What’s That Leaking From Your Flex Drill Battery?

In the past year, we’ve tested four tools from Flex that use the leaking 24-volt battery: a cordless drill, two cordless impact drivers, and an oscillating multitool. We bought all four tools with the standard battery and charger. 

While none of the batteries leaked during the course of our initial testing, three batteries went on to leak after testing was completed. Two of those batteries leaked when used in a cordless drill, and the third battery leaked while in its storage case at room temperature. Two were larger 5.0-amp-hour batteries (included with the cordless drill and impact drivers), and the third was a smaller 2.5-amp-hour battery included with the oscillating multitool. To minimize the risk of injury, CR’s testers immediately stopped using the tools when they noticed the leaking batteries.

While our engineers had a theory as to what was leaking, we also contacted a representative from Flex’s parent company, Chervon, who confirmed that the liquid wasn’t harmful.

“The liquid is a waxlike substance called a phase-change material,” said Ravi Voruganti, Chervon’s vice president of product development. A phase-change material is typically a substance that shifts from liquid to solid, or vice versa, for the purpose of absorbing energy in the form of heat. The liquid is a compound used to protect the battery from overheating.

Chervon also attributed the leak to a defect with a single lot of batteries. While there’s no recall, and the company says consumers can safely continue to use a leaking battery after wiping it off, Chervon will replace defective batteries under the brand’s warranty program. 

Contact Flex customer service or call the company at 833-353-9496. With registration, Flex power tools come with the same 5-year warranty on the 24-volt battery. 

To safely dispose of your old battery, you can usually take it to a home center like Lowe’s and Home Depot. Or go to Earth911, a searchable online database that can help you track down nearby recycling points for lithium-ion batteries and other materials.