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#41
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Advice on motor glider wanted - FES - Jet - Engine
On Tuesday, January 10, 2017 at 8:50:49 AM UTC-8, wrote:
...Which was it, over-temperature, or under-voltage? These are two very different things. Not necessarily. I=V/R says that as the battery voltage goes down, the amperage required for specific power level is greater. So when you have a computer-controlled system trying to maintain a commanded power level by regulating current upwards, you can get a situation where low voltage is the direct cause of overheating of specific parts of the system. Full disclosu I'm not an FES expert, but I am an FES reseller. --Bob K. |
#42
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Advice on motor glider wanted - FES - Jet - Engine
On Tuesday, January 10, 2017 at 10:50:49 AM UTC-6, wrote:
Thanks for the additional detail, CJ. The fact that the motor was run previously in the flight changes the picture significantly. However, it's still not clear why the pilot had to shut down the motor. In your original post, you said the battery was overheating, but the incident report says "battery power was low", which suggests the battery voltage had reached it's minimum. Which was it, over-temperature, or under-voltage? These are two very different things. If it was low voltage, then most likely the battery power was simply exhausted. If it was overheating, that suggests a failure of some sort. An OAT of 86F is not extreme, so it would be surprising to me if the battery overheated. Does the FES have any known limitations on motor run-time? My assumption was that it could safely be run continuously until the battery was empty. I am also a fan of FES and am considering purchasing a sailplane equipped with it. I hope it's not true that the battery could overheat under such seemingly normal operating conditions. My experience self launching the Silent 2 Electro is that Battery temperature has never been an issue. I have once or twice gotten a yellow warning for the motor temp when launching in Uvalde and Kansas on 100ish degF days. Slightly "throttling back" cured that with no issue. Finding a thermal helps a lot too. The power consumption when cruising level is very low and motor temps have never been a problem at all when i've had to cruise on hot days. One of those days was a fairly long cruise in Lithuania where I ran the motor for about 35 minutes: http://www.onlinecontest.org/olc-2.0...htId=495576510 |
#43
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Advice on motor glider wanted - FES - Jet - Engine
The bottom line: Did the FES overheat before the battery was exhausted? CJ, can you give us an answer?
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#44
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Advice on motor glider wanted - FES - Jet - Engine
Hi Ben,
Sometimes work has to come befor gliding (and RAS). An abhorrent thought, I know I apologize for the ambiguity but battery temperature leading to shutdown was the reason given to me by an individual involved in the incident review. However, that's not to say the situation wasn't misunderstood. Thus, the only way to be sure is to ask the pilot himself which I'm happy to do but that will take time as we're not expected to catch up for a while. If you reply with the portion of your email address that's between the 'hir' and the @ I'll email you his response. FES are very open with their documentation. Have you reviewed their manuals? Available at http://www.front-electric-sustainer.com/download.php , they specify the temperature limitations for motor and battery, among others. Note that the level to shutdown the system to prevent battery damage occurs prior to battery exhaustion. CJ |
#45
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Advice on motor glider wanted - FES - Jet - Engine
Thanks, CJ. The FCU manual states that temperature is monitored for each battery pack, the motor, and motor controller. It's possible any one of them overheated. There's no rush, but if you could get more detail from the pilot, that would be great. Please post it here so others can benefit as well.
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