What’s the Difference Between a Low Voltage Cutoff and a Buck Converter?

When you’re building a DIY boombox, you’ll probably come across two pieces of gear that sound similar but do completely different things: Low Voltage Cutoffs (LVCs) and buck converters. Both are important for battery-powered projects, but they serve very different purposes.

Here’s a simple breakdown to help you understand when you need one, the other, or both.

What Is a Low Voltage Cutoff?

A Low Voltage Cutoff is a device that disconnects power from your system when the battery voltage drops too low. It’s there to protect the battery from being over-discharged, which can permanently damage lithium-ion packs.

When using tool batteries in DIY builds—especially ones that don’t have internal protection like DeWalt or Milwaukee—an external LVC is absolutely required.

What the LVC Does:

Monitors the voltage of your battery pack.
Automatically cuts power when the voltage drops below a safe limit.
Protects the battery from over-discharge and extends battery life.

What the LVC Does Not Do:

It does not change voltage.
It does not stabilize voltage.
It simply turns off power when it gets too low.

What Is a Buck Converter?

A buck converter is a device that reduces (or “steps down”) voltage from a higher input to a lower, usable level. It’s basically a voltage regulator that lets you power components that need a lower voltage than your battery provides.

For example, if you are using a 24?V battery but your Bluetooth board can only handle 12?V, you would use a buck converter to safely drop the voltage.

What the Buck Converter Does:

Steps down voltage to a lower, steady output.
Allows you to run 12?V or 5?V devices from higher-voltage batteries.
Can often be adjusted to your desired output voltage.

What the Buck Converter Does Not Do:

It does not protect your battery from over-discharge.
It does not cut off power when the battery gets too low.

Quick Comparison

Feature	Low Voltage Cutoff	Buck Converter
Purpose	Protects battery	Steps down voltage
Cuts power automatically	Yes	No
Regulates voltage	No	Yes
Prevents over-discharge	Yes	No
Common DIY Use	Protects tool batteries	Runs lower-voltage components

Do You Need Both?

In many boombox builds, yes—you may need both.

The Low Voltage Cutoff protects your battery from running too low.
The Buck Converter makes sure sensitive parts like Bluetooth boards, amps, and LED displays get the voltage they need.

For example:

You might use an 20?V DeWalt battery.
Your amplifier might work fine on 20?V, but your Bluetooth module might need 5?V.
You would use a buck converter to drop 20?V to 5?V for the Bluetooth board.
You would also use an LVC to cut power around 16?V to protect the battery from over-discharge.

Final Thoughts

Think of it this way:

The LVC is a safety device for your battery.
The buck converter is a voltage manager for your electronics.

They work together but serve completely different purposes. Understanding the difference will help you keep your boombox running strong and your batteries lasting as long as possible.