At any rate, I do not use guess work. I know how aproximately how many mah I use for each flight from experience. I know how many flights I will fly between charges. I use a battery that leave me a very conservative reserve. I discharge the batteries so I know how the general health of the battery is. So if I use approx 150mah a flight and fly 5 times between charges I use about 750 mah. This out of a 2300 mah battery. I hardly think that I am just guessing whether I'm safe to fly. While I agree these numbers fluctuate, not enough to remotely threaten the reserve.
Just curious, what loaded voltage reading do you find safe to fly?
You just said it. Experience. This is a beginners forum. Most pilots here fly with a lot of overcorrection which shortens battery life more than it would for you and I. The prediction method is fine for experience but probably not for beginners.
Yes, LiFe packs have a very flat discharge curve as compared to NiMh or NiCd packs. But, the voltwatch is simply a tool to monitor the voltage of teh battery pack under the on-board load. No more, no less. A prudent pilot will keep a close eye on the condition of their battery pack and not fly when there is any question about the charge remaining in that pack. Experience tells you that you can fly x number of flights for your pack and you fly that with that in mind.
The inexperienced pilot will fly, say 5 flights, because someone said he or she can fly 5 flights on a charge. Is that the right approach? Maybe... maybe not.
I'm not being negative here, I'm trying to be practical and trying to point out... probably not very well, that predictions work for experienced pilots. For beginners, there has to be a tool. Even your method will put you in a position of that "last few milliamps".
I fly my Skylark 70 with voltwatch and the LiFe packs. I watch it constantly... of course, when it's on the ground. As I've said before, I check it before and after each flight. When it begins to flicker down from the top green LED, I know that it's about ready to charge. Many here will push it to the point where they will try to get one more flight out...
Don't get me wrong, here. Your information is good stuff... mainly because it points out that the curve is very flat and has a very sharp knee. We've had all sorts of discussions about battery packs and how they should be used. Some advocate using LiPo packs with a regulator and I always say that it adds another point of failure and that beginners should keep it simple, meaning maybe they should consider using LiFe packs after they become more experienced. There is no really easy answer. All I can say is that your prediction method works for you, an experienced pilot, but may be slightly over the top for a beginner with everything else that they have to think about before, during, and after each flight.
CGr.