In a regulated mod, you'd want to use unprotected batteries, but QUALITY batteries, such as the ones from LG, Samsung, or Sony. Sony batteries are getting harder and harder to find (that aren't clones, seconds, or re-wraps), but if you can find authentic VTC4, those are good to use, and rated at 20A discharge. LG and Samsung batteries are my go-to batteries, but both are still only rated to 20A continuous discharge (30-35A peak @ 1-sec burst). Still though, even in your dual-battery box-mods, in parallel, that will give you 40A discharge (same Voltage as single battery, doubles the Amps)... Either way, as a single battery, they are good for running coils down to 0.22 Ohms without any issues or danger. If you are buying Samsung batteries, the 25R (Tiffany Blue wrapper) or 25R5 (green wrapper) are the ones to have... the green wrapped ones are the newest version. The pink wrapped 26F are 2600mAh, but I've not tried these yet, so I've no opinion on them for vaping. If you are buying LG... the brown wrapped HG2 are highest mAh rating @ 3000 mAh, and appear to be the current "king" of vaping batteries. The HE2 (red wrapper) and HE4 (yellow wrapper) are similar in function and 2500mAh, and I regularly use several of the HE2 without any problems. NOTE OF CAUTION: When using batteries in pairs for your box-mods... label them "A-B", "C-D", "E-F", etc., and keep that pair together forever... rotate their position left-right in the mod each time you replace them to ensure even use, and when one battery of the pair dies, do not re-marry the good battery to a brand-new battery... only re-marry it to another orphaned/divorced battery.