What is a Low Voltage Cutoff and Why Your Boombox May Need One

When building a DIY boombox, tool batteries like DeWalt, Milwaukee, Makita, Ryobi, Bauer, Hercules and Snow Joe offer portability and power. But to protect these lithium-ion batteries from damage, you need to know which packs include voltage protection and what cutoff voltages to use.

What is a Low Voltage Cutoff?

A Low Voltage Cutoff (LVC) is a circuit that disconnects the battery when its voltage drops below a safe threshold. For lithium-ion cells, draining past roughly 3.0 volts per cell can cause permanent damage and possible safety problems.

How Tool Batteries Handle Voltage Protection

Tool batteries rely on different systems for protection:

Protection Inside the Tool Only

These brands place LVC protection circuits inside the tool rather than the battery pack itself:

DeWalt
The cutoff is managed by the tool at about 15volts for an 18V (5-cell) pack. Cellular voltage shuts off near 2.5V per cell when the tool stops taking current.
Makita and Milwaukee
Similar design to DeWalt. No internal pack cutoff means the tool enforces shutdown. When used outside the tool—for instance in a boombox—there is no protection. You need an external LVC to prevent over-discharge .
Bauer, Hercules, etc
Not documented in detail, but most budget brands follow this same pattern—protection is in the tool only. These packs need external LVC when used in boombox builds.

Protection Inside the Battery Pack

These brands include electronic protection within the battery:

Ryobi, Ridgid, Snow Joe
Packs include internal cutoff protection, typically disabling output when cells dip around 2.8–2.9V per cell (approx. 14.4–14.7V for an 18V pack). This is designed for tool use, not continuous low current drain. It's recommended to still install an LVC in boombox builds for more reliable cutoff.

Recommended Cutoff Voltages by Battery Voltage and Brand

The table below shows typical nominal voltages, cell counts, and recommended low voltage cutoffs for each major battery type. These values are based on common lithium-ion chemistry (around 3.6V nominal, 4.2V full, 3.0V empty per cell). Exact cutoff voltages can vary slightly by brand and BMS behavior, but these are safe general targets for external Low Voltage Cutoff circuits.

Brand	Labeled Voltage	Cell Count	True Nominal Voltage	Recommended LVC Cutoff
DeWalt	20V Max / 18V Nominal	5S	18.0V	15.0 – 15.5V
	24V Max / 21.6V Nom	6S	21.6V	18.0 – 18.6V
Kobalt	24V Max	6S	21.6V	18.0 – 18.6V
Milwaukee M12	12V Max / 10.8V Nom	3S	10.8V	9.0 – 9.3V
Milwaukee M18	18V Nominal	5S	18.0V	15.0 – 15.5V
Makita	18V	5S	18.0V	15.0 – 15.5V
Makita XGT	40V Max / 36V Nom	10S	36.0V	30.0 – 31.0V
Ryobi One+	18V	5S	18.0V	14.5 – 15.0V (pack protected)
Ridgid	18V	5S	18.0V	14.5 – 15.0V (pack protected)
Hercules	20V Max	5S	18.0V	15.0 – 15.5V
Bauer	20V Max	5S	18.0V	15.0 – 15.5V
Snow Joe	24V Max	6S	21.6V	18.0 – 18.6V (pack protected)

Note: “5S” means 5 cells in series, “6S” means 6 in series, and so on. The cutoff should generally be no lower than 3.0V per cell, and ideally closer to 3.2V per cell for battery longevity.

Voltage Protection Tip

If you're unsure of a battery's internal configuration, check the total voltage output at full charge with a multimeter. Divide by 4.2V per cell to estimate the number of cells in series, then multiply that cell count by 3.2V to get a safe cutoff target.

What About TalentCell and KBT Battery Packs?

In addition to tool batteries, many builders use rechargeable lithium-ion battery packs from brands like TalentCell, KBT, DC House, and others. These battery packs are often sold as general-purpose DC power solutions for LED lights, routers, security cameras, or portable electronics. They are usually advertised as "12 volt" or "24 volt" batteries.

The good news is that most of these battery packs already include internal protection circuits, including:

Low voltage cutoff
Overcharge protection
Short circuit protection
Overcurrent protection

These features are built into the battery’s management system, and they are designed to protect the pack during regular use. That means if you are using a TalentCell or KBT pack, you usually do not need to add an external LVC. The internal circuitry will safely cut off the output when the voltage drops to the lower limit, typically around 9.0 volts for a 3-cell 12 volt pack or 18.0 volts for a 6-cell 24 volt pack.

Important Notes:

These packs are generally safe for boombox use right out of the box
Always verify the specs for your specific pack. Look for terms like "BMS" or "protection circuit" in the product listing or manual
These battery packs usually come with a barrel connector. Make sure your boombox accepts that input or use a proper adapter
Even though they include protection, it is still important to monitor battery performance over time. If the pack ever runs completely flat and will not recharge, the protection circuit may have triggered to prevent further use

Final Takeaway

Always add an external LVC to DeWalt, Milwaukee, Makita, Kobalt, Bauer, and Hercules battery packs used in boombox builds.
Recommended LVC settings:
- ~16.0V for 18-20V packs (DeWalt, Milwaukee, Makita, etc.)
- Not needed for Ryobi, Ridgid, or Snow Joe packs
External LVC modules are inexpensive, easy to integrate, and highly effective at protecting valuable tool battery packs from over-discharge.

What is a Low Voltage Cutoff and Why Your Boombox May Need One