6s lipo question

[john420]

hi guys what is the good voltage rate for 6s first level and second level protection thanks

 

[Carapau]

It doesn't' matter what the cell count is it is the individual cells that matter. If you stick to the 'only use 80% of the batteries capacity' rule then you will be landing with each cell at around 3.7v/3.8v. This not only ensures a good life for the battery but also gives you a small reserve should you have a problem etc etc. If you go below 3.2v per cell then you are beginning to damage the battery and there is also a chance that you may hit the ESC's low voltage cut off (this is when the ESC's suddenly just stop- hard cut off, or start to slow down- soft cut off)). Thus I like to set my timer for the 80% rule and my low battery alarm at around the 3.4-3.5v per cell. In my mind if the low battery alarm goes off then I have screwed up but it is a good final warning so to speak. Please bear in mind that the cells will quite quickly drop off from 4.2v a cell when you start to fly and then the voltage drop slows right down until you get to about the 3.4v ish area and then they begin to drop off more and more rapidly. Each battery is different so these discharge curves can vary although on by small amounts.

You will also need to work out or guestimate what your voltage loss is under load which will differ depending on the weight of your aircraft and setup. Live telemetry of flight pack voltage is a big help here. Just bear in mind that ESC's dont account for this voltage drop. If they see their low voltage then they will immediately start their cut off be it hard or soft. Hard or soft cut offs are normally programmable ie you can select which one so do check what your ESC's default setting is and how to change this if need be. ESC cut offs are often at the 3v per cell but again this depends on the ESC. This is why it is not necessarily a good idea to gun a heavy multi towards the end of its flight.