Just out of curiousity and for bettering my knowledge,why do the batteries I put in a dual battery box mod have to be married, and why can't I put one in a single battery device? What would happen if I did? Would it damage the mod or something? Thank you
It could potentially result in a catastrophic failure, it is a
huge deal that batteries in series have matching nominal voltage when they're put in a device.
So let's say you've got 2 batteries and you've been using them in your dual battery mod since you bought them. Those batteries have virtually identical wear and tear, they've been through the same number of charges, their voltages
should drain at identical rates in your device. This is what you want.
Let's say for example you pull one battery out of your sig, and throw it in your mech for a while, and then pop it back in your sig. Uh oh. Now one battery might have 4.2V nominal voltage (the one that you didn't pull) and the one that you used in your mech is now down to 3.6V. One battery will see its brother with low voltage and say, "hey, let's even ourselves out" and
potentially (though I hope the circuitry in protected devices would prevent it) dump its voltage to its less-charged brother in a VERY short period of time, likely exceeding the CDR of
both batteries. The result, in this worst-case-scenario, will be thermal runaway, and it won't be pretty.
Again, hopefully the circuitry in devices like the sigelei150 will prevent batteries "loaning" voltage in the event that they're unmarried (and I suspect they do), but I am not about to leave something like that up to chance.
In a dual-battery series mod with no protection, I doubt there would be anything to stop your batteries from venting in your device if you used unmarried batteries with drastically different nominal voltages.
I'm not 100% sure, as the intricacies of parallel batteries confuse me, but batteries in parallel don't actually need to be married. In fact, I think a dual-battery parallel mod will work with 1 battery.
Hope that helps, and I'm sure someone has some corrections to make on what exactly could go wrong with unmarried batteries (as I've heard different explanations).