Ok, so I filmed in a remote cold location (10-15F ) all day, 6 Hours film time. I was charging 2 at a time like I always do using my generator, power supply, hyperion duo (they were all out in the cold) . Towards the end of the day I start getting 15 seconds of flight on most of the batteries. I get home, discharge all the batteries and charge them all at 1amp. I take one out and test it on the heli, get 5.5 minutes of flight with camera. Don't test any others. I then go on a remote shoot on a snow-covered mountain side. I have handwarmers and all my lipos in an insulated lunchbox. At least 5 of my 7 lipos give me a telemetry warning after 10-15 seconds of flight. Are my lipos bad? Is my charger bad? is my power supply bad? Has anyone had similar issues? Appreciate any help!
How old are the batteries? Does the charger report that the voltage is up to its max (e.g. 16.8V for a 4S bat)? Have you tried doing a bench test with the copter secured in a garage or something where it's warmer and you can test the longevity of the batteries? LiPo batteries do not last forever, and some of your batteries could actually be dying.
Hey Steve! Yes the charger reports that they are full. I haven't tried doing a bench test. I'm guessing they probably are dying, just weird they all died at the same time. Must be that one cold shoot ?
Also, Chris, what's the current situation after the second shoot when you're in an environment that's a bit warmer than your second shoot? Are the batteries now back to giving you a reasonable fight time? Certainly cold is a battery-killer, but I'm surprised to see your report on the mountain side shoot -- it sounds like you were keeping the LiPos warm in the insulated lunchbox. Following on from Steve's line of thought, when you re-charged the batteries after the second shoot, how long it take and how much charge did the Hyperion indicated the batteries accepted (it's one of the menu items if you press the Down key after charging is completed). Andy.
I will check the charge on the hyperion. My telemetry on my receiver reads around 16.3-16.6 on my batteries before a flight.
Chris: A couple of other questions: 1. How on earth did you get through the shoot with batteries giving you 15 seconds of flight time. Ugh. I hate those situations. 2. Do you happen to have any GPX files recorded from these flights? The reason I ask is that I've had situations where the bird takes off and the Graupner MX-20 beeps a low battery warning tone group and then stopped -- but the battery is obviously NOT low because the Cinestar kept flying... I've never figured out what the warning tone was actually for! Andy.
Hey Andy, 1. It was a horrible. I was filming people sledding off of ramps over trees that were on fire. So the takes were quick and I missed many, many jumps. Overall I was not happy with my shots. 2. I don't have GPX files. I do know that the telemetry is telling me the truth. My last shoot (the experience I neglected to share) I was filming ice climbing, started to fly, immediately gave me a warning, but I held it up for too long. Came crashing down from 60 feet as it smashed into pieces as it fell down the frozen water fall. Pretty spectacular crash footage :/ I lost 2 booms, 3 motors, 6 props, tilt pulley and my 16-35mm is no longer functional but the glass is ok. So I know it's telling the truth!
Ouch! That sounds really bad... you say crash footage... implying you have footage of this... that would be interesting to see! Maybe try and do a couple full charges/discharges at room temp and see if that brings them back to life. Also try flying in a warmer area and see what kind of life you get from them. Maybe they are on their way out but the cold is just affecting them more? What kind of batteries are they? Josh
You haven't mentioned the brand of batteries. ?? I've had some give up he ghost with as little as 60 cycles. What is the measured IR? If you say it's about 100 cycles then it could be many more if you haven't been counting. Maybe the cold just set them off.
Josh, I may post the crash footage sometime..... The batteries are the flat quadropower 6200's. Sorry, What is IR?
Thanks for posting that video. Oy vey. If you're consistently working in very cold conditions, the batteries may just go bad after a while. There also could be problems with moisture or other things relating to going from warm to cold and vice versa. I bet the QC guys have some thoughts on the matter, as they seem to do a lot of flying in cold, snowy places. Do you store them in a warm place when they're not in use? I really think you should strap your copter to a large, heavy object (I use my assistant) and run the motors up and watch the current draw and see if you can replicate the problems. I don't know much about batteries, so maybe others can weigh in with their thoughts.
Chris: IR = Internal resistance. It's displayed by some chargers, e.g. Hyperion SuperDuo and gives a general sense of the battery health. Typically you'll see numbers in the 20-40 milli-ohm range. Crash video: My palms are damp. Andy.
I had this happen when I first flew in the cold. A question is how long we're the batteries exposed to the cold before flight? I had the same thing happen when I had the battery on the craft for ten minutes in the cold before start up. I took off and about 15seconds in the flight I immediately landed once I got the bat warning. I thought i had inadvertantly put a used battery back on but realised that it got cold enough on that day to cool down the battery just enough to reduce the electron flow i.e. current due to internal resistance going up. I later found hat I was able to mitigate it by letting the motors rev a high enough rpm too not take off but to allow for the exothermic reaction heat the battery up a bit then I took off and it was fine. I don't know wwhat happens if you charge in the cold, never tried it. I assume it's not good, because the cold temperatures slow the electron flow, that is why you can get a low bat warning on fully charged battery, it is not able too push the current at the potential. There is a give and take relationship. Potential ie voltage will go down conciderably when it is cold because of the change in internal resistance. This is similar to car bats cold cranking amps vs total amps. Even if you store your batteries in a thermal case they can cool pretty rapidly in the temps you mentioned once exposed. I only take the bats out right before stratup on cold days. Hopefully you did not damage them, but if in doubt throw em out. I used the battery temperature loop on my telemetry and I make sure the battery is at least 50 degrees or so before advancing the power to take off. 50 degrees is my own anecdotal number no science behind it. I figure it is 20 above freezing so it is warm enough to not have thermal issues.
Here is some insight about Lipo charging from battery university.com http://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures