Molicel P42a cycle test

[goatman]

i left a battery out all day, its about 3 celcius outside and ill do the test at the temp to see

heres 7.5amp volt sag

battery temp peaked 92f/33c, discharge mah 3334. the last discharge was cycle #205-3325mah

ill charge it up and stick it the freezer overnight, see if it blows up on the next discharge :lol: :lol: :lol:

 

[bigboy061293]

i left a battery out all day, its about 3 celcius outside and ill do the test at the temp to see

heres 7.5amp volt sag

battery temp peaked 92f/33c, discharge mah 3334. the last discharge was cycle #205-3325mah

ill charge it up and stick it the freezer overnight, see if it blows up on the next discharge :lol: :lol: :lol:

Very nice!
Could you go with higher current please, from 15A is a great appreciation.
Thanks.

 

[goatman]

my freezer is -10c, you want 15 amp discharge at -10?

 

[bigboy061293]

my freezer is -10c, you want 15 amp discharge at -10?

actually, 15Amp at room temperature: 25 to 30 degreeC

 

[goatman]

15amp discharge to 3.0v, starting temp 75f/24c

volt sag

temp 105f/40c at 3.5v

temp 120f/49c at 3.2v

temp 125f/52c at 3.0v

 

[goatman]

when your cells were assembled into a pack, are they touching each other or did you use cell holders to maintain an airgap between cells? how many layers of nickelstrip?

 

[bigboy061293]

when your cells were assembled into a pack, are they touching each other or did you use cell holders to maintain an airgap between cells? how many layers of nickelstrip?

that's really helpful. Thanks a lot.
In my case, stopping at 36V (for 12s, so 3V for each "s"), the cell could reach up to 77 degreeC, really hot (ambient temp was 25-30degreeC). Still looking for the causes!!

I used the cell holders, of course they have the air gap. I used copper but not nickel strip.

Some photos from FLIR camera

 

[goatman]

maybe you got a lower grade p42a and not an "A" grade cell, i googled, spot a fake molicel p42a,and didnt get any hits

 

[bigboy061293]

Our company orders huge amount of them, directly from the factory. However, it could be like what you said - not "A" grade. By the way, any tips for packing?
Thanks!

 

[goatman]

im not sure what you mean by packing

 

[bigboy061293]

I meant, "battery packing" (combining cells into a 12s6p battery). Could you give me some tips on this "packing" technique (any remarks on the using strips, welding...)

 

[goatman]

i dont know, im playing with magnets and copper slug tape but the magnets are N42 rated for 80 celsius max working temperature.
the testing im doing is for pack temperatures of 40 celsius with max discharge of 10 amps with plasti dip insulation/waterproofing for marine application

 

[goatman]

ive had the battery in the freezer fully charged when it went in for 2 days, pulled it out and did a 7.5 amp discharge to 3.2v

heres volt sag

at 3.7v battery temperature was 75f

3.6v was 85f

3.5v was 88f

3.2v was 95f

 

[wiredsim]

Thank you for testing that! Looks like the low temp didn’t affect discharge too badly and it warmed up pretty quickly.

 

[goatman]

Thank you for testing that! Looks like the low temp didn’t affect discharge too badly and it warmed up pretty quickly.

did the same test with 40T and it wasnt as good as the P42a, here it is for comparison

battery temp reached 95f

 

[wiredsim]

Yeah I heard they were decent low temp performers and the spec sheet seems to reflect that. Good to get confirmation. I’m thinking of using them in a snow mobility application.

FYI Molicel has made low temp specific batteries- including for NASA:

https://trs.jpl.nasa.gov/bitstream/handle/2014/49949/CL%2318-5560.pdf?sequence=1&isAllowed=y

However a lot of that seems focused on low temp charging, of which I am not nearly as concerned about.

 

[pwd]

I was wondering if you'd mind sharing where you got your P42A cells from? I was going to do another 40T pack but they seem to be out of stock many places and the P42A would do nicely. The lowest price I can find (shipped to Canada) is https://www.bulkbattery.com/ Your cell testing is also appreciated/valuable.

 

[goatman]

I was wondering if you'd mind sharing where you got your P42A cells from? I was going to do another 40T pack but they seem to be out of stock many places and the P42A would do nicely. The lowest price I can find (shipped to Canada) is https://www.bulkbattery.com/ Your cell testing is also appreciated/valuable.

i cant remember what it cost but this quote is from the 3rd? post of this thread


"i got this battery from 18650 Battery but had a problem. they shipped the battery and it supposedly left Florida enroute to Canada June.14.

july.15 i sent 1 email with 3 words, Wheres my battery?
next day they replied, It seems to have been lost and weve sent you another battery

2 weeks later i had the battery. Excellent no BS customer service "

i know a vape shop in Toronto has them but i think it was cheaper to get it from the States because of the crazy costs we pay up here for shipping inside Canada

 

[pwd]

Thanks for the info, glad to hear that about 18650battery.com.

 

[goatman]

the P42a has a similar curve to the 30Q, 40T and vtc6 going to try desulfating it

heres the first capacity test curve



here the capacity test after 100 cycles



after 205 cycles i do the capacity test (desulfate) at 0.8 amp discharge to 2.5v



did it again



now ill cycle it and compare to these last numbers

#203 d-3326, c-3275
#204 d-3326, c-3273
#205 d-3325, c-3270

capacity tests
new numbers
#206 d-3317, c-3265
#207 d-3313, c-3260
#208 d-3308, c-3251
#209 d-3301, c-3243
#210 d-3294, c-3239
#211 d-3290, c-3235

desulfating straightened the line but didnt seem to do anything to capacity
the cell is losing alot more mah/cycle, i think it might be the charge i was doing.
i charged to 3.6v with 2amps then switched to 3.75amps to 4.2v with 0.10a c/o

trying just 2amp charge to 4.2v 0.10 c/o

#212 d-3288, c-3228
#213 d-3283, c-3219

did capacity test at cycle #287 in below post (#205 was d-3739mah)
#287 d-3688, c-3541

 

[goatman]

going easy on the cell doesnt really improve its mah/cycle loss

trying higher amp discharge
ive set these settings by temperature



step 1- 90f/632mah 15amp
step 2- 101f/821mah 10amp
step 3- 103f/1271mah 7.5amp reached 103f and held steady
step 4- 99f/ 461mah 5amp
step 5- 96f/107mah 2.5amp
start of charge 86f

#214 d-3292, c-3226
#215 d-3281, c-3227
#216 d-3279, c-3224
#217 d-3278, c-3222

the numbers have stabilised
i went and re-read this thread, looked at the mah numbers
compared it to the 40T's numbers and theyre pretty close after 200 cycles

after the capacity test at 100 cycles, it looks like desulfating works

https://endless-sphere.com/forums/viewtopic.php?f=14&t=107573#p1577214

just didnt know what i was observing

will do another 100 cycles

#218 d-3276, c-3219
#219 d-3275, c-3218
#220 d-3274, c-3216
#221 d-3272, c-3217
#222 d-3272, c-3215
#223 d-3269, c-3210
had the cycle set for 9 and test had stopped, battery was 4.173v, gave it a charge and resumed test
#224 d-3283, c-3211
#225 d-3268, c-3212
#226 d-3269, c-3212
#227 d-3267, c-3210
#228 d-3265, c-3206
#229 d-3264, c-3206
#230 d-3263, c-3207
#231 d-3262, c-3206
#232 d-3259, c-3203
test stopped, battery was 4.169v charged to 4.2v
#233 d-3277, c-3202
#234 d-3258, c-3205
#235 d-3261, c-3207
#236 d-3263, c-3205
#237 d-3260, c-3202
#238 d-3260, c-3202
#239 d-3258, c-3204
#240 d-3257, c-3196
#241 d-3254, c-3196 each group of 9 cycles takes about 24hrs, ill keep giving it an hour break every 24hrs
charged battery
#242 d-3274, c-3194
#243 d-3249, c-3193
#244 d-3250, c-3194
#245 d-3248, c-3195
#246 d-3251, c-3193
#247 d-3250, c-3195
#248 d-3252, c-3197
#249 d-3251, c-3195
#250 d-3251, c-3200
1hr break and then top up charge
#251 d-3279, c-3194
#252 d-3250, c-3193
#253 d-3250, c-3192
#254 d-3247, c-3190
#255 d-3245. c-3190
#256 d-3248, c-3191
#257 d-3247, c-3192
#258 d-3248, c-3193
#259 d-3248, c-3191
1hr break/charge
#260 d-3271, c-3186
#261 d-3244, c-3188
#262 d-3245, c-3186
#263 d-3244, c-3187
#264 d-3244, c-3186
#265 d-3243, c-3188
#266 d-3245, c-3189
#267 d-3244, c-3185
#268 d-3242, c-3188
1hr break/charge
#269 d-3271, c-3187
#270 d-3242, c-3183
#271 d-3240, c-3184
#272 d-3240, c-3185
#273 d-3240, c-3185
#274 d-3241, c-3184
#275 d-3242, c-3187
#276 d-3241, c-3186
#277 d-3242, c-3185
1hr break/charge
#278 d-3263, c-3181
#279 d-3239, d-3181
#280 d-3238, c-3179
#281 d-3236, c-3181
#282 d-3236, c-3181
#283 d-3238, c-3179
#284 d-3236, c-3180
#285 d-3239, c-3182
#286 d-3239, c-3180
doing 0.8amp capacity test
d-3688, c-3541

#287 d-3296, c-3236
#288 d-3288, c-3229
#289 d-3281, c-3223
#290 d-3275, c-3217
#291 d-3270, c-3208
#292 d-3264, c-3206
#293 d-3260, c-3203
#294 d-3257, c-3201
#295 d-3258, c-3201
1hr break/charge
#296 d-3284, c-3193
#297 d-3251, c-3196
#298 d-3255, c-3196
#299 d-3251, c-3188
#300 d-3247, c-3188
#301 d-3245, c-3187
#302 d-3243, c-3185
1hr break/charge
going to cycle with no break between discharge/charge/cycle
#303 d-3265, c-3182
#304 d-3241, c-3184
#305 d-3239, c-3182
#306 d-3238, c-3183
#307 d-3240, c-3179
#308 d-3237, c-3178
#309 d-3236, c-3176
#310 d-3234, c-3176
#311 d-3231, c-3174
1hr break/charge need to do another 9 cycles to see/compare the numbers
#312 d-3252, c-3171
#313 d-3229, c-3172
#314 d-3228, c-3168
#315 d-3227, c-3170
#316 d-3228, c-3172
#317 d-3228, c-3170
#318 d-3229, c-3169
#319 d-3225, c-3167
#320 d-3225, c-3166
1hr break/charge- adding wait times in between dicharge/charge /cycle
#321 d-3253, c-3162
#322 d-3222, c-3162
#323 d-3219, c-3165
#324 d-3223, c-3164
#325 d-3221, c-3163
#326 d-3222, c-3164
#327 d-3223, c-3163
#328 d-3221, c-3163
#329 d-3222, c-1498 stopped test and put battery on shelf at 3.774v

 

[goatman]

Canada Post delivered the "lost in shipping" P42a to my house with an apology letter
they had it for almost 1 year!!!! :lol: :lol: :lol:
its sitting at 3.52v

 

[Frank]

Why do you think the charge is always less than the discharge? Shouldn't it be the other way around? Or am I misreading the numbers?

Sent from my SM-T380 using Tapatalk

 

[goatman]

i dont know, its like that with all the battery tests ive run

 

[Hillhater]

Why do you think the charge is always less than the discharge? Shouldn't it be the other way around? Or am I misreading the numbers?

i dont know, its like that with all the battery tests ive run

Its not huge, and may not be important, but it is fundamentally impossible..!
...so personally, i would want to understand why before drawing too many conclusions.