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Getting the most flying time out of your batteries

#1
I just got in four 1800 mAh 25C 3S lipos from HK USA. I've been flying two 4S 1500 mAh 25C lipos since I got into flying a couple months ago. I figured I'd give the 3 cell's a try since they are really affordable. Right off... ton less power. My plane still flew great though and had climbing power. It just didn't have that, oops, I put the plane in a bad situation, now slam the throttle and climb out of it straight up kind of power which is nice to have. But for just putting around they are great.

I got a 3S battery monitor along with the batteries, since I think I ruined my 4 cell batteries because I ran them down too far, at least one is toast. Hooked her up and she works great. I decided to see what kind of flying time I could get out of the batteries. I probably get 5 to 10 minutes out of the 4S bats I have.

1st flight - 16 minutes, mixed flying, on and off throttle heavy, hardly any dead stick flying
2nd flight - 14 minutes, gave my brother the tx, mixed flying, on and off throttle heavy, hardly any dead stick flying
3rd flight - 30 minutes, very easy on the throttle the entire time, basically just enough throttle to keep it in the air, putting around and doing practice low passes, still really fun

I couldn't believe how much more time you can get by taking it easy on the throttle. Still miss the power of the 4S batteries though.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
Wes, had good success with these:

http://www.hobbyking.com/hobbyking/...2_8S_Cell_Checker_with_Low_Voltage_Alarm.html

or similar (there are many, they all look very similar).

Only features that are *MUST* is a loud beeper and a selectable alarm voltage. The light strip versions are hard/impossible to see from the air, and the non-selectable voltages are usually too low -- on many of my planes they wouldn't alarm until I was down below 10%.

Since battery voltage drops with the motor running, and the target should be 3.7v *at rest*(~20% capacity), they do need to be "calibrated", and used differently among your different power setups. From playing with it I've settled on setting mine at 3.7v -- Setting to 3.6, for me, drew down too much. For my sport/parkflyer models, I ignore it if I'm punching WOT, but land when it alarms at cruise throttle. usually leaves 20-30%. For my powered glider I completely ignore it if the motor is on, but listen to it after shutoff -- if it lasts from more than 30s, that'll be my last launch.


BTW, might just be flying taste, but the "oh crap" throttle direction should be down. More thrust is a bad gamble -- pumping more energy into an endangered aircraft will only make the crash sooner and worse. Recovery with throttle back will give you more time to correct and if that's not enough, you haven't WOT'ed your plane into the dirt nap.
 
#3
I'm getting better with each flight, so I'm not putting my plane in as much trouble as when I started, but for example, I might get it close to trees and the only escape is pretty much straight up. With more power, I could pull back and power out.

I wish I got that monitor, will have to order one. I got this one:

http://www.hobbyking.com/hobbyking/store/__39085__Hobby_King_Battery_Monitor_3S_USA_warehouse_.html

Once I heard the beeping I brought her in. The documentation that came with it says it starts beeping at 9.9v for 3S, which is what I got and the batteries I'm using with it. I'm going to actually test the depleted batteries and see where they are at.

I put my 30 minute battery on the charger, it read 10.63V if I'm correct which means the monitor worked, says it beeps at 9.9V, though it seems it actually must alarm around 10.6V.
 
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pgerts

Old age member
Mentor
#4
The throttle management is the key to flight times. No need to max out on level flight unless it is a racer round pylons. I get aprox 30% less time when flying in high winds due to more Power all time.
 

Tritium

Amateur Extra Class K5TWM
#7
Call me the skeptic, but,I find it suspicious that the craft spends most of its time in front of a blue sky (think blue screen).

Thurmond