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Red Sanyo 18650 Cells Getting Hot While Charging
#11
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!
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#12
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 without reaching 4.2V).  The results were lower than expected at 85,85,95 and 80 mili-Ohms. Testing the internal resistance does not seem to be a way to identify bad Sanyos, at least in the limited case of my four bad Sanyos. I know this is a very small sample does everyone else observe consistent higher internal resistances?

Its now been a couple of weeks they are sitting at 4.0V. All cells were recovered at 2.0-3.0V. To investigate further I have just put them back on the charger, they are up to 4.17V 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.
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#13
(02-01-2017, 01:09 PM)Battery Wrote: Its now been a couple of weeks they are sitting at 4.0V. All cells were recovered at 2.0-3.0V. To investigate further I have just put them back on the charger, they are up to 4.17V 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.
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#14
(02-01-2017, 01:35 PM)mike Wrote: 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 here the four cells are just getting to 4.19-4.20V and still taking 330mA all cold. This heating is a strange and transient effect. It is unfortunate that there can be times when there is no measurable difference between the bad cells and the good ones. I am very hesitant to use red Sanyo cells in anything now.
I am going to investigate Sanyo battery chemistry a little further tomorrow could they be older style 3.6V/4.1V cells?


I am also using a different charger than before, It feels unlikely but I might also see if different chargers play a role just in case.
I might check their capacity tomorrow (Perhaps that's how we can tell).
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#15
(01-24-2017, 04:13 PM)mike Wrote: 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.
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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.

(02-01-2017, 01:09 PM)Battery Wrote: 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 without reaching 4.2V).  The results were lower than expected at 85,85,95 and 80 mili-Ohms. Testing the internal resistance does not seem to be a way to identify bad Sanyos, at least in the limited case of my four bad Sanyos. I know this is a very small sample does everyone else observe consistent higher internal resistances?

Its now been a couple of weeks they are sitting at 4.0V. All cells were recovered at 2.0-3.0V. To investigate further I have just put them back on the charger, they are up to 4.17V 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/artic..._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
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#16
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.
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#17
Send them to me, I use them.
You just have to be NICE to them.
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#18
(08-10-2017, 08:47 PM)1958 greyhound Wrote: Send them to me, I use them.
You just have to be NICE to them.

The hot saynos? How much do you pay? I have a big box of them!
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#19
Free Wink since no one wants them.
You might be able to talk me into paying for the shipping.
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#20
(08-10-2017, 09:02 PM)1958 greyhound Wrote: Free Wink 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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