18650 cell question

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you can check the cells resistance on the imax charger

i also have some of these so i can charge 4 cells at a time from the i max.
https://www.ebay.co.uk/itm/XD-3-1-2-3-4x-Li-ion-Lithium-18650-Battery-Box-Holder-Case-3-7V-Pin-Pole-Sold/142131077352?ssPageName=STRK:MEBIDX:IT&var=441208306869&_trksid=p2060353.m1438.l2649

 

[billym1967]

so ran a test the way he said, using a samsunge and a grey battery dont no the brand, but charge and discharged they have good mAh

15 minute run
samsunge start v 4.188 end 3.938 a loss of 0.250
grey start 4.118 end 3.814 loss of 0.304

so i rang him back as he said to let him know. he says he would rank that used battery as good on that test the new one lost around 5.97% the the used 7.38% he would expect that to happen. my logic tells me that thats quite a good cell, also it was one with not to bad Vs

also the battery s didn't get overly hot. also you could run them for longer take the Vs down lower. next to try a really dodgy battery

 

[billym1967]

you can check the cells resistance on the imax charger

i also have some of these so i can charge 4 cells at a time from the i max.
https://www.ebay.co.uk/itm/XD-3-1-2-3-4x-Li-ion-Lithium-18650-Battery-Box-Holder-Case-3-7V-Pin-Pole-Sold/142131077352?ssPageName=STRK:MEBIDX:IT&var=441208306869&_trksid=p2060353.m1438.l2649

they look better, but i think it was more the As i was drawing. the ones that had ,melted i used the other day a 5A x5 of them to charge 5 cells and they were fine.

 

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[billym1967]

yes mine melted athe spring out, to be honest they were cheep.

single cell at 30 minutes should let me know without damaging anything. could set 2 or 3 up so you can do a few at a time. the IMAX takes 5 hours to drain a battery down to 3v at 1A discharge. this way is going to do a discharge to 3v in 90 minutes, so a lot more stress.

 

[billym1967]

so test 3 lol. i set it away for 90 minutes. not doing the maths lol. so went back after 70 minutes to find both bulbs out. and both batterys down to 2.3v but as 12v 50w converts to 4166mAh then oops. so set them away for 60 minutes but still think thats wrong as distarge will encress as Vaults drop. so i think 30 or 45 minutes is gonna be the best test. trial and error.

 

[billym1967]

so testing well under way. i'm doing quite a few to make sure its a sound as possible. different sizes and ages of battery's.

so this is the test and i recon its heavy. i fully charge the battery. i then rung a single cell on a 4A 12v bulb for 45 minutes. i then finish discharging to 3v on the imax. recharge it and work thinks out.

so all the battery's have discharged down to 3.5 to 3.6v the small older ones tend to go lower. the second part on the IMAx there big difference depending on the size and age of the battery. but the figure i get from that if i deduct it from the recharge figure every battery has discharged 1500mAh in the light test. so an example would be Samsung new, after the light test discharged 1000mAh in the imax recharged to 250mAh.

so the light test is drawing around 2000mAh with i think i would say is heavy draw on a battery cell. if you were draining your e-bike battery in 1 hour your definitely using it hard.

so good test i think. will do some more though. problem i have is i do have battery s with very low vaults, but there charging and i dont no the reason 100% why there low. so either the test is good and ive good good battery's. or the test isn't good at all. im doing a brand new sony 2900mAh cell now so i'm hoping if it comes out at 1500mAh drain then it show the test is good. only real question is is 1500mAh in 45 minute heavy enough.

 

[billym1967]

so samsunge new just finished and the same result used 1500 just over on the test.

so i though can i stress more and quicker. so ive just tried a few 2 x 12V 50w 4.25A bulbs running of one cell, the Vault draw is hugh. from 4.2 down to 3.4 straight away lol. i think at 5 minutes at that if it survives its good.

 

[billym1967]

so this is a strange thing to say, some of my cells have failed the test. so i'm quite sure now it works. it will pull of week or damaged cells. 3 up to date, so i will retry them just to make sure.

 

[billym1967]

so just an update. my test running a 12v 50w bulb of 1 cell has been pulling week ones out. so depending on the age and mAh it drops a cell from 4.2v to 3.4 to 3.6v in 45 minutes.

so ive been waiting for some bits coming so i could speed things up, 3 cells at a time.

did a test and not sure what to make of it, think its putting even more pressure.

i ran 3 cells 12.6v ish on 1 bulb. 25 minutes instead of 45 minutes and they went down to 3.5v but also got warmer. not hot but warm. so i think the 3 cells together is better test. though i'm not sure why,

i'm hoping someone can tell me why lol