If you are thinking about going down to 0.5 ohm I would recommend at least a 20A battery.
18650 BATTERIES
1. Orbtronic SX30 2100mah 30A
2. Sony VTC4 2100mah 30A
3. Xtar 2100mah 30A (re-wrapped Sony VTC4)
1. AW 1600mah 24A
2. Orbtronic SX22 2000mah 22A
3. LG HE2 2500mah 20A
4. Samsung 25R 2500mah 20A => these have performed very well for me. RTD Vapor is my go to for batteries.
5. AW 2200mah 20A (new)
BATTERIES - WHERE TO BUY
Only buy batteries from a reputable supplier (not ebay or Amazon) as there are many counterfeit batteries being sold. Here are several reputable battery suppliers in the US.
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RTD Vapor
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Illumination Supply
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Lighthound
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Orbtronics