Originally Posted by aeajr
Frankly this was one of the reasons I was warned away from LiFe. No way to read charge level. They stay flat, then voltage drops off the table. True?
Well, yes you are right. The majority of their discharge cycle is at ~6.6v so if a voltmeter says 6.6v you don't exactly know how much charge is left. But there are quite a few benefits to LiFe that win out over NiMH packs. Greater energy density per ounce of pack weight, negligible self discharge rates, more consistent voltage under extreme (high G) loads, no weird cell discharge states that require cycling to recover, etc, etc.
When you use LiFe packs you get in the habit of watching how many mAH you put back in after a day's flying. If you find a charge cycle requires either way more or way less than what you expect, that's a sign to do a full discharge/charge cycle to verify the pack's capacity.
In the 2+ years I've been using Hyperion 1450mAh LiFe packs in my planes I have never had one go bad or even test funny. Never.
The only downside to using LiFe is that servo manufacturers are still playing a bit of catchup to offer products that are spec'ed to handle LiFe voltages.