Red Sanyo 18650 Cells Getting Hot While Charging

LithiumSolar

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We have all experienced the heat phenomenon behind the Sanyo 18650s in one way or another. So what's the deal with these cells? What is wrong with them? I have tested close to 3000 cells now. I try to charge them up to 4.2v for capacity testing and I would estimate at least 50% of the time, they get scalding hot around 3.9v.

Points of interest...
* They all have a healthy voltage coming out of the packs.
* I tried all kinds of charge currents between 0.25A and 1.0A. It doesn't seem to matter.
* Recently someone suggested letting them sit for a bit then trying again. I stopped them around 3.9v when the got hot, let them sit overnight, then put them back in. They charged up to 4.2v just fine without heat this time. They discharged normally to 3.0v. Then on the recharge cycle, they got scalding hot again.
* It can't be an "old chemistry" that limits them to 4.10v since they get hot well below that.
* For those of you who are going to say "don't use scavenged laptop packs", this statement carries no weight here considering it only happens with the red Sanyo 18650s, and approximately 3000 cells of mixed brands have been tested.

So what's the deal? Are they just cheap garbage? We have all experienced it, yet I see very few hypotheses.


image_nueess.jpg
 

Sean

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I'm not a chemist - but it has to be the chemistry within that has been degraded by use/abuse.

When new the "chemistry" will allow an applied amount of energy to be stored, and released later on demand - during this process of energy storage (charging) the voltage will rise - at a certain point, the charger will see the voltage rise and cease applying energy.

When past its prime, the "chemistry" will be unable to either receive or release energy - the inability to release energy is shown by capacity testing - the inability to store energy is shown by the inabity of the chemistry to convert applied energy into a voltage rise, which is seen by the charger as a cell that isn't fully charged - so it keeps applying energy.

If that energy isn't being converted by the "chemistry" into a stored form, it'll be wasted and converted into heat.

Those red cells don't because warm/hot over a short period of time - all of the ones I've had have taken a good few hours,, which would take them far past the point at which they should have been fully charged - and because we are mostly using smart chargers that sense voltage and current delta, they'll never see the expected charge profile - so they keep pumping in the amps.

Which is why nearly all chargers have cut off timers.
 

DanielD

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Hi mike,

I'm quite new at this 18650 recycling process, but the first thing that I've noticed was the bad quality of this cells:

- A lot of heat(45C)charging at 0.5A;
- Almost impossible to charge up to 4.2v (from my point of viewisn't a problem, but this fact brings a huge voltage drop (>0.1v)in 3or 4days without using it. Resuming: I made 4.0v charging, 4 days after I've checked it again 3.85v);
- The internal resistence is always high (300mOhms)
- For last but not least, i found the major part of this cells inside Toshiba laptops with flowing lable (Rev 1.0 6 Cell Recycle, you can check in the image). So, I've some concerns about the recycling processadopted.

I've a a lot of this cells and I'll not use them in a powerwall.

Best regards,
Daniel
 

AZ_Tekkie

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I've had many Sanyos that don't wait until the end of charging to get hot. Usually if they're going to get hot it's within 10-15min of being on the charger. Most of the time if they don't go above 110f/43c i just let them cook a bit and see what happens. A lot of the time they stay a bit warm but still complete. Once they get up to 140f/60c to the bin they go.
 

Sean

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DanielD said:
- Almost impossible to charge up to 4.2v (from my point of viewisn't a problem, but this fact brings a huge voltage drop (>0.1v)in 3or 4days without using it.

Whats your logic behind thinking an inability to reach its fully charged voltage isn't a problem ?
 

DanielD

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Sean said:
DanielD said:
- Almost impossible to charge up to 4.2v (from my point of viewisn't a problem, but this fact brings a huge voltage drop (>0.1v)in 3or 4days without using it.

Whats your logic behind thinking an inability to reach its fully charged voltage isn't a problem ?

Yep, It's a indication that the cellisn't very good.I've notexplained it very well... Sorry :).
I was trying to say that, if you want to use that cell for a powerwall with a max voltage per cell of 4.0v, you could avoid someheat. But, in the other hand i think that's not a good policy, because you're just hiding a future problem.


Best regards,
Daniel
 

station240

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Recent video where someone looked at the capacity spread of all his cells.

I was reading somewhere Sanyo use a different electrolyte to other cell manufacturers, not found that article yet.
However I did find this technical teardown of various cells.
https://batterybro.com/blogs/18650-...sonic-a-panasonic-b-sanyo-and-ultrafire-cells
The difference between the Sanyo and the Panasonic cells are an increase in ohmic resistance (how much is the cell opposing the flow of current). This is due to the battery chemistry type, notably the electrolyte formulation which is outdated.
 

alfu

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I have noticed this heating too, and Jehu says to chuck 'em.

But I don't. I have re-charged the heaters with the dippy little 2-cell wall chargers. I have found these wall chargers a quite good at getting any cell to 4.2V. The Sanyos don't heat nearly as much in them, and reach 4.2V. I solder a bump on the + termninal and give them to my friends: they make fairly decent flashlight cells. But I certainly wouldn't use them in any other application!
 

Battery

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I just tested the internal resistance of four red Sanyo's in my discard pile.These four cells all got very hot while charging(2/4 took over ~3000 mA withoutreaching 4.2V). The results were lower than expected at85,85,95 and80 mili-Ohms. Testing the internal resistance does not seem to be a way toidentify bad Sanyos,at least in the limited case of myfour bad Sanyos.I know this is a verysmall sample does everyone elseobserve consistenthigher internal resistances?

Its now been a couple of weeks they are sitting at4.0V. All cells were recovered at 2.0-3.0V. To investigate furtherI have just put them back on the charger, they are up to4.17V with no heat at all yet. It would be good to find a way to identify Sanyo cells with this heating problem because I will not always be sitting around to touch charging cells.
 

LithiumSolar

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Battery said:
Its now been a couple of weeks they are sitting at4.0V. All cells were recovered at 2.0-3.0V. To investigate furtherI have just put them back on the charger, they are up to4.17V with no heat at all yet. It would be good to find a way to identify Sanyo cells with this heating problem because I will not always be sitting around to touch charging cells.

Be careful with those. I tried this a few times. Charge to 4.0v, cell gets hot. Let sit for a few days. Cell charges fine to 4.20v without any heat what so ever. Cell discharges normally. Cell starts burning up again on the recharge cycle...

I tried to test 16 last night, all of which had healthy voltages coming out of the packs. Within 2 hours, I was down to 6 cells left. Of those 6, 3 had a capacity below 1000mah. The remaining 3 were around 2300mah and were good.
 

Battery

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mike said:
Be careful with those. I tried this a few times. Charge to 4.0v, cell gets hot. Let sit for a few days. Cell charges fine to 4.20v without any heat what so ever. Cell discharges normally. Cell starts burning up again on the recharge cycle...

Yeah careful for sure, I'm not planning on walking away.
As I've been sitting herethe four cells are just getting to4.19-4.20V and still taking 330mA all cold. This heatingis a strange and transient effect. It is unfortunate that there can be times when there is nomeasurable difference between the bad cells and the good ones. I amvery hesitant to use redSanyocells in anything now.
I am going to investigate Sanyo battery chemistrya little further tomorrow could they beolder style3.6V/4.1Vcells?


I am alsousing a different charger than before,It feels unlikely butI might also see if differentchargers play a role just in case.
I might check their capacity tomorrow (Perhaps that's how we can tell).
 

Aspendell

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mike said:
We have all experienced the heat phenomenon behind the Sanyo 18650s in one way or another. So what's the deal with these cells? What is wrong with them? I have tested close to 3000 cells now. I try to charge them up to 4.2v for capacity testing and I would estimate at least 50% of the time, they get scalding hot around 3.9v.

So what's the deal? Are they just cheap garbage? We have all experienced it, yet I see very few hypotheses.
-----
Mike,
I have had the same experience with these cells. They seem to be constructed differently than the other cells and don't like a charge rate of much over 0.2C. However they seem to be fine at discharging at 1.0C without much heat.


Battery said:
I just tested the internal resistance of four red Sanyo's in my discard pile.These four cells all got very hot while charging(2/4 took over ~3000 mA withoutreaching 4.2V). The results were lower than expected at85,85,95 and80 mili-Ohms. Testing the internal resistance does not seem to be a way toidentify bad Sanyos,at least in the limited case of myfour bad Sanyos.I know this is a verysmall sample does everyone elseobserve consistenthigher internal resistances?

Its now been a couple of weeks they are sitting at4.0V. All cells were recovered at 2.0-3.0V. To investigate furtherI have just put them back on the charger, they are up to4.17V with no heat at all yet. It would be good to find a way to identify Sanyo cells with this heating problem because I will not always be sitting around to touch charging ce
Remember that when Lithium Ion first hits 4.2v on a charger it is only charged to 85% of max capacity, and it will settle back to near 4.0v if you don't allow enough time for a saturation charge at 4.2v. Source: http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
So for anyone using a cheaper charger that doesn't allow for saturation, you are probably prolonging the life of your batteries but you wont get an accurate Capacity test.

btw most of my Sanyo reds came in around 2000mah +/- 300mah. I wont use them in packs, but the are great for devices like flashlights. And any of y'all that have those old LED flashlights that take 3 AAAs, 18650s work great in those after you just remove the 3 AAA holder!

~Aspendell
 

Joost2

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I charge all of my cells infarct place af 200Mah until it full. Then I messure its internal resistance and then decide what further. Below 100mohm charge and discharge (refresh) above charge test.

I have many cells that have laid down for more then two years en they work perfectly 80% off total cells are useable.
 

LithiumSolar

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1958greyhound said:
Free ;) since no one wants them.
You might be able to talk me into paying for the shipping.

I can get $0.50/cell selling them on eBay. And by that, I mean selling the honestly, blatantly pointing out everywhere in big bold red font that they got hot and are being sold for scrap.
 
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