18650 temperature

allend83

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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?
 
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.
 
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.
 
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? 43C is generally nothing to worry about.
 
The manufacturer considers these temperaturesto 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

image_mkkrjj.jpg

Here are some temps during a Sony US18650GR G8 charge and discharge cycle on my SKYRC. The cells approach 34C.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.

image_ehxrhe.jpg


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
 
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.
 
allend83 said:
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 testbut 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 gunand see what temp they are and post the picture.Well its actually already starting. Just barley can feel warmth on the 1000mA one.

image_hdezng.jpg


There still are some other factors to consider.
1 What was the initial V before charging?
2 At what A werethe 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 kelvinmeter?

At a 2100mAh result thats not bad.
Here is the few that I have tested and the results.Maybe they kind of matchyours. The Foxnovo doesn't do IR but it was measured before testing with a YR1030.
Wolf

image_wyrfly.jpg
 
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.
 
allend83 said:
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 ~40C 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 referenceto 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 longeruse cells with an IR of >100m? because there is no point. I do measure initial IR to see if the cell qualifies to be charged. If it is below 100m? it gets a chance and acharge.
Eventually I will be able to tellwithjusta preliminaryIR 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

image_jozchy.jpg
 
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 >100m? not being worth it. Is this just because of the risk of overheating?
 
allend83 said:
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 >100m? not being worth it. Is this just because of the risk of overheating?

Charge level does affect IR but not a whole lot I have found. Take a look at the pretest IR and the IR after 30+ days of rest most cells have a slight drop or slight increase. The exceptions prove the rule. Sheet will explain.

image_vcqwwv.jpg



Well no it's not so much the overheating part as more of the performance side. I find that "most" cells over 100m? seem to just not have the umph anymore. There are some LGs that seem to hang on for dear life at that resistance but not enough.

image_pvzyle.jpg

Also when building a 200p pack I would like to keep my resistances as similar as possible,All cells within a 40m? to 70m? range. I feel a consistent resistance range will just assist the parallel cells in apack to humm happily together. After all the packs made by manufactures use the same cells in each pack with the same resistance. I haven't pulled a pack apart that has a mix of panasonic,sony and lg mixed together. I mean that is what we are doing so it begsthe question do wekeep the cell chemistry and certain parameters as close as possible. I think so!At this point I have 1180 cells that meet my criteria. Hopethat explains my strategy.

image_fnpude.jpg


Wolf
 
All makes complete sense. I was thinking ohm's law when I was asking you that question. Obviously a cell is a resister in itself hence we are having this conversation about IR. I had seen significant differences between the same cell, full capacity Vs whatever capacity the cell was at point of first charge. Based on your last comment about the Liito-Kala I'm now uncertain how much I can rely on the results that I am seeing. Time to invest in a YR1030!!

This is a minefield!

I can understand your logic in trying to keep packs equal. I suppose this is the reason also why one would also want to ensure equal charge and mah (pack to pack), why would you therefore not want to use this concept with IR, makes sense.

Wolf you have been very helpful, thank you ?


Wolf slightly off subject and just a quick question. I'm finding the Liito-Kala doesn't take the cell to full 4.2v it's suggesting on screen. I've waited watching to catch a cell as soon as it's charged pulling straight out of the charger and testing with multi metre with results ranging from 4.14-4.18v. Have you seen this behaviour with your Liito-Kala?
 
allend83 said:
..... you have been very helpful, thank you ? ......


Wolf slightly off subject and just a quick question. I'm finding the Liito-Kala doesn't take the cell to full 4.2v it's suggesting on screen. I've waited watching to catch a cell as soon as it's charged pulling straight out of the charger and testing with multi metre with results ranging from 4.14-4.18v. Have you seen this behaviour with your Liito-Kala?



Thank you with a question mark? LOL I hope I have not scared you off!

I do find the LiitoKala a little lacking in the V accuracy. Also the charging side may be off also. I have never done a test on that.I did a test on a bunch of V and m?readings from different testers a while back though.

image_wdytmd.jpg

I think it would be a good Idea to revisit that chart with my Fluke and maybe expand on it a bit. I will have someresults this weekend or maybepossibly tonight.

image_ibqudi.jpg

If you want a jump on the results see if you can get some salvaged nickel strips (from battery packs) and put them between the battery terminals and the LiitoKala's contacts. Get some alligator clips that attach to your DMM that way you can monitor the V and see what the difference is. That is if your DMM is accurate.:p


Wolf
 
Sorry Wolf I have absolutely no idea where that question mark came from and didn't realise it was there until you mentioned it! Sorry and genuinely you have been very helpful. I did put a thumbs up on my phone maybe that explains the misplaced punctuation mark?

Oh my word so it could also be my DMM, Ahhhhhhhhhhh. What have I started?

I might give that test a go and see what happens?
 
allend83 said:
Oh my word so it could also be my DMM, Ahhhhhhhhhhh. What have I started?

I might give that test a go and see what happens?
You have opened the door and started to go into another dimension in time and space ...................... you have entered

image_mpjzse.jpg

Wolf
 
LOL

Wolff I've just had a Samsung ICR18650-26F reach 60c!!!! Now that must be to hot?
 
allend83 said:
LOL

Wolff I've just had a Samsung ICR18650-26F reach 60c!!!! Now that must be to hot?

That my friend is too hot yes. what does the LiitoKala show for IR?
Where you charging at 1C(1A) not that that is high. Standard charge is 0.5C (1300mA).


Wolf
 
I'll be honest Wolf I've not been taking much notice of the IR reading from the Liito-Kala because I've been getting massively inconsistent results from them.

I was charging at 1000mAh (1A).

In your opinion when is hot too hot?
 
Me personally?

I get nervous if acell gets more than 40C but then again I charge at 500mA. On my SKYRC I charge at manufactures standard which is usually 0.5C basically half of capacity. but it has 2 turbojet fans under it so the temp never gets above 38C.

I have seen specs on cells being discharged at 10A and going to 65C to 70C but that was discharge.
I suppose the upper limit would be somewhere near there as cell actually are rated to withstand much higher tempsthan that.


But the question come down to this. Is this a cell you want in your powerwall or pack or whatever you are building.
I say no. There are plenty of cell that do not exhibit this phenomenon so that's all I have to say IMHO.

Wolf
 
I'm thinking of reducing my charge current and have also been contemplating introducing some fans. I was only at 1000ma to speed up the charge. I may be doing my testing arse about face! I charge to full and check for SD, then IR (when yr1030 arrives) and finally capacity.

I've seen specs on cells like that as well. Also some loon on another forum suggested 90C which quite frankly is eye watering and scares the living hell out of me!

Absolutely couldn't agree more do I want such rouge cells in my build probably not. But assuming IR is not an issue (which I can only assume seeing as I can't test it. At this moment can't think what else could cause a high cell temp other than IR) I'm going to be building a small powerwall so therefore the draw per cell is never going to get anywhere near 1A not at least for a sustained amount of time. Therefore am I worrying un unnecessarily? As I said before minefield!


PS side note where are you based?
 
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