How far can LiIon be discharged?
- Thread starter HKJ
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It seems you may be missing the point. As I said above, the goal was to provide a simple explanation of the role that internal resistance plays in voltage dropping / bouncing. Lack of knowledge about this is at the heart of many FAQs here (including the matters you address above).
More precise models are not required for such basic qualitative understanding of the underlying phenomena.
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HKJ
Flashaholic
If that is the goal, then write an article about it. Again: This article is about when batteries run empty. The voltage recovery in this case is more than twice the value compare to a battery with some energy left and if it happens instantaneous or over some time do not really matter (The model your published covers neither case).
The interesting part is that there is a significant voltage recovery, it is fast enough to prevent measure the discharge end voltage and it varies with a couple of factors. I believe I have covered all of that.
Great write up HKJ - thank you.
In my experience it is VERY noticeable when a cell is close to empty -i.e. The light gets dimmer or steps down.
Even with my direct driven lights being left on Ive rarely had a cell go below 3v unloaded/resting.
I much prefer the dimming or stepdown on bare/unprotected cells than th cutoff of a protection circuit.
Seems like even in a direct driven led scenario it's hard to drain a modern cell to dangerous levels due to the VF of the emitter and rising IR of the cell.
In my experience it is VERY noticeable when a cell is close to empty -i.e. The light gets dimmer or steps down.
Even with my direct driven lights being left on Ive rarely had a cell go below 3v unloaded/resting.
I much prefer the dimming or stepdown on bare/unprotected cells than th cutoff of a protection circuit.
Seems like even in a direct driven led scenario it's hard to drain a modern cell to dangerous levels due to the VF of the emitter and rising IR of the cell.
See above - I already posted a short exposition by an expert in the field.
For qualitative understanding it matters little that the bounce is bigger at the end of discharge. What matters is that it is significant and prevents said naive measurements from succeeding. The same holds true for the termination of any (dis)charge at any point, or, more generally, for any nontrivial change in current (for nontrivial time). But this will not be clear from what little is said in the OP.
The models convey accurate qualitative understanding of the reason for the voltage bounce. Precise quantitative understanding is not required for the above purposes (nor is it conveyed generally by the single graph in the OP).
Yes, but simply pointing at a graph and saying "this is what happens" is not the same as imparting some conceptual understanding of the underlying phenomena. Unlike a graph, models apply generally and allow one to make very general inferences. For example, from what little is said in the OP it will not be clear that, by symmetry, a voltage drop occurs at the end of a charge, and that these bounces are (roughly) proportional to the current, and that analogous bounces occur with any nontrivial change in current. These and related inferences are all immediate if one understands any basic model incorporating internal resistance (which requires only basic knowledge, viz. Ohm's law).
Of course one needs more complex models to deduce more precise quantitative information - which requires understanding how internal resistance depends on various parameters (SOC, temperature, etc), and the role played by time constants of various internal processes, etc. But none of this complexity is required in the OP.
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sidecross
Flashlight Enthusiast
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Arguing the exact count of 'how many angels can dance on the head of a pin' is in the next room down the hall. :wave:
scintillator
Enlightened
Thank you for the great post HKJ.
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SubLGT
Flashlight Enthusiast
I only understood about 15% of this "brief exposition". I understood 100% of the original post.
MAD777
Flashlight Enthusiast
My thoughts exactly! 👍
It goes without saying that diving deeper into the underlying science requires further effort. But you only need to understand a small part of that article to grok the role played by internal resistance. Once you do, you'll have a much deeper understanding of the essence of the matter.
Milw light
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Thanks HKJ, you the best.
KeepingItLight
Flashlight Enthusiast
I, for one, appreciate the extra detail. I copied out the section Gauss123 posted from a battery textbook. That's okay for me. As it turns out, I am minimally qualified to understand it! It is right at the boundary of my existing knowledge, so I learned something.
What bothers me, however, is the tone that these discussions sometimes take on. When they become contentious, they are uncomfortable to read.
What bothers me, however, is the tone that these discussions sometimes take on. When they become contentious, they are uncomfortable to read.
HarleyXJGuy
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I agree but if you are able to understand 50% of this material my hat is off to you. Still that said I learn more everytime I come here.
HKJ
Flashaholic
It is possible to ask questions to my articles and reviews and there are usual some that answers (either me or other).
ven
Flashaholic
There is always something to learn, i know for a fact what i know today(not much
) will be not as much as tomorrow............thanks to many members and certainly a mr HKJ. What seems complex over time falls bit by bit into place.............No need to get anal with stuff(unless you want to of course), enough to understand the basics and a bit more.........Cells and chargers are a whole new world, made interesting by HKJ and the time he takes in his threads.
Then just ask, no such thing as a stupid question as long as you dont mind stupid answers :laughing:
Not sure just fire away!!!
sidecross
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+1
I agree about it being 'uncomfortable to read', but from my reading of science history the arguing about who is most correct is a characteristic that is often found.
recDNA
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Great work! I usually charge at 3.7 volts but have occasionally charged batteries at 3 volts and a couple that protection had tripped with no reading at all. Now I kind of think I should recycle them because they may have been very low under load. I never knew that.
degarb
Flashlight Enthusiast
Excellent info. I must save it. Read it slower next time.
My Panas.3400s from fasttech cut off at 2.5, while the kiadomain cutoff at 3.0 volts. I know the capacity, and use only cc 700ma driver. I am guilty of relying on the runtime and protection in cells for recharge indication. I do try to keep a volt meter near charger, since overcharging is reason for explosion. But need to invest in a one handed voltage check. Though a charger should have a button to press to display voltage. I am dreaming, probably.
My Panas.3400s from fasttech cut off at 2.5, while the kiadomain cutoff at 3.0 volts. I know the capacity, and use only cc 700ma driver. I am guilty of relying on the runtime and protection in cells for recharge indication. I do try to keep a volt meter near charger, since overcharging is reason for explosion. But need to invest in a one handed voltage check. Though a charger should have a button to press to display voltage. I am dreaming, probably.
