According to the datasheet, up to 40% capacity may be lost after 250 cycles. Assuming the pilot only discharges the battery 75% each flight, this gives around 300 hours of flight time prior to the battery capacity being reduced wherein the flight time is only 30-35 minutes.
The only thing I can think of that might affect this is the discharge rate - the datasheet uses a 35A discharge rate and I presume with the high quantity of cells that this will be much lower, which may improve lifespan?
in comparison, the sony vtc 6 a / 21700 / samsung 40 t / 21700 and the molicel 42 p are all pretty much identical. all of them deliver up to 20 A continuous output with good cooling. with a discharge from a mix of 7 A to 20 A, as is common with eppg. (around 4 kw cruising, 5-6 kw fun, up to 10 kw take-off and climb to a safe altitude with a 2 kw/h pack als example in the numbers ). that is, flights are based on many practical flights. I can say that these cells allow up to 200 cycles and remain over 90% capacity. with 300 cycles around 85% is still available. all of this if you discharge to a maximum of 3 V under load. around 15% will then remain in the battery after the flight. if the cells are operated constantly in the range of 12-20 A, 100 cycles are realistic before the battery can only be used as a camping light battery. If the cells are operated between 20 and 25 A, a maximum of 20 cycles is realistic. over 25 A is impossible with eppg in continuous operation! even briefly over + 25 A damages the cells extremely as soon as the temp of 60 degrees celsius is exceeded. Conclusion: if you do everything correctly, 200 cycles are possible without any problems. for most ppg pilots that means 3-4 years of flying fun. if you want to fly more it makes sense to simply buy or build 2 batteries. the values come from 84 practical flights and 620 cell measurements on my battery test bench.
Yeah I didn’t read the whole sentence. It’s early in the morning here.
However, I hope to see 400-500 cycles from my Bonkas. I’m drawing around 20amp/cell for climbing out. Cycling from 4.15V / cell charged and ready, down to 3.7 or 3.8 resting. I’ve got maybe 50 cycles on them now and they feel as good as new.
if you use 4 packs there are 2 S / 2 P configurations. This means that during level flight you take 50 - 60 A from a cell. With a slight climb it is 80 - 100 A. At full throttle it is up to 160 A per cell.
The x4 needs when the wing is big and good and the pilot is not too heavy: at level 100 -120 A, in a slight climb 160 -200A and at full throttle up to 320 A.
from experience in the field of large copters, I know that lipos are in the range of a maximum of 150 cycles and then get worse very quickly. with at least less load than in the x4.
you are doing everything right with storage, storage charges, etc. that is very good! however, the lipo technology has its limits due to the aging process which is much more pronounced than with li ion technology. there is only one exception and that is kokam industrie lipo which have a different chemical composition than hobby lipo.
still to the li ion. if values are given in data sheets from manufacturers, this refers to laboratory measurements of single cells. that means in a pack it is different because each cell would give heat to the other neighboring cell. As a result, the values for the samsung 40 T in the pack with 35 A are completely impossible as long as no liquid cooling is installed around the cells.
that’s not bad news. all 21700 and some 18650 cells have more than enough power for electric flight. there have been hundreds of successful ultarlight and eppg projects worldwide for years.
As bratwurst said also, you can expect many more cycles then 250 to 60%.
As they are using extreme discharge and charging ratings. You will never see anything close those numbers. I have close to 100 hrs one one of my SP140 4kwh battery’s and im still getting around 95% of the original capacity. Even if you were full throttle the whole flight you still wouldn’t be pulling 35A per cell.
it is just like other batteries. when connecting in parallel, all should have the same voltage. e.g. fully charged. then it is easily feasible. you can just do it like that or as it is, for example. geiger or hacker uses a bus plug to connect the packs to one another. so all the data can then be shown on the display. simple standard eppg is also possible without data. Depending on the system, you have to tell the throttle / display that the more capacity is used so that the state of charge is displayed correctly. there are different ways to do this.
I would imagine by the time the pilot reaches 250 hours a newer battery option will be available with more flight time. Anyone who owns one would probably want the new battery anyway is my guess.
Hey Wes, how’s going buddy, haven’t seen you in a dogs life
at 1850$ for the 4kw no taxes – 250hrs – so 7.50$/hr just for the battery alone not including the cost of energy to go in it – you want to make sure you can get as many hrs squeezed out of it as possible
Say for me – lucky to get to 30hrs to 40hrs for a season with the blessing of the weather/wind Gods…
Cheers
Molicel rates the P42A cell with over an 80% capacity retention after 500 cycles if they use a 5 amp charge to 4.2v and a 20 amp discharge all the way down to 2.5v with the room at 23 degree Celsius. The sp140 will be a little more harsh when it comes the temperature, but a lot easier on the charge and discharge rate. My prediction is that if you limited the charge voltage to 4.15v/cell, you could see the sp140 battery get over 750 cycles and 500 hours of real world use. Also you get a $400 discount on a replacement battery if you own an sp140. So I believe battery replacements would come closer to about $3/hr if you go easy on the battery and possibly lower depending on battery operating temperatures, flying style, charger voltage, and discharge voltage.
Also realized that a typical petrol PPG frame only lasts 500 hours anyway as the engine vibration causes the frame to fatigue. Also the engine is toast after about 500 hours and will still require between two to three rebuilds to even get it to that point.
So when you have flown 500 hours, used $250 worth of electricity and you are worrying that you need to replace your $1450 battery(total of $1700), just realized that your friend with a gas PPG who has also flown 500 hours is paying $7,500 to replace his entire paramotor and he has already spent $500 on engine rebuilds and $2000 on fuel(total of $10,000).
Wow. I did not know this. Same issue for aluminum, titanium, or CF frames? I wonder how that new Gravity (monoque plastic fuel tank) frame will hold up?
I would imagine titanium frames would fatigue just like aluminum, but I’m not positive. Not sure on the CF either, but most of those frames have an aluminium base which we know fatigues. Also most carbon paramotors use a clear coat finished so they look cool rather than use a UV protective paint like what is required on structural carbon aircraft components. So I’m not sure how long past 500 hours a CF frame would last anyway with or without the vibration due to their degradation in the sun.
I guess the biggest thing is that most paramotor pilots don’t get their frames to 500 hours because most people don’t actually fly that often or for that long and by the time they start getting close to 500 hours, technology have evolved enough that they replace the entire unit anyway. Although for people who do fly a lot, E-PPG is perfect as it is far cheaper than IC PPG in both the short term and long term.
40 hours a year gets you to the 6 year mark. By then SP40 will be in its third or fourth release. People are going to want the newer battery types anyway. Compared to a 2 stroke ppg engine that I feel is unreliable with that many hours and needs replacing, the cost I think balances out. I had an engine out on a MZ34 and a Rotax 582. My 912 on a fixed wing was great but sold that as I want to drag feet again. Point is I think most people hate 2 strokes if other options exist. I almost got back into ppg when some of the 4 strokes started coming out but their weight made me decide not to. Electric just has so many more benefits than 2 or 4 strokes. Electric is more of just a charge and go fly. Much like flying my drone in terms of work that goes into it before you fly. For me and most people I think they would be happy to have something that is easier in that way. 1,800 for less headaches and being able to just turn it off and glide will attract alot back to the sport.
