I have a BVM electric df fan set up that uses two 5s packs and one 2s pack in series. One of my 5s packs has one cell that shows an internal resistance that shows about 2 to 3 times the reading of the 4 other cells. Is tihs a problem ? The pack seems to be delivering/performing as it should.

If your getting the preformance you should be getting - it's not a problem.

They will all eventually change. No battery will ever keep it's resistance the same after 10 cycles or so. They all start to slowly degrade.

ok. Thats good to know. I felt like I had possibly slightly overheated them and had them puff up slightly and was concerned that I had done so permanent damage. I had never paid attention or noticed the screen with the internal resistance untill after the flight where I thought I might have overheatd/damaged them. I have only flown one flight since then and I recharged the packs when i got home I recharged to see how many milliamps I had used from the packs. The pack in question ( the one with the one cell with higher resitance) required about 700-800 more milliamps to be fully charged compared to the other 5 cell pack and I didnt know if this meant something bad.