Faulty batteries ?

Hello,

I ordered Liitokala Engineer Lii 500 from alibaba for 18$, including 12V DC PSU. Not sure what i expected for 18$ but certanly not my house burning.
Anyway, i used charging, nor and fast test on 8 batteries and encountered no problem. 1 thing i noticed is that both nor and fast test count capacity when charging, not when discharging. But ok, i dont mind.
But today i put in 4 batteries that were 3.5V. I set it on fast test. And maybe an hour later i touched 1 of the batteries just to see if it was warm and i burned myself. I unplugged the charger and measured 70C on the battery. Now as far as i know, the max safe temperature for lithium is 60C.
So my question is, what the hell happened ? Shouldnt like a million safety things go off ?

Anyway i did notice some strange things. First, it takes a long time after its 4.20V to display end. Right now i have a full battery in charger and its charging, reading 4.20V and already it says 250mAh. It should stop charging long ago. Battery is at 23.6C. Well, the other battery (the one that almost burned), its charging with 1A, its at around 4.17V and it heats up pretty quick to 38C.

So do i have a defect battery, defect charger or both ? I am afraid to leave charger on when i am not at home now :frowning:

What batteries are involved? Please post pictures or product links if possible.

70C is fine for lithium-ion. Not good for cycle life, but above 80C would’ve been dangerous for the cell though.

What cells did you charge?

…never leave these kinda chargers on when not at home.

Amen

Or any other kind.

Basicly its cells from old laptop batteries. The thing is, when i took the cells out of batterie packs, they were at 3.5V, which would indicate healty cells. Well, the result isnt healty. I am thinking it might be something wrong with them. But protection in charger should kick in long before cells are at 70C. I am afraid now that i could actualy been injured by this.

Pure voltage alone will not tell you if a cell is healthy. That cell may not have been discharged too low but it easily could have gone through many many cycles and have high internal resistance.

Cells that get hot during charging are not healthy and should be recycled. Salvaged cells are probably good if they:

  • Hold their initial voltage for a few hours sitting on a shelf
  • Don’t get too hot to comfortably touch for an extended period of time when charged at a reasonable current. 1A should be acceptable for any quality 18650, a temperature of 60C or more definitely indicates a problem.
  • Hold their full charge for several hours after charging. Dropping below 4.10V definitely indicates a problem.

I’m don’t take as hard a line as some about never charging batteries unattended. It’s mostly safe to do that with known-good batteries and chargers, but freshly salvaged laptop cells are not known-good. They should be supervised while charging and their temperature monitored.

The charger is probably fine, though you may want to double-check its termination voltage with a multimeter. It sounds like you have some bad cells.

Like it was already mentioned, voltage alone does not tell you anything about the health of the cell. If the cell is old and has high internal resistance, charging it with high current can result in excessive heat.

Also, I don’t think the Lii-500 has any temperature sensor/protection. You are expecting too much from what is basically a cheap charger.

Might be a good idea to change the title of your thread too. You placed the blame on the Lii 500 when that was not the case.

Charging unknown laptop cells & not being super attentive to what was going on appears to have been your problem.
Glad nothing bad happened.

Welcome to BLF, enjoy your stay. :slight_smile: . :beer:

That explains it.

I’ve also tested some 18650s salvaged from bad laptop battery.

My only lithium-ion charger back then was an Xtar VC4 charger. I left them charging, and when I came back, the batteries were very very hot. And mAh capacity reading (charged capacity) was over 2500mAh (considering that those batteries were nominally rated at around 2200mAh), and the battery is not getting “Full” status. I manually removed those batteries from the VC4 charger.

Since then, I have invested in several more chargers (including the very advanced SkyRC MC3000), I tried to charge those known-bad batteries again (I don’t use those bad batteries in actual use, but sometimes use for other testing purposes). Now the MC3000 has a temperature sensor, and also shows the voltage and more other info.

I notice that with these “bad” batteries, the charging is “OK” until around 3.95-4.05v. From that voltage onwards, it just keeps on charging (mAh capacity count will keep on increasing), but the voltage barely goes up anymore. The only thing that goes up is the battery temperature (MC3000 allows interfacing with a PC, so I can see the temperature graph plotted along with the voltage and capacity graph).

I was able to “fully charge” those bad batteries by stopping the charging when the batteries get hot, letting them cool down, then charge again (about 3 times of cooling down), until they were finally charged to Full.

When I did a discharge test, the capacity of these bad batteries were only around 900-1100mAh (nominally 2200mAh).

From doing more testing, I find that for “good” Li-ion batteries, the charged capacity and discharged capacity should match up quite well , but bad batteries will just keep on charging, without the battery getting fully-charged (they just get hotter and hotter).

The Lii-500 Engineer does not have a temperature sensor (I’m not sure if it has a built-in timer to stop when charging for more than X hours), so it could be dangerous to charge bad cells on them.

Something like the MC3000 would be good, but it’s a very expensive charger. Maybe can try a charger with temperature sensor (the only other charger I know with a temperature sensor is the Miboxer C4-12; I’m sure there are others, just that I’m not familiar with — that way, if temperature is too hot, indicating a bad battery, the charger should terrminate charging by itself — I’m not sure what is the temperature limit for the Miboxer C4-12; but on the MC3000, the temperature cut-off limit is user-configurable). I think some chargers have a timer cut-off (like some Nitecore chargers, which will terminate charging after (around) 10 hours of continuous charging, this is a failsafe mechanism in case it tries to charge bad batteries, which won’t get “fully charged”…

I thank you again for all the replies, what a great community !

I changed the topic. Today i will do some serious testing. I have to find out if all the batteries from this pack are bad, i will only charge 1 battery at a time for thsi test. I will use my digital temperature meter and stop the test if during charging battery goes above 50C. Also from now on i will only test when i am at home.

I do not want to do any modifications to the charger itself, since if it breaks down i want to be able to get a refund at alibaba. But i am thinking it might not be a bad idea to make some kind of temperature protection. Since i will charge only when i am at home, i was thinking of making a protection out of sensor and a very loud high frequency sensor, that will let me know as soon as things become to hot. I could use a fan, but i would rather be notified when things are dangerous instead of prolonging it. Any ideas ?

If you ask for a refund, Alibaba is going to tell you to send it back, which depending on where you are will likely exceed the cost of the charger itself. Forget it.

That’s not exactly correct.
The ‘NOR Test’ on the Lii500 records ‘Discharge Capacity’.

I know, but i tested it many times. It charges, discharges, and then while it is charging again, it is counting mAh.

Anyway i tested the batteries from yesterday (the ones that went to 70C) and i dont understand it but today they are fine. I tried fast test, i tried normal charge, i tried 1A discharge on my other machine. Is it possible that they just needed to be charged once to become ok ? Or would you reckon i better throw them away ?

I find the Li-500 to be a nice charger, but only at low charge rates. It maxes out a 1 amp, which is fine if you’re only charging 1 or 2 cells. But, if you try to charge four 18650’s at 1 amp, they will heat up quite a bit. The charger just generates too much heat.

If charging 4 cells, just use the default rate of 500mA. They’ll stay cool that way, assuming the cells are good.

BTW, NOR test should give you discharge current. The way it works is to first charge your cells up to 4.2v, then discharge down to 2.8v, then charge back up to 4.2v. The reading for discharge current shouldn’t change on the final charge cycle.

Well i guess my unit is either broken or fake, because it is not counting capacity during discharge, but instead during charge.

That’s interesting. I do not have any problem charging 4 x 18650’s at 1A with my Lii500. Nothing heats up past mildly warm…. nothing even close to hot.

And your desctiption of the NOR Test is the 100% correct. :+1:

I suspect it’s possible for internal shorts that have formed in a cell to dissolve or burn out when that cell is recharged such that it doesn’t get as hot the next time it’s charged. I’d put relying on that behavior firmly in the “don’t try this at home” category.