Build Your Own Ultra-Cheap NiMH/NiCd Battery Charger

I Don’t Like Disposable Batteries

I’ve realized that my house is full of them, especially AA and AAA sizes.

After reviewing dozens of circuits, I’ve chosen the simplest one!

In this article, I’ll show you how I built the easiest and most affordable charger for NiMH and NiCd batteries.

Some time ago, I also made a video on this topic.

Enjoy the read!

Diode 1N400X

Resistors (120 Ohm)

5mm Led

Magnets (optional)

Connector (micro Usb - type C)

5V Charger

Breadboard

Jumper wires

This easy-to-make circuit consists of just a diode, two 120-ohm resistors, and an LED.

It uses a trickle charge method, which provides slow and continuous charging while keeping the current very low to prevent overcharging the batteries.

Warning: Never use this circuit with lithium-ion or lithium-polymer batteries, as it can be dangerous.

This charger is specifically designed for 1.5V NiMH (Nickel-Metal Hydride) and NiCd (Nickel-Cadmium) batteries.

How It Works

The diode blocks passive discharge from the battery back into the circuit.

One 120-ohm resistor ensures proper LED operation.

The second 120-ohm resistor limits the charging current to safe levels.

Using a 5V power supply, and applying Ohm’s Law, the circuit delivers a maximum charging current of approximately 40mA.

While this means the charging process is very slow (requiring several hours or even days), it ensures optimal safety and extends the lifespan of your NiMH and NiCd batteries.

This method is ideal for hobbyists and DIY enthusiasts looking for an affordable and reliable way to recharge AA or AAA rechargeable batteries.

As you can see, I simply placed the circuit components on the breadboard!

I used jumper wires and magnets to connect the battery. This way we can easily connect both AA and AAA batteries.

From my tests, I found that charging an 800 or 1000 milliampere-hour NiMH or NiCd battery takes a very long time. Easily 20 hours or more. During the charging process, the LED’s brightness gradually decreases, and when the battery is fully charged, the LED turns off. This simple yet effective feature helps you clearly identify when the charging process is complete.

Why Build Your Own Battery Charger?

One of the key advantages of this DIY NiMH charger is its incredibly low cost. Using basic components that cost only a few cents each, the total expense for the entire circuit is under one euro!

Additionally, the trickle charge method used by this charger is very gentle on the battery. By providing a slow and consistent current, it helps maximize both the performance and the lifespan of your NiMH and NiCd batteries. This makes it an excellent choice for anyone looking to care for their rechargeable batteries while saving money.

If you’re passionate about DIY electronics, this project is perfect for you. Check out the links to the components in the description. Your support through these links helps me finance future projects and share even more content with the community.

Watch the Video and Join the Community!

I’ve also created a video tutorial about this simple charger. Take a look, and if you find it helpful, don’t forget to subscribe to my channel! Your engagement and support mean so much and motivate me to bring you more DIY electronics projects.