The airline staff don't concern themselves with the contents of your carry on luggage under normal circumstances, what you can take on is up to airport security. Last time I went abroad I took 6 18650 batteries, a mech and a regulated mod and 4 drippers. Put my juice and coiling kit in hold luggage.
I flew with Ryanair to Bratislava, from what I remember, their company policy is no more than 4 lithium-ion batteries per person. But I don't see how they could enforce that without having their own staff check everybody's hand luggage, which they didn't on my flights.
Just keep your batteries in cases and not in the mods, looks more honest and not like you're trying to hide something.