Unintentionally. I was getting the battery out of winter storage. It was all paralleled up (mains and balances). I went to series the pack up, but forgot to disconnect the balances. Snap, crackle, pops ensued. Time to build a new balance harness. No harm done to batteries, just the harness.
You can/should always keep your smallest group of paralleled packs connected at the balance level. For you it looks like you'd have 5 groups of 6s 3p. So, parallel the 3 packs in each group. If you charge like I do, you'll have a main wire harness that parallels the 5 positives, and 5 negatives. Also, if you want to balance charge, you will need to temporarily parallel the 5 (already paralleled) balance taps via a balance tap harness. I only balance charge once in a blue moon. The batteries just don't seem to get out of balance.
The way I've explained it is probably clear as mud. If you want pics, I can take shots of my 2 harnesses.
9c 9x7f w/ 12awg phases
9c 8x8r w/ 10awg phases, temp sensor, vented
9c 6x10r w/ 10awg phases, temp sensor, liquid cooled, 3rd Place Pikes Peak 2012!
"Don't argue with the galactically stupid...they drag you down to their level and beat you with experience"