Completed Endurance Flight Test - Disappointed In Results

GlassKnees

GlassKnees

Well-Known Member
I have an Elev-8 (V2) quad that I had modified - replaced the stock motors with Tarot 4006 620 KV motors, driving carbon 1355 props. I'm using an APM 2.6 flight controller with external GPS, telemetry, Tarot 2D gimbal and a TS832 600 mW video transmitter. The full up weight is 3.0 lbs:

Elev-8%20Pic_zpsvaejfxq0.jpg


I used a fully charged Glacier 6000 mAh 30C 4S Lipo, which is a little over a year old. This morning, the air was calm, temp was 63 Deg. F. with 59% humidity. When I power up the aircraft, the gimbal and video transmitter are drawing power from the battery.

I started the stopwatch as soon as I began to throttle up for takeoff right after achieving GPS lock. I flew to an altitude of about 8 - 10 feet and switched to Loiter mode, and moved the aircraft from the driveway over to the grass and let it hover. Occasionally, I would yaw the aircraft or move it slightly:

Endurance%20Flight%201_zpsyvvzwlrk.jpg


Voltage failsafe (set at 14.5 V) kicked in shortly after 6 minutes. Total endurance: 6:12. I was hoping for a better result. I'm wondering if perhaps my battery is not holding the charge as well??
 
I measured the battery voltage with my multimeter (old analog type), and it indicated over 15 V. I then plugged it into my charger and it started indicated 15.68 V as it began charging. Here's a screen shot of the log file showing voltage during the flight:
Voltage%20Level_zpsvxsuqaby.jpg


Notice how it dropped immediately from 16.8V to around 15.7 as I throttled up. Then it gradually drops until it hits the 14.5V failsafe at 6 min. I guess I just don't know enough about batteries - why the voltage popped back up to almost 15.5 V when the aircraft landed and I disarmed the motors..
 
GlassKnees said:
Notice how it dropped immediately from 16.8V to around 15.7 as I throttled up.
Click to expand...
An initial voltage drop is to be expected under load. The type of battery and the load influence the drop.

AW_SAM2000_10A.png
Here's two 2000mAh batterries. Note the immediate drop from 4.2V once a 10A load is applied. The Samsung is a higher drain battery (22A rated) does much better than the AW (10A rated).

GlassKnees said:
- why the voltage popped back up to almost 15.5 V when the aircraft landed and I disarmed the motors..
Click to expand...
That's cuz you removed the load. Though a big drop and big jump when the load is removed may denote a weakened/tired battery. With my Tri when I first installed a LiPo alarm (left with the default voltage) after about a minute of flight, every time I punched it the thing would start squealing. I finally lowered it to 3.3V, x 3s = 9.9V, which is below the official 10.5V which is often recommended. But when I checked it after a flight it was always it was always ~10.6V.
 
Thank you Jackson - I always appreciate your comments! I suspect that perhaps my battery is weak - I've used it on both this aircraft as well as on a Tarot 680 Pro hexcopter. I'm thinking I might go ahead and replace it. Thanks again foro your comments!
 
I think I may have solved my problem. I posted my issue on another forum and some questions directed to me made me think I was not properly using my Tenergy battery charger. The manual is kinda thin and I had to resort to my friend, YouTube; there, I discovered that when programming it for a particular battery, you need to match the battery capacity, in my case, 6000mAH. The setting was considerably lower, like 3300, so I changed it. I am charging it up now and will try another endurance test.
 
I hope that works out but when I looked at your graph it looked like it was fully charged. 4S X 4.2 = 16.8V. Was that what you had? FWIW a tired battery can show full charge right off the charger (4.2V/cell), but if you retest it after sitting 10 minutes the voltage will have dropped.
 
Yup, you're right. Made no difference. I did a video flight earlier this morning to shoot video of the creek behind our house to assess it's condition after the rain we had. Later, after charging up the battery again, I did another flight - optimistically increased the length of the mission.

When I took off and switched to the autopilot, it went off in a different direction and I realized that I forgot to load the revised mission - DOH! So I took over manually, landed and remotely loaded the revised waypoints and took off again. I had good telemetry and clean video. As the aircraft flew it's mission, I was watching the onboard battery voltage, and when it dropped I hit RTL and prayed that I could get it back before the failsafe was triggered. I came back within sight and landed (I made a couple manual adjustments as it was landing on my back patio and the space is tight). It landed okay and I shut it down. But when I glanced at the Mission Planner screen, I saw the Failsafe had been triggered.

Bottom line - got to replace the battery!
 
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