Hi Martin, i re-read about the continuous power and what you said about : in level flight..
If you run the motor at a needed 30kw of power and you read a 30 amp with your 35kw batt pack : so what is the flight duration with like only 2 takeoff ? (no thermaling.. engine running all time)
Do you also base the calc on the prop low efficiency and always with the 30min flight reserve ( as per regulation) ?
thanks for precision
Hi!
Well.... I summary my experience.
Motor is designed for 80 kW be we limited max, power to 60 kW because Phoenix really doesn´t need more (maybe except aerotowing).
Battery has nominal Voltage 345 V. Max. voltage 398 V.
For TakeOff I need +-160 Amps, for 30 kW climb I need +-80 Amps and for horizontal flight I need +-30 Amps.
You can see it here:
I can use 60 kW for max. 3 minutes, but usually I reduce 60 kW earlier and I continue to climb at 25-30 kW.
During level flight I use 12 kW at speed 120-130 km/h.
I really take care of batteries so typically I don´t cross 2 hours flights and I land with min. 30% reserve.
In Denmark I did 10 takeoffs / 1x recharge with pilots interested to test electric Phoenix. In this case I typically climb to 300-400 m and than I fly rest or circuit with no power.
I will now repeat myself, but I beleive that (at least in EU) make more sense to install smaler battery (20-25 kWh) and install to airplane also 10-15 kW charger. Here is no net of chargers and make no sense to wait till chargers are available. So to make electric airplane independent is etter to decrease endurance to +-90 min with reserve but with large advantage to recharge everywhere. In EU are 220 V or 400 V sockets on nearly all airfields.
In US (maybe also in Canada) is situation different.
I don´t know what is max. power available on typical airport. If I remember well it is typically 1 phase 110-120 V and 15 Amps. Much better would be to use 3 phase (as we do - 400 V / 16 or 32 Amps).
I beleive that key is to use variable pitch prop to keep efficiency of motor at 90%. It will increase efficiency of whole system + it will help to cool down the motor. But this has to be done automatically
As battery capacity is limited is important to "play" with details. Every % is important.
If I see 12 kW going from battery it means that Phoenix needs less than 8 kW.
Efficiency numbers I normally use is:
Prop 80%
Motor 85%
Controller 95%
+ something for wiring etc.
So finally you get max. 65% eff. of propulsion.... what a waste of energy
Best regards!
Martin
