Hi Dan. I don't know this information off the top of my head, but over the years I've kept notes on things I've learned about batteries. From these notes, here's what I published in the September 2021 RC Pylon Racing column of Model Aviation...
A 2S LiFe operates at about 6.0 – 6.6V, so make sure your servos/receiver are rated for that voltage (receiver/servos that are okay with 5-Cell NiCd should also be fine with 2S LiFe). Here are some figures I scrounged up about LiFe batteries:
Minimum discharge voltage: 2.8 – 2.5V/cell
Maximum discharge rate: 1C
Nominal operating voltage: 3.0 – 3.3V/cell
Maximum voltage: 3.6V/cell
Recommended charge rate: 1C
A fully-charged 2S LiFe will come off the charger at about 7.2V, but even without a load will just about immediately drop down to 6.6V, then remain. It is said that LiFe batteries don’t require balancing as much as LiPo – especially if not over discharged. Unlike a LiPo (where voltage may be correlated to capacity), a LiFe has a flat discharge curve with a sudden drop at the end, so it is not advisable to use the voltage of a LiFe as a cue when to stop flying. Instead, use capacity used/remaining to indicate when to charge. A typical LiFe discharge curve for typical discharge rates shows a rapid drop off at about 83% capacity used. But you want to avoid this point because the drop off is so fast. A safer figure would be about 65% or even 50% to play it really safe. If we estimate that one flight of a Q40 airplane consumes about 30mAh, and we are using the typical Zippy 650mAh LiFe, we can get over ten flights before approaching 50% capacity used. (50% of 650mAh = 325mAh / 30mAh per flight = 10.8 flights)
That's the end of the article. But if you want a little further reading there are always enlightening conversations on RC Groups, like this one...
https://www.rcgroups.com/forums/showthr ... arge-Curve
Tim Lampe
