ive made changes to the charge settings to see if I can slow the degradation of the cell in, 1-7 of the new settings/ d-cc 2.50a to 3.2v
the change in fast charge settings seems to be working, when I first started cycling I was losing about 2.85mah/cycle, I continued to make slight changes and got to about losing 1.85mah/cycle. I didn't think the cell would last 300 cycles but with the new changes im losing 1 mah or less/cycle. I might make 750 cycles with 80% capacity now.
heres cycle 1 charge numbers 3156 mah , discharge #2 3191 mah
heres cycle 49 charge numbers 3153mah, discharge #50 3189 mah
heres cycle 54 charge numbers 3149mah, discharge #55 3185 mah
#100 discharge capacity was 3176 mah
made more changes this is discharge #149, 3184 mah, yes it increased
at cycle 95 I changed the discharge settings to make the battery run warmer, the weather cooled off and the room temperature was 69f, battery temp dropped to 71f for its low and the capacity was suffering so I increased amps, now battery temperatures remain steady between 90f and 75f and capacity is recovering.
it also seems if I can keep the start of charge temperature around 80f/81f I can maintain capacity loss to a minimum but at 82f/83f I start losing.
heres the battery temps at different stages
start of charge 80f
when 2amp charge switches to 3.75amps is 78f
when 3.75ap charge switches to cut-off amps 83f
end of charge 75f and start of discharge 75f
10amp to 7.5amp switch 85f
7.5amp to 5amp switch 90f
5amp to 1.5amp switch 88f
end of discharge 82f
the battery is performing almost too good. im at 3173 mah after 104 discharges. it started at 3191mah. that's only an 18mah loss after 104 cycles or 0.17mah/cycle. im going to do the 0.8amp discharge from 4.2v to 2.5v tomorrow to compare with the original test I performed before cycling to see the capacity and compare.
I think capacity loss is from charging initially at 5amp
heres a capacity test of a different 40T that I was playing with, at 7amp discharge from 4.2v to 3.0 volts the battery temperature would peak at 107f. I thought it was heat that was killing the capacity down around 3.4v to 3.2v but now I think it was the 5amp charge
i made some changes, I want keep atleast 50% of the cells discharge capacity being used at or above 7.5 amps. it raised peak battery temperature to 95f. then I gave the battery a 5 minute rest between charge/discharge/charge heres the new graph and numbers
im testing the battery inside a closed cardboard box with a towel ontop to keep battery temperatures up. I don't open it up.
the other morning I noticed the discharge mah numbers were getting higher??? so I checked the battery temperature on my dmm and all the temperatures had increased by 5f.
I opened the box and the battery had slid up against the side of the cardboard box, just touching the cardboard increased battery temperature to 95f peak and improved the capacity available numbers.
I guess a ghost had moved my box
I moved it back and temperatures dropped 5f and the capacity dropped again
ill do another 4.2v to 2.5v capacity test at cycle 250
I noticed on the charts once I switched the rest time in between charge and discharge from 1 minute to 5 minutes, the at rest voltage dropped from 4.2v to 4.194v at 70 seconds then at 90 seconds it dropped to 4.191v and at 4m50s to 4.190 and discharge starts again at 5 minute mark.
90amps powervelocity 18 get with a muxus 3,000 4t v3 or it fits my Kona kukapu triangle. So thinking of cyclone 3,000 or a lr long block frist gen so 7 yrs old or what motor you suggest ? Buying now as my muxus 150mm wouldn't fit frame. So the battery sould be extra large for it's needs plus copper series buss bars wrapped in nickle.
Ok 90amp BMS continuous and 180 amp peak.
im just looking at running a phaserunner at 60 amps with 4p of 40T and a 15amp charger for fast 1 hour charging.
I was looking at the mxus v3 4t to go with it but the hs3540 that im running seems about the same on grins simulator only lighter. haven't decided which one yet. I like the silence of a DD
I bought a molicel p42a 21700 to test when im done this at same settings.
I made more changes to increase battery temperature, it was also rainy today so I turned on the furnace to warm up the house.
that increased the battery temperatures and the battery seemed to like it. heres the temperatures.
start of discharge 80f/26c, 10/7switch 94f/34c, 7.5/5 switch 100f/38c, 5/1.5 switch 97f/36c, end of discharge 89f/32c, start of charge 86f/30c, 2/3.75 switch 82f/28c, 3.75/cut off amp 90f/32c, end of charge 80f
after 100 cycles 3176 mah
after 149 cycles 3184mah
im trying to get the battery to run as close to 10 amps as I can without getting it too hot, im just going to let it cycle for awhile at these settings, its been putting out a steady number.
the 200th cycle numbers are posted, I need to adjust the 1-d-cc and 2-d-cc voltages lower about 0.02v to raise peak temperatures to 100f to increase capacity again. peak temperature had dropped to 97f.
house was warm last night and checked the battery, temp was at 104f peak and the capacity had dropped. I was running the cycle settings so the battery temp would peak at 100f and after a few cycles the capacity would level out with steady numbers. im going to change peak temperatures to 99f on cycle #231.
edit to add pictures.
never saw these glitches in the discharge chart before, but this is #231 with new settings for 99f
discharge #2 was 3191mah, that's 95% after 290 cycles. you really cant go with the cycle numbers because its too easy to manipulate the capacity numbers with temperature and I have been, at cycle #149 I was using closer to the temperatures im using now and the capacity was 3184mah.
the 4.2vto2.5v capacity test will have to be the reference
im running the battery a little hotter where it peaks at 101/102f and only lose about 0.3mah/cycle right now
the cycle time has been increasing and its the charge cycle that is taking longer. I might have to drop the charge amps so I can make the charge faster, might try 3.25amps
I changed to 3.7a charge no real change except the curve
3.85 is a little faster
4.0, a little slower
4.25a is faster,
the charging mah was 5mah higher than the previous 5 cycles but the problem was the battery temperature at end of charge, it was 77f/78f and took 7 minutes for temp to reach 76f/75f. I need the battery cycle test to start at 75f/76f or else peak discharge temps get too high
I saw fully charged voltage had dropped to 3.184v, I put charge amps back to 3.75a from 3.82a
when cycling, normally start of discharge voltage is 4.191v, ive increased the 10amp discharge time, im still within peak temperatures, to speed up cycle time and will play with lower charge amps to see if I can increase the 4.191v at Start of discharge.
tried 3.5a and 3.0a with no observable change to voltage or mah, tried 2.5amp charge and again, no change so put charge amps back to 3.75amps
the cell was getting damaged by the 3.6amp charge and was losing about 2mah per cycle over the first 100 cycles until i switched to starting charge at 2amps and finishing with 3.75a-0.10c/o, you could see the damage at the 4.2-2.5 capacity chart at cycle 125 and then the damage stopped.
makes me think if you kept the charge to 2amps this cell would do 1000cycles. i had to change the 2a/3.75a switch to 3.62v because the cell still suffers loss where it was switching at 3.6v, that was 150/200? cycles ago and it needs to be moved again to 3.64v.
the other thing is temperature, max temp is about 102f and if you keep battery temp between 102f and 95f it gives its best consistent capacity.
im going to be testing a molicel p42a and mnke 26650 20amp 5000mah at the same settings.