High drain, or high C, batteries are able to discharge more current, without damaging the battery or tripping a protection circuit, than a typical battery. The cheapest Li-Ion batteries can barely discharge a single amp before this tripping and damage occurs. (Note that cheap is not the price, just a reference to the manufacturing. Some places offer high drain batteries for less than other places sell cheap batteries. And I have a number of high drain batteries and never paid close to $20 for one, in fact the last pair I purchased cost me $24 for a pair shipped, or $12 each.)
Let's assume you went with the really cheap $3 18650's and they can discharge 1 amp but it makes them a bit warm. Since we know V=IR, Voltage is equal to the product of current and resistance, we have our 1 amp that the battery can discharge and a 2.5 Ohm atomizer. Our voltage is 2.5*1, or 2.5 volts. This is less than the battery's nominal voltage, but due to the battery's chemistry and/or protection circuitry, the actual current discharged is what will produce the voltage in our circuit. This assumption means we paid $3 for a battery to damage itself and only give us 2.5 Volts for
vaping. (This is referred to as voltage clipping.)
Power=Heat=Work=VI, or Power in Watts is equal to the product of voltage and current. My assumption gives us only 2.5 Watts. If I were to spend a bit more money and get a high drain battery my power would be more than double and the act of
vaping does not damage the battery. Less damage to the battery's internals means a longer useful life.
Or, if you really don't like math, I could give you a story. I purchased 6 18650's Li-Ion batteries before I knew I liked to vape over 8 Watts. They were cheap, literally $3 each, Trustfires that I had shipped from China. Within 3 months all the batteries except 1 would not last half a day of vaping, but made it a full day when they were new. Once batteries reach the half life point, they tend to go down hill very quickly. I ordered a single pair of high drain batteries for about $14 bucks a pop. By the time they arrived to my house my original cheap batteries were down to 2 being able to hold a charge at all. Now fast foward to now and I have had these new batteries for over 6 months and they still hold a full charge. All the original 6 batteries have been disposed of so $18 in the trash in about 3 months. The $28 I spent for two has lasted twice as long.
(I did recently purchase a second high drain pair when I caught a sale at $12 each, but these are not in use yet.)
Since I am not selling you anything, nor making any kind of profit from your battery purchases, the above cannot be marketing hype. I do have some schooling in electronics and have become a big fan of good quality high C batteries for vaping because they can save me money. When I first started with battery mods, I had the notion that I could get cheap Li-Ions and still come out ahead. I noticed the voltage clipping to be a pain when I wanted more power applied to my juice for a better vape and the damage to the batteries was quicker than I expected.
Whichever way you go VAPingRObot, keep track of your costs and life cycle.