Discussion K2 Energy Solutions

[everydayflyer]

Steve (BattlePacks.Com) started a Thread here on these earlier but I wanted my own.

He was nice enough to supply these cells for my use / testing. I elected to build two 4S packs so that I could run single 4S in my Foamies and duel as 4S2P in my Extra 300 SHP.

I will be uing my CP10 for charging as it provides some rather nice charge graphs and data.

Al 8 cell read 3.27 volts. Cells solder nicely with a 40watt iron(chisel tip)63/37 solder and just a touch of solder paste. I used 16 gauge< Edit / correction 14 ga.> wire which is perhaps mariginal but 12 gauge would have added weight and they are already heavy for a foamie.The packs weigh 6.3 oz. each with 4 3/4" power leads , PQ/Hyp. balancing pigtails,and Dean Ultra connectors.

Specs. list standard charge rate 1.2A / Max. 2.4A . Well if they can not stand atleast 5A then so be it.


Photos of pack(s) here.


5-26 Added a logged K24S2P 2500 Extra 300 SHP flight.
Type on graph Ke should be K2.
Charles

[everydayflyer]

I removed part of the cardboard sleeves to see if it would help reduce heating. Beware that it is possible to cause a direct short with the cells negatives so exposed.
Cell IRs hard to read in photo so they are: 11.0 / 11.9 / 11.5 / 10.6 this was after the first charge cell at 80F.
first charge was at 5A.

Second charge at 10A. Cells reached 105F ,ambient 78F.
IRs 9.0 / 8.8 / 9.2 / 8.7 , 22:55 on Cell Pro 10

Can you say pucker factor? I was either very brave or very foolish and flew my Extra 300 with a 4S 2500 (CID) packs. Now the CID is suppose to be good for 50 amps. and I barely exceeded that and only briefly but.........
All's well that ends well but I do not plan on making a habit of this. I will feel much better when the non CID cells arrive. These cells made a bit more power than the 4S2P2500 pack(s) and are a bit lighter also 12.2 versus 13.7 oz.
FYI Same setup produces 650 watt on 4S A123 2300,960watts on 5S A123 2300 and are you ready for this 1112 watts on 4S 25C 3300 LiPoly.

As a side note my Extra has 445 flights on it now.

Power setup Scorpion 3026-10 , CC Phoenix 60 A ESC, Dimension Engineering Sport BEC, APC 12X8E prop. AUW 3 Lbs.


Charles

[batman]

Thanks for the testing data, Charles, and to Steve for supplying the cells. It doesn't look like they will be the equal of A123s but perhaps for the price a worthy sport substitute? I guess we will find out as the testing progresses.

[everydayflyer]

It is far to early to reach any conclusions IMO. Steve's Dsch. Graphs look treally good to me and is the reason I was interested in testing these. Some other LiFePO cells I have tested were not nearly as good.

First few cycles on a pack just show that the pack needs cycling. I expect to see the IRs drop and capacity improve. At less than 4C there is not enough heating to get cells to ideal discharge temps. and I stil do not feel that constant rate discharges make much testing sense for our applications. There has / had been talk in the past of a programable discharger capable of some serious amps. but non were ever marketed to the hobbiest that I am aware off. If I had the ambition I would do it myself as it is really fairly simple.

One large cheap BL motor and ESC, a programable servo tester,a data logger and battery to be tested.


From long ago a post by one of the original premerie testers.

http://www.rcgroups.com/forums/showt...highlight=test

Charles

[Ken Myers]

Still waiting on getting some to put into practical, everyday use. I'll be able to do a direct comparison, flight to flight, using the Son of Swallow.

[PeteB]

Originally Posted by everydayflyer

One large cheap BL motor and ESC, a programable servo tester,a data logger and battery to be tested.

Charles

The Medusa Power Analyzer Pro has the ability to create custom ESC output waveforms and play them back all while capturing the data on the PAP.

[everydayflyer]

First flight om new pack in my 3D HobbyShop extra 300 SHP 47" version.

I have 437 flights on this plane so have a very good feeling for available power with different batteries. I have flown it with 4S and 5S A123 2300s, 4S2P VPX 1100s,A123 4S 2300 and 1100 in parallel and even with a 4S 3300 LiPoly.

Flying with the K24S2P (2500) power felt real good. Not quite as strong as with 4S A123 2300 but mighty close.It will do and sport / pattern manuver at 60% Throttle or less. WOT climp / punch outs wery very strong. The extra 2 ounces over a 4SA123 2300 was not noticeable.
Flew my normal 5 1/2 min. flights and wheels down at 6 min. I recharged it as a Single pack(8S) on CP10 at 5Amps. and here is the shocker, 915 mAh in 21:54. That is a total of 1850 mAh and for me that is low and I was not trying to take it easy on the battery. Battery was 112F after the flight and ambient was low 80s. Was planing on several more flights but a nasty thunder storm changed my plans.


Charles

[sjslhill]

Nice work! Ken, the 2500's are the CID versions. I will be sending you and Charles some Non/CID versions when they arrive in a week or so.

[everydayflyer]

these 2500's are the CID versions

Just to help prevent confusion.

Not in this thread ,well atleast not up to this point. Cells I have tested / posted in this thread are the 1250 mAh ones. Pack tested is two 4S 1250 in parallel.



Charles

[foamiesrfun]

I just happened to run into this thread, These sound good.

Have you tryed a single 4 cell in the Foamy 540 yet? I would love to try a 4 cell on my profile edge. They charge the same as reg 1100's right? if your calculations are correct from what you said other day then these packs are same weight at the 1100's and that means longer flight times.

I realize someone needs some long time testing to see how they will hold up.
EDIT: Cause I do not read correctly, I thought you said need balancing, but you said cycling. Sorry Steve.

[sjslhill]

Charles,

I read everything again, did you state that they needed balancing? All I could find was cycling. This would be good to know, do they get out of balance?

thanks,
Steve

Originally Posted by foamiesrfun

I just happened to run into this thread, These sound good.

Have you tryed a single 4 cell in the Foamy 540 yet? I would love to try a 4 cell on my profile edge. They charge the same as reg 1100's right? if your calculations are correct from what you said other day then these packs are same weight at the 1100's and that means longer flight times.

I realize someone needs some long time testing to see how they will hold up and you said they do need balancing, well the cell pro 4 does good balancing charging.

[kgfly]

here is the shocker, 915 mAh in 21:54. That is a total of 1850 mAh and for me that is low

I must be a bit thick but I don't get quite what you are saying ? The recharge was 915mAh so where does 1850 come from? Was it that you charged the two 4S packs separately, one on each half of the CP10, so the total was 1830mAh for the 4s2p pack ?

When you say it was shockingly low, do you mean a low total mAh usage for the flight profile or low performance of the batteries ?

Sorry, just seeking to understand?

[everydayflyer]

Charged the two packs as a single on the CP10 so yes charger saw it as an 8S pack which means 915 mAh into each pack for total of 1850.

Low as in I would have expected flight to have used over 2000 mAh most likely closer to 2100. Power was that good..

Charles

[kgfly]

Thank you for the clarification Charles. I guess the low mAh usage correlates with the static tests showing the cells holding higher voltage at moderate load. Encouraging results so far

[everydayflyer]

Originally Posted by sjslhill

Charles,

I read everything again, did you state that they needed balancing? All I could find was cycling. This would be good to know, do they get out of balance?

thanks,
Steve

Steve see third attachment in first post. Note cell #4 was a bit lower than the rest. These cells seem to behave like A123s in that they need some cycling to get them to form.

I flew each pack seperately on one of my Foamies(Blue FanFold Edge 540) this evening. I charged them with parallel power adapter and parallel balancing Y- harness. Nine minute flight on each pack.

Charged at 10A (5A per pack) 2160 mAh and cells in pairs are 3.656 / 3.634 / 3.632 / 3.513 so cell #4 in pack #1 is draging down cell #4 in pack #1 due to be paralleled. Guess I willl go back to split packs for charging / balancing until that one cell settles down or not.
Reconnected as single pack and charged at 5A cell #4 is now at 3.400 and all others at 3.413. I expect by the time thay have 10-15 cycles ob them they will stay matched. I have ran into this on a lot of my A123 packs.

FYI I had one 4S A123 in a SPT (no taps) dump on me two mintues early or approx. 2/3 into a normal flight. Ever since then I do not fly A123s without balancing leads.IMO overcharging them slightly helps keep them in balance however charger manufactires do not want to go past 3.65 per cell. The 3S pack which I Zip charge to 3.85 per cell is always in near perfect balance. It gets charged at a 20 amp. average and has 458 flights on it.

Guess I should remind everyone that I am charging at 4C which is 4X recomended charge rate and 2X max. charge rate. My logic here is that if they take longer to charge than LiPolys then they lose part of their appeal atleast to me they do. Even at these rates it takes me longer than A123s.


Update: After setting for one hour cells at
3.384 / 3.386 / 3.387 / 3.350 / 3.393 / 3.394 / 3.397 / 3.398 so cell #4 lowest and cell #8 is highest and extreme inbvalance is 0.048 . If you took out cell #4 next lowest is #1 and inbalance would be 0.014.

Once again this is nothing to be concern about. fact is the total difference is most likely less than 10 mAh.


Charles