...I'm losing 5-7 minutes from new condition. Should I just replace them. No signs of bulging, but who knows...
A LiPo battery will lose it's capacity to store energy when you use them ... that's normal, even your phone battery does that, so only that isn't a clear sign that something worse is soon going to happen.
We also know that other thing's is happening inside the batteries during use that we can't see or notice on the outside ... they get hot, they get charged, they are commanded to discharge fast & deliver a lot of amps, they get left either with too high or too low cell voltage occasionally. All this break down the chemistry inside the battery, leading to an increased internal resistance & in some cases gassing (which makes them swell).
Internal resistance is what generate heat & makes it harder for the battery to deliver the amps we want out from them when we give it all at once ... full forward & full ascent in Sport mode. This leads to voltage drops, cell deviations & again increases in the internal resistance.
So it's a constant never ending degradation from the day they were made ... which one day, often when you demand that little extra, makes one cell just say "I've had it..." & it falls under 3V.
So without following how the battery performs over a longer time of mixed use, it's hard to say where they are in the life cycle.
...the same thing happened to me with my Air 1 I went back over the records of that battery and there really wasn't a clue...The battery was not bulged even the least and had never shown a problem...
... - so you're saying that even when you looked at the data in Airdata, there were no major cell voltage discrepancies etc? The battery looked healthy?
The battery data isn't black or white ... usually the degradation is sneaking in & during high amp draw show signs of cell deviations & that they are more prone to voltage drops in overly hot or cold ambients... by this you can divide the batteries use in the way that
@RobotBee have done now or even take the battery off use & dispose of it.
In other cases the critical state occurs suddenly if you just for this flight decide to really try out full speeds (higher amp draw than usual) ... & it happens to be somewhat colder/hotter then usual ... & the battery fails abruptly. And the reason for this may very well be due to earlier misuse that degraded the battery back then ... but now much later the battery needed that lower internal resistance in order not to fail.
But
@hiflyer201 ... surely the battery looked shoot at Airdata from the flight when it failed, voltage drop under 3V & major cell deviations..?
