If we can’t get hummie off this thread then it’s no longer a good source for battery building knowledge.
And should we erase what battery university says? I can post many sources saying the same. If u find something showing it’s unsafe please post it. I’ve been looking and as I say all the sources I’ve found post 1-2v as the minimum beyond which it’s not safe.
Im looking for answers. I don’t have an answer.
If you watch that through and still go "hurr durr not absolute undeniable 100.000% proof " then i genuinely think you have a mental disorder that doesn’t let you agree with any ideas that you perceive as popular or not your own.
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YouTube 
That’s one source. There are many. I’m looking for them but preferably more scientific.
These folks seem to be going with 1.5v
@jack.luis your video is related to charging “a dead battery. Totally flat”.
You dumb fuck.
Should I write to them on endless sphere and battery university and tell them they’re dumb?
I don’t let any endless sphere user within 200ft of my house with their electronics. That’s where boomers go to exchange fucking shitty advice
The absolute WORST esk8 build I’ve ever seen came from a endless sphere user
Manufacturer’s data sheet
I have found much on the Battery University site that contradicts a decade and a half of close observations, and experiments, regarding care and feeding of Lead Acid batteries, for maximum lifespan and performance during that lifespan in deep cycle applications.
Some of their statements, on Lead Acid batteries, need a list of qualifiers before it can be construed as accurate, sometimes, in some situations, on certain batteries.
It’s easy to tell that the person in charge of the wording has never actually watched an ammeter, or voltmeter, or Columb counter even once, much less so over the hundreds of potential cycles the battery is subjected to.
But they blanket statement so much, with no qualifying asterix saying when and or under what conditions the statement is, or might sometimes be true.
Likely as they do not know and/or misinterpreted the actual engineer’s experienced opinion.
Often, they are just flat out wrong.
I’d not trust what they say about Lithium, any more than I do on Lead Acid. I think it is more like’ Battery Preschool’, and that ‘University’ is a serious injustice to actual universities.
Lithium has far more potential consequence.
I think any one saying that lithium can be safely restored to functionality after depleting to under 2.5v, needs to prove it with actual data, not:
“It has not yet burnt down my workshop, or the workshops of anyone I know personally, therefore doing so is perfectly safe.”
Seems it would not be too hard to identify how much capacity is lost when Cell A is depleted to less than 2.5v, and for how long it resided there, before being recharged.
The recovered cell, how long did it take, when CC, switches to CV, for amperage to taper to 0.05c, before and after that overdischarge event.
With the same charge current, before and after overdischarge, how hot does the cell get?
How about on discharge?
Cycle life testing, accounting for all the known variables, is amazingly time consuming.
I don’t really trust that the time is being spent testing, for any authoratative safe/not safe declarations to be made.
The pros have identified that a cell that is overdischarged below 2.5v is far more likely to become dangerous than one which has not.
Good enough for me.
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@hummieee ur littering this thread with absolute nonsense. If u wanna have pointless, toxic debates, facebook already exists.
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far from pointless or nonsense. Again I’m just asking if there’s any valid sources anyone can post stating what is the lowest a cell can go and still be safely used.
I’m not even debating anything other than that it’s debatable and there’s no solid data
Everything is debatable. Stop muddying the waters. You got your explanation and you’re still going on please stop.
This is a dangerous activity. You are making it more dangerous. You have been given plenty of information and are still doing your stupid thing.
There are some people who should be gate capped from working on batteries and I think you belong on that list.
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Your problem is that you’re looking for things that assume definitions for things that aren’t clearly defined, or ascribed to value judgments.
“Where’s your source” gets fairly useless without good faith discussion, and I don’t really see much good faith discussion here.
You’d have to describe what “safe” is, and then come to some sort of agreement of that, since risk assessments are largely personal choices in this hobby.
There’s very little that’s “safe” regarding lithium ion batteries in general, and most things about them are better put in a spectrum of less dangerous to more dangerous.
As for low voltage cutoffs, you’d also have to first lay out what cell model, its age, how long it’s spent below the manufacturer’s LVC, what conditions it took to get there, and if that number is a dynamic or static measurement.
At that point, you could try to lay out rationale to arrive at something like a general guideline set for uses that fall in many of the cases we’re likely to see.
Regarding my video, that’s an old one, and I’ve learned a lot since then. Mostly, practical data collection and in-practice life of packs.
I still stand by what I said in that video, and the reasons for maintaining my position are based on what I admit, is a conservative figure of roughly ~300 packs made and shipped at this point in my career. It’s not as large as some vendors, but I’ve paid enough close attention and collected enough field information, to have what I believe are reasonable ideas about pack failures and their failure modes.
Over discharge is one, and in my current field, it’s simply not advisable to say that a lithium ion pack that’s drained and settles with cells below the LVC for the BMS (or as outlined by the cell manufacturer) should be “revived” or “awoken” or whatever nonsense term Battery University wants to use.
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Safe?
We don’t know and you won’t find any good numbers because no one has tested it for the cells we use. All you’ll ever find is numbers chosen just to make things easy (based on zero actual data) or what they think seems reasonable as a cutoff (again, based on nothing).
You’ll have to define “safe” too.
Is crossing that threshold what will cause thermal runaway 100% of the time? Or has a group of cells become unsafe to use if a certain percentage of them go into runaway? Or is something unsafe if even one cell might go into runaway?
The different answers could create a range of numbers/situations ranging from unsafe being…for examples…1.8V or lower for six hours or longer at 24°C or higher for a cell of a certain age and model number. As the cell ages this will change though. This might cause one in a million cells to be “unsafe”.
The other end of the range could be that unsafe starts at being at 0.2V after 1000 hours at 45°C or higher for an average cell cycled 200 times within certain charge/discharge current levels. This might cause all cells to be “unsafe”.
Which scenario is the one that we feel defines when a cell is safe or not? It all changes for each cell model too.
All this is why there is no data we can use to flirt with disaster. No manufacturer allows use at below the 2.5V cutoff, none of the big customers for these cells would ever operate that low (for liability and performance reasons). Few researchers will spend all the time and $$$ testing scenarios that these cells will never see.
Any numbers you see…1.5V, 2.0V, whatever…are chosen without any science or data to support the choice. It just seems like a good number to use for the article’s author.
If you want numbers you can actually use you’re going to have to test some cells.
Having said all this, there are research papers with cycling down to zero volts and lower (“reverse charging”) and discussions of dendrite formation that can cause a cell to be unsafe. But I’ve never seen papers talking about where a safe/unsafe threshold might exist…even for a particular cell.
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Can’t wait to see how hummie dismisses this.
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I haven’t dismissed anything. That’s the point. There’s many sources and none have solid evidence so I’m not dismissing.
When batteryhookup sells me the cells and tells me they will cycle fine as long as over 1v it makes me wonder.
Tell me if I’m wrong but it seems dendrite formation is the danger in the case of using over-discharged cells and also a danger that forms and increases in cells that have been cycled toward the end of their life when capacity is down to maybe 80%. Are cells supposed to be discarded that drop below 80% capacity?
This bafoon is still arguing
What do u think I’m arguing? YOU and ur insults are what make this discussion toxic. I’m just asking questions. I haven’t dismissed any answers.
I’m getting toxic like the gasses that will fill your house when you try this shit lol
Battery building isn’t the place for your hate for technical authority
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That is the typical end-of-life spec set by cell manufacturers (some cells are 70% or 60% though).
What happens then is up to the company designing those cells into a device. Most devices don’t track capacity with their BMS’ and very few BMS’ that do track capacity will lock out a user once the cells drops 80%. It’s almost always left to the end user to decide when to stop using a cell.
The longer a cell is used though the greater the risk for trouble. Dendrite formation continues, IR keeps rising (creating more heat), electrolyte keeps decomposing, SEI layer thickens, active material particles crack, etc. At a certain point the loss in run time and the increased risk makes continuing to use the cell a silly thing to do.
This all happens long after the 80% point as that’s set to create a good safety margin. Many cells can be used in a “second life” application after reaching 80%, like energy storage (ESS) where the current draw is low. Depends on the cell though and how much it was abused, or not, during its first-life.
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