Lipo Battery Testing and Balancing

[johnrobholmes]

While a true rating of the pack certainly depends on the wire and all resistances involved, cells are just rated by themselves for simplicity. I would like to see both side by side actually, to get an idea of how big a difference wiring and plugs can make on heat or capacity.

Some standards I had considered before, taking ques from TP testing and enerland quality standards:

Continuous rating capacity within 10% of 1C discharge capacity.
Continuous rating limited to 50*c cell temperature with ambient temp of 25*c- no cooling air flow
Capacity cutoff at 3v/cell
Continuous amp draw should not draw cell below 3.2v until 80% of capacity is spent (off the cuff starting point)
Cells should all start at 25*c temp

As we know, internal resistance drops with increased cell temp, so controlling and recording this aspect is very important. A cell that shows a greater increase in temp over discharge will have a higher resistance too. The steepness of the discharge graph will show how well the voltage is held through the cycle.

Some inferences we could make

Lower quality cells will heat up more
Lower quality cells will have a steeper discharge graph
LQC will not hold 90% capacity under higher discharges
LQC will not hold as high of voltage under high discharge

Once enough cells are tested, standards can be set for quality that quantify the averages and the standard deviations from the norm. Then we can simply use statistics to pick out where a cell is lagging- such as voltage under load or capacity.