B or C grade cell ideas ... test & use

I have been processing some laptop packs and get some cells that get extremely hot during charging Not Sanyo cells, but ones like this
https://secondlifestorage.com/t-Panasonic-CGR18650E-Cell-Specifications
and
https://secondlifestorage.com/t-Panasonic-CGR18650D-Cell-Specifications

I decided not to use the Lii-500 chargers to charge them for testing because if I just limit the charge to 4.0 or 4.1, I can control the heat much better. They tent to get too hot to handle while its trying to reach 4.2v, and often times take forever for charge to terminate. They just sit there cooking. I will charge using my iCharger, and discharge test only with the LitoKala. Also, does the heat subside after multiples cycles, has anyone tested this?

If these cells still test with some capacity what would use you them for? I was thinking of making a portable battery pack for some camp lights... non critical things or smaller projects where the loads are extremely low current for both charge and discharge.

I have run into Panasonic cells with the same behaviour as the well known Sanyo cells. Panasonic bought Sanyo back in 2009 and maybe some of the reasons why Sanyo cells do that were transferred over to Panasonic cells.

Potential usage for them, yes, sure, for any below 4.2V situations, just like the Sanyo cells. Doesn't even need to by low current as the cells have no problems with current, you have tested exactly that. It's just that they won't reach 4.2V and turn the excess energy into heat.

Just like the Sanyo cells they may stop heating up after several cycles. However, my sample size of affected Panasonic cells is tiny, just six cells. So I assume they maybe would, just like some Sanyo cells, but unlike with Sanyo cells I've not witnessed this myself in practice.

I appreciate the insight My sample size of those two specific types of cells are growing, and the ones that do get very hot are not testing particularly well at around 1000mah to 1300mah. Sufficient for the types of small projects I will use them for, but certainly not grade A for powerwall building.

I use them for practicing to throw them into the bin. I would personally never use any cell that shows sign of damage

Well, if they have so little capacity left then I wouldn't use them for anything.

When they overheat, just remove them and retry the charge after 3 days. Some will fully charge, some will overheat at a higher capacity, in which case give them another 3 days for chemistry stabilization. I found this method to be able to recover many cells and most had over 50% capacity.

I would comment about checking the IR of the cell but you all know my position on that and the spreadsheets to back it up.
But I won't do that as you all know my answers.
Ah I can't help myself
Results of IR and capacity on the CGR18650E and D cells.
Oh by the way most of the high IR ones had high charge temps. Sorry I don't have that documented but your just going to have to trust me on that.
Sample of the E cells.



These are all the D cells I have tested so far.




Oh wait I just did comment on that darn i was going to stay quiet.

Wolf

@Wolf

I remember when you started this data collection and testing project, and to be honest at the time I thought it was a tab bit overkill, but now even I am starting to benefits from the fruits of your labor.

Thanks for putting this together. Nice to see how my cells stack up to their peers. I will proceed with a charge, 3 day rest, discharge/charge/IR testing and see what happens. Doing it for the fun and science at this point.

CrimpDaddy said:

@Wolf

I remember when you started this data collection and testing project, and to be honest at the time I thought it was a tab bit overkill, but now even I am starting to benefits from the fruits of your labor.

Thanks for putting this together. Nice to see how my cells stack up to their peers. I will proceed with a charge, 3 day rest, discharge/charge/IR testing and see what happens. Doing it for the fun and science at this point.

Click to expand...

@Crimp Daddy
I am glad you found it useful.
It makes it worthwhile to have this data and be able to reference it at a moments notice.
It is also nice to see the trend that is becoming evident IR is an important factor in all this.

Wolf