Ry024 sir you can use dual coils at lower voltage, it's the amperage draw you have to worry about. This is where mah and c rating on the batt comes into play. Dual coils at 1.5ohms will pull 2.46a. If it's a 1300mah batt rated at 2c it's limit is 2.6a of current. Why dual coils are usually suggested for mods with high drain or multiple batts. Dual coils give you the experience of vaping at high voltage without needing the extra voltage. Horizontal coils at 2.9 ohms or less will burn juice at anything over 3.75v. The lower the ohms, less voltage needed to scorch the juice. Ie- a 2.4 ohm horizontal coil will burn juice at anything over 3.61v on most juices. Vgo batts by kranger ar unregulated, don't know yet about the 808 ego, but know smoktek's 510 egos are unregulated, so guessing the same applies. Higher mah doesn't translate to higher voltage necessarily, just translates to longer run time. Non regulated fat batts usually come in around 4.04-4.12v on load freshly charged. Regulated ones come in at 3.2-3.4v depending on the manufacturer. Hope this helps.