What comes out of the cabin suitcase if it is checked at the gate?

People, dialogue, journeys and prices are fictional.

‘If they take the case at the gate, we'll just leave the electronics zipped inside,’ Alex says while packing for a US domestic flight. His daughter Priya pulls out a power bank. ‘Does this count as electronics or as a spare battery?’

They have paid £38 for one cabin suitcase on their imagined booking and want to keep their small personal bags light. The case contains clothes, a phone charging cable and two power banks. One has a readable 74 Wh label; the rating on the older one has rubbed off. Their airline has not yet been checked for its own battery restrictions.

The FAA's [passenger battery guidance](https://www.faa.gov/hazmat/packsafe/airline-passengers-and-batteries) says spare lithium batteries, including power banks, must stay in carry-on baggage and cannot be checked. It also says airline and other applicable restrictions can be stricter. That answers where the power banks cannot go; it does not clear the unlabelled one for travel.

Priya wants a small pouch ready to remove if the suitcase goes into the hold. Alex thinks they are creating a packing problem for something that might never happen. What would you settle before leaving home, and what should they ask the airline rather than guess from the size of a charger?