Cutoff voltage for LIpo 3s?

[kevinmuff]

I have a 3s 2100mah LIpo battery. When I am done flying, and I check the voltage on the battery after unplugging it from my plane, it should read 9v correct? ( for the cutoff voltage)

So fly it until it reads 9v right?
I'm using a multimeter.

[flydiver]

Nope, WAY too low. ALL rechargeable batteries have voltage sag under load and rebound after the load is removed. LVC is based on LOADED (in use) voltage. You should see a higer voltage after the load is removed.

The only way you'll see in-use voltage is on the bench with a wattmeter in place or with special measuring tools while flying (Eagle Tree and the like).

Multimeter is OK but is not as helpful for the individual cells. You might want to get one of these. Not dead accurate but awfully handy and easy to use.
www.headsuprc.com/servlet/the-2079/Battery-Checker/Detail

At 3.0v/cell (unloaded) your lipo is essentially dead. You want to see ~ 3.5-3.7v/cell after flying. Yep, that high. If you want a long lipo life you want to leave about 20% of your capacity. If you don't care....fly to LVC and dead stick it in. Buy batteries more often.

FWIW the LVC on the SC is set too low for safe lipo use. No, you can't re-set it. Yes, that kind of thing is not uncommon. GWS and Electrifly both have ESC with destructively low LVC settings. Learn to read ESC specs. Expect it to take awhile to make sense.

[realbob]

@fly

WHile speaking of LVC, I have a chiness checker that can be plugged while flying with an alarm, but when I give lots of throttle, voltage is very low and beeps, but battery not really at this voltage. So except telemetry, nothing better to have a more realistic value without spending over 50$ ??

[flydiver]

Yes, battery really is at that voltage. That's the 'sag' under load. How much it sags is a function of the load and quality of the battery. Larger batteries, newer batteries, better quality, and higher C-rating all tend to sag less.
The stock PZ lipo that comes with the club is the opposite of all of the above. It's not a very good battery. It's as good as the rest of the electrics, functional, but not much more.

[realbob]

So you mean that with stock battery, if I am flying couple minutes, then batt is at 3.85 per cell (example) then I put full throlle and it goes 3.3, it could result in damage even if after my burst it goes back to 3.80 ?