So as we know there are hundreds of different batteries on the market. Seems like anyone with a printer can make and market their own brand of batteries. Of course anyone with a printer can also print whatever they feel like on the label to sell those batteries, as long as they can back up the claim. I'm not saying they can back the claim with safe information, just they can show some indication that the claim they made on the label is somewhat accurate. Here is where knowing a few things before you buy these re-wraps and end up blowing your face off. (losing face)

First. There is no such thing as a 40A Continuous Discharge Battery. They don't exist. 30A is the highest CDR battery there is. 2 are made by LG and one by Sony. (LG HD2, LG HB6, Sony VTC4) ***BEWARE COUNTERFEITS*** so buy only from trusted sources that sell only authentic.
Second. Use only the charger that came with your device or Nitecore charger or Xtar charger. I use Nitecore as it is fairly inexpensive, and I heard Xtar is a bit better, though I haven't used one. Again, make sure these are also authentic.

For beginners, I am going to focus more on batteries for Regulated mods, and briefly on Mechanical mods.

Regulated mods contain software and chips that prevent injury to the user. They limit the Ampere draw and adjust voltage to ensure an uniform vaping experience from full charge (4.2v) to depleted (3.2-3.4 volt-depending on manufacturer setting). Regulated mods will say low battery and shut off power to the coil when you get to the low charge limit. Now although these are much safer than Mechanical mods, they still are not 100% safe. Maybe the IC board fails, or the 510 positive drops inside the box and shorts with the mod casing. So here is where batteries come in..

Generally, a Regulated user will want to have a nice all day vape and not have to recharge their batteries as often. So a good 2500Mah to 3000Mah high drain battery with a CDR of 20A is the way to go. (see links below)
LG HG2 3000MaH at 20A one of the longest lasting vape batteries
Samsung 25R (2500MaH at 20A CDR) not quite as long lasting as the LG HG2, this is still a great battery and ties for first place due to the Samsung 25R stays a few degrees cooler than the HG2. In other words, if you have your mod in your pocket and something goes wrong, you get a little extra time to get it out of your pocket before you burn your filberts off. Both are great batteries for Regulated mod users. See link below for more choices and details on each.

Mechanical mods. are literally a battery, power button and heating coil. There are several kinds, but since this is for beginners, we will only mention single cell Mechanical mods. . Of these there are 2 types. Non-hybrid and hybrid. A non-hybrid has a floating 510 pin just like regulated mods do, hybrid mods allow the positive pin on the atomizer to set directly on the positive cap of the battery. Hybrids are much more dangerous because if the positive pin on your atomizer is to short, then the negative part of the post also contacts the positive cap of the battery. Remember, the entire mod is the negative lead, so contact with the negative directly on the positive of the battery creates a hard short, heats up, goes into thermal run, vents and explodes. The Big 3 usually do not explode. They may vent to 0 volts and ruin your mod, but they won't blow your fingers off. (you will drop them long before they get hot enough to pop... 100 dec C is where Mooch considers a max safe limit for testing, and 100C = 212F.. the boiling point of water.)

Thirdly... Good brand name batteries NEVER list a "pulse rating". They don't need to. A pulse rating is a bull shit value designed to trick you into buying cheap rewrapped batteries. There is no defined value for a pulse.. is it 1 second? 5 seconds? 30 seconds??? How many times did they test it and how long did the cell rest between pulses? No way to know. Therefore, we not only ignore pulse rating, we don't buy those batteries. I mean, if the sellers have to use deception to sell their product.. are you willing to risk your safety for the sake for $2 or $3?

So here are the links I promised.
The Best 18650 Batteries for Vaping

Please read all the way though. Mooch put considerable time into gathering this information and performing these tests for us vapers at no charge. (He does accept donations, but those are fully accounted for and he even discloses, to the penny, what the funds are spent on.)

Be sure to read the charts and tables. I don't mind providing links to them, but it is up to you to read them.

All credit for information in that link goes to Mooch. I am just passing the information on. It is his work, he gets credit and kudos!

Respect your batteries. Check them before you charge them and again before you use them. (Measure twice, cut once, remember?)

* Every single incident of a vape device exploding is due to user error or carelessness. Don't be "that guy" on youtube. And please, if you do have an accident, take responsibility for the mistake, and pass along what you did and what happened. You could prevent someone else from making that same mistake.* Lets hope this post prevents any mistakes or at least prevents harm to vapers. Mods can be replaced.