is it possible to do a top balance and what is the correct procedure with only inverter, bms and Neey balancer? Thank you
If you don't have a power supply to charge each cell to at least 3.40 volts, then your only option is to build the battery, and let the BMS balance the cells. It could take MONTHS under a worst case scenario.
Not based upon any experience, but this might work:
See how unbalanced the cells are.
Set the BMS to start balancing at something close to the lowest cell voltage (start it balancing right away).
If the cells are close, then charge to 54.0v, and slowly increase in 0.25v increments until you reach the desired pack voltage.
If the cells are not close, then charge at pack voltage + 0.25v, and slowly increase in 0.25v increments.
You can increase the charge voltage when the pack is near the charge voltage, and the cells are not too far apart (hi-low no worse than when you started). You want to avoid the highest voltage cell getting anywhere close to 3.60v until the pack voltage gets to 56.0v.
With each increase in voltage, the cells will charge a little more, and let the BMS balance the cells. If a few cells are running away (charging faster), you may need to wait a while for the BMS to bring them down. Rinse and repeat.
With a 280ah pack, you are shooting for the cells to be within 0.005v when fully charged. I'm guessing a 0.1v differential when under 53.0v would be fine.
A more bolder approach would be to:
Charge at pack voltage + 0.25v.
When near charge voltage, check voltage of highest cell. If 3.5v or less, then you can increase by another 0.25v.
If a cell ever gets to near 3.5v, then I would switch to the more conservative approach.
The idea is never to get close to the 3.65v max on one cell until all cells are at least 3.50v.