Hi I was on a gig today in coolish but not cold (in Finnish terms at least) weather. The temperature was around +5C. I am using original Movi 4s 2600mAh lipos. The problem was, whenever the Movi was even lightly touched, like when setting focus or aperture from the lens or when accidentally touching ones belly with it, the Movi went limb very easily and needed to be booted. The batteries were fully charged with a good balancing lipo charger. The batteries are good. I checked them with a lipo checker. Also when the Movi went limb, it started flashing one LED. After the boot the Movi was OK for a while, until it went limb again. This happened at least 20 times during a 10 hour shoot. What could be the reason for this? The Movi was well balanced and the camera is Red Epic. I was using the lipo to supply current to a Teradek Clip too via the balance connector but other than that, everything was stock.
Tuukka sounds like weak batteries. Though they might show a full charge they might be worn out and any load saps their strength. Did you try them without the Teradek turned on? Any difference?
The cold affects the performance of lipos. As the temperature goes down the Internal resistnce go up Cooler equals higher IR which causes aditional heating. As temp. go up IR goes down and voltage goes up. I have used 75F as mininum battery temp. for a number of years and I do not drop the hammer on one even at this temperature. Some use the 12 volts coolers / warmers,some use rice bags heated in a micro wave and an insulated food carrier. I keep mine inside and place them where the heater blows on them on the way to the field. I also use a min. number of batteries,charge at 3 to 5C (which helps keep them warm) and block off part of the cooling vents needed during the summer. On flat plate foamies I make a sock out of thin high density foam such as is used for packing / wraping. Below 50F I stay home but that is only because I am retired and can wait a few days for the weather to get better. Charles P.S. - this was posted on a RC group so try to keep the batteries warmer.
Tuukka: Did you happen to notice, when the MōVI went limp, how many of the green LEDs were illuminated? It certainly sounds like voltage sag in cold weather as the other folks have said -- but when that happens it should show in the LEDs. Andy
Hi All We had the same problem a while ago and then we noticed that by rebooting with the same battery the 2 LEDs illuminated. We went to an RC club to check our batteries and there they noticed that 2 of our 6 batteries where not in balance at all after charging with the Freefly charger. We had contact with Darek from the Freely support team and he's sending us a new charger right now ... In our case outside temperature was still 15 degrees celsius so that's 59 degrees F. Kevin
Kevin: Could you provide any additional details, please? For example: Did you happen to make a note of the voltages for each cell when they were in imbalance? Also, what was the total voltage for the LiPo (the sum of the individual cells)? Thanks Andy.
My problem was caused by temperature (+2C) and the fact that Movi uses so little battery that the little stock Movi lipo just gets too cool to supply enough current even around 0C. The solution was to make a wiring harness that supplies the Movi, Red Epic, Redrock FF and Paralinx Arrow+ via a 4s 5000mAh 30 to 40c lipo. This way the battery is used more and it stays within reasonable temperature. In other worlds it does not get too cool. After this (and after insulating the lipo with a "sock" and aluminium foil), the Movi has worked fine in minus 5C.