Ok, well a lot of the Efest batteries have tested out to be 20A batteries from manufacturers like LG and Samsung, but you can not be entirely sure with re wraps which is why they are not recommended.
Which Samsung battery will you be going for that is 30A? I mainly use 25R's, those are 20A though, or LG HE4's which are also 20A. They offer 2500MAH, and are my preferred battery for mechs. There are 30Q's and HG2's which are 3000MAH, but I use these in regulated mods.
I don't own any HB6's myself, but if you plan on builds above 20A, and up to 30A the HB series is the only real, safe option, but due to the capacity you won't get the best run time.
You may be surprised though what you can get out of 20A, so I would look into different coils and try some different builds, and on your regulated box mod if you can while learning.
It is better to use an external charger for mods that use more than one battery, some mods like the DNA200 have a built in balance charger so charging in one of those is OK, but many others don't offer balanced charging so you do really need an external charger, and it will make things much easier for you in the future too
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