stacking 18350's what should I know?

[Baditude]

Most authorities warn against stacking batteries in mods. I challenge anyone to find an authority or link to a reference which promotes stacking batteries in a mod that was not "designed" to use stacked batteries.

"Stacking batteries- The warning: Stacking batteries is not suggested- and hugely warned against. Stacking improper batteries can place a strain on the battery cell and cause venting and/or explosion. When stacking batteries, the risk goes up.
Read more: ecigs, mods and battery safety | Guide To Vaping"

http://www.e-cigarette-forum.com/forum/general-e-smoking-discussion/470790-pairing-batteries-cant-find-answer.html

Vamo and stacked batteries

One of the issues of stacking batteries in a tube mod is should a battery fail and vent, it can become a potential pipe bomb. Yes, mods "should" have a collapsable hot spring and vent holes, but those only go into effect once a battery decides to become a potential firecracker. A battery in thermal runaway can swell in size and block off vent holes located in the bottom of a mod. The expanding hot gas has nowhere to go as the pressure continues to build up.

I don't present this info to be fear mongering, but I speak from personal experience. Below is a protected li ion battery of mine which failed in a mechanical mod:

"protected" li ion battery after thermal runaway

Yes, there are a minority who stack batteries against conventional wisdom, and most of those who do have a strict methodology of doing so a little more safely than using random same-type batteries together. The batteries must be new (same age, same type) and be "married or mated" from that point on. They must be alternated in the order they are put into the mod each time they are used. Depending upon which battery ends up nearest the positive contact in the mod, the two batteries will not drain equally. Hence they must be alternated with each use to keep them equally drained over time. Not being OCD with this methodology can make the two mated batteries unequal over time and creates a dangerous situation with the weaker of the two.

I would ask why you would want to stack batteries in the first place. If it is to gain longer battery time, that will not be accomplished. If it is to gain higher voltage, that will be accomplished, but for what gain? If you are using standard stock delivery attachments, the heating coil resistance is not designed for such high voltage and you will likely burn it out. In all cases, a single large battery is preferred over two smaller batteries stacked (safety-wise).

Additionally, I counter the recommendation of using protected batteries instead of IMR. IMR's are presently recommended for use in PVs over protected li ion by the battery experts of ECF for all applications (reference http://www.e-cigarette-forum.com/forum/ecf-library/129569-rechargeable-batteries.html).

Once the protective circuit of a li ion battery fails, it then becomes an un-protected li ion, which should NEVER be used in a mod. Li ion battery chemistry is unstable and volatile (flamable) when stressed, and more likely to hard short into thermal runaway and venting violently with flames.

A safe chemistry IMR battery is inherently more heat and stress tolerent, and even if it should fail it will do so less violently than a Li ion. This info is all backed up by battery references in the below battery guide:

Battery Basics for Mods: IMR or Protected?

 

[Myk]

I would ask why you would want to stack batteries in the first place. If it is to gain longer battery time, that will not be accomplished. If it is to gain higher voltage, that will be accomplished, but for what gain? If you are using standard stock delivery attachments, the heating coil resistance is not designed for such high voltage and you will likely burn it out. In all cases, a single large battery is preferred over two smaller batteries stacked (safety-wise).

I thought I already explained why.

Let's say you build a dual coil. You're going to need about 1.5Ω to have a safe cushion to work on a Vamo. That's at least 3Ω coils.
I'd guess 4.4v is over the limit. The Vamo can do 4.7v at that reading.
That only figures out to be around 7.3w per coil. The math of electronics may not come out where wattage is doubled that but the reality of vaping does.

I liked my 1.5Ω dual about 11w (I didn't like that build and went low ohm with that RDA on a mech), but I tend to like lower wattages.
I did not dislike it up as high as it would go with me noticing any changes.
When I got a RBA I will want it on a Vamo which means I will need to get a build figured out that I like above 1.2Ω and that may require being able to go higher than the Vamo can do with a single battery.

 

[JeremyR]

Hey bucket, the low rider you could use a heavier gauge wire soldered in. That may help reduce the resistance. If you wanted to take the risk and precautions involved in stacking in a mech mod, it could be done but you would probably need to be near 4 -5 ohms for it... Thinking of it.. It may be good for a long like 20+ wrap high ohm coil that never has enough power on normal setups.

In the Zmax you would/ will need stacked 18350s to reach the 4 amp limit. Imr cells. With one 18650 you can only reach around 2.8 amps or so from the booster circuit. .. It has protection and is safe to do as long as te batteries are pair and evenly charge.

The 1.33 ohm with stack bats was putting out about 35+ watts when you popped it. What gauge was it? The heavier the wire the more wattage it can Handle before popping.