by Burgerman » 02 Nov 2019, 11:39
The time spent at CV depends on several things.
Charge rate. The faster you charge, the longer the CV stage. Because it pushes the volts up (high impedance, so low C cells do it faster) earlier in the charge cycle.
Theres a box that says BALANCE MUST BE DONE if ticked it will end charge only if all cells are within the 2 or 4mV or whatever you set deadband. But remember that the PL8 may still be applying a 'brake' of up to 1A to the full cells. And so it can end while the low cells are still being charged at 1A or so. Meaning that while CV was maybe 30 mins to 2 or more hours, the LOWEST cell, was still charging. Its voltage was supported by the 1A charge.
So even if that is ticked, it should be!, then thats not the only thing that determines CV time.
You can set CV timer to none. This is then only imited to a hidden timer, a charge limit for overall charge time. Which is determined by a few parameters, such as if the cell count is auto, for e.g. So it needs to be set to 8S not auto, on a new or out of balance pack at which time the total charge time limit is 16 hours. If theres a cell fault that prevents it reaching its low termination mA point, and you have no CV timer limit (set off) then that means you could end up charging a bad cell at 40A for 16hours if theres an internal short... So is a fire risk. All of this needs to be considered. So if set to NONE, then you really need to monitor whats happening.
So, for e.g. if CV limit is set to 2 hours, and say 500thC termination current, and all cells are withinn choosen bandwidth, it will end due to low correct termination current once reached. In around 30 mins to 1 hour after CV starts typically.
If after you do that, and monitor cell voltage afterwards, and one cell drops a lot faster than the rest, do an extended charge with maybe 2 hours CV as limit and 1000thC termination. It will bring the slightly low cell up to full. But the other cells wont loke being held high for the extra hours. Everything is a compromise. However a WAY better compromise than any BMS that tortures the cells.