I've been looking into this as an electric wheelchair traveller, there are guidelines, but it's also up to the airline. I'd talk to them first and see what they say.
"Lithium ion battery size is limited to 300 watt hours (Wh). One spare battery not exceeding 300 Wh or two spare batteries not exceeding 160 Wh each may be carried in carry-on baggage.
Lithium ion batteries must be removed from this type of mobility device and battery terminals protected from short circuit. The battery must be protected from damage (e.g. by placing each battery in a protective pouch). The lithium ion batteries must be carried in carry-on baggage only. The passenger must advise the airline of the battery location. The airline must notify the Pilot-in-command of the battery location in the cabin.
For complete passenger instructions contact your airline or the mobility device manufacturer on how to transport your battery as a passenger. Advance arrangements and extra check-in time may be necessary.
Individual airlines may have more restrictive rules regarding the acceptance of any dangerous goods, including lithium batteries that power mobility aids."
I've never been asked to open my bag by an attendant in the plane. Generally the battery checks are done in the carryon bag scan by CATSA. So if you have a 160Wh (Watt hour) or smaller battery bank, and if a battery bank is considered a device rather than a spare battery, then you should be okay to have them with you.
I think you'd have to be a camera crew or something for them to apply the 15 device/battery rule.
I frequently fly for work domestic and international, thats 2 giant laptops, my switch, 2 phones, 2 controllers, power bank etc... I look insane unpacking, and it takes a lot of baskets because the bigger devices should be in individual baskets. It's also a bit stressful looking after all your stuff.
Most of the battery laws are for checked-in luggage, I bring all this in my 2 carry-on and have no trouble (I dont put the controllers in my checked bag just in case).
I generally brought my Switch, my laptop, and a fairly beefy battery bank, and of course my phone. Never had problems; take them out at the baggage scanner and put them in the tray, mostly because they block the scanner's view