Iphone air Magsafe battery pack

Hello guys, I have the iphone air and its battery magsafe pack, I havent use it like a lot tbh, funny thing is, I had it at 100% the battery btw, 5 days later I was trying to charge my phone and the battery pack was 40% blinking red.

Is that normal? I´ve had before other magsafe battery pack from anker and mophie and the 100% lasts for a long time beofre draining by itself.

Thank you.