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Red Sanyo 18650 Cells Getting Hot While Charging
#31
(10-02-2017, 11:39 PM)Korishan Wrote: I thought about it, but haven't done anything with it yet.
To get it to work ya need to cut the trace to ground and put the NTC in place, and then connect that to ground. Altho, I'm not sure how you regulate it, tho. It uses the voltage difference to determine when to flip the switch and stop charging. So how do you know what size resistor to use with each NTC? Reason I say each NTC, cuz it'd be nice to use the NTC's from the laptop packs we all pull out.

While looking for something else I had come across this


Quote:So for protecting charging for lower temperatures than 0°C and higher than 50°C we should use a NTC of 10K with a beta of 3477K and R1 = 4K7 and R2 = 56K.

Calculation and RolfNoot's explanation is reply#4 at -
https://www.eevblog.com/forum/projects/q...batteries/ 

and I wondered whether it was a commonplace bit of knowledge that wasn't being applied because the chip didn't deliver accurately enough on its promises. 
Worth a try for someone who's 4056s have arrived and are operational? 

If the cell being charged by the 4056 was thermally guarded, then there shouldn't be quite so much need for human monitoring during evaluation. 
And the concern about, or even danger from, dodgy red Sanyos would be greatly reduced.
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#32
I have also come about quite a few Sanyo cells, and my bin is full of cells that I have trashed because they get hotter than I like during charge.

This has made me wonder.  Huh

Toshiba makes a lot of laptop computers and having hot Sanyo cells in their battery packs must have given Toshiba quite a lot of  customer complaints, forcing then to forward the complaints to the cell manufactorer.

Getting a complaint from Toshiba, must have forced Sanyo to do something to remedy the problem.

However, my search for the answer has turned out nothing.

Have any of You had any better luck?  Shy

ChrisD
Dietmar Rheeder-Kleist likes this post
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#33
You say that, but have you actually found any complains about this from customers? You make some assumptions, but I think this never happened as such and especially not in the required numbers to cause a stir.

I don't have any proof either, but here is a theory:

This might be normal behaviour after extended periods of time where the cells haven't been used. This is supported by the fact that some of the cells produce less heat after I've cycled them once, some almost stop heating up completely. Maybe they stop completely after more cycles.

If this is true then you wouldn't experience this with a laptop battery as long as you use it more or less regularly. But even if it isn't true or you don't use the battery regularly you might never experience it. The BMS monitors the temperature of the cells and I guess it kills the battery once the temperature reached a certain threshold.
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#34
(10-09-2017, 01:04 PM)DarkRaven Wrote: You say that, but have you actually found any complains about this from customers? 1)

 but I think this never happened as such and especially not in the required numbers to cause a stir. 2)

1) No I have not been able to locate any complaints over Toshiba Laptops with battery problems. I specified that this was only an assumption by writing: 

"However, my search for the answer has turned out nothing.". 

You seem to have missed that, but at least You have made it clear to all readers, that You think it was unwise of me to make such an assumption.

2) If my continued search turns out nothing, You are assumed right.

 Btw. have any of You other users found anything?
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#35
(10-10-2017, 08:50 AM)ChrisD5710 Wrote:
(10-09-2017, 01:04 PM)DarkRaven Wrote: You say that, but have you actually found any complains about this from customers? 1)

 but I think this never happened as such and especially not in the required numbers to cause a stir. 2)

1) No I have not been able to locate any complaints over Toshiba Laptops with battery problems. I specified that this was only an assumption by writing: 

"However, my search for the answer has turned out nothing.". 

You seem to have missed that, but at least You have made it clear to all readers, that You think it was unwise of me to make such an assumption.

2) If my continued search turns out nothing, You are assumed right.

 Btw. have any of You other users found anything?
I haven't seen complaints generally online (haven't really been looking tho...), but my mother has a Toshiba laptop about 5 years old. Always on mains, almost never ran on batteries. I picked it up one day and the battery was red hot. It would burn your legs if you put it in your lap. It had a temp sensor taped to the pack, so I'm surprised that the BMS didn't cut it before it got that hot. 

I unplugged it and it ran for only 5 minutes or so before shutting down. I pulled the cells from the battery and they were very low capacity. 

From packs I had processed, I was under the assumption that Toshiba always used Sanyo cells. Recently though I've found a few Panasonic green cells and even one with a set of dark blue LG cells (first one I've seen with non-Japanese cells)
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#36
(02-04-2017, 11:07 PM)Aspendell Wrote: 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.

The four-cell Opus certainly doesn't let anything soak. I fail to understand why its charging algorythm gives up on cells well before 4.2V. Maybe it knows something about Li-ions that I don't.
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#37
I have too many of these to waste. I am going to build a pack with an elaborate temperature monitoring system, and only charge it to 4.1v. Even though they only test about 1500mah. I have more than 600. I will keep my good packs separate.
winny likes this post
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#38
An important topic
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#39
So, this weekend during my charge/discharge testing, I came across a bunch more sanyo red cells and they really did get hot.
These images show heat buildup (temperature measurements) from my bench during a simple charge test (the cells were resting discharged for a few days prior) - the red cells are # 5,6,7,8 in one of my opus chargers.  Yes, they get HOT HOT HOT, and I am thinking it is a waste of time to test the sanyo red's anymore. When I pulled them from the charger, they were another 5 degrees Fahrenheit hotter.   They all started to really heat up at around 3.95 volts, and continually got hotter from there.  I was only charging at 500ma, and these suckers were in the charger for over 4 hours.   I checked the IR on these previously and they were all between 50 and 70.

The images of the red cells in the opus are to show my temp sensors and the display - this is when I stopped the testing of these 4 cells and pulled them out of the charger.    If you look at the chart, the temperature gradually increases.



For those who are asking, unlike a few folks who disassemble the opus to put in the temp sensors, what I did was get a bunch of DALLAS 18B20 DS18B20 TO-92 3 Pins Wire Digital Thermometer Temperature IC Sensors, and also a bunch of FOXNOVO Temperature Probe Sensor Cable Cords for Imax B5 B6 B6AC Lipo Battery Charger - I removed the analog sensor in the sensor cable and put in the digital ones... then connected the set to my raspberry.  Easy to grafana this - more on that set up if anyone wants info, but it is pretty straight forwards.
Dietmar Rheeder-Kleist likes this post
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#40
And for those who wanna se how easy adding the tempsensors i did a video about that:



I dont have any answer either regarding why some heat up as much. They are perhaps in such a bad shape inside that the self-discharge is very very high. Thats my only Guess. 

Have you guys let them sit to see how much they discharge after?
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