Easy-to-understand tips, diagrams, and examples for beginners, makers, and electronics enthusiasts.
Battery charger circuits are used to safely charge rechargeable batteries. You’ll find them in everything from small gadgets like flashlights to big systems like solar power banks.
In this guide, we’ll break down how battery chargers work, the different types of charger circuits, and how to build your own using popular components like LM317, 7805 and TP4056.
Whether you’re just getting started with DIY electronics or looking to improve your existing battery charging setup, this page will walk you through the basics — in plain language, without skipping the important details.
What You’ll Learn
- What battery charger circuits do, and how they work
- Different types of chargers (linear, switching, smart)
- Which ICs are most popular for DIY projects
- Example battery charging circuits
- Safety tips when charging batteries
- More projects coming soon!
⚡ 1. What Is a Battery Charger Circuit?
A battery charger circuit is a system that gives power to a rechargeable battery — but in a controlled way. It manages how much current (amps) and voltage go into the battery, so you don’t damage it.
Most chargers work in two steps:
- Constant Current (CC): At first, the circuit sends a steady current into the battery.
- Constant Voltage (CV): Then, when the battery reaches a certain voltage, the circuit switches to holding that voltage steady while reducing the current.
This two-phase method helps charge batteries safely and efficiently.
🔋 2. Charging Different Battery Types
Each battery type needs a specific charging method. Using the wrong one can reduce battery life — or cause safety problems.
| Battery Type | Charging Needs | Notes |
|---|---|---|
| Li-ion / Li-Po | Constant current + constant voltage (CC/CV) | Needs careful voltage control and protection |
| Lead Acid | Constant voltage + low current | Can handle some overcharging, but still needs limits |
| NiMH / NiCd | Pulse or delta-V detection | Monitor temperature to avoid damage |
Lithium batteries are more sensitive — always use a proper circuit!
🔌 3. Types of Battery Charging Methods
There are different ways to charge a battery. Each method is better for certain battery types or situations.
| Method | How it Works | Good For |
|---|---|---|
| Linear Charging | Uses simple regulators like LM317 or resistors | Small, low-cost DIY projects |
| Switching Charging | Uses buck/boost converters for higher efficiency | Medium to high power circuits |
| Pulse Charging | Sends short pulses of current to avoid heat | NiMH or NiCd batteries |
| Smart Charging | Controlled by a microcontroller or smart IC | Lithium-ion (Li-ion) and Li-Po |
Some advanced chargers switch between these methods automatically.
🧰 4. Common ICs and Components Used in Battery Chargers
Here are some popular chips and parts used to build battery charger circuits:
- Transistors – Simple components but great for uses
- LM317 – Adjustable voltage regulator; used for basic linear chargers
- 7805 – Fixed voltage regulator; for simple current constant chargers.
- TP4056 – Easy-to-use chip for charging 1-cell Li-ion batteries; comes with built-in protection
- MCP73831 – Small charger IC with low current output (great for small devices)
- BQ24195 – Smart charger IC with USB support; used in commercial products
- MOSFETs, diodes, thermistors (NTC) – Help control current, protect from short circuits, and detect heat
Don’t forget to check each IC’s datasheet before using it.
🛠️ 5. DIY Battery Charger Circuit Examples
We’re building a collection of easy-to-follow charger circuits. Here are some examples (more coming soon!):
Gel Cell Battery Charger Circuit
Let’s take a look at this gel cell battery charger circuit using LM317. Why did I recommend this particular circuit? Because of its low voltage charging, merely 13.4 volts. As a result, it generates next to no heat.
Explore the project → Gel cell battery charger circuit
Simple Li-ion Battery Charger Circuit with Automatic Cut-Off
We made the circuit with commonly used components such as the NE555 timer and TL431 shunt regulator. It uses the principle of charging the battery with a low-current pulse signal. Making it a safe and impressionable performance charger.
See the full schematic →Simple Li-ion Battery Charger Circuit with Automatic Cut-Off
Ni-MH Battery Charger Using LM317T
Here is Universal Nicd and NiMH battery charger circuit. It use IC LM317T ( Hot IC) Control Current less 300mA, Size battery 2.4V,4.8V,9.6V. Low cost circuit.
Check out the full guide → Ni-MH battery charger using LM317T
Automatic Battery Charger Circuit
I suggest an Auto dry battery charger using SCR for 12V battery. Also, it uses the 6V battery. It looks like the above circuit.
The Zener diode and SCR are main parts. But the SCR works instead of the relay. The SCR is working in DC pulse on filters with a capacitor.
Explore the project →Automatic Battery Charger Circuit
Simple NiCad Battery Charger and Discharger Circuit
I love NiCd batteries. But they have an important disadvantage is a memory effect. Before charging this battery. It needs to have power is zero only.
Read more why I love it and see more other circuits
LM317 Lead Acid Charger | 6V, 12V, 24V
See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery, with automatic charging and full charged Indicator Easy to build.
Check out the full guide → LM317 Lead Acid Charger | 6V, 12V, 24V
- 🔗 Simple 12V Lead Acid Charger using LM317
- 🔗 Li-ion TP4056 Charger with Protection
- 🔗 Solar-Powered Li-ion Battery Charger (Coming soon)
- 🔗 Auto-switching Dual Battery Charger (Coming soon)
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🔒 6. Safety Tips for Charging Batteries
Charging batteries the wrong way can be dangerous. Follow these tips to stay safe:
- ✅ Use a fuse or current-limiter to protect the circuit
- ✅ Keep an eye on battery temperature and voltage
- ❌ Never charge lithium batteries without a protection circuit
- ❌ Don’t leave batteries charging unattended — especially Li-ion
Always test your circuit with a multimeter before connecting a real battery.
💬 Have Questions or Suggestions?
Is there a battery charger topic you want us to write about?
Let us know through the contact and leave a comment below!
Simple Solar Powered Bank with 5v USB ports
Thanks for your request!
We do not have that circuit ready yet because we have not tested it myself.
In the past, we shared some untested circuits, and a few of them didn’t work as expected — which caused problems for some readers.
Because of that, my main rule now is to share only circuits that have been tested and confirmed to work.
This helps everyone avoid mistakes and confusion.
We plan to test this circuit in the future, and once it’s ready, we will be happy to share it here!
Thanks
Apichet & Kids