After much testing, reading and comparing notes, here is my input....
You can say, always start with a fully charged battery if you want to avoid _any_ details on the subject. It's nice and safe. However, it offers no information on the subject so it's more or less a blind statement. There are two things you need to keep in mind about the battery... once it drops to a critical level it will turn off and, that percentage you see on the Go app or the LED bars you see on the battery.... not completely accurate when the battery is not under load. Now don't get too worried about that critical battery turning off statement. It's not the same as the battery simply getting low. It's important to keep this in mind.
As msinger mentioned, I'd highly recommend turning on (in setting) the battery voltage being displayed in the Go app next to the battery percentage. It's more reliable and detailed.
If a lipo battery is allowed to sit around, you put it into the Phantom and you then look at the percentage it _might_ show you a number much higher then is actually correct. I can't know for sure (as I can't talk to anyone in the know at DJI) but I'd say that a battery coming out of discharge state may stand more of a chance of reporting an incorrect battery level. Once that battery is placed under load (especially something like full throttle) the battery shows it's true voltage. Still, this is still not usually an issue. What we are seeing now is the perfect storm... a lower than "full" battery, full throttle and colder battery. A colder battery is probably going to report lower voltage as well. The thing to keep in mind is that lipo batteries go from good to low _VERY_ quickly. They are designed this way. Here is an example:
This is why it's recommended that you start to land around 30%.
But the thing to keep in mind is the voltage amount. I'm a little fuzzy on the numbers (others should be able to correct me) but I think the number you need to look at is right around 3.3v. When you get to that mark you should start to land pretty quick.
Now the issue. If you leave a battery sitting around and/or in discharge state it might report at something like 3.5v which might be around 60%. However, it might really be lower, especially if it's cold. So you start to use this "60% battery" and take off. It's cold and you kick in full throttle. Well, that voltage takes a nose dive, let's say to 2.xv which is critical (2%?) so it turns off.
If you have been flying with a battery then you've been drawing current and the battery is warm. So it's much more likely that the percentage and voltage being displayed is correct.
DJI has also changed the characteristics of the battery in this last update to prevent this perfect storm. When the battery is cold, it lowers the amount of full throttle so the battery's voltage does not drop as far. Perhaps they adjusted the critical battery level as well... we don't really know. We do know (from FranknFly) that the beta testers have tested this firmware and it appears to work.
MY recommendation... start with a charged battery. If you've been flying with a battery and land with a good charge, that charge amount is probably correct so you should be fine starting up again. Avoid using a battery that is in partial discharge when it's been sitting unused for a day or so. Change your auto discharge to a higher number and use a manual discharge method such as the light devices for sale online.
*** Just my 2 cents ***
