Battery Test Results

[K3CFPV]

Decided to run one of my batteries thru a discharge analysis on my Hyperion EOS 0720i. From my research, I decided that a good estimate for a battery's capacity is to start fully charged (4.2V/cell or 16.8V) and discharge at a slow rate (I used 0.5C) to 3.2V/cell (12.8V). Some information suggested 3.0V/cell at 1/5C, but I felt that 3.2v/cell was a safer level, and I didn't think that the difference between 1/5C and 1/2C would make all that much difference. I entered the battery's capacity as 5400 mAh as per the label on the battery, set the discharge to terminate at 3.2v/cell and a discharge rate of 0.5C (2.7A) to determine where the dropoff was, and where on that curve, the ST-16 is first giving it's warning (14.7V for me). Below is the discharge curve. Several things immediately pop out. One is that Cell 1 terminated the discharge at 3.2V. The other cells were all higher with Cell 4 150mV above Cell 1. Most importantly, and strangely, is that the battery capacity seems to be much, much higher than specified by Yuneec. Mine came out about 17% higher at 6300 mAh. I ran this test twice just to verify I didn't screw something up. With a capacity of 6300 mAh, the 80% point corresponds to a pack voltage of 14.8V (close). Is it possible that the packs are being under rated? I will repeat the test when I get my Western Mountain Radio CBA IV. Also, I have a new motor coming to run some wattage and thrust tests with the Yuneec provided prop and others for comparison. Once I have that number, I can better estimate the system draw at 50% throttle, and given the flight times (16:40 for this pack), I can get another estimate of capacity used.

 

[JB1]

Nice work K3C it would be nice to know if it's 6300 or 5400 mAh's. The numbers as others have stated don't add up causing a **** of a lot confusion.

 

[DroneClone]

Good Job! let us know what load test reveals! Thank you!

 

[seabee]

Very interesting. The early Chroma batteries were labeled 5400 mAh but HH published that they were/ are all 6300 mAh. Think all are made by or for Yuneec.

 

[Drone Dreamer]

Thanks K3
Very technical, good information, keep us posted...

 

[Typhoon Charlie]

Nice work K3C, this confirms my findings.
1. Battery is about 100gr heavier than a regular 5200ma battery.
2. eCalc shows that for a craft with the specs of the H would need 6000ma to fly anywere close to 20min.
I think Yuneec of trying to make us believe they have a much more efficient craft than they do.

 

[Ahab]

I tried recharging my pack on my old Imax B5 charger once so I could measure how much it put back into the battery. I had flown it 16 min when the battery low warning came on. I was surprised to see the charger put over 5569maH back into the pack. I thought either the charger was miscalibrated or that I was losing some of the charge due to inefficiency. Maybe it wasn't off as much as I thought.

 

[Bobjazz]

I can also confirm that these batteries seem to be more than 5400mAh. I flew mine down to the low voltage warning (14.3v) and charged it back up. Took about an hour @6.4A and put back 5721mA. Definitely not a 5400mAh battery, 6300mAh sounds about right.

 

[JohnL]

@K3CFPV Excellent work man. It's great when someone not only takes the time to do this sort of analysis, but then has the courtesy to post their findings for others to benefit.
What really jumps out to me here is where we're seeing the voltage drop off. If I'm reading your graph correctly (just eyeballing it as I sit here in the waiting area of my mechanic), we're seeing the classic Lipo voltage drop at around 3.6v. Do you concur?

This bothers me in that normally I would expect to see this drop at a lower voltage, say 3.3 or 3.4. To me this indicates a low quality Lipo battery in general. With that said, it doesn't surprise me at all that the battery is under spec WRT capacity.

It would be interesting to see the same curve generated under 20-30C conditions, i.e., under full load. Thank you again for the info!

 

[raptorheli2]

I posted this a few days ago. I bet the reason for under spec is no 1, it gives you a higher c rating and no 2 it would put it over the magic 100w number for taking them on a plane.

 

[K3CFPV]

The TSA limit is 100W. For a 4S, the nominal voltage is 14.8V (3.7V x 4), so the 100W limit is reached for batteries rated at 6756 mAh or above.

 

[raptorheli2]

Have you found info confirming the tsa limit is at nominal?

Most things certainly are at nominal but wondered if air was the strict side of it.

 

[K3CFPV]

They don't elaborate, but this is what I was told by the FAA. Also, you should never travel with a fully charged battery anyhow. I always put mine in 50% storage mode which puts you close to the nominal voltage. You will have to fly some of the charge out if your only charger is the Yuneec charger. You also have to cover the contacts. I use rubber tips over my XT-60 connectors and use electrical tape over the end of the Typhoon H batteries.

 

[glider]

@K3CFPV Excellent work man. It's great when someone not only takes the time to do this sort of analysis, but then has the courtesy to post their findings for others to benefit.
What really jumps out to me here is where we're seeing the voltage drop off. If I'm reading your graph correctly (just eyeballing it as I sit here in the waiting area of my mechanic), we're seeing the classic Lipo voltage drop at around 3.6v. Do you concur?

This bothers me in that normally I would expect to see this drop at a lower voltage, say 3.3 or 3.4. To me this indicates a low quality Lipo battery in general. With that said, it doesn't surprise me at all that the battery is under spec WRT capacity.

It would be interesting to see the same curve generated under 20-30C conditions, i.e., under full load. Thank you again for the info!

A graphene battery follows a similar curve. Once it hits 3.6v, the discharge curve changes dramatically. I've been testing a Turnigy 6.6 15c 4s battery on a 2.47 kg quadcopter. Although no gimbal/camera is attached to the copter, the voltage drop is very small, but you'd better be on the ground or near it with 3.5/cell because 3.2 is ~30 seconds away.

 

[K3CFPV]

I tested another of my 4 batteries and got about the same result. This one came out to 6350 mAh (see graph below). I'm starting to believe that something similar to what seabee stated with Chroma batteries being under rated is happening here. I'll do one more, but I think it's fair to say that the batteries that Yuneec is supplying are not 5400 mAh but closer to 6300 mAh.

JohnL re your suggestion for a curve at a faster discharge rate, my Hyperion EOS070i only goes up to 5A (~1C for this battery). I have a Western Mountain Radio computerized battery tester on it's way which can handle 150W. Their 500W amplifier is $929 (580% more than the actual tester). Besides, even at 550W, you can only discharge this battery at around 36A or about 6C. There are plenty of curves around that show how lipo curves change at various discharge rates. As you increase the discharge rates, the knee happens at lower and lower voltages and, yes, at around 30-40C, it drops to 3.3V, but at slow discharge rates, the knee is typically around 3.6V. Where the knee appears is not really indicative of a poor battery. One of your best measurements is the IR of the cells, and how that changes over time. Based on flying times, my guess is that the total system draw is a around 4C or 25A.

As soon as I get my spare motor, I will test it's trust and current draw at 50% and 100% throttle with the factory prop. Maybe we can find another prop that's a bit more efficient.

 

[Larry Cochrane]

Hi, I am new in flying my Yuneec Q500+. My question is about a upgrade charger. I just purchased & haven't received yet a Hyperion EOS720I NET 3 charger. Other than what is included with the charger. Are there anything else I need to charge more than one battery at a time??? Which cables or parallel box?? Should I only charge one battery at a time?? I currently have three. Two stock Yuneec batteries that came with the drone & I purchased one Venom 6000 battery. Any help would be highly appreciated...

 

[PatR]

It may well be Yuneec is understating their battery capacity to remain within a "safe" watt hour rating for shipping purposes. They would not be the first to have deliberately mislabeled batteries to avoid additional shipping costs. One battery manufacturer went so far as to apply a false label over the correct one, completely to conceal watt hour values.