The Difference Between Constant Current Charging and Constant Voltage Charging

Several different methods are used to charge batteries. Constant current charging and constant voltage charging are two methods to charge battery among multiple others. Use of these methods is quite common depending on the type of use and equipment.

In this article, we will lean in detail how constant current charging and constant voltage charging are different. Before jumping to differing points, let us look at the definition of both charging methods. 

Constant Current Charging

Battery gets constant and steady current on constant current charging. The charging current remains steady during the whole charging until it reaches predetermined threshold. 

Current remains constant throughout the charging cycle.

This method charges battery fast, especially in the beginning when the battery voltage is low.

This method is often used for batteries with high energy density like lithium-ion batteries, commonly used in electric vehicles, laptops, and smartphones. 

Constant Voltage Charging

Constant voltage charging means constant voltage supply to the battery throughout the charging process. The charging voltage remains unchanged until it reaches the predetermined level. 

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The charging voltage remains content throughout the process.

Use of this charging method is common for lead-acid batteries and some types of nickel-based batteries.

This method employed where maintaining a steady voltage is critical like emergency lighting, telecommunications equipment, and standby power systems. 

The charging voltage must be accurately regulated with proper control mechanisms to avoid damaging the battery.

Charging Mode

Both constant current charging and constant voltage charging have different sets of charging modes let us look into one by one. 

Constant Current Charging Modes

Bulk Charging Mode: In bulk charging mode, battery receives constant supply of current until it reaches a predefined voltage threshold. This charging mode is specifically used to achieve certain charging level, typically around 80%. This is an ideal mode for rapidly replenishing the battery’s charge for a deeply discharged battery.

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Absorption Charging Mode: As the battery reaches the predefined threshold in bulk charging mode, absorption charging mode switches on. In this mode, the charger maintains a constant voltage. Charging current reduces simultaneously as the battery approaches full charging. This mode makes sure battery is fully charged, preventing overheat. 

Float Charging Mode: Some constant current chargers switch to float charging mode as the battery is fully charged in absorption charging mode. To maintain battery at full capacity without overcharging, the charger supplies a lower constant voltage in float charging mode. This mode is commonly employed where the battery needs to be connected for extended period like standby power systems and uninterruptible power supplies (UPS).

Constant Voltage Charging Modes

Bulk Charging Mode: Charging starts similar to constant current charging from bulk charging mode. This charging mode is commonly used to quickly replenish the battery’s charge, especially for fully discharged batteries. 

Topping Charging Mode: Constant voltage chargers may switch to topping charging mode as the battery reaches a predefined threshold in bulk charging mode. In topping charging mode, charge reduces to a low trickle charging level, and maintains it until the battery is fully charged. Use of this method is common for standby power systems and emergency lighting.

Maintenance Charging Mode: This mode comes in some constant voltage chargers that provide a low constant voltage to the battery to compensate for self-discharge, and keeps battery fully charged in inactive state for longer period. This mode prevents deep discharge and salvation, and extends battery lifespan. 

Charging modes can be different based on the charger’s design, battery chemistry, and application requirements.

Charging Setting

There are several factors like the type of battery, its capacity, desired charging speed, and manufacturer recommendations that determine the type of charging setting. Here’s an overview of different charging settings for constant current charging and constant voltage charging.

Constant Current Charging Settings

Charging Current: A value of the constant charge is set in amperes (A) or milliamperes (mA) that remains unchanged throughout the charging process. This is selected based on the battery’s capacity and the desired charging rate.

Maximum Voltage: Constant current chargers have limitation of maximum voltage when it is fully charged. Selection for this is done based on the manufacturer’s recommendations to avoid any damage or hazard.

Charge Termination Criteria: Constant current charging typically terminates as it reaches the predefined voltage threshold, which is the signal of fully charged battery. Chargers may also incorporate additional termination criteria like specified charging time to ensure accurate charge termination.

Constant Voltage Charging Settings

Charging Voltage: Everything happens similar to constant charge. The charging voltage may vary based on the battery chemistry and the desired state of charge. 

Maximum Charging Current: Just like constant current, constant voltage may also have maximum limit to avoid any damage. 

Charge Termination Criteria: Termination happens based on the predetermined charging threshold, showing battery is fully charged. There are charges that may incorporate additional termination criteria like specified charging time to ensure accurate charge termination.

Applications

Constant current charging and constant voltage charging have several applications depending on the battery types, charging requirements, and performance considerations.

Constant Current Charging Applications

Constant Current Charging use is common in EVs and HEVs. It allows efficient and fast charging. Portable devices like smartphones, tablets, and laptops use this method for their lithium-ion or lithium-polymer batteries.

Constant current charging is employed in solar and wind energy storage batteries like renewable energy sources. Efficient charging of batteries with high energy density allows using later.

Portable oxygen concentrators, defibrillators, and wearable health monitors like medical devices widely use constant current charging to recharge their batteries. This charging method is reliable and efficient to provide energy in emergencies.

Constant Voltage Charging Applications

Its use is common in lead-acid batteries. These batteries are found in standby power systems, and uninterruptible power supplies (UPS). This method is ideal for controlled charging.

Emergency lighting systems used on exit signs, emergency lights, backup lighting fixtures use this method. This method maintains batteries at full capacity, and readies them to use in any emergency.

Telecommunications equipment like base stations, towers, and communication devices use constant voltage charging as a backup for their system. This is a reliable solution to provide power during network outages or disruptions.

Solar or wind power systems like off grid renewable energy systems use this method to charge their battery banks. 

Final Thoughts

These different aspects of constant current charging and constant voltage charging give you detailed view of how they are different from each other. Mainly types of uses, chemistry, etc. define which charging method is ideal for you.