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Battery Charging Technology Part 1

by: May 20,2024 429 Views 0 Comments Posted in PCB Basic Information

Summary:       This article concentrates on terms used during the battery charging process, basic battery charging methods, and battery charging rates.


Introduction

Demand for green forms of energy is gaining momentum worldwide with the market growth for technology involving green energy, such as solar panels, batteries, and charging technologies, creating motivating revenue in the recent markets. The introduction of new technologies in the area of batteries has triggered research on how to charge batteries in the shortest time possible. Remember, batteries have been of great use in the automotive industries, especially in electric cars; hence, such applications require that the battery be charged to total capacity within a very short period. The function of the charging system is to charge the battery, which is referred to as charging, ensuring that there is an optimal charging rate, which we refer to as stabilizing, and finally, understanding when it should stop charging, which we refer to as terminating. Therefore, the battery charging technology must combine the battery charging and the methods used to terminate the charging.  Let us look at what you should be equipped with regarding battery charging technology.

Terms Used in Battery Charging

Below is a discussion of terms used when it comes to battery charging.

Charge Termination

Immediately after the battery is fully charged, it is advisable to dissipate the charging current. The outcome of dissipating this current is the generation of gasses and heat that do not serve well with batteries. The best charging system can detect when the chargeable battery cells are well constituted and stop them from further charging, preventing damage to the cells and ensuring that they retain the advisable temperatures. The detection of the charging cutoff points and charging termination improves battery life. Charge termination occurs when the process has attained termination voltage. Charging termination is advisable when working with first chargers where overheating occurs with a more significant impact.

Charging Times

 The charging system likely pumps electric charge into the battery at a higher rate than the chemical reaction during fast charging, which can damage the battery.

Figure 1: Cell Chemical Reaction Times

Three essential processes are involved during the chemical conversions of the cell.

  •  Charge transfer is the chemical reaction that occurs at the electrode and electrolyte interference, which happens quickly.
  • Mass transfer is the second process, also known as diffusion. In this process, the material that has been transformed during the charge transfer process is moved away from the surface of the electrode, creating space for more material to get on the electrode and participate in the transformation process. This process is slower in allowing the transformation of all the materials.
  • Other processes are involved during the charging process, such as the intercalation process, which allows the charging of lithium cells. Lithium ions are placed in the crystal lattice of the electrode that acts as the host.

Hysteresis

During battery charging, the chemical reaction creates a lag situation behind the charging voltage application. This is similar to when a load is applied to the battery to help discharge it.

The diagram shows the hysteresis effect that occurs during the charging and discharging of the lithium-ion battery.

Figure 2: Charge-Discharge Profile

Allowing settling times in charging and discharging the battery to initiate the completion of the chemical reaction process time will reduce the voltage difference, but not entirely due to the effects of hysteresis.

Charge Efficiency

This originates from the property of the battery being charged, not the charging system. It is the ratio of the energy discharged from the battery compared to the energy charged to the battery. It is also known as coulomb efficiency or further charge acceptance. It is expressed in percentage.

Basic Battery Charging Methods

Below is a list of modern power electronics and systems' most common battery charging methods.

Constant Current

This type of charger varies the voltage applied to charge the battery while ensuring the current is constant. They switch off immediately after the voltage attains the maximum whole voltage level.

This type of charger varies the voltage applied to charge the battery while ensuring the current is constant. It switches off immediately after the voltage attains the maximum whole voltage level. It is suitable for nickel-metal hydride and nickel-cadmium cells or batteries.

Constant Voltage Method

In simple words, a DC power supply is made up of the stepdown transformer and rectifiers that rectify AC to DC, which is used to charge the battery. They are also applied to car chargers. In car battery charging systems, you will come across constant voltage chargers.

Pulsed Charging Method

This type of charger feeds charges to batteries in the form of pulses. The charging rate is controlled by varying the pulse width to about one second. The chargers allow charge rest times of about 20 to 30ms to give room for chemical reactions to complete during charging. The method is suitable for eradicating unwanted chemical reactions, such as gas formation, passivation, and crystal growth.

Figure 3: Pulse and Burp Charging

Burp Charging Method

 

This is also known as unfavorable or reflex pulse charging. It is used together with pulse charging, and it stands for a very short discharge pulse that is typically 2 to 5 times the charging current. It works to dislodge any gas formation on the electrodes during the charging process, hence speeding up the stabilization process and, therefore, improving the charging process. This process of releasing the bubbling gases is what we refer to as burping.

Taper Current

 This is charging that occurs using crude, unregulated constant supply voltage. It is not controlled like the constant voltage method. The current state of this process will diminish as the cell-back EMF builds up. The process is used to charge the SLA batteries.

Float Charging Method

The load and the battery are connected to the DC charging source in parallel. This process is used when charging emergency backup power systems, especially those that utilize lead-acid batteries.

Other battery charging methods include random, trickle, and IUI charging.

Battery Charging Rates

Batteries can be charged at different rates. Some of the rates are slow to charge, which is done overnight at a period range of between 14 to 16 hours of charging at a 0.1C charge rate; quick charge, which takes a time range of 3 to 6 hours at a rate of 0.3C charge rate, and finally fast charge which takes less than an hour with a charging rater of 1.0C charge rate.

 Slow Charging

This charging rate is possible because simple chargers do not initiate overheating problems. The battery should be disconnected from the charger immediately after it has charged.

Fast and Quick Charging

This one uses a more sophisticated charger that must be specific for specified cell chemistry. If the charger is universal, it must sense the connected device and determine the cell type to apply the necessary charging specifications and profile.

 

Summary

  • Several terms are used in battery charging technology: charge termination, charging times, hysteresis, and charge efficiency.
  • Charge termination is how the battery charging technology disconnects the battery from the charging system once fully charged.
  • Charging times are the time it ultimately takes for a battery to charge by the charging system. They include both resting and active times.
  • Hysteresis is the curve that compares battery voltage to the state of charge in percentage during the charging and discharging process.
  • Charge efficiency is the ratio of the discharged energy to the energy used to charge the battery.
  • Basic battery charging methods include constant voltage, constant current, pulsed charging, burp charging, taper current, float charging, random charging, trickle charging, and IUI charging methods.
  • Battery charging rates are the rates at which a battery can be charged, including slow, quick, and fast charging.

 

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