I’ve never needed to buy a battery until now so I’m not very familiar with them. The device I’m gonna get is the SMY 60 TC Mini:
https://101vape.com/variable-voltagewattage-devices/729-smy-60-tc-mini-box-mod.html
The required battery is 1 18650 @35 amps. For current, is it needing 35 amps discharge, or pulse discharge? Also, would it be best to get the highest mah rating as long as the other specs are compatible?
It’s 60W, minimum resistance is 0.1ohm (even for temperature) that calculates to just under 25 amps 
I’d get some Samsung 25R or LG HE2(?)
Thanks for the link… very helpful. As far as the discharge rating goes, I was going by the specs here:
https://101vape.com/batteries/708-efest-2800mah-35a80a-18650-battery-each.html
The box mod looks pretty sweet btw… Check out this review if you wanna:
I wish I had another link for you about this subject, but when it comes to batteries there only 4 manufacturers of the 18650 batteries you want to even consider. Those companies are Samsung, LG, Panisonic, and Sony. Other than I believe 2 other asian companies you’ve never heard of, the batteries being marketed are just rewraps of the 4 big guys. And they are B grade batteries at that. Yes, that includes EFEST. I totally agree with @Daath and if you read that link completely, you know the articles backs up @daath when he said Samsung 25r. The experts will all tell you. There is no better for vaping…
There’s a couple posts here on the forum about batteries. Always better to be safe than sorry, IMO. I’d rather pay a little more and know I’m getting a good, name brand, legit battery than save a few dollars and have my mod explode or them catch fire in the charger. 
I think I already posted this elsewhere, but I use Samsung 25Rs and they’ve been great for me.
I hear you. I wouldn’t trust some off brand battery for a second when it comes to vaping. What’s the reason SMY would say it needs at 35 amp battery when it will run fine with 25 amps? The dude in the review I posted is even using a 15 amp battery.
FYI - 60W with a single 4.2V battery will only be about 14.3A drain from the battery. It will increase up to about 18A as the battery drains down to 3.3V. The output current to the coil is about 25A (at about 2.45V), but that is independent of the drain from the battery.
Between the posts in this thread and the links provided, I’ve learned a ridiculous amount of info about batteries tonight… 
thanks dudes (and woman).
This is info I posted on another thread I had found on a forum dealing with flashlights…
18650 Manufacturers
Let’s lay out the major 18650 battery manufacturers. There is
Panasonic, Samsung, and LG. Sony cells have fallen in production, as
they focus more on li-po - soft cells for use in mobile and tablet.
Panasonic provide some of the best cells for electric vehicles. LG,
Samsung, and Panasonic all produce 18650 batteries for laptops. LG and
Samsung produce more high-drain cells. But after all is said and
done, all three of these manufacturers have very similar battery lines.
Here’s a quote from another forum that deals with flashlights, electronics, ect.
Originally Posted by phantom23
Panasonic makes the best 18650 cells (3100mAh).
Companies such as AW, Redilast, Callies Kustoms, XTAR, EagleTac,
EnerPower+ use them and just add their own protection.
There’s just a few who are using other manufacturers batteries
More info…
An 18650 battery is a set of chemicals inside a protective steel
case. Then PVC shrink wrap is applied over the steel case, which gives
the 18650 its color. Some companies buy cells from large manufacturers
like Panasonic, and rewrap it with their own custom-branded PVC tube.
The following companies rewrap cells:
Efest, Vamped, Keeppower, AW, Ultrafire, Trustfire, Orbtronic, EHGTL,
Robiton’, Imren, MXJO, Nitecore, AWT, EagleTac, AmpMax, Basen,
BattEnergy, EnerPower, Fenix, Intl-outdoor, Redilast, Xtar
Rewrapped cells can be used for good or for evil.
Some companies add value by providing quality control or adding
protective circuitry when needed. However the darker side is it opens
the doors for deception - exaggerated or completely fabricated battery
specifications.
Are any 18650 batteries rated higher than 30A?
No. The highest continuous discharge
rating for any 18650 battery is 30A. Some companies claim higher ratings
like 40A or 60A. These are however based purely on pulse discharge
ratings or fabricated out of thin air.
Also note that pulse ratings are
completely meaningless without noting their duration. The Samsung 25R
for example has the following pulse specifications when written correctly:
The 25R can safely be discharged at a continuous 20A (amps). Pulse
discharge levels are [95A - .5 sec, 65A - 1 sec, 40A - 5 sec, 30A - 6
sec].
Recommendation
For vapes and mods we recommend the Samsung 25R.
For general electric vehicles we recommend the Panasonic BE.
Laptops, high-performance electric vehicles, flashlights,
power-tools, etc. all have special needs and there is no exclusive
answer to which battery is best. It all depends on your application.
There you have it, stick with your Samsung 25Rs…
he summed it up in one sentence. 25r’s are the leading batteries right now on the market for vaping all around. never had a problem with any of mine and I have about 12
Should I only vape with the 2500mAh batteries or is it OK to use others like 2700, 3000 or even higher ones?
You should be using the samsung 25r. They are a 2500mah battery and considered the best for vaping…
So the 25r’s are 20 amps, correct? ( http://vapenw.com/mod-batteries/samsung-inr-18650-25r ). One thing I’m having a hard time understanding is how a device will work when using 2 batteries. If I’m using 2 25r’s, would that mean there are 40 amps available? I’m assuming that’s where series and parallel configs come in. For example, from what I’ve read a 160 watt box mod wouldn’t be able to fire wide open with one 25r, but would with 2. Is that right?
There would be 40ish amps available if batteries were parallel.
However though the 25R’s can pulse almost 100A (don’t push it though) they are rated a continuous drain of 20A a lot of mediocre battery brands are generally only telling you the pulse discharge limit when they rate them.
Series batteries allow more Voltage
Parallel batteries allow more amps
Most VW mods use batteries in series rather than in parallel to achieve up to 8.4v output the chips and mosfets etc handle current draws etc to keep batteries from discharging to far or venting on you.
I’ve been using a mech mod until recently as a single 18650 using 4x25R’s in rotation and I’ve happily been vaping builds as low as .15ohms with only a moderate amount of heat being generated by the battery.
25R’s are freaking tanks man.
CMJ
Thanks for the info. Im teetering between the 25r’s and LG HE4’s because the LG’s have a higher current rating and apparently handle heat pretty well.
http://vapenw.com/lg-he4-18650-2500mah-35a
How many watts do you like to push when using the Samsungs?
I’ve only used them in a mech mod and at .15ohms on a fresh charge it was pushing nearly 120w through the coil at pretty much 28Amps.
The battery got warm but not stupidly hot.
I’m not in anyway though advocating that people should put a .15ohm build and use a single 25R build safely and following battery safety or risk blowing yourself up.
CMJ
Living on the edge! Wild man!