Battery critically low! 85% left

[protorox]

I flew up in the air got to about 85% and my phone voiced "Battery critically low" I looked and voltages were fine and levels were still at 85% I still brought it down and changed batteries but...what would cause it to trigger that dialog?

 

[The Editor]

I flew up in the air got to about 85% and my phone voiced "Battery critically low" I looked and voltages were fine and levels were still at 85% I still brought it down and changed batteries but...what would cause it to trigger that dialog?

Were you at full climb out/throttle when the message triggered?
If so I would say the pack is sagging under load, then recovers when heavy load removed.

 

[protorox]

Were you at full climb out/throttle when the message triggered?
If so I would say the pack is sagging under load, then recovers when heavy load removed.

that sounds like exactly what happened.

 

[The Editor]

that sounds like exactly what happened.

I wouldn't worry too much unless this a particularly old pack with a lot of charge/recharge cycles on it.
As packs age their internal resistance increases and they will not give up their charge so easily under load. Additionally they will exhibit a larger voltage drop when high demand is asked of them and this can trigger a 'low battery' alarm. Also cold temperatures can cause packs to perform poorly.
As long as you are seeing normal flight times out of the pack and the cells are tracking close to each other without one particular cell very out of balance I would not be concerned.