Thanks Wayneo, I had to pop out and forgot to unplug the mod from the usb. I have just got back and the mod fired straight away as it had obviously charged the batteries via usb. I only ever charge my batteries externally on a nitecore charger, so this would lead me to believe my charger is faulty. But only with some batteries. I always keep the batteries in pairs and never mix them. Cell 1 is reading 4.114 v and cell 2 is reading 4.291 v.