Possibly a silly question about the LIPO 80% rule

R

R6Media

Member
I'd just like to get verification of this "rule"
Things I've read make it sound that the 80% used is what is shown remaining AFTER a flight is complete and the battery is at rest (put it on my charger and it will show 20% remains - or basing it on mAh put back in during a charge. - 4000mAh back into a 5000mAh battery)

The rule IS NOT "80% under load" right????

I ask because if you fly off 80% of the power and your left with 20%, Didnt you technically use more than 80% because of the loaded condition in flight but then you remove the load and the battery stabilizes higher? Or am I comparing apples and oranges.

Just want to make sure I'm understanding it correctly.

If I'm correct in my original understanding of the rule, moderator - please feel free to delete the posting as I'm sure this question has been asked a million times over.
 
Last edited by a moderator:

G

Ghostrider

Member
When we are talking about 80% we are referring to the capacity of the battery in mah. So your example of using 4000mah out of 5000mah is the correct line of thinking. That number does not change under load conditions. You are consuming watts and mah as your flight progresses. Your voltage and current change under load. Your battery will gradually lose voltage as your flight progresses and then there will be a sharp drop off near the last few percent of capacity. Many of us use battery monitors to monitor the voltage of each cell and we then fly until the alarm goes off. For example a 3S lipo battery charges to 12.6v or 4.2v per cell. Then during the flight it will drop and I would fly until the pack voltage reaches 10.5v or 3.5v per cell under load and then land. After the load is removed the cells will then show about 11.1v or 3.7v per cell. Then I charge the battery and monitor how much capacity or mah I put back in. It should be close to that 80% of the battery capacity.
 



S

Silverburn

Member
+1 on ghostrider.

One additional note: in colder weather (it's -5'c here in Switzerland), the voltage under load will drop further than normal, especially if you "juice it". Don't be tempted to ignore the 3.5v alarm - land as always. Your flight times will be shorter, but you'll be looking after your batteries.

Battery care in cold conditions is another topic in itself.
 

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