Below is an excerpt from Apple’s support page for the MagSafe Battery Pack-
Charge your MagSafe Battery Pack
Before you use your MagSafe Battery Pack for the first time, fully charge it using a Lightning to USB cable with a 20W or higher power adapter.
- Plug one end of a Lightning to USB cable into the Lightning connector on your MagSafe Battery Pack.
- Plug the other end of the cable into a 20W or higher USB power adapter, then plug the adapter into a power outlet.
- You'll see an amber status light while your MagSafe Battery Pack is charging. When the MagSafe Battery Pack is fully charged, you'll briefly see a green status light.
To review the full document click here ➔ How to use your MagSafe Battery Pack.
Back to your question. The way the document is worded suggests that the Amber light should be ON throughout the duration of the charging process. Is your iPhone almost fully charged when the battery pack was connected and charging? I ask because the charge management feature may have an influence of the charging process and charging was put on hold. I am not sure about this one.
I recommend that you contact ➔ Apple Support and ask them the same question or have the folks at the Apple Store call other stores and confirm which is the normal behavior of the Amber light when the Battery Pack is charging.
Axel F.