charging methods.
The main challenge with CC-CV charging is defining suitable constant values for each model. The suitable current value will provide a balance between charging performance and battery safety. Having a current that is too high or too low can cause negative effects as previously discussed.
Bill Of Materials
The TP4056 is a complete chip for designing a constant-current/constant-voltage linear charger for single cell lithium-ion batteries.
Features
Programmable Charge Current Up to 1000mA
Preset 4.2V Charge Voltage with 1.5% Accuracy
Two Charge Status Output Pins
Circuit Diagram of Lipo charger using TP4056 with out protection unit
Power Pin
Starting with the power pin, Pin 4 is Positive input supply voltage. We can provide voltage from 4V to 8V in this pin. In this project, we are providing 5V from any external source to this pin. For bypassing unwanted voltage spikes and noise, a capacitor is also connected from Vcc to ground. However the large value of capacitor (C1.10uF) need to decouple with a series resistor(shown as resistor R3 in the circuit diagram) of 0.2 ohms to 0.5 ohms which reduces the ripple voltage.
Pin 3 of this pin is connected to ground which mean to sayo, this pin has been directly connected to the supply voltage to enable the IC. that negative terminal of battery is connected to this point as a common ground.
Pin 8 of TP4056 is chip enable pin. A high input to this pin enables the chip and low input disables this chip. In our case, we have directly connected this pin to input power supply. so, our chip is enabled.
Programming pin
Pin 2 is very important pin of TP4056 form where we can set the charging current. The charging current plays a important role in charging a battery and it must be programmed according to the battery used. The main advantage of using this TP4056 chip is we can program the charging current by selecting the proper resistor as per our requirements.
The Programming resistor with corresponding current value shown in the table below :
The value of program Resistor can be calculated by using the below formula
RPROG = (Vprog/ Ibat) 1200 (Icharge =1A and VPROG = 1V)
Charge Indication Pins
The charge pin or pin 7 of TP4056 is use to indicate the charging process of the battery. This pin goes to the low state while the battery is charging otherwise it remains in high impedance. A Red LED is connected with a resistance (R2) in series to this pin for the visual indication of the charging process.
The STDBY pin or pin 6 is used to indicate the full charge of the battery. This pin goes to the low state while the battery is fully charged otherwise it remains in high impedance.
The resistor R1 and R2 is used to limit the flow of current from the LED.
The Led indication is shown in the figure below:
Output Pin
The BAT pin or Pin 5 is connected to the positive terminal of battery. This BAT pin provides the regulated 4.2V and charging current to the battery. In this circuit, a capacitor is connected in parallel with the BAT pin which connects to the ground for bypassing unwanted voltage spikes and noise.
Working Principle and Working modes
This chip TP4056 operates is 4 different modes. We can observe these mode from the following graph.
1) Trickle mode
When the battery voltage is less than 2.8V then the IC will enter in trickle charge mode to bring the voltage of the battery in safe mode. In this mode, the charging current (value of current by which battery will be charged) reduces to 13% (Typ 130mA) of the full-scale current. When the battery voltage reaches above trickle voltage (Vtrickle(2.9V) Delta Vtrickle (0.08V)), the IC enters in constant current mode.
2) Constant Current Mode
The current flowing out of the PROG pin will be constant. This current is used to charge the battery and is called charging current. In this experiment, this charging current is 1A (Icharge) (as set by the programmable resistor at pin 2) and the battery will be charged through this constant current of 1A until the terminal voltage of the battery will reach its maximum rated voltage (4.2 V).
3) Constant voltage mode
when the battery voltage has reached peak value of 4.2 V then the battery voltage tries to exceed the 4.2 V. Then, the IC will not allow more current to flow through the battery. The current in this mode will slowly start dropping down by maintaining a constant voltage of 4.2 V at the battery.
4) Standby mode
The IC automatically stops the charging when the charge current drops to 1/10Th of the programmed current/charging current after the maximum voltage (4.2 V) of the battery is reached.
In this mode, the IC will draw maximum 100uA current as per the datasheet.
5) Shut down mode
When the RPROG Pin is not connected and the input voltage is less than battery voltage then the IC will be in shutdown mode.
Simple 18650 battery charger circuit– Charge controller with Auto cut-off
An 18650 battery charger circuit is specifically used to safely charge 3.7 volt lithium ion batteries. 18650 batteries are lithium-ion cells that are commonly used in several electronic devices such as laptops, bluetooth speakers, portable consumer electronics and power banks. They are called 18650 batteries because they are cylindrical, 18mm in diameter and 65mm in length.
In this piece, we will discuss common 18650 battery charger circuits and popular charge controller modules. Also, it will be helpful for DIY lithium battery charger circuits.
There are different ways to design an 18650 battery charger circuit, all of them have common basic building blocks. This circuit consists of a charging controller, a power supply, and a charging port:
The main block from above is the charge controller. The charging controller regulates the charging process to ensure that the battery is charged safely and efficiently. The charge controller sets and monitors the battery’s voltage and charge current to determine according to specific needs of a particular lithium battery. It also prevents the battery from being overcharged and deep discharge. This helps increase the life of a lithium battery and thus the device.
The power supply could be any AC adapter, a USB port, or a solar panel. The power supply provides stable DC voltage that directly can’t be used to charge li-ion batteries, thus a charge controller is used. The charging port is usually a female DC jack or a micro USB port. The charging port is an input to the charging controller, which monitors the battery and controls the charging process.
8650 battery charger circuit using TP4056 charge controller IC:
The TP4056 is a popular and most widely used battery charging controller IC. It is a simple and cost-effective IC that is designed for low-power portable electronic devices such as power banks. One of the main advantages of the TP4056 IC is its low cost and simplicity. It has a simple circuit and does not require any additional components to function. It is also widely available and can be easily purchased from online retailers or electronics suppliers.
The TP4056 IC has a built-in charge controller and voltage regulator that is capable of charging lithium-ion or lithium-polymer batteries. It supports USB and AC/DC power sources, and has several safety features to protect the battery and the charger from being damaged.
You could implement an 18650 battery charger circuit using TP4056 in two ways, one directly with the TP4056 module available in the market and other with the TP4056 charger IC. Both are discussed and explained in detail below:
Tp4056 circuit diagram
Below is the simple circuit diagram for the 18650 battery charger schematic according to the datasheet of Tp4056 with temperature sense disabled.
Only Red LED glows when the battery is charging and only Green LED glows when the battery is fully charged. These indicators are connected to pin number 7 and pin number 6 respectively.
So here’s the diagram: How to wire a TP4056?
IC TP4056, 2x LED indicator, 2x Cap= 10uF, Rprog= 1.2KΩ, 2x Resistor= 1KΩ, Rs= 0.4Ω, 3.7V Lithium cell, micro USB/ USB c female connector, pcb.
This circuit can be used only for charging purposes. Rprog is chosen to be 1.2KΩ for 1000mA of output current, this can be changed by setting different values of Rprog. If you have two 18650 lithium batteries, then by connecting them in parallel, each battery will charge at 500mA of current. If you connect three then it will charge them at 1000/3 mA each, thus it will take longer to fully charge each battery.
The charging current (IBAT) of the Li-ion cell can be set manually by choosing the value of Rprog. In all modes during charging, the voltage on pin 2 can be used to measure the charge current as follows:
The Rprog(KΩ) vs Ibat(mA) can be determined using following table :
Tp4056 module: 18650 Li-ion 3.7 v battery charger circuit
For more technical information, here is the TP4056 datasheet at the end of page or Datasheet of TP4056
Overall, the TP4056 is a good option for charging single-cell lithium-ion or lithium-polymer batteries in low-power applications. It is simple, cost-effective, and widely available, which makes it a popular choice among designers and manufacturers.
How many batteries can charge in TP4056?
You can charge one or more lithium battery cells with TP4056, but note that it has max 1000mA of charging current. So, when charging multiple cells you have to connect them in parallel. Also the charging current will be divided among them, which will make charging slower. It is recommended to utilize one or two cells at a time with this module.
What is the maximum output current of TP4056?
The maximum output current of TP4056 is 1000mA. It can be programmed to provide charging current from 130mA to 1000mA by changing the value of Rprog.
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