As you can see, I am charging battery #2 separately. It has been depleting at a faster rate than the rest. A few months ago, #5 was the weak one. Currently, #1 is the strongest, #2&3 are a little weak, and #'s 4-6 have stayed consistent for some time. Below is a graph of the last few measurements. It is plain that #2 is the weakest. The middle bar represents a particularly cold day, hence the lower voltage reading.
