How much swelling is o.k.?

[rustyj]

Recently bought 2 NEU 4S-4000 packs, charged them on Saturday for the first time, one pack started at 15V, the other started at 12V?

Both seemed to charge properly, looked at them on Sunday, and one of the packs is swelled? It is 40mm thick, the other is 34mm?

Will be calling Neu, but thought I would get opinions.

p.s. the swelled pack is now in a fire box until I determine what to do with it. Didn't even get to run it yet, less than 30 days old.