Quadcopter Elev8 not leaving the ground

albln

After a long time building it during my spare minutes, I have finished the Elev8 quadcopter. I have done all the checks and balances with the ESCs, the motors rotating in the right direction, correct propellers, etc. However, after trying to fly it, the Quad does not have enough force to leave the ground.

I believe that the problem resides in the battery. I am using a new (bought last year, never used) Turnigy Nano-Tech 4000 mAh, 3 Cell (11.1 Volts) LiPo battery. I am charging it with a Turnigy Mega 200W Balance Charger/Discharger, and I use a rate of charge of 4.00 A

However, the charger stops 1240 mAh. It started charging at the specified current of 4.00 A and continued doing this until the charge in the battery reached 920 mAh. After this point, the charging current diminished until the charger stops at 1240 mA (4.2 Volts in each one of the cells).

I am now discharging the battery with the same unit. I set a discharge rate of 5.0 A (the max that the Turnigy can discharge). However, the discharge happens at only 2.0 A as shown on the screen of the charger/discharger unit.

Does this mean that the battery that indicates a max discharge of 70 C can only supply 2.0 A? That would explain why the Quad does not have enough juice to leave the ground. What am I doing wrong here? Before asking for help, I have charged/discharger the battery a couple of times in a couple of days. What’s my next step?

Thanks for your help!

Al

W9GFO

I don't have that charger but it may be that it is limiting the discharge to 2 Amps in order to control the amount of heat it has to dissipate. A 3 cell discharged at 2 amps creates more heat than a single cell discharged at 5 Amps.

JasonDorie

A couple things to check:

Did you set the throttle end points on your ESCs to match the range of the throttle stick on your transmitter?

What's the weight of the finished product?

What size and pitch props are you using? (They'll have a number, like 10 x 4.7)

Do you know the kV rating of the motors you're using? (Probably a number like 920, 1000, something like that)

How long ago did you purchase the battery? Was it ever charged before? Was it stored in a very cold or very hot location? Lithium batteries don't store well if they're empty, and don't handle temperature extremes well.

albln

Yes, I set the throttle points as per the calibration procedure. As for the weight and other details, I am using the kit from Parallax, so nothing should be diffferent.

However, the battery was purchased several months ago (maybe 10) and had not done much with it. It was, however, stored at room temperature. So probably having it stored while discharged may be the reason to this problem?

thebigmacd

albln wrote: »

So probably having it stored while discharged may be the reason to this problem?

I think that is probably your issue. Lithium-based batteries should always be stored at full charge, on a charger if possible. The Tesla Roadster's $20,000 battery becomes useless if you let it sit discharged for several months.

W9GFO

thebigmacd wrote: »

Lithium-based batteries should always be stored at full charge, on a charger if possible.

I've read that infrequently used lithium batteries should NOT be stored fully charged. Here is one reference; http://uterc.org/files/LipoStorageTips.pdf

And another; http://www.electricwingman.com/guides/lithium-polymer-battery-guide.aspx

JasonDorie

Yeah, they shouldn't be stored "full", or "empty" - either of those can damage them. About 10% to 20% below full is one measure I've seen for long storage.

Albn: If you have access to another battery (without having to buy it) you could verify it. Take the other battery with a full charge and try to lift off. If it has enough power that's probably the issue.

Also, and this may *sound* obvious, but if you're new to R/C it might not be: make sure the propellers are on right-side-up. The measurement numbers (10 x 4.7) should be on top. They'll work backwards, but will be much less efficient.

You should also double check that the ESCs cut-off voltage is set to 3.0v or 3.3v per cell, and that it's registering your pack as a 3 cell. If it thinks it's a 4 cell pack, you'd be hitting low-voltage cutoff pretty much all the time.

Shawna

That sounds like your battery. Do you have any other batteries that you can charge and discharge with your charger to see if it behaves the way you expect. I never store my batteries fully charged and I have a couple of them that are 2 years old. I also never discharge my 3 cell batteries below 10 volts.