SP140 Battery Cycles / Lifespan versus Cost

Power System
#1

Hi folks

Referencing this page: https://openppg.com/compare-top-electric-and-gas-paramotors/

And then looking at the specifications for the SP140 battery cells: https://cdn.shopify.com/s/files/1/0697/3395/files/samsung-40t-datasheet.pdf?6001754416888422053

  • What is the expected lifespan of a battery when determining the SP140 ‘cost per 100 hours’ of $54?
  • At what level of capacity loss do you consider the battery to be ‘spent’ and in need of replacement?

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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?

Open to everyone’s thoughts on this

Thanks
James

1 Like
#2

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.

#3

1000 cycles?

#4

100 ! no 1000

1000cycles is only possible at 1-2 A per cell.

#5

Yeah I didn’t read the whole sentence. It’s early in the morning here. :blush:

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.

#6

how many 6 S or 7 S bonka packs you fly? 2, 4, 6 or 8 packs

#7

Four. Planning to add four more in the spring or earlier. Also I generally charge them the morning before I fly to minimize storage at full charge.

#8

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.

#9

I found this website a few months ago.

https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

It has a lot of good information and I feel it may be useful for anyone trying to extend the lifespan of their batteries.

#10

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.

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#11

That great, glad to hear it and thanks everyone for answering.