It looks like the next generation of Lipo’s will be arriving soon.
(based on my tests)
Are you ready for the possibility of:
>900 flights? 3/10/2016 update: @ 1106 cycles
<20% loss of capacity at 900 cycles?
Basically no loss in IR rating after 900 cycles?
Perhaps no more puffed packs?
Back in early December 2015, I was asked by Hobby King to do another round of testing on a battery line, this time on a new lipo line that they were considering releasing in February or March 2016. My contact was adamant about me not being a shill (I was thinking… I WOULD NEVER). Instead, he insisted that I call it as it is (always do). If they are a flop be honest and say it (I will).
His next email had a picture of the packs and I immediately got excited. Why? They had the word Graphene on the label. He did not mention that yet.
I don’t know how much you know about graphene but this is (may) be the next BIG thing the semiconductor industry (and many others) is waiting on (the semiconductor industry is my 9-5 job).
Graphene has also been known in all industries as being almost impossible to use. Well, up to a few years ago anyhow. Engineers have since figured out how to apply it to many applications but can it be done cost efficiently?
A few weeks later I received some 4S 1300 packs. I frowned some when I looked closely at the shrink wrap around the cells. It was not the typical PVC that I am used to and I resist change. Instead, it resembled the smaller black shrink we use around our wiring. Measurements showed it to be 13 thousandths of an inch thick (.013) and a dull, sorta satin, black. Just like our tube heat shrink. (.010 on my 3/16” heat shrink)
Over a month later I can honestly say that I LOVE THIS SHRINK. It is more resistant to hanger rash too.
I also noticed these carried more weight and were slightly larger than my other 4S 1300 packs. My scale showed these to be .3750 pound / 6oz / 170 grams.
L = 2.93” / 74.4 mm
W = 1.35” / 34.2mm
H = 1.43” / 36.3mm
I have the Wayne Giles IR tool so I tested IR and V of every pack. All came in at 31C to 33C but I have to admit the temps were not verified. True IR testing must be in a lab type environment at 72F for 2-3 hours for the most accurate readings. WOW, that is some low IR.
I charged pack #1 up on my PL8 at 5 amps and all cells sat at 4.20. OK, no biggie, seen that before.
I then set my PL8 to discharge at 30 amps (23C; the most my PL8 would discharge into my lipo source) down to 3.6 volts so it will cut off when the first cell touches 3.6 volts. I began the regenerative discharge into my 7S5P and she held 30 amps all the way down. That is a 2:10 discharge cycle.
I also noticed all cells were within .01 of each other during this discharge. OK, did not expect that one.
Pack temp was 107 but I do not recall ambient though it was around 75F for a high that day. I was expecting more heat.
Next up was another charge and a slow discharge down to 3.0 volts at 1 amp. All packs delivered 1280 to 1290mah; that’s a 1300mah pack in my books.
I now have (are you ready for this) more than 897 cycles on this pack; I call it pack #1. You know the saying “If it’s too good to be true…” This is the real deal guys and gals.
Anyone that knows Lipo’s will ask how the capacity is now after >900 cycles (20 more cycles are running as I type this). Well, a few nights ago I let the pack soak in my 72F house and the IR was 29. That’s right, basically NO LOSS of C rating at cycle 729. Really? Yulp, and the IR has been holding around there the whole time. The worse I had tested at 27C but the pack was at 68F based in my IR thermometer. Too low, I know, but I wanted to fill in my spreadsheet. Remember, IR is directly affected by temperature and it isn’t linear in temperature or between packs.
Next up you should be asking about the true capacity now. Well, are you sitting down yet? At cycle 894, again at a 1 amp draw down to 3.0 volts, I got 1109 out. That is still 85% capacity. Really? We always say a lipo is pretty much gone when we lose 20% capacity. Usually with this loss we have a loss in IR but I have not seen this…yet.
OK… so I abused this pack on one flight in my stock EDF Meteor. Amps stated at 52 and ended up at 47 as the cells neared 3.4. Oh, that was on cycle 504. Really? Pack temp was only a bit higher than my 30 amp discharges and I recorded 127F one minute after my 60 second flight.
I am continuing to run
23C cycle life tests in the coming weeks. If the true capacity drops below 80% but it still dishes out the amps, I will keep going. I will retire this pack when the IR goes up to a point where the amp delivery is worthless. Hopefully I will not be Rip Van Winkle’s age when that happens.
"Graphene 4S 65C 1300 = 175g. Energy density = 4 x 1.3 x 3.7 / 175 = 110Whr/kg"
