Poor Battery Performance and Reliability

We have been using the IRIS over the past couple of days with 2 stock batteries and testing some other packs. The stock packs seem to be very low quality. We determined one had a bad cell which was sent back for RMA. The other still does not function well. While hovering 20 feet in the air in loiter we let it trigger the battery fail safe (10.5) and by the time it lands the voltage is in the low 9 volt range. If the copter had been any higher it may not have had enough power to land. I have never seen voltage fall that quickly from 10.5v with a 12amp load and I have been doing this a long time. Also the pack does not balance well, even when using a very good charger. The cells were likely out of balance out of the box since it only had 2 flights on it before we checked the balance. The is not enough cycles, not to mention being balance charged, for cells to get more than .1v out of balance fully charged with such a light amp draw on this system. I hope this is a isolated incident as I consider ourselves advanced users (been using APM for years and rc even longer) so others with less/no experience with lipo batteries may not understand what to look for or diagnose this issue.

The other batteries we tested would only drop to about 10.3v by the time it auto landed given the same situation.

Taylor I think you may have hit on what happen to me… But I can’t tell if Failsafe kicked

Should be easy to figure from the logs.

I figured I would chime in to say that my Iris batteries also exhibit poor performance. I consistently get only 3000 mAh of discharge before the voltage is so low that I can’t fly. I’m not sure if this was a bad batch of LiPo’s or what but it is quite unsatisfying to lose power at “15%” charge remaining.

The Iris itself is awesome though. A joy to fly.

[quote=“MrRocketman”]I figured I would chime in to say that my Iris batteries also exhibit poor performance. I consistently get only 3000 mAh of discharge before the voltage is so low that I can’t fly. I’m not sure if this was a bad batch of LiPo’s or what but it is quite unsatisfying to lose power at “15%” charge remaining.

The Iris itself is awesome though. A joy to fly.[/quote]

3000mah isnt to bad depending the voltage you are ending your flight at. Total capacity varies with every battery based on how old it is and the quality. These batteries seem to be low quality and it is possible you battery could of sat on a shelf for a year before 3DR purchased them. Expect to lose about 5-10% of rated capacity a year unless you store them with a storage charge in a fridge (not freezer) in between long gaps of use. Then you can expect to see only a couple percent year drop. Obviously the number of cycles and how hard you use them plays into it as well. With the battery fail safe set to 10.5v there is still some charge left. It should be enough to land with a little reserve for safety. Draining the entire capacity of the battery, or close to it, will shorten its lifespan. The problem we are seeing is the rate of voltage drop once the battery hits 10.5v. Within 30 seconds the voltage will drop below 9v, which is hard on the battery, will shorten its life span, and risk the copter falling out of the sky at any moment. Other batteries we tested drop to about 10.3v in the same amount of time.

Well you got me curious so I looked back through logs and mine also show a very rapid voltage drop once around the 10.5V range. Quickly dropping to 9V. This rapid drop has also caused for some exciting falls out of the sky from 10-15m when I still thought I had 20-30% remaining.

I’ve never looked that closely at the voltage before, but I also noticed that after it is on the ground the voltage slowly comes back up to around 11V. So when I put it back on the chargers it’s as if nothing crazy happened. Which is probably why I haven’t looked into the voltage in detail before.

I think I’ll get me some Turnigy’s. I fly Turnigy’s in my planes and I’ve never had problems with them.

James

[quote=“MrRocketman”]Well you got me curious so I looked back through logs and mine also show a very rapid voltage drop once around the 10.5V range. Quickly dropping to 9V. This rapid drop has also caused for some exciting falls out of the sky from 10-15m when I still thought I had 20-30% remaining.

I’ve never looked that closely at the voltage before, but I also noticed that after it is on the ground the voltage slowly comes back up to around 11V. So when I put it back on the chargers it’s as if nothing crazy happened. Which is probably why I haven’t looked into the voltage in detail before.

I think I’ll get me some Turnigy’s. I fly Turnigy’s in my planes and I’ve never had problems with them.

James[/quote]

We’ve had good luck with Turnigy in the Iris, 18min in loiter without a gimbal. Still looking for the highest capicity/lightest battery that will work well for the Iris. Even testing some cheap batteries there has been a much greater reserve for landing compared to the stock batts. I have a feeling this is going to give a lot of people problems when they expect to be able to safely land once it hits 10.5v on stock batteries. It might be a good idea to bump up the failsafe voltage to 10.6 or 10.7 when using the stock battery.

I’m facing similar issues. Also flying with 2x stock 3DR batteries and 4x Turnigy 3600mAh 3S 30C. The stock batteries appear to drop the voltage extremely fast once they hit a certain threshold.

In one case that threshold appears to be well over 10.5 V for the pack: Telemetry was telling me that I had about 30% left, only 2-3 seconds later the battery failsafe kicked in and landed IRIS on the spot, while the light was flashing yellow indicating low battery.

What’s weird: Going through the logs I can’t see that the voltage ever dropped under 10.8 V for the pack.

Sitting in a loiter yesterday testing my setup with the gimbal it did not initiate a failsafe until about 10.3. I even checked the setting in the failsafe tab to make sure it was set to 10.5 while it was hovering to make sure it was correct. I went back and verified the voltage it kicked in on the dataflash log. I’m not sure if there a time buffer before it kicks in so if it sees voltage jumping above and below 10.5 it doesn’t kick in right away. Either way I am going to bump my failsafe to 10.6 or 10.7 to get an extra minute of reserve flight time.

Have a look at copter.ardupilot.com/wiki/batter … y-Failsafe.
It states that the Battery Failsafe will only kick in after the voltage has dropped below the configurable threshold for more than 10 sec.

[quote=“kangajump”]Have a look at copter.ardupilot.com/wiki/batter … y-Failsafe.
It states that the Battery Failsafe will only kick in after the voltage has dropped below the configurable threshold for more than 10 sec.[/quote]

Thanks! I figured that much just never looked it up.

I stumbled over something interesting: Here is the voltage curve from a flight that KFayal did, before crashing his IRIS in a subsequent flight:

[attachment=0]Flight17_Battery.png[/attachment]

Look at the orange box I drew over it: After the Battery Failsafe kicked in at 10.5V the IRIS initiated a RTL sequence. But the voltage thereafter dropped very quickly. In KFayal’s case even below the safe minimum voltage of 3V per cell (9V total).

But keep in mind that the default IRIS parameter (see here: copter.ardupilot.com/wiki/arduco … ATT_ENABLE) call for “Land” as Battery Failsafe action and not “RTL”. Would IRIS have landed right away in the flight above instead of taking almost a minute to complete the RTL, the LiPo might still be OK today.

there’s nothing safe about 3v/cell , - the battery cannot sustain any decent current by then.
3V/cell is fine to prevent deep discharge, but not in a multirotor in the air.
You cannot expect much flight time left when below 3.4v

Speaking of, what have you guys tested as far as bigger batteries??

I found this thread on another forum: rcgroups.com/forums/showpost … stcount=43

They got a Zippy 5000mAH 3S li-po to fit apparently…

hobbyking.com/hobbyking/stor … p_20c.html

Thoughts? Drawbacks?

I use Zippy for my RC cars (Traxxas e-REVO) and they work great, no problems!

Also, can I use my Turnigy charger on the stock li-po 3S batteries? It has a balancer port.

Agree that with 3v/cell you shouldn’t be in the air anymore. What I meant with my previous comment, was that below 3v/cell, the LiPo is permanently damaged.

Also agree with your other comment about 3.4v per cell as lower bound by when you want to be on the ground. That’s why I would highly recommend that the Battery Failsafe at 10.5V be a LAND and not RTL. At this point you don’t have enough juice for a RTL.

@IPvFletch
I use the 3500mAh Zippy Flightmax without problems. Only drawback: They come with 4mm bullet connectors. As I don’t want to revive my poor soldering skills on the rather thick discharge leads, I’m using adapter cables for the XT60 connector of the IRIS. That ends up being quite a bit of cables that you need to cram into the battery door.
The 5000mAh LiPo is a bit longer than the 3500mAh and you probably won’t be able to use an adapter cable and close the battery door. So you will most likely need to change the discharge lead adapter as described in the post that you posted.
If you go down this path, let us know what flight tine you can get out of IRIS.

I haven’t yet taken a look at that thread but that is a heavy battery. I am using a 3s 4500 that only ways 278grams. That 5000 you posted weighs 400! I don’t think that would work to well with a gimbal. Probably much higher amp draw in a hover and the motors are probably going to vet toasty. With my 4500 I get 10 minutes with a gimbal, 400mw 5.8 vtx, osd, etc. And the motors get pretty warm.

What brand 4500 3s battery are you using. The lightest 4500 that I can find so far is around 375gms. Any fitment issues with it?

@cctaylor410 yes what 4500mAh battery did you get, please post up a link, thanks!!

Not sure I want to give away all my secrets… :slight_smile:
hobbyking.com/hobbyking/sto … ouse_.html

They fit well but are kinda long. They just barely fit with the LED in the stock location. Speaking of which I cannot believe how tight that cable is. I already replaced it with a longer one. Will likely just move the LED all together.