I made a 14.8V (4s) lithium ion battery pack (18650 cells 4s3p) and after gluing the batteries together into the pack, I used a multimeter to check if any of the cases were shorted anywhere (some of the thin plastic covering on the batteries was removed). Before conneting the batteries in series, I noticed that the third and fourth section of the battery (11.1V and 14.8V) had a measureable 0.1V and 0.5V voltage across the terminals of the batteries.
gnd-3.7 (3p 19650 batteries)3.7-7.4 (3p 19650 batteries)
7.4-11.1(a) (3p 19650 batteries)
(b)11.1-14.8(c) (3p 19650 batteries)
The four 3p packs above are glued together but not electrically connected in series yet, but when measuring the voltage from a to b, the multimeter shows 0.1V and from a to c shows 0.5V.
All four of the 3p battery packs are individually at 3.8V.
I haven't tried to short (through a load) the 0.5V to see if it is a low impedance short, but the main thing I was curious about is where the 0.5V can come from. I am guessing that if I put a 220ohm resistor across it the multimeter would read zero, but still 0.5V seems high!