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Old September 14th 20, 09:38 PM posted to rec.aviation.soaring
Matthew Scutter
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Posts: 42
Default FES underpowered for 18m ship?

On Monday, September 14, 2020 at 10:07:18 PM UTC+2, wrote:
On Monday, September 14, 2020 at 3:52:25 PM UTC-4, Mana wrote:
...the whole point of a "turbo" is to be able to regain altitude :-)


Right, but many have extremely slow climb, especially in high/hot locales..
There electric of course doesn't loose much efficiency,
but batteries/motor may suffer.

Antares at Uvalde required low power settings and could only launch
to low altitude before battery temp hit max.
It could be that the pilot in question used FES regularly
during his flights and found himself with battery low towards the end....
I'll report if I'm able to reach him.

That would be most helpful, Thanks!

PS: Does FES motor ever overheat (again especially in hot locales)??


BTW battery low = lower voltage, so for same output power to the motor you need more amps, hence the battery warms faster (P=U*I = R*I*I).

Right, but output power is continually coming down as the voltage comes down as it seems amps stay more or less constant or decrease.
I only have a tenuous understanding of electronics and battery chemistry, but I'm told because the FES uses pouch cells rather than cylindrical cells the internal resistance is much lower, which would explain why the battery doesn't seem to meaningfully heat. I have not seen my batteries get above 25c.

I'll be flying it in Australia later this year so I'll return with my experience on motor temperatures. So far in Europe it seems to plateau around 55c at high power. When I asked Luka about Australia, he seemed to think it wouldn't be an issue and told me there was a very large margin of safety on both the motor and controller temperature. Theoretically if you did manage to overheat it though, you could demagnetize the permanent magnets.