Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Wire housing split open, shorted out against my leg. Lost some hair.

First time I wore these hunting, the wire on the left one split open and shorted out. I noticed a burning against my leg, and realized the battery pack was getting extremely hot. Took a few moments to access the unit to turn it off. Rechargeable batteries have expanded slightly and the wrapping on them is split.Sent back for refund. Also, the insoles only get slightly warm, doesn't help when the ambient temperature is below 20. Going to stick with hand warmers in each boot.