Alright, no problem.

If it's possible, I want to improve battery life a bit - would flashing another kernel make sense? any particular one to recommend?
Thanks
Pascal
Any other kernels rather than stock are huge battery drainers for j5. Because they can't focus properly on the camera, include new wifi drivers which consume more wifi power (based on my experience) and includes a lot of tweaks (that just make the battery even worse).
Just use stock kernel and and app called BATTERY SAVER PRO (it gives you 4 levels for battery saving, using root acces to reduce kernel frequency).
This phone is not intended for gamming, so there is no reason to overclock it, stock kernel can handle everything ok without any bugs(issues).
The app was paid, but now it's no longer developed by Antutu, but you can still find it online.