Looking forward for the telemetry data from the Batch4’s!
Meanwhile here is the average watt usage from data I found here:
Is the pilotweight here the systemweight or the naked pilot without anything?
2, 4 or 6 packs? And what are the %??
Pilot weight = naked pilot
2, 4 or 6 packs is irrelevant because the wattage use is not changing.
Amps and Volts change but not watts.
The percentage is only there to display that weight and average watts is not linear.
The heavier you are you loose less but the lighter you are you gain a lot.
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I think my calculations are quite accurate. The fact is we use way too much watts.
A lot depends on your weight/size and sink rate of your glider…
Hopefully with the changes to my Batch4 I will reach around 5200 watts even with
95kg…
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hello, I would like to tell you something to calculate the flight time: batteries have a nominal capacity that is usable at a discharge of 0.1 C when the battery is new and the ambient temperature is about 25 degrees Celsius. this is a simple example: in the ideal case, a 10 Ah battery can deliver about 9.5 Ah without great stress. as soon as the usual use comes, such as a level flight, only about 8.5 Ah are available. as soon as you are fully loaded eg. on the way up. it is only 7.5 -8 Ah that are usable. if you have connected a telemetrics you will notice the following: you loaded the battery medium and then read from the exactly 8 Ah were consumed. everything OK. but when you recharge the battery, the charger shows 9.5 Ah as an example. what’s wrong now? everyone is right! The capacity that has “disappeared” has been transformed into heat that heats the battery. the battery emits permant parts of this heat to the environment. you can calculate it exactly in terms of heat output due to the mass and surface of the battery. it will be pretty much the difference. (a small part is also the charge loss performance). I would like to say that to calculate the flight time best 80% of the battery capacity can be used as a usable power. I myself only expect 70% because I do not discharge my batteries until the end to get a high number of cycles. (my oldest batteries are 5 years old and as good as new / sony vtc series 5 and 6).
to set the flight time then in real values are also facts to note. as an an example. in the level you need 5 kw. in the light climb 10 kw. in full throttle climb 15 kw. that means if I give 2 minutes full throttle at the start, I need as much energy as usual 6 min level flight. I use a lot of climbing and mid-climb I must also take into account that the battery as previously told can not deliver as much total as in the constant level flight. This additionally shortens the flight time. In addition, this is due to the higher angle of attack, the efficiency of the wing decreases. that simply explains: to calculate the flight time always subtract from the purely computational time 2 -3 minutes for climb, losses due to wind, too much brake on the wing at the curve flight etc. Conclusion is simply no matter which system e-ppg one flies , between mathematical values and reality, there is a big difference. If you take this into account and calculate the losses you can calculate the flight time very accurately.
Yes, I agree generally what you said. For example the flight time for the 85kg pilot is from a member who was flying 100 times in one year.
My thoughts are more how can we change this and use closer to 100% battery capacity… My ideas are more related to LiPo batteries.
One way to look is why we generate so much battery waste heat. It is not only at full throttle! Since the ESC’s work even more between 60 - 90 % throttle and switching on and off. When it is On it presents a near short to the battery, causing the battery to try to supply very high current. But batteries have internal resistance so the high current will cause the battery output voltage to drop significantly. What happens at high current flow is the ability to sustain the power demand and thus the Internal Resistance goes up.
This means that the needed Watts is based on Volts x Amps. Because the IR increases causes a greater voltage drop - the amps goes up to compensate. This in turn raises cell temperature which then raises IR. Because Amps are compensating - this means the capacity is drained faster.
This gives the appearance of reduced capacity where in fact it has not - its the rate in amps it is being used.
The same applies when Lipo batteries are aging>
The only time capacity does change - is physical damage / change in the cell itself.
Generally LiPo batteries do not lose capacity - but loses the ability to deliver good performance of duty.
Loss of capacity :
- Physical damage by user
- Chemical degradation
- Electrode failure or reduced effective surface area causing poor ion transfer
for apparent loss of capacity far more relevant here :
- Poor charging or faulty charger
- Increased internal Resistance causing shorter run time
- Faulty connections causing high resistance
One of my ideas is to use bigger capacitor banks between batteries and ESC’s>
The capacitors operate as buffers between the battery and the ESC. The ESC switches on and off at a high rate. When it is On it presents a near short to the battery, causing the battery to try to supply very high current. But batteries have internal resistance so the high current will cause the battery output voltage to drop significantly. The capacitors are there to smooth out the current required from the battery. Capacitors can discharge very rapidly at very high currents. The battery charges the capacitor when the ESC is off allowing the battery to supply current at a lower rate.
I will use 22160u Capacitors between batteries and ESC’s to decrease the amps draw as well split the power supply since we have 4 motors and use the shortest possible wiring between batteries and ESC’s. I hope this will help.
Our Lipo’s have 1 - 2 mohms resistance and I think if you have one cell with a higher resistance than 4 mohms you have unfortunately to replace the whole pack. The far greater problem we have with Lipo’s is that if one cell discharges faster we have to stop flying even when the other 35 cells still have capacity.
In the past the active balancer which where available would balance if the difference is 0.1V - this was not
practical for Lipo’s since this is already 15% of the capacity lost. The newest generation of active balancer uses capacitors and balance at a difference at 0.03 V. Next winter I will experiment with this balancer and
maybe this could bring Lipo battery users closer to 100% capacity use.
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you can do a test with eg. strong light bulbs. you will still be able to use only 80% of the lipo. internal heating can not be prevented even with capacitors. lamps have a constant discharge. Nevertheless, the lipo gets warm during operation. but it is true with small esc it makes sense to use capacitors when the cables are long. this reduces the high voltage that can occur.
Just for fun I calculated the flight times from the Paracell single prop ePPG:
The 55 minutes number is from the video where Javier Hernández is flying real 55 minutes, his weight is
67kg. The 85 kilo pilot number is from the german test magazine.
The 75 Ah 14S battery would be the equal to a 88 Ah 12S battery…
The single prop uses 22-27 % less watts which translates to 10-12 minutes longer flight times than
the OpenPPG with 4 motors.
hello, on 12.10. In 2019, together with two friends who accompanied me with their gasoline engine, I flew exactly 1 hour 17 minutes and 17 seconds in the level. exactly 104 Ah from my 15 series li-ion system were consumed. at the airfield EDPD in Germany. It was in the evening without thermals. All data was recorded. IGC, KLM and the drive data. 6 gopros have filmed. There will be videos in the coming weeks. It is not an e-ppg the sale is intended. I’m interested in showing how highly efficient a system of motor- esc adaptation and, above all, the propeller can be. the frame was intentionally selected classic without tuning the air resistance. my weight is 86 kg. takoff all includet with the wing and rescue system =150kg.
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Yesterday with 4 Bonka batteries I flew 24 minutes. When I landed I still had 17% power left. The flying conditions were getting decreasingly stable with my wing having tip collapses, so I set it down. As I’ve stated earlier, I fly an older Axis Pluto wing so it isn’t the most efficient. I feel that under good conditions I should be able to reach 28-30 minutes, which is about the amount of time I usually fly my gas powered ppg. I’ll give it a try next with a sunset flight in stable weather conditions.
For 4 Bonkas and older wing - sounds good!
Based on what I see from battery development - might be 3 years before we see a decent increase in battery capacity at the hobby level.
Cheers