Anker A1247 In Cold Temperatures

I have a Garmin Zumo XT. I bought it for ATVing, but I also use it on my e-bikes. Lately, when I am using it on my e-bike I run off the internal battery. The temperatures have been about 20 degrees Fahrenheit. I have noticed that the battery doesn’t last as long. I know that batteries are affected by colder temperatures.

May I safely use a portable power bank to run the Garmin Zumo XT in colder temperatures? The reason I ask is because someone suggested that it’s not advised to charge lithium batteries below freezing. They stated that you can damage the battery chemistry, which may reduce the capacity even further.

One of my power banks is an Anker A1247.