Have Batteries, Want PHEV, Need Advice

This info is posted for informational purposes only. I do not suggest or recommend anyone else does this. These are simply my observations for your reading (if you care).

Here's some info I've observed about Headway cells and the need for BMS.

I have been riding my PHEV (pictured above in my previous post) to work, the gym and home (about 13 miles) daily for about 3 weeks. I have a 24V/30ah pack that uses 16 headway cells. I use a Schumaker Pba 12V/10A charger to charge the pack by hooking it up to a point in the middle of the pack that equals ~12V (Positive on cell 3 and neg on cell 4) then switch it to Pos cell 5 and neg cell 6.

Here's a diagram of my pack (attached).

I have no BMS (don't be too hard on me) but, I have noticed the pack will balance itself if I let it sit or, ride it for a short distance. The charger will charge each 12V portion of the pack to 14.1 (3.5V per cell or 96% charge per cell). If I charge both middle 12V portions (as listed above), I have 3.3V on cells 1, 2, 9, 10 and 7, 8, 15, 16 and 3.5V on cells 3, 4, 11, 12 and 5, 6, 13, 14. If I ride for a short distance (about .5 miles) and recheck all the cells, they all read about 3.38 (+ or - .09) or if I let the bike sit overnight, I get the same result.

Can anyone explain this? Are the cells w/ the higher charge discharging into the lower charged cells thus balancing the pack?

I can also charge each 12V portion (4 total) to get 3.5 on all cells (which nets me about 17 miles AER). This takes a long time because the Schumaker charger goes to slow charge above what it thinks is 95% (which is really about 90% on the Headway cells).

I know I should buy a 24V Charger but, I'm too cheap. I've already spent about $500 on this project (including the batteries) and numerous man hours.