Milwaukee 18V to Hercules 20V Battery Adapter

Use your Milwaukee M18 batteries on Hercules 20V cordless tools, without buying into a second battery platform. Constructed from durable molded ABS with pure copper contacts, for a secure fit and dependable current transfer. Your existing batteries do more work, and there is no second ecosystem to buy into. It also carries battery protection electronics (BMS) inside.

Specifications

• SKU PTA-MIL18-HER20
• Fits this battery Milwaukee M18 (Lithium-Ion)
• Battery voltage 18V
• Runs these tools Hercules 20V (Lithium-Ion) from Harbor Freight
• Tool voltage 20V
• Housing ABS (Injected)
• Terminals Copper
• Current rating 40A continuous (80A peak at 18VDC for up to 2 seconds)720 Watt continuous at 18V nominal
• Internal wiring 5 mm²
• Weight 124 g (4.4 oz / 0.27 lb)
• Colour Red, Yellow
• Operating humidity 5–95% RH
• Operating temperature -10 °C to 50 °C (14 °F to 122 °F)
• USB port No
• Built-in BMS protection Yes
• What's in the box Battery adapter
• Warranty 12 months after the date of delivery
• Revision Revision 01 (released on March 10, 2025)

Why choose this adapter

• A Battery Management System inside the adapter cuts power before the battery is drained too far — protection your battery may not have on its own.
• Injection-moulded ABS, not 3D printed — no layer lines to split under load.
• Solid copper terminals, so less of the current is lost as heat.
• 5 mm² internal wiring, rated for 40A continuous with 80A peak at 18VDC for up to 2 seconds, so a high-draw tool is not held back by the adapter.
• Covered by a 12-month warranty from the day it arrives.

Milwaukee M18 and Hercules 20V compatibility

It works in one direction only: Milwaukee batteries powering Hercules tools. For the opposite pairing, see adapters that run on Hercules 20V batteries.

Compatibility can vary with the exact battery and tool model. Before ordering, confirm that your battery belongs to the Milwaukee M18 platform and that your tool takes Hercules 20V batteries.

Important charging and safety information

This adapter is for powering cordless tools and nothing else. It cannot charge Milwaukee or Hercules batteries and must never be connected to a charger of any kind. Always take the battery out of the adapter before charging, and charge it on the original charger made for your Milwaukee M18 battery.

Before you buy