I have already submitted all my information to the IRIS Hardware support forum, so I thought I'd share this video with my fellow IRIS owners. I had heard about the IRIS props just stopping but I thought I was immune since I have been having so many good flights. As you will see from the video, the IRIS went down from a pretty good height. Luckily into grass. The Tarot Gimbal does a good job of keeping the camera still even during the fall.
Looks like I'm out a Tarot Gimbal mount, one arm and 4 props because it cratered. The gimbal PCB and motors are all still good. Even the GoPro survived as you will see.
Now I have to figure out how to get my new parts.
Here's the video:
I've had the IRIS shut down completely twice. Once it was at 11.3 volts and then slam. All data stopped in the logs at that time and the Pixhaw quit telemetering. Both times it was when I was using the stock batts. I have a ThunderPro battery that it has never happened with.
Not enough data to prove anything yet just stating some facts. Both times it shut down I was in loiter and about 5 feet from the ground. It could be a problem with loitering so close to the ground?
When you are looking at your logs, are you downloading them from the IRIS with Mission Planner or are you physically taking them from the SDCard inside the PixHawk? If you download them from Mission Planner, it will appear that they just stop, but in reality the logs are getting truncated. That was my exact situation.
You get a much better reading of your logs when you get the .bin files right off of your SD Card. That's why they sent that SDCard adapter with the IRIS.
I discovered the hard way that when LIPO batteries experience too many deep discharges they suddenly drop in voltage like "off a cliff" instead of slowly discharging.
I am retrieving them directly from the card. Don't get me wrong, I have had plenty of successful flights. Those 2 times when it dropped out of the sky it lost comm with the computer, props stopped and it fell but when it hit the ground motors were still trying to run. Lost 3 props on that one. The logs showed desired yaw, pitch and roll going all over place and then data stopped. Battery was at 11.3 when it happened. None of my batteries have been below 9.9 volts but I noticed the Thunder Pro battery I bought has a much flatter discharge curve below 11 volts where the 3dr batts discharge much faster below 11 vdc.
like I said I may have been too low in loiter. I was only about 5 feet off the ground. I had telemetry going both times it died as well. I have many flights where the computer wasn't on (no telemetry ) and have never had any issues.
I'm sure I will learn more about it as I go forward. I'll be doing more flights next weekend. I'm going to fly it around a lot in loiter before I do an auto mission.
So, here is what I take from this. I HAVE to be watching the droid planner to keep an eye on my voltage levels while flying. At first, I thought that the Droid Planner was just a thing you would use if you want to fly autonomously. It appears that flying with the gimbal will require me to NOT be able to rely on the battery failsafe, or I should set the failsafe to a higher voltage than 10.5VDC, maybe 10.75 (unless someone else has a recommendation). The reason is because sometimes I have the IRIS at such a height that it draws down so much current just to maintain the automatic descent.
These are my recommendations to everyone who flies with the gimbal, take it or leave it.
Driodplanner cab be configure to verbally announce your battery voltage every minutes, 30 seconds, 20 seconds etc. After a while you will get used to the discharge rate. In that crash flight I bet you would have noticed the the battery voltage was dropping at an abnormal level. The key is :
Start with a full battery
Always know your voltage and have the bird on the ground before the failsafe is reached. Failsafes are very last resort. They should not be routinely depended on.
do like I did, get a $2 battery monitor/alarm and disable the battery failsafe on IRIS.. These little external devices work perfectly, you will have enough juice to land as soon as you hear the low battery alarm.
I personally think failsafe doesn't work properly, after loosing my APM2.6 (radio signal out of range failsafe was active) and experiencing intermittent low battery failsafe performance on my IRIS, I disabled it completely and have been using the external monitor/alarm on the IRIS and have a piece of mind.
I also experienced that Mission Planner/ IRIS does NOT calculate battery consumption properly - for example after the external battery alarm goes off, Mission planner still displayes around ~20-25% juice left, so don't rely on that either (yes my fully charged battery size and reserve limits are set properly on MP)
Well when it comes to customer service, I called them once and told them I was disappointed with IRIS and wanted to return it. He said "did you read the fine print at the bottom of our web site"
I kept the IRIS, upgraded the FW to RC5, it made a difference.
I also find it very difficult to fasten the props w/o being able to hold the motor body. I have been using a pliers to grab the bottom of the prop shaft - so IRIS fliers make sure your props are fastened properly.
Well sorry for venting here but I hope these will help you and many other IRIS fliers out there.
Thanks Murat. The battery alarm seems like a good idea. I plan to use the stock charge and use this device to check balance across the cells.
I think we need to find a better battery. Carrying anything with weight (like the gimbal) will severely shorten the battery life.
My advice would be, as soon as you find you need to increase throttle to maintain altitude due to low voltage, LAND THE IRIS. At wide open throttle on the quad dyno, I noticed that once the LIPO battery gets down under 11v it can drop to single digits within a few seconds. This may be faster than someone could react and land safely.
The deep or rapid discharge will leave you with a swollen/puffy appearing battery that won't perform very well.
PS: Sorry for your troubles. I hope the repairs aren't too costly.
Joe, thanks for the advice. I've made a determination that despite the simple instructions that are provided to us on how to charge, plug in and watch for "puffy" batteries, I need to become an expert on LIPO battery maintenance - and get all the necessary tools to do so. This charger doesn't seem to be all that is necessary to do it. Like finding a good internal resistance tester, and investing in a better charger than the one that is provided with the IRIS.
Simply looking for a "puffy" battery pack is apparently NOT the only indication apparently that your battery is damaged, as mine are still the same thickness that they were when I bought them, and I'm talking within a 16th of an inch.
So, what do you use for your batteries?
If anyone wants to sell me some M.A.I.L prototypes I'd be willing to test them for you.
To be honest, I'm not sure what I'll use yet. I'm still doing research and haven't decided if I want to invest in in a good LIPO/LIFE charger or try some more exotic batteries.
I found this URL interesting. Not sure how much of these options you could actually buy in the US.