Rereading my previous post I see that it is a bit of a ramble, I apologize for that. Perhaps that was due to thinking in terms of a LA system and not how a Li system operates....Still learning
Doing a Google
search for papers on Li batteries I came across this;
"DEGRADATION ANALYSIS AND HEALTH
MONITERING OF LITHIUM ION
BATTERIES By Nicholas Dane Williard "
Various charge/discharge methods were tested and their affects on life capacity were determined. Continuous charging
(float voltage) and shallow cycle degredation would be of the most interest to us. While these tests were performed on LiCoO2 the paper does mention LiFePO4
and implies results should be similar.
The continuous charging test was performed on an “A” battery
to examine the effects of float charging on battery reliability
. The cell subjected to this test was given a float charge at 4V for an extended period of time and was periodically discharged to measure capacity. A float charge refers to a low current
charge which counteracts the battery’s self discharge effects.
The float charge allows the voltage to remain constant over the duration of the rest time. Figure 34 shows voltage vs. time plots collected during various discharge times throughout the continuous charging test. There was no significant change in capacity during the continuous charging times. In a previous study , extended periods of float charging at voltages above 4.2V resulted in accelerated capacity fade. This is likely cause by the
instability of the cathode material at higher voltages.
Because the float charge in this test allowed the battery to remain within the battery’s stable operating region below 4.2V, no significant degradation was observed. This would be an important consideration for BMSs that wish to keep a battery maintained during down time. By applying a float charge in the battery’s stable operating voltage, the battery can remain fully charged and ready for immediate use without undergoing significant degradation during storage
The paper cited  is the one by Choi & Lim that Dave mentioned where the float voltage was 4.2V and caused damage to the cell. So it would seem that a float voltage in the stable voltage region which for LiFePO4
a bank voltage of 13.1V or 3.275V/cell would be safe.
Shallow cycle capacity degradation (pg.79) is also of interest in a house bank. Shallow cycles did cause some capacity degradation but that can be recovered after a rest period or by a full 80%DOD and 100% charge. I believe that was exactly what was seen by those of you that performed bench tests.
There is also a good explanation of Peukert's exponent on pg. 7,8. While Peukert did develop his equation in 1897 using LA batteries the equation is independent of battery chemistry and does apply to Li batteries. It just may be that for LiFePO4 used as a house bank the exponent is close enough to 1.0 so that it is of little practical use.
I agree that terminology has been misused or inconsistent and I have been guilty of that myself. A carryover of LA terminology does cause confusion and there should be something different used for LiFePO4. I do like Maine Sails
term "drop voltage" for when the pack voltage has dropped to a point where charging can be reconnected.
Here are the voltages that I have come up with so far with using LiFePO4 as a 12V nominal house bank.
>14.4V >3.6V/cell HV fault, alarm
on, disconnect all charge sources
13.9V 3.45V/cell Charge complete, disconnect charge sources
13.1V 3.275V/cell Drop Voltage, reconnect charge source (solar/wind)
11.6V 2.9V/cell Low voltage warning, recharge immediately
<10.4V <2.6V/cell LV fault, alarm
on, trip contactor to disconnect
The HV fault and LV fault are conditions that should never occur in a properly functioning system and are used to protect the cells from damage.
The exact voltages above are open to discussion and may change with different cell manufacturers or even as the cells age. A BMS with adjustable settings would accomplish this but at the cost of increased complexity and reduced reliability
. Maybe best to keep it simple and use conservative fixed settings.
Hope this helps,