Battery Observations (Flight Times)

[loftrat]

I read that the ideal storage voltage for Lipo batteries is 3.7 - 3.8v (ish). So I thought I'd see what the batteries I'm using in the 120SR were at when I'd flown for the 'recommended' 5 minutes.

Aside from the stock battery that comes with it, I also have some Turnigy 600mAh nano-techs.

So I checked the voltage of the stock battery and one of the nano-techs before flight, both read around 4.2v. Then I flew for as close to 5 minutes as I could get on each (countdown timer setup on the DX6i, landed when it reached 5). I confined the flight to a straightforward nose-out hover, and whatever inputs were required to maintain height and position (so, not much).

After the 5 minute flight I measured the voltages of the two batteries.

BOTH batteries measured 3.8v.

To be honest I found that a little surprising. I'd assumed that as the nano-techs were 600mAh and the stock battery is 500mAh there would be some sort of difference in the final voltages (I don't know why, just an uneducated gut feeling based on the numbers). I now know that I was clearly wrong

I was also expecting to see the little blinky light come on to tell me my flight time was up, but I'm guessing that must be calibrated to a lower voltage?

I've previously flown until it flashes, and not really taken any notice of how long it takes for that to happen (I sort of assumed it was 5 minutes). But I've since read that I shouldn't just fly until that flashes because that's bad. Do I have to stick to the recommended 5 minute time or is there a way to determine if I could safely fly for a little longer than the 5 minutes?

[airshot]

Keep testing, lipo batteries discharge differently than conventional batteries. You may find that the battery will hold that 3.8v for a little while. Another thing....are the batteries new? Batteries must be cycled (charge/discharge) a number of times before optimum run time will be achieved. I would add 30 seconds on to your 5 min and see what voltage you get then.....don't be surprised if it still reads 3.8v. If so add another 30 sec until you reach that sweet spot. The battery rating is the lowest voltage it should be discharged to (3.7v) 3.8v seems to be the optimum storage voltage.
Just be sure you have cycled your batteries about 6-10 times to get them to full capacity before any serious testing. I get a solid 6 minutes of flight (outside) and can get 8 min of just hovering inside with my nano tech and hyperion batteries.

[Pfloyd]

Originally Posted by loftrat

I read that the ideal storage voltage for Lipo batteries is 3.7 - 3.8v (ish). So I thought I'd see what the batteries I'm using in the 120SR were at when I'd flown for the 'recommended' 5 minutes.

Aside from the stock battery that comes with it, I also have some Turnigy 600mAh nano-techs.

So I checked the voltage of the stock battery and one of the nano-techs before flight, both read around 4.2v. Then I flew for as close to 5 minutes as I could get on each (countdown timer setup on the DX6i, landed when it reached 5). I confined the flight to a straightforward nose-out hover, and whatever inputs were required to maintain height and position (so, not much).

After the 5 minute flight I measured the voltages of the two batteries.

BOTH batteries measured 3.8v.

To be honest I found that a little surprising. I'd assumed that as the nano-techs were 600mAh and the stock battery is 500mAh there would be some sort of difference in the final voltages (I don't know why, just an uneducated gut feeling based on the numbers). I now know that I was clearly wrong

I was also expecting to see the little blinky light come on to tell me my flight time was up, but I'm guessing that must be calibrated to a lower voltage?

I've previously flown until it flashes, and not really taken any notice of how long it takes for that to happen (I sort of assumed it was 5 minutes). But I've since read that I shouldn't just fly until that flashes because that's bad. Do I have to stick to the recommended 5 minute time or is there a way to determine if I could safely fly for a little longer than the 5 minutes?

Both my ThunderPower and imax chargers store my batts at 3.8volts.