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18650 temperature
#1
I'm currently in the processes of harvesting cells from used laptop packs. I am confident I have a hold and good understanding of the selection and testing process for selecting good cells. The one thing I can't decide on is cell temperature during these tests. I've a number of Panasonic cells that are reaching around 43 degrees Celsius at 1amp charge. Now these are obviously not too hot to touch and I expect some heat during energy transfer. I would like to get an idea of general opinion on this. Would you throw or keep. Is this normal?
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#2
Depending on what tester you are using, the tester might be transferring heat to your cells. When your tester is discharging your cells, it is applying a load to a resistor, which is turning the electrical energy into heat. Unless you physically separate the cells from the tester, or eliminate the heat by introducing more fans, you won't know for sure how much the cell heats up on its own. And anyway, 43*C seems pretty normal to me.

One other thing, warmer cells will show more capacity than cooler cells. I had cells lose 3-4% capacity with a 10-15*C drop in temperature.
allend83 likes this post
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#3
Okay once again thank you for your prompt reply. Now you come to mention it I didn't think of the potential for heat transfer from the charger to the cell, very good point. For your info I'm using Liito-Kala lii-500. One would also assume ambient temp will have an impact. Seeing that 43*c hasn't scared you I shall worry less about these temps. Thank you for the reassurance.
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#4
You always need reference values. Is it only a few Panasonic cells (out of a larger amount of Panasonics) or is it all Panasonic cells and/or only Panasonic cells? 43°C is generally nothing to worry about.
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#5
The manufacturer considers these temperatures to be normal during discharge.
If you have the cell number and can find a spec sheet on it it will tell you what to expect during discharge. Here is an example of a NCR18650PD.
Note the Temp during a 10A discharge compared to a .55A discharge
 
Here are some temps during a Sony US18650GR G8 charge and discharge cycle on my SKYRC.  The cells approach 34°C. Now mind you the SKYRC has dual fans for cooling not like the LiitoKala which has none. So more temp is to be expected. You can see the red line bouncing up and down with the different stages of the CDC cycle.


Capacity testing will show you if there is a problem with these cells
I had several Panasonic cells that did the same thing got very warm during charging and then were not very good in capacity.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 70mΩ or less Smile
Last count as of 3/20/2019
Total Number of Cells           3619
Cells  >80% of Capacity        2317
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1590
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#6
DarkRaven - I had four of the same sells in the charger at the same time and all were about the same. I can't remember but would imagine that these four cells were from the same laptop pack as I have no more than four and so therefore cannot make any real reference.

Wolf - the cells in question are Panasonic CGR18650D. I did check the data sheet and could see some reference to charge and discharge temps. I am talking temps under charge not discharge and didn't see anything like the temp I was experiencing referenced. This is the reason why I posted here. Interestingly the capacity is 2100mah on average according to the data sheet new would expect to see 2350mah. They also have a low IR so on the face of it seem like good cells. Would seem a shame to bin them but wouldn't want to take the chance if these temps seem unusual which based on yours and one other comment 43*c would seem acceptable.
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#7
(02-28-2019, 10:03 PM)allend83 Wrote: Wolf - the cells in question are Panasonic CGR18650D. I did check the data sheet and could see some reference to charge and discharge temps. I am talking temps under charge not discharge and didn't see anything like the temp I was experiencing referenced. This is the reason why I posted here.  Interestingly the capacity is 2100mah on average according to the data sheet new would expect to see 2350mah. They also have a low IR so on the face of it seem like good cells. Would seem a shame to bin them but wouldn't want to take the chance if these temps seem unusual which based on yours and one other comment 43*c would seem acceptable.
Yes the charging temps in the specs usually are the ambient temp not the cell temp.
At present I don't have any CGR18650D cells free to test but I do have 4 CGR18650CGs the younger cousin.
I am putting them into my Zanflair to charge 1 at 1000mA 1 at 700mA 1 at 500mA and 1 at 300mA. In about an hr I will check them with my thermal gun and see what temp they are and post the picture.Well its actually already starting. Just barley can feel warmth on the 1000mA one.


There still are some other factors to consider.
1 What was the initial V before charging?
2 At what A were the cells charged at? You mentioned 1A I looked it up
3 You say the IR was low. According to the tester or a 4 wire kelvin meter?

At a 2100mAh result thats not bad.
Here is the few that I have tested and the results. Maybe they kind of match yours. The Foxnovo doesn't do IR but it was measured before testing with a YR1030.
Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 70mΩ or less Smile
Last count as of 3/20/2019
Total Number of Cells           3619
Cells  >80% of Capacity        2317
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1590
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#8
Wolf - I really do appreciate your effort and help. Going to these lengths.

1. The initial voltage was 3.61v
2. I was charging at 1a
3. According to the Liito-Kala. I'm not sure how accurate this is on this device? Some reviews suggest it should be taken with a pinch of salt however looking at your attached spreadsheet results Vs YR1030 seem fairly consistent. I will add that the reference I made to IR was at the initial voltage.

Looking at your image it would appear and cements the previous comments within this thread. The temps that I was seeing look normal.
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#9
(03-01-2019, 08:14 AM)allend83 Wrote: Wolf - I really do appreciate your effort and help. Going to these lengths.  

1. The initial voltage was 3.61v
2. I was charging at 1a
3. According to the Liito-Kala. I'm not sure how accurate this is on this device? Some reviews suggest it should be taken with a pinch of salt however looking at your attached spreadsheet results Vs YR1030 seem fairly consistent. I will add that the reference I made to IR was at the initial voltage.

Looking at your image it would appear and cements the previous comments within this thread. The temps that I was seeing look normal.

Yea I would say they are normal as far as 4 Cells being charged at 1A in a close environment like the LiitoKala. I would not say ~40°C is out of the norm.
Now if you were charging them at 500mA and you got that warm I would be very suspicious.
As far as IR on the LiitoKala is concerned  it seems to go through spurts of accuracy sometimes it's pretty close other times it is way off.
Examples in the sheet. That is why I trust my YR1030 as it is consistent. I enter the IR of the testers just for reference to see how good or bad they are. You can also see how IR affects the outcome of each cell. At this time I record almost all cells to build this database. I no longer use cells with an IR of >100mΩ because there is no point. I do measure initial IR to see if the cell qualifies to be charged. If it is below 100mΩ it gets a chance and a charge.
Eventually I will be able to tell with just a preliminary IR and V measurement if the cell is worth investing time into. All models and manufactures have different cutoffs for this and my quest is to find them. 
Wolf
beserker786 likes this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 70mΩ or less Smile
Last count as of 3/20/2019
Total Number of Cells           3619
Cells  >80% of Capacity        2317
Cells <80% of Capacity         1265
Cells ≥2200mAh & ≥ 80%     1590
Google Drive for info https://drive.google.com/drive/folders/1...sp=sharing
Not your average Wolf       
            Cool



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#10
Wolf just a quick question, I've heard that charge levels at point of test can affect the IR. Would agree or disagree with this?

Also you make ref to cells >100mΩ not being worth it. Is this just because of the risk of overheating?
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