If rechargeable batteries aren’t charged regularly then they are useless during emergency. I keep about 2-3 dozens of AA and AAA in a battery organizer and rotate them. To rotate them, I use battery powered LED strips in bathrooms and in closets. I do that to save energy and to practice blackout situation. For gadgets that run on C or D cells, I use a 2 AA converter case. I have them on my 3D maglite and Coleman lantern and they work great.
For chargers, I use Nitecore brand that has different charging current and 12V car adapter. I try not to use quick charge mode because it tends to heat up batteries and that shortens the life. I also own an USB charger just in case power goes down and I can hook up a portable solar panel if needed. – P.L.