I got one of the xstar mc1 ant single battery chargers to start, wich is fine for single battery mod. Now im using a dual battery nitecore charger wich works out better for me now I have more mods and batteries. I tend to use the same mod in the day and switch to something different in the evening which is when I charge/top up 2 batteries. As I only use single battery mods it doesn't matter wich 2 batteries I put on to charge/ topup together.
batteries for dual battery mods should always be married, that is kept in pairs and always used and charged at the same time together.
Thanks for that, good information to have. And thanks to everyone else who gave advice, much appreciated.