# I have a simple battery use question

Is the 20% use rule on a battery relative to the voltage rating of the battery (22.2v) or to the charge that it can hold when fully charged. When I charge my 22.2 volt 5000mAh batteries they top out at about 25.4 volts when fully charged. 20% utilization means It can be used down to 20.3 volts based on the 25 volts, but based on the the rated voltage I can go as low as 17.8 volts (80% of 22.2 volts).

How should I set my battery failsafe in Mission Planner for APM 2.6? Do I set it so that even though I charge to 25.4 volts the actual failsafe value is 17.8 volts, based on a rated voltage of 22.2?

@yomamma7,
If these are LiPos, then the minimum voltage per cell is 3.3vdc with the maximum around 4.2vdc when fully charged for a total charge of ~25.2vdc for a 6S.
Many users, including myself, allow the battery to go to 3.6 vdc per cell before recharging which is around 21.6vdc for a close to depleted LiPo.
The LiPo damage point will start when the cell voltage is taken below 3.3vdc per cell or 19.8vdc for a depleted LiPo.
Regards,
TCIII GM

[quote=“TCIII”]@yomamma7,
If these are LiPos, then the minimum voltage per cell is 3.3vdc with the maximum around 4.2vdc when fully charged for a total charge of ~25.2vdc for a 6S.
Many users, including myself, allow the battery to go to 3.6 vdc per cell before recharging which is around 21.6vdc for a close to depleted LiPo.
The LiPo damage point will start when the cell voltage is taken below 3.3vdc per cell or 19.8vdc for a depleted LiPo.
Regards,
TCIII GM[/quote]

Sir, is the minimum voltage you are mentioning here the one [color=#FF0080]during [/color]flight or after the landing when the battery has recovered a few decimals of volts?