Samsung 29E- E6 and E7 What differences are there and what are your experiences of these cells?

[leffex]

Regarding the two versions of these cells.

What is your experience?

For me I have had a really bad experience while welding a Samsung 29E version 7 China made cells. I was making a 10s1p for testing purposes without cell holders and on the last weld with solder. As I was soldering the balance leads with a hot iron the cell bursted into fire and I had to rid the pack outside.

facts:
The cells were new
The cells had been revived from 1v
The cells were at 4v charge level

This was a very bad experience for me which makes me hold my distance from these cells.

Are these Samsung 29E cells bad or more prone to failure than other samsung cell modells or other cell brands? Also does the China version of the cell have other type of shell than the original Samsung 29E version 6 cells?

Should I just keep away? Are there something hidden in the shells or in the secret mixture inside the cells that makes the E7 version different than the other version of the cell? My question is if I should reconsider my fellings and take into account real facts rather than my single bad experience.

 

[E-HP]

The cells had been revived from 1v

This may be an issue.

 

[harrisonpatm]

As I was soldering the balance leads with a hot iron the cell bursted into fire

And this is another. There is plenty of info online regarding reducing risk when soldering cells, but that's all it is, a reduction of risk.

My question is if I should reconsider my fellings and take into account real facts rather than my single bad experience.

It's not recommended to 1.) recover cells from lower than 2v, and 2.), solder cells. As someone who has done both, I'd recommend you take a step back and reconsider risk, before something worse happens than a single cell fire.

 

[Zambam]

Was there a spark before it burst into fire? Where was the balance lead soldered (middle of 2 cells or on the welds)? How many seconds on average was the iron on the cells to solder each balance wire? How many balance wires were soldered before the fire?

Good you were able to get it outside and not burn the place down. Was there a lot of fumes? Did you burn yourself? Did the pack completely burn down and how long did it take?

 

[docw009]

Wow. Thanks for sharing. Reviving dead lithium cells is too risky for me.

 

[amberwolf]

The cells were new
The cells had been revived from 1v
The cells were at 4v charge level

If they were new, they wouldn't have been at 1v. If they were at 1v, they weren't new, even if they were "unused". They'd either have to have been recovered from something else, or been stored so long they self-discharged (years), or stored in environmental conditions that caused them to discharge (shorting across cells against things, etc).

The source of the cells may also make a difference--there are plenty of places selling "new" cells that are either not really new, or they are scrapped cells that were rejected from the factory and supposed to be destroyed or recycled for materials. Whether those get into the regular supply lines available to DIYers that usually carry reputable cells, I don't know, but I'm sure they're in the supply chain for really cheap suppliers and probably pack builders.


Either way, i wouldn't use cells that have dropped that low. (myself I wouldn't use them below whatever the minimum on their spec sheet is). ***

and on the last weld with solder.

The wording is unclear, but if that means soldering to the actual cell case, I wouldn't do that either--enough heat could damage the cell internals, and either allow an internal short or actually start a chemical reaction leading to runaway. ***


***just because some people have gotten away with doing these things doesn't mean it's safe to do.

(it's possible to not get run over when stepping out into traffic, too, if all the traffic is able to stop in time and is paying attention, but people die doing it because sometimes the stopping doesn't happen).

This was a very bad experience for me which makes me hold my distance from these cells.

While it's impossible to know after the fire, I honestly don't think it's the cell brand or model that was the cause here.

 

[docw009]

It seems that Google AI has determined it is safe to revive dead cells. Bummer. Going to be a lot more incidents.

 

[amberwolf]

It seems that Google AI has determined it is safe to revive dead cells. Bummer. Going to be a lot more incidents.

Well, it *was* on the internet, so it *must* be true, especially since a *computer* said it was ok!

 

[leffex]

It seems that Google AI has determined it is safe to revive dead cells. Bummer. Going to be a lot more incidents

Haha. Ye. It sure doesn't know the risks yet. They have to input that manually to the AI for it to be correct or risk-adjusterd to real life conditions. AI won't help as this information with 18650 and lipo cells aren't on the web. It is in peoples head and experiences.

Was there a spark before it burst into fire? Where was the balance lead soldered (middle of 2 cells or on the welds)? How many seconds on average was the iron on the cells to solder each balance wire? How many balance wires were soldered before the fire?

Good you were able to get it outside and not burn the place down. Was there a lot of fumes? Did you burn yourself? Did the pack completely burn down and how long did it take?

No spark. I was on my last balance cell and I put pressure on the end cap on the positive side to weld the balance wire onto it. The nickel piece bent inwards while I put pressure on it and went into the cell perhaps. It bursted into fire like they do and I grabbed it and walked out the door. My college but a lid on it outside, well box lid and it smoked lightly and burned most or all the cells. 10s1p pack fully assembled in a row.

I got small burns on my fingers aching but not visually broken more than red. They ached for a few days and then nothing.

I just had to build a test rig and

I'm killing the cells. They might be fine but I have no wish to use them or any usage so the value of them is zero anyway.

Normally I would trust a 18650 to hold hight voltage charge as stated by test from our famous ebike.ca guy but the questions is not if the cell can take it but how long it will hold that witout being a security risk. That is still unknown. Noone has done a longer test as of yet to my knowledge.

In the end it is handling or user error to be the cause of this. IE: me. A solution is to weld nickel plates onto the balance wires and then use a spot welder to add these to your pack.