I use Samsung 25R for my mechanical mod. I use LG HG2/HE4 for my regulated. Don't skimp on batteries, and don't by rewrapped. Rewraps are factory 2nds that failed LG/Samsung/Sony quality testing (if they passed, they would be sold as BRANDED sony/samsung/lg batteries. )
Here is a photo from another forum I am in. A member had an issue with his regulated mod which caused the batteries to hard short and vent. What probably happened was he had his mod in his pocket, it moved around, the RDA wiggled and loosened the positive pin, which likely dropped inside the mod, contacted the casing, and hard shorted. The safety hard short protection either failed or got by passed and the batteries vented.
"2 month old LG HG2's perfect wraps. Got home from store went to pull mod out of my pocket and it vented" (Quote from post.)
So there are a couple dead LG HG2s. Hard short and the batteries vented. What they did NOT do... was blow up.
Due to the design of the LG HG2s the owner was not injured.
Yeah, you can buy batteries that cost a couple dollars less... but is it worth it? The person that posted this was using a regulated VV/VW/TC mod, not a mechanical, and still due to some failure in the mod, this happened. But, he bought the proper batteries, and it saved his .... (later in the post, he stated he was wearing loose shorts and had the mod in his pocket.. use your imagination as to what it saved... ) lol.
Now, 3rd degree burns on the face would have been bad.. but on Captain Happy...oh just kill me now.
BTW these LG HG2s are nice batteries.. 20A sustained. 3000Mah 18650 cells.( $10? They love you long time!)