Hi ecf, first post but been lurking for a while. I'm currently sub-ohming until i get a strong enough regulated device. Question is in a dual batt mech box (parallel) are you also doubling the amp rating of your batts? Does it make the two vtc 5's 60 amp capable? Tia
single vs dual batts in parallel
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Simple answer, yes.
In parallel you add the amps and in serial you add the volts.
The circuit will draw from both batteries. If one battery has a higher voltage it will have a heavier draw and the voltage will eventually even out. If you do something stupid, like pair a 6 amp easy fire with a 30 amp Sony, and the circuit wants 30 amps then it will draw 15 from each and cause a problem, but we're not that stupid.
Also, for a mod with a charger, charging works well. The less full battery will take more of the current until they are equal so things will be good.
In series there are some problems. The weaker battery will be called on to do more work, heating it up and making it weaker, causing it to do more work, and get even hotter, etc. If the bats are in series they need to work the same. Start off with a fresh pair and keep them together and check the voltage when you take them out and when you finish charging them. When the voltage differs it is time to split them up and start with a new pair.
When charging in series the weaker battery will charge first and then the charging current will continue to flow through it increasing heat and weakening it further.
Some of the new 100 watt regulated devices have the batteries in series and that is a problem as far as I can tell.
In parallel you add the amps and in serial you add the volts.
The circuit will draw from both batteries. If one battery has a higher voltage it will have a heavier draw and the voltage will eventually even out. If you do something stupid, like pair a 6 amp easy fire with a 30 amp Sony, and the circuit wants 30 amps then it will draw 15 from each and cause a problem, but we're not that stupid.
Also, for a mod with a charger, charging works well. The less full battery will take more of the current until they are equal so things will be good.
In series there are some problems. The weaker battery will be called on to do more work, heating it up and making it weaker, causing it to do more work, and get even hotter, etc. If the bats are in series they need to work the same. Start off with a fresh pair and keep them together and check the voltage when you take them out and when you finish charging them. When the voltage differs it is time to split them up and start with a new pair.
When charging in series the weaker battery will charge first and then the charging current will continue to flow through it increasing heat and weakening it further.
Some of the new 100 watt regulated devices have the batteries in series and that is a problem as far as I can tell.
Also want to mention that some batteries react terribly to being put in parallel with each other if they are not at the same voltage (or very close) at the time. The immediate surge to balance themselves can be dangerous. It's good to toss batteries on a voltage meter before pairing them in any fashion - just to be safe. 
A .06v differential should balance practically unnoticed by either of those batteries.
Also, as I do plan on getting a dual parallel box at some point, just to be sure I may as well clear up another question. You said that your amp limit is doubled? So you could safely build lower than, say, .15?
Why would you even consider going lower than .15? There's not a battery out there that will be safe at those loads. Dual batteries are inherently unsafe due to the variability of charge levels and internal resistance unless they are diode locked to prevent reverse EMF.
.15 is so close to a dead short that it's not even funny. Add to that the inherent inaccuracy of cheap ohm meters and you really don't know what value you are vaping. The average set of meter leads is about .40 ohms and the meter leads and sockets drift in connectivity if there's oxidation.
.15 ohms at 4.2v is 115 watts and 28 amps. There are no batteries out there I'd trust for vaping at that level.
Why not 1 ohm at 4.2v for 4.2A and 17.6 watts? Or use a high watt electronic mod and not worry about your .15 coil turning to a dead short? Consider a DNA mod.
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My personal opinion but I wouldn't put a parallel mod to my face and push the button unless I know how it is wired and the batteries had an appropriate fuse for each one. As stated above a weak battery will cause the other battery to take a larger amp draw. More importantly a bad battery will cause the other battery to take the full amp load. Even more dangerous if the batteries are not individually fused and they are wired together a bad battery will cause the other battery to continually push amperage into the bad battery.
Where do you plan to find a 100 amp switch for that box mod?
So the bats can produce 60 amps continuous (100 amp pulse). How does that play out with a 3-5 amp switch?
There is no such thing as a SAFE parallel semi mechanical mod.
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DaveP and tj99959, this is why I asked, to clarify any misunderstandings I had, thank you. Dave, if I understand correctly though, let's say two fresh VTCs (30 amp continuous) at 4.2 volts in a dual parallel mod, with a build of .084 ohms, that's 50 amps. That would mean you are "only" pulling 25 from each battery, correct? At this point I'm just trying to better understand these types of mods, I'm not saying I would actually vape such a build. I find all of the math and science behind this stuff rather interesting and it's never too late to learn something new.
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