CC/CV (constant current / constant voltage) converter modules are widely used as adjustable power supplies and battery chargers. While lithium batteries require very strict charging control, CC/CV modules are especially useful for charging non-lithium batteries such as lead-acid and, with care, NiMH batteries.
This article explains how to use CC/CV converters safely and effectively for battery charging applications.
What is a CC/CV Converter?
A CC/CV converter is a DC-DC module that allows you to set both:
- Maximum output voltage (CV mode)
- Maximum output current (CC mode)
The module automatically switches between modes depending on load conditions.
Why Use CC/CV for Battery Charging?
- Prevents excessive current during charging
- Allows controlled charging voltage
- Protects the battery from damage
- Flexible for different battery types
This makes CC/CV converters ideal for adjustable charging setups.
Basic Charging Principle
The typical charging process using a CC/CV module:
- Start in constant current mode
- Battery voltage rises gradually
- When target voltage is reached, switch to constant voltage
- Charging current decreases over time
This behavior is similar to many standard charging methods.
Charging Lead-Acid Batteries
Lead-acid batteries are well suited for CC/CV charging.
- Set voltage according to battery type (e.g. ~13.8V-14.4V for 12V systems)
- Limit current to a safe value (e.g. 0.1C-0.3C)
Charging phases:
- Bulk: constant current
- Absorption: constant voltage
- Float (optional): lower maintenance voltage
CC/CV modules can handle bulk and absorption phases.
Charging NiMH Batteries (With Caution)
NiMH batteries are usually charged with constant current and special termination methods.
- CC/CV modules can be used for simple setups
- Current must be carefully limited
- No automatic termination detection
This approach is not ideal for precise charging but can work for basic applications.
Important: Lithium Batteries
While CC/CV is the basis of lithium charging, simple CC/CV modules are NOT sufficient on their own.
- Precise voltage control required (typically 4.2V per cell)
- Protection circuitry required
- Charging termination must be controlled
Dedicated lithium charging modules should always be used.
Setting Up a CC/CV Module
Step 1: Set Output Voltage
- Adjust voltage to battery charging voltage
- Measure with a multimeter
Step 2: Set Current Limit
- Adjust maximum charging current
- Typically based on battery capacity (C-rate)
Step 3: Connect Battery
- Ensure correct polarity
- Monitor initial charging behavior
Typical Charging Currents
| Battery Type | Typical Charge Rate | Notes |
|---|---|---|
| Lead-acid | 0.1C-0.3C | Safe and common range |
| NiMH | 0.1C-0.5C | Requires monitoring |
Practical Applications
- Charging 12V lead-acid batteries from DC sources
- Solar charging systems (with proper control)
- Adjustable lab power supplies
- DIY charging setups
Safety Considerations
- Never exceed recommended voltage
- Limit charging current properly
- Monitor temperature if possible
- Do not leave charging unattended
Common Mistakes
- Using CC/CV modules for lithium batteries without protection
- Setting voltage too high
- Ignoring current limits
- Not monitoring the charging process
Conclusion
CC/CV converters are powerful and flexible tools for battery charging, especially for lead-acid and simple NiMH applications. They allow adjustable and controlled charging when used correctly.
Understanding their limitations is essential, particularly when dealing with lithium batteries, where dedicated charging solutions are required.