|
Post by mike leger on Jul 29, 2018 15:42:42 GMT 1
Hi Matt, 2 weeks ago i performed some approach/landing training so i took of 4 times climbing to an altitude of 400m AGL. So in total i did 1600m. At this point i reached the temperature limit of 60 degC of the battery only having consumed 40Ah until then. When hitting the 60degC limit the battery management system controller reduces the power to enable holding your current altitude. I assume with only one take-off (which consumes the highest energy) you could continuously climb to perhaps 2000m AGL before you overheat the battery. In theory this will be more if you climb in intervals, allowing sufficient time to cool down the battery and this is what happens in practical life if you use your swift as a pure XC machine. Air cooling the battery with an external airflow is not recommended by Geiger (i already asked the same question), since it will generate to high temperature gradients in the battery pack. It is helpful if in Summertime you start with a 'cool' battery. (store the battery in a cool location and place it into the Swift just before flight) Have fun, Rob. Once again, great information Rob. Thanks to you for taking time to answer. Mike Leger
|
|
|
Post by urs häusermann on Jul 29, 2018 20:36:06 GMT 1
Hi Rob,
I am very sorry, but realistically thats not ok. you used 66% and the temperature limit is reached... What about the rest of 15-20 ah? my experience with my swift and one battery says: its not possible to use all the capacity when i have only one battery. a solution is to fly with 2 batteries, combined to a pack of 120 ah. i use this configuration. when i ordered the swift i did not know anything of the problems of the temperature... so the thermal problems are eliminated.
I say: that is not a good possibility which the constructor delivers...
cu urs
|
|
|
Post by mike leger on Jul 30, 2018 18:48:31 GMT 1
Thanks for your input into the discussion Urs. The reason I am asking these questions is that a friend and I (we both have swifts on order) will sometimes need to climb to 1000m and stay there for a while to find good lift at our home soaring location. It would also be nice to have some battery power remaining to help with a return flight if necessary.
I would like to do this with a single battery setup to avoid the extra weight since I weigh about 85kg (je ne suis pas mince:)
Mike Leger
|
|
Rob Van der Poel
Junior Member
Posts: 24
Name / Surname: Rob van der Poel
Main flying location: Region, Country: Luxemburg
Two or three axes controls: Three axes
|
Post by Rob Van der Poel on Jul 30, 2018 22:37:40 GMT 1
Hi Urs,
I agree the single battery is not a solution for permanent motoring. But the swift-E is not a motorized glider but a glider with an auxiliary engine. The 2x60Ah battery solution may solve the overheating issue but will in many cases (pilots above 80kg) exceed the MTOW of the Swift. I think with 32kg of batteries on board the swift will have a hard time climbing in moderate thermal conditions and landing speed will be higher too. Best solution would be to have 2x30Ah batteries weighting no more then the single 60Ah Battery. For me lightweight is the key to performance flying. Good discusions🙂
|
|
|
Post by mike leger on Jul 31, 2018 15:56:42 GMT 1
It would be nice if Geiger would provide input into this discussion regarding batteries. I imagine that they are very busy and may not have time. Does anyone know them (him) well enough to request input?
Mike Leger
|
|
Josef Stellbauer
Junior Member
Posts: 27
Name / Surname: Josef Stellbauer
Main flying location: Region, Country: Hahnweide
Two or three axes controls: Three axes
|
Post by Josef Stellbauer on Jul 31, 2018 22:11:38 GMT 1
Hallo ,ich fliege seit 3 Jahren den Swift E,ca.150 Flüge mit 450 Flugstunden
ich hatte nur 1 mal das Problem das die Batterie 60 grad erreicht hat und keine Funktion mehr hatte (Swift mit Accu stand 2 Stunden in der Sonne)
wichtig wie Rob schon erwähnte Batterie erst kurz vor dem Start in den Swift, wichtig die Batterie ist nur mittel zum Start es macht den Swift nicht zum Motorflugzeug, je schneller ihr Thermik findet um so weniger benötigt ihr die Batterie (das ist die Aufgabe)und deswegen ist es immer wieder spannend. sorry mein englisch ist nicht so gut bitte Google Übersetzer verwenden
|
|
Josef Stellbauer
Junior Member
Posts: 27
Name / Surname: Josef Stellbauer
Main flying location: Region, Country: Hahnweide
Two or three axes controls: Three axes
|
Post by Josef Stellbauer on Jul 31, 2018 22:14:31 GMT 1
Hello, I am flying the Swift E for 3 years, about 150 flights with 450 hours of flight I had only once the problem that the battery has reached 60 degrees and had no more function (Swift with Battery stood for 2 hours in the sun) Important as Rob already mentioned battery just before the start in the Swift, important the battery is only medium to start it does not make the Swift to the airplane, the faster the thermals the less you need the battery (that's the task) and that's why it's always exciting. sorry my English is not so good please use google translator Read more: swiftpilots.freeforums.net/thread/183/new-swift-first-flight-luxembourg?page=2#ixzz5MrwLKLDj
|
|
David Chaumet
New Member
Posts: 9
Name / Surname: David Chaumet
Main flying location: Region, Country: -Serra da Estrela-Portugal
Two or three axes controls: Three axes
|
Post by David Chaumet on Aug 11, 2018 23:13:11 GMT 1
Actually the VTC6 18650 Li-Ion cell from Sony is at the edge of the available techno for our application (best ration safety-capacity-weight-discharge rate) Geiger use it for his 20P 60AH pack and I use it for my E-Swift 2x10P packs (one pack on each main tube cage) 20P mean 20 cell in parallel, so at 230 amps "engine power" = approx 12 kw continuous power, each small cell (diam 18mm* length 65mm) need to provide 11.5 amps; this is huge for so tiny battery and obviously discharge at this rate produces some heat. Here is a diagram of the VTC6 at different discharge rate and the temperature that it reaches; note that is done in the ideal conditions (probably starting at 20 °) for a single cell that can dissipate some heat around it by convection. So imagine your very compact closed pack of 280 cells (14S20P), with no convection possibility, used during a hot summer day and starting working sometime already above 30°: any chance to discharge completely the pack at 230 amps before it reaches the safety temp managed by the BMS (Battery Management System) or Controller So there is some limitations with this technology; high continuous power without heating is possible but has a weight cost (increase the n°of cells p/ex), more weight need more power… and so on… it's a matter of compromise. So we need to be aware, and manage carefully the available power and pack temperatures - Before flying, during sunny hot day don't leave your pack for a long time in your car or swift, exposed to sun or high temps..
- Use full throttle just for take off, then reduce to 10 kw for climbing (2m/s)
- Just use the batteries as needed for catching the first thermal (I rarely use more that 10 Ah, and some time no more that 5 Ah...)
- During long use of the power for climbing, always be aware at the battery temperatures evolution and try to set the used power to not reach the limits
- For "thermal prospect", a fraction of the power in enough (less than 3 kW) to get level flight (at this discharge rate there is any heating pb), so if you have already some comfortable altitude, sometime it is a better option to cruise, that still climbing hard to find a thermal.
|
|
|
Post by mike leger on Aug 12, 2018 2:55:20 GMT 1
Thanks Josef and David for the added information and advice. All of this makes good sense. David I do have couple of additional questions if you don’t mind.
So I assume your 10p packs are 30 amp hours each, is this correct?
Do you think there is an advantage to having two 30 amp hour batteries versus a single 60 ah battery ? I was wondering if the smaller batteries might dissipate the heat more efficiently.
I also have information from Mr. Geiger regarding this subject. He basically gives the same advice. He did provide an excel chart that can be used to estimate battery usage. I tried to post, but I am on holiday right now and have limited computer resources. Robert Twiss also tried to help but he is on holiday too and did not have success either. I will post as soon as possible. Regards, Mike Leger
|
|
|
Post by mike leger on Aug 13, 2018 17:37:19 GMT 1
Below is Mr. Geiger’s response to my questions regarding battery usage. Thanks to him for his input. There is a link to a copy of the spreadsheet below his response. You may have to copy and paste the link into your browser. To change the input parameters (green cells) you might need to download the Google spreadsheet application (I think for iOS devices). Many thanks to Robert Twiss for converting the file and providing the link/location for the file. I hope this all works since I am doing all of the entries from my phone while on holiday. Cheers Dear Mr. Leger, thank you for your interest, for your questions and your meaning about our drive systems. The swift was one of the first electrified aircraft we did 11 years ago with Manfred Ruhmer. Till today a predestinated aircraft for electro, because the energy consumption is very low. To your questions: Attached you find the battery simulation with three examples 1pack, 2 Packs and 1 and a half pack. You can see the also a simplified calculation for the climbing rates and altitudes to reach. Depending on the power you are applying to the drive, the battery will increase the temperature. The algorithms for temperature rising behind is I² * R. This means the current you are applying will increase the temperature in the second power. If you reduce the climbing power (of course there is a lower limit), you can increase the altitude you can reach, with the same thermal result. You can play with the values in the simulation and see the new results. If you want to climb longer, the better choice would be two packs or one and a half pack, or to reduce the climbing power The manual in English and further information you find on our website: www.geigerengineering.de/avionik-elektroantriebssystem/downloadbereich/ best regards, Joachim Geiger docs.google.com/spreadsheets/d/1thzLMStCjQ8m8E0coz1XBv3ZLxcouyVRFJu4Q6PuzeU/edit?usp=sharing
|
|
|
Post by Robert Twiss on Aug 13, 2018 17:46:10 GMT 1
With all this interest in the electric drive alternatives, I will ask Manfred Ruhmer if he is prepared to write a post on this subject and attach the current pricelist.
|
|
|
Post by Robert Twiss on Aug 23, 2018 17:06:33 GMT 1
Here is Manfred' answer, translated into English by me: Hello Robert, I had a look at the posts on the E-Swift and in my opinion especially Rob, Josef, Urs and David got to the heart of the matter. With the current 60 Ah battery, and also the 50 Ah version, you cannot climb at full power until the battery is (almost) empty. Long before that, the Battery Management System will kick in and reduce power or even shut down the engine to prevent damage to the battery. With the current battery technology and the compact, light-weight batteries currently in use unlimited full power is not an option. The Kokam LiPo batteries we used before (40 Ah, 16 Kg) had a lower internal resistance, and no battery temperature problem occurred. With these batteries you could climb under full power until they were almost empty. 1) In summer, the battery temperature could then Rise to about 55 - 60 degrees Celsius. A 60 Ah Kokam battery weighs in at a little over 23,5 Kg, so there is a distinct difference with the current 60 Ah batteries. These weigh 8 Kg less even with their BMS included. Note: true, the battery endures climbing under full power for a long time, but the ESC doesn’t. Especially with warm weather, it heats up quickly under full power and shuts the engine down when the critical level ( 85 °C ) is reached. This can happen after about 3 - 5 minutes! In the E-Swift prototype, I used LiFe 2,3 Ah A123 cells. These had a capacity of at most 20 Ah ( 1 Kw/h at a total weight of 12 kg) and they were arranged in two rows suspended from the main cage tubes. With these batteries, only a climb of 700 M was possible, but thanks to a 5 kw rapid charger they were recharged in 12 - 15 minutes. Because of the division into two smaller batteries, the heat transmission to the environment was rather good, so you could fly intermitently all day long without overheating the battery. Which is what I did mainly in my first trike prototype. The flying time was longer than the charging time. Where do you get that nowadays? Today i still use the A123 cells (the newer version with 2,5 Ah capacity) in my tandem trike also with a total battery capacity of 60 Ah - at the price of a weight of 34 Kg. Here the cells are arranged in cubes which makes for a less good heat loss capacity, so that after a flight I can at most make one rapid recharge. And, at a charging current of 90 Ah that takes 40 minutes.. If someone wants to use the engine a lot and accepts limitations in thermalling and useful load, he could use two 60 Ah batteries as I made for Urs and another Swiss pilot. But then the pilot should be light, the upper limit lying at a pilot weight of about 75 Kg. Just as a reminder: the E-Swift-Light has been designed as a self-starting ultralight sailplane. It has been optimized for soaring, so the engine should only be used as a means for starting and, later in the flight, as an additional security that can help to prevent outlandings. You can find the current price list on Aérianes homepage: www.aeriane.com/products/aircrafts/swift/downloadable-document/The E-version is priced the same as the PAS version. I have recently spoken with Aériane’s Bernard Bleeckx. Swift production will be brought to a higher level, in the expectation that this will shorten delivery times. Also, the E-Swift drive train will in the future be made and built-in by Aériane. Another future project is a solar Swift, with solar cells covering the real area of the wings recharging the battery during thermal flight. So, after a long flight, you could just land with a full battery again..
|
|
|
Post by Robert Twiss on Aug 23, 2018 17:08:30 GMT 1
Und hier noch Manfreds Antwort auf Deutsch:
Hallo Robert,
habe mir die Beiträge über den E-Swift angesehen und vor allem Rob, Josef, Urs, David… haben es auf den Punkt gebracht. Mit dem 60 Ah (aber auch der 50 Ah) ist es nicht möglich mit Volllast zu steigen bis der Akku leer oder fast leer ist. Es kommt unweigerlich zu Rückregelung oder sogar zur Abschaltung durch das BMS. Aber so ist sichergestellt dass der Akku vor Schädigung geschützt ist.
Mit der derzeitigen Zelltechnik und dem erforderlichen kompakten, geringen Gewicht des Akkus ist „Dauervollast“ nicht möglich. Die früher verwendete Kokam Lipos (40 Ah, 16 kg) hatten einen geringeren Innenwiederstand und es kam zu keinem Temp.-Problem. Damit konnte mit Volllast gestiegen werden bis der Akku ziemlich leer war. Im Sommer waren aber auch da dann so um die 55-60 Grad dann zu messen. Ein 60 Ah Kokam wiegt dann schon gute 23,5 kg und man sieht schon den Unterschied zum jetzigen 60 Ah Akku mit BMS. Das sind in etwa 8 kg weniger bei gleicher Kapazität.
Beim Proto E-Swift verwendete ich die LiFe 2,3 Ah A123 Zelle. Allerdings hatten die nur knappe 20 Ah Kapazität (1 Kw/h, 12 kg Gesamtgewicht) und waren in 2 Stangen angeordnet an den Cage-Rohren aufgehängt. Damit waren zwar nur max 700 m Steighöhe möglich aber dank eines 5 kw Schnelladers waren die in 12-15 Minuten wieder geladen. Aufgrund der Stangen Anordnung war auch die Wärmeabfuhr sehr gut und im Prinzip konnte so den ganzen Tag geflogen werden ohne den Akku zu überhitzen. Das machte ich dann speziell im ersten Einsitzer Proto-Trike. Die Flugzeit war etwas länger als die LadezeitJ. Wo gibt es das heute noch?
Auch derzeit verwende ich die A123 Zelle (die neuere Version mit 2,5 Ah) in meinem Tandem Trike auch mit 60 Ah (wiegt aber schon fast 34 kg) . Da ist die Anordnung in Würfelform (2 Packs) und hier ist die Wärmeabfuhr schon schlechter, sodass ich nach einem Flug nur mehr bedingt eine super-schnell-Ladung machen kann. Gut, bei 90 Ah Ladestrom dauert das dann auch schon 40 Minuten…
Wenn jemand viel Motorbetrieb machen will und dabei Abstriche beim Thermikfliegen + Zuladung macht, dann sind 2 x 60 Akkus möglich, wie ich es beim Urs und auch schon früher bei einem anderen Schweizer gemacht habe. Aber der Pilot muß halt leicht sein. Die Obergrenze sollte bei etwa 75 kg Pilotengewicht liegen.
Zur Erinnerung: Der E-Swift-Light ist als eigenstarfähiger Mot-Hängegleiter (UL-Segler) konstruiert worden. In erster Linie ist es ein sehr gutes Soaring Gerät. De Motor sollte wirklich nur als Starthilfe und für unterwegs als Überbrückungs-hilfe (zur Vermeidung von Außenlandungen) verwendet werden.
Die aktuelle Preisliste gibst bei Aeriane auf der HP. Die E-Version kostet gleich viel wie die PAS Version.
Habe vor kurzem mit Bernard von Aeriane gesprochen. Die Produktion vom Swift wird wieder auf ein besseres Niveau gebracht sodass in Zukunft die Lieferzeit kürzer wird. Auch wird der E-Antrieb in Zukunft direkt gleich bei Aeriane gemacht. Als Zukunft Projekt sollte es dann auch eine Solar Version geben. Ich denke mit einem Teil Belegung der Solarzellen im hinteren Bereich des Flügels, welche dann den Flug Akku bei Thermikfliegen wieder nachlädt. Es könnte also sein dass nach einem ausgedehnten Flug mit vollem Akku gelandet wirdJ
Beste Grüße
Manfred
|
|
|
Post by mike leger on Aug 24, 2018 4:07:42 GMT 1
Thanks to Manfred for his input, and to Robert for requesting and translating!
I have run several simulations with the spreadsheet that Mr. Gieger provided. The simulation results agree with what Manfred and other contributors have stated about their real world experiences. Namely, the starting temperature of the battery has a significant effect on how quickly the maximum operating temperature is reached. Also, for a given battery capacity, the power level used for climbing is the major determinant for the rate of temperature increase.
Note that in the data below, I have made basic assumptions and calculations to address the maximum battery operating temperature cutoff, which may or may not be accurate. But these are only simulations anyway, and hopefully the estimated values help with understanding.
In the chart below are results from simulations for a single 60 Ah battery pack. In each case, the climbing power is constant at 10000 watts which per Mr. Geiger’s spreadsheet results in a climb rate of 2.1 m/s. The 10000 watt value seems to be a good compromise to maximize total altitude gained without exceeding the temperature limit of the battery. In these simulations the time climbing is maximized in order to estimate the maximum altitude achievable while maintaining battery temperature below the cutoff (60 C). The “Remaining Sustain Time” is the remaining battery duration at 3000 watts, which is what Mr. Geiger’s spreadsheet indicates is the power required to maintain altitude.
Battery Starting Temp. (C) 15 Climb Duration (Minutes) 10 Max. Altitude (meters) 1260 Remaining Sustain Time (minutes) 29 Battery Starting Temp. (C) 20 Climb Duration (Minutes) 8 Max. Altitude (meters) 1008 Remaining Sustain Time (minutes) 36 Battery Starting Temp. (C) 25 Climb Duration (Minutes) 6 Max. Altitude (meters) 756 Remaining Sustain Time (minutes) 42 Battery Starting Temp. (C) 30 Climb Duration (Minutes) 4 Max. Altitude (meters) 504 Remaining Sustain Time (minutes) 49
These results suggest that a single 60 Ah battery should provide more than enough power to climb to altitudes necessary to find lift while maintaining a good reserve for loitering or help in returning back to the starting location. Note that according to the manual, the lowest battery starting temperature in the simulations (15 C) would have slightly degraded performance (roughly 5%). I assume that this reduction in performance will be quickly rectified as temperature in the battery rises during initial climb.
Simulations with two 60 Ah or one and one-half 60 Ah batteries indicate that climbs to ridiculous altitudes are possible without reaching the battery temperature limit. I would speculate that even if one had to motor for a distance to the soaring area, that it may be possible with these multiple battery pack combinations.
Mike Leger
|
|
|
Post by Michel Paté on Aug 25, 2018 19:22:29 GMT 1
Hi SwiftLight-E pilots,
I fly my SwiftLight-E N° 138 for 1 year and half , and my return on experience is the following:
1°) I fly mainly in flatlands where thermals are not always frequent and very strong , but also in southern Alps where they are frequent and tough. 2°)To climb and find first thermal I usually never use more than 20 to 30 % of the battery power ( which is a 50Ah under 56V), and very often 10%. 3°) The process I use to take off is full power the 100 first meters of climbing then I reduce roughly to 80% the power until finding the first thermal. 4°) With this process I never had over heating of the battery. 5°) Nevertheless I had an overheating of the motor management controler this summer in Aspres ( error 2) . The temperature at take off was 34° celsius (probably 45°C in full sun) ,and I had to climb 800m and run 6km to join the start zone. The error signal occurred at after 700m climb and the motor stops. I glides 2 or 3 minutes , and the airflow at this altitude refresh quickly the controler and I restart the motor to achieve the climb to the start zone.
So after more than 50 flights with the SwiftLight-E I can confirm my way of flying this Ultra Light Glider: 1°) It is not a trike, but a glider with an auxiliary propulsion for take off. 2°) When there is conditions for ultralight glider flying, you have far enough power to catch the first thermal and keep good battery reserve to prevent outlanding. 3°) If no thermal forecast ....go play golf.
Have good flights and fun !
Michel
|
|