Hello everyone,
first post here (in three parts) - but long-time lurker in this (sub-)forum
And now finally registered as I have questions about li-ion batteries, hoping someone has some thoughts on them. I just read the forum rules and concluded that to comply with rule 13c I need to split it into three different threads to avoid a cluttered thread with a meaningless title.
I apologize if that was incorrect and ask for merging the threads if that was the case.
So in this thread only the things about some strange things in connection to a certain battery model.
OK, I admit - this is a strange one. I have already made up my mind to recycle these cells as I don't think I should continue to use them, but my interest in the topic still fuels my curiosity about what was going on with these batteries
The battery in question is the E-Stream ES18650-26EP.
I have 8 of them in four 'married' pairs.
These are high cycle life cells - that's why I bought them.
I only buy cells that were tested with good results by either Mooch or by HKJ (aka lygte-info); in this case the test was from HKJ and was pretty positive. Also I buy only cells where a full datasheets and safety reports are available, which is the case here.
They are specified with 2600 mAh and a CDR of 7,5A (for high cycle life) or 15A (for "normal" cycle life on the same level as other cells). I always used them in the recommended way for the higher cycle life, that includes not only a max. CDR of 7,5A but also a slower charge speed.
But here's some things I find a bit strange:
- It's nothing new that cells get exaggerated ratings, but these were highly UNDERrated - they have almost 2700 mAh and as the mods normally turn off at 3,2V I guess their true rating is more like 2800 mAh.
- The cells were in married pairs, but started to "diverge" pretty soon - and that has gone really extreme now! Sometimes the difference between both cells in a pair is 300-500 mAh!
- In three of the four pairs one cell discharges MUCH faster than the other.
- Several cells have started to self-discharge at a high rate!! It's noticable that after a rather short time (2-3 weeks) they loose a significant amount of charge. (Internal short?)
- They never got noticably warm in use or during charging.
- All eight cells had and still have low IR measurements (around 30 mOhm).
A long time ago I had a very similar case with a pair of Samsung 30Q where I just gave the "misbehaving" cell to the recycling and used the surviving cell for single battery devices. I was thinking about doing the same thing here, but decided against doing that as I feel that it's only a matter of (not that much) time until the other cells start doing the same thing.
My questions are:
I came to the conclusion that whatever happened to these batteries - the self-discharge shows that they are potentially very dangerous in their current state, perhaps even when not used. Would you agree?
I decided that it's best to recycle all of them without trying to use the non-suspicious one as single cells. As I always try to minimize waste and replace things only when needed I ask: would you agree?
And what could have happened to them to cause this? Is there a common, a typical reason for these phenomena (given the fact that I once had a 30Q pair diverging quickly)?
Again: This is not about me wanting to continue using these cells. I have already decided to sort them out as I don't trust them anymore. This is just out of my interest for that topic (that was incited by Mooch's YouTube videos some years ago).
Any thoughts on that would be highly appreciated and thanks for reading!
Greetings,
Axxe
first post here (in three parts) - but long-time lurker in this (sub-)forum
And now finally registered as I have questions about li-ion batteries, hoping someone has some thoughts on them. I just read the forum rules and concluded that to comply with rule 13c I need to split it into three different threads to avoid a cluttered thread with a meaningless title.I apologize if that was incorrect and ask for merging the threads if that was the case.
So in this thread only the things about some strange things in connection to a certain battery model.
OK, I admit - this is a strange one. I have already made up my mind to recycle these cells as I don't think I should continue to use them, but my interest in the topic still fuels my curiosity about what was going on with these batteries
The battery in question is the E-Stream ES18650-26EP.
I have 8 of them in four 'married' pairs.
These are high cycle life cells - that's why I bought them.
I only buy cells that were tested with good results by either Mooch or by HKJ (aka lygte-info); in this case the test was from HKJ and was pretty positive. Also I buy only cells where a full datasheets and safety reports are available, which is the case here.
They are specified with 2600 mAh and a CDR of 7,5A (for high cycle life) or 15A (for "normal" cycle life on the same level as other cells). I always used them in the recommended way for the higher cycle life, that includes not only a max. CDR of 7,5A but also a slower charge speed.
But here's some things I find a bit strange:
- It's nothing new that cells get exaggerated ratings, but these were highly UNDERrated - they have almost 2700 mAh and as the mods normally turn off at 3,2V I guess their true rating is more like 2800 mAh.
- The cells were in married pairs, but started to "diverge" pretty soon - and that has gone really extreme now! Sometimes the difference between both cells in a pair is 300-500 mAh!
- In three of the four pairs one cell discharges MUCH faster than the other.
- Several cells have started to self-discharge at a high rate!! It's noticable that after a rather short time (2-3 weeks) they loose a significant amount of charge. (Internal short?)
- They never got noticably warm in use or during charging.
- All eight cells had and still have low IR measurements (around 30 mOhm).
A long time ago I had a very similar case with a pair of Samsung 30Q where I just gave the "misbehaving" cell to the recycling and used the surviving cell for single battery devices. I was thinking about doing the same thing here, but decided against doing that as I feel that it's only a matter of (not that much) time until the other cells start doing the same thing.
My questions are:
I came to the conclusion that whatever happened to these batteries - the self-discharge shows that they are potentially very dangerous in their current state, perhaps even when not used. Would you agree?
I decided that it's best to recycle all of them without trying to use the non-suspicious one as single cells. As I always try to minimize waste and replace things only when needed I ask: would you agree?
And what could have happened to them to cause this? Is there a common, a typical reason for these phenomena (given the fact that I once had a 30Q pair diverging quickly)?
Again: This is not about me wanting to continue using these cells. I have already decided to sort them out as I don't trust them anymore. This is just out of my interest for that topic (that was incited by Mooch's YouTube videos some years ago).
Any thoughts on that would be highly appreciated and thanks for reading!
Greetings,
Axxe
