Its OK mateI do seem to have hit a nerve with you Roy, certainly NOT my intention. Regards low battery voltage, why do you think nearly ALL reasonable kit shuts the circuits down at about 3v? No need to drain to 2.7v, and doing so can further complicate charging if the charging circuit does not attempt to kickstart the protection board into waking up again. Surprisingly common! I have also seen some boards not kick in until below the 2.7v level, which again, is not ideal!
Also, there really is no capacity between 2.7 and 3v. I suppose you could argue you do not want to stop at any voltage with caving lamps, but then again I suppose that is what backups are for!
I forgot to add that the low voltage cutoff could be micro-controller considerations but most these days have quite a wide operating range with low voltage modes down to 1.8v and below.
Not sure what you are referring to with regard to 5A. Did I state something to advocate such a current?
Yes, the devil is in the data sheets.
Some Li Ion cells have higher recommended cutt off, generally earlier ones. Protection boards bought off the shelf may have a cut off set to a "catch all", to match to a specific array of cells may require some tuning so as to get the max burn time out of the battery by setting cut off to the recommended. Or more importantly, these last dregs before manufacturer recommended cut off often supports a diminishing output, we call the "slow death". Note "manufacturer recommended", I seem to be repeating myself here.
As far as accuracy of cut off is concerned, its all about testing components before using them.
One can wonder into the realm of "opinion" on this, with me the manufacturers data sheet is good enough.
I note the "no capacity between" commment above, I have graphs that I have prepared reflecting test results that indicate otherwise, but note my comment about slow death. Obviously a decreasing output will extend the burn time.