I lost one of my 4 RCR 123a 3v but found a 3.2v laying around. So now I have 3 3v and 1 3.2v. I tossed the 3 and the 3.2 in my silver bullet and it vapes awesome, but is it safe to mix the two? I am thinking of ordering another 3.2 and vaping at 6.4 V.