Nitecore is a reputable brand, I've used the i4 and D4, but I've seen a few reviews of people having problems with them, do they have a customer service line? Maybe give them a call..
Lithium manganese oxide = IMR
(I had to look it up) basically they are high drain batteries, rated for higher (faster) discharge - heating that coil can take quite a bit of amperage (which is the dangerous part of electricity) - drawing more amps from a battery than it is rated for will cause the battery to fail, possibly catastrophically. ICR batteries were a problem when I first started vaping - if you don't buy from a reputable source you could have ICRs re wrapped as IMRs... which could cause your vape to explode in your face. Hope that helps!
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