Lipo charging in parallel = Self balancing cells (?)

Hi,

My bike uses 15s1p composed by 3 Lipo packs of 5s1p connected in series.

Normally I never go down 3.65v per cell (never below 54.8v for the 15s). I do charge the 3 packs in parallel and so far I have never needed to balance-charge the packs.

But today it was an extremely windy day and when I checked the voltages the average was 3.60v, some cells at 3.65v and some at 3.55v.

So I proceed to charge them as always in parallel at very low current (1A selected with Imax B6), without balance leads. After half an hour I re-checked the voltages expecting a self balance of the voltages of the three individual(5s) packs, but what I encountered is also a perfect balance of all the 15 cells, which had voltages between 3.68 and 3.69v.

My question is: did I commit an imprudence doing that?
Next time should I start directly with a balance-charging each individual pack or could I balance-charge the 3 packs together in parallel?

Thanks

The cells individual voltages will almost always diverge when voltages are lower than 3.65 v. Unless you bottom balance, the cell voltages should converge as you reach peak voltage (assuming you had top balanced prior). Its not unusual.

Yup what he said! You could also bulk charge them in serial (and faster @ 1c), and they rebalance. Always be careful to keep an eye on the cells of course.