Hi, this is AnkerDirect.
Kindly be advised a little warmth is to be expected, but excessive heat could indicate a fault. Below is the temperature of our batteries. You can serve as a reference
Storage temperature: -40℃ to 75 ℃
Product temperature (maximum temperature):
Metal case: <45 ℃
Plastic housing: <56 ℃
Use of the ambient temperature: -10℃ to 45 ℃
If you have any questions in the future then please do not hesitate to get in touch. Our customer service email address is firstname.lastname@example.org.