First time Pela owner and wondering if it has independent charging channels. I haven't found where Pela states they are independent channels. I've seen posts that say they only charge the same size 3.7v batts in pairs on their Pela, which means they don't mix them, such as 14500 & 18650. Does anyone mix batts on a Pela and what's your take on it? Also, is there anything wrong with using just a single channel?