My AGM to Lithium conversion

BFL13 wrote:

time2roll wrote:

BFL13 wrote:
Some think it is ok to zero% and experience shut off--except this LFP brand's BMS cuts off higher than that at 5%. There is a lot of confusion over how far down is zero!

The prismatic LFP cells are 2.5 volts minimum x4 = 10 volts. However the cut-off is at the cell level so it would be incredibly rare to get all to 2.5 at the same time. Some might be 2.7 -2.9 but the low cell calls it done.

Scroll down a bit for the general specs. Bulk cells on Alibaba

A pre-made battery may allow cells a little beyond the range or a little inside. That is a warranty call made by the builder.

OK, so the monitor measures SOC based on total voltage of the cells, but BMS uses lowest cell.

If not been to 100% and balanced for a while like itinerant1 operates, what is the risk the monitor will not warn in time before BMS LVD?

And that is top balancing

The risk is dependent on the quality and the cells being equal or matched to each other. When charging and nearing full or discharging nearing the bottom of capacity of cells you could possibly have a "runner" meaning one can start to climb or dive in voltage, this is were the bms comes into play protecting the cells or battery. Also, if the cells weren't properly top balanced you could have a runner in a lower state of charge compared to the other cells in the group. Some folks are anal about having every cell equal in voltage at x.xxxv level I can say since day 1 mine have been with x.04 of each other and never worried about because it's close enough for me and doesn't trip the high/ low voltage at any time even when drawing high amp current items in a low soc. I can view every cell live time while they are all in constant flux of each other.

It sounds more confusing than it is. If you were to have one of these batteries and had the proper charging device/ safe guards in place they truly are a set and forget battery/ system or atleast mine has been.