Li-Ion(LCO/LMN) Voltage⇌Percentage Table [NUMBER HEAVY]

Batteries and Chargers Rechargeable Batteries
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I made this table a couple weeks ago since I had free time. I asked myself if the ranges 2.5~4.0 were a 0% charge baseline, and 4.2 was the 100% charge, then I could have a voltage increment per percent, and possibly calculate them in a table. And voila. I was hesitant at first to post this, because I could totally be wrong with the math (I could still be wrong now). I do apologize if this is totally super-wrong and would love feedback for possibly correcting this (unless it isn't). I also do apologize if something like this already exists. :P

This is an estimation of percentage by voltage for LCO/LMN (as topic states) and is no means a way to measure the numerical capacity of a cell. Also this is a best case scenario (linear curve) by which I am not factoring cell health, quality, load resistance, internal resistance, and discharge current.

Other resources to refer to:

https://docs.google.com/spreadsheets/d/1ygwio-7ZwkRUf82A_cFYFU2jic3Io6IFMmizxDjurKI/pubhtml?gid=0&single=true


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Spreadsheet/Google Docs Link

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Could this in any way be graphed out and plotted and look something like HKJ’s and others battery discharge diagrams?

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I don't see why not. There should be enough values to make a visual diagram, but this table for me is enough. So I'll trust the plotting to someone else who would care to do so. :)

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Hi Otanacious,

I think that you got some interesting information here, but I'm not sure because I have difficulty reading your table. Call me lazy, I tried for a few minutes and have not got it yet.

As Warhawk already suggested: could you represent the information in a way that the 'raw table challenged' folks have a bit more access to the story? :-)

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I couldn't do all of the columns simultaneously, so I used the 3.6V column as a sample. Cooked it up in Google Sheets.

There's a link to a pseudo-interactive table in the pic. Now visually you can see how linear that table will be :D!

Col1

3.6 0
3.63 5
3.66 10
3.69 15
3.72 20
3.75 25
3.78 30
3.81 35
3.84 40
3.87 45
3.9 50
3.93 55
3.96 60
3.99 65
4.02 70
4.05 75
4.08 80
4.11 85
4.14 90
4.152 92
4.164 94
4.17 95
4.173 95.5
4.176 96
4.179 96.5
4.182 97
4.185 97.5
4.188 98
4.191 98.5
4.194 99
4.197 99.5
4.2 100
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the data feels wrong, maybe some expert can chime in, i cannnot tell why i am feeling :)

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But maybe too much. You point out in the top left some of the limitations of the ‘purely mathematical’ table. Then that tends to get lost in the ‘noise’ the table itself makes. It is SO detailed it tends to make you think it’s accurate. It’s not, it’s just an approximation. As there is considerable variation in cell history, quality, and chemistry the actual discharge level vs. capacity varies a lot.

I think this simple table often use for lipos (functionally similar chemistry to Lion) for radio control is much easier to look at, use, and since it’s just a rough approximation anyway is all that is really needed.

(Note-the last column is simply x3 for a 3S pack, commonly used in RC. Also note that the 2 approximations don’t totally agree with each other. This reflects the variable level of these approximations.)

4.20v = 100% 12.6v
4.03v = 76% 12.09v
3.86v = 52% 11.58v
3.83v = 42% 11.49v
3.79v = 30% 11.37v
3.70v = 11% 11.1v
3.6?v = 0% 10.8v

Or if you must have a bit more detail.

Voltage per cell (no load) capacity remaining in %
4.2 100 12.60
4.17 98 12.51
4.13 –95 –12.39
4.1 –92 –12.3v
4.07 - 89 –12.21
4.03 - 86 –12.9v
4.0 - 82 –12.0v
3.96 –78 –11.88
3.93 –74 –11.79
3.9 –69 –11.7
3.87 –64 –11.61
3.83 –59 –11.49
3.8 –53 –11.4v
3.77 - 47 –11.31
3.73 –36 –11.19
3.7 –22 –11.1v
3.66 –12 –10.98

Take it to the field, don’t take it to the bank.
For folks that fuss over the last 0.1 charge and pretty much any discharge under 3.0v are mostly chasing trivial amount of capacity, and hammering the cell harder.

Addendum - just noticed a link to HJK’s work was at the top of the first post. At the very bottom of that page is a chart that is similar to what I’ve posted and reflects about all the accuracy required.

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I don't understand what the diagram attempts to show.

What has been calculated and how?

When do you have 4.01 volts and 5% of max capacity in mAh? Or should that be 5% of max capacity in Wh? (Top right)

What are the actual units of the different labels and the values in the diagram?

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OP, dude, this is BLF not the other place. You don’t have to apologize for anything. Thanks for taking the time to post your results.

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I use HKJ’s excellent work for reference:

http://lygte-info.dk/info/BatteryChargePercent%20UK.html

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Yes, same link OP has on the top of his page and at the bottom of my posting.

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Sorry my eyes had already glazed over from all the numbers….

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Yes, that’s the problem with the ‘big’ table. :slight_smile: Lots of work obviously went in to it but it’s difficult to look at and use.

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That graph looks alot like a charge curve (capacity) on a Li Ion battery

They look a little different from HKJ’s because he uses a line, but if you compare it to most of his charge patterns it follows that distinct curve as LowLumens suggested

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Thanks for the feedback guys. I understand the table is a cluster**** of numbers, and is quite hard to read. I'll throw up more of those pseudo-interactive graphs in a bit. Google sheets can't make hi-res charts :(.

As for the accuracy of the calculations, they are all approximate results and linear, but should be near or in the ballpark for a charge/voltage comparison. I assume there is still a modest margin of error and peer review is encouraged :).

Also I want to be able to throw in values for resistance (in ohms) and have the numbers adjust respectively, but that is beyond my capable math skills.

@Adoby The columns that are greyed out are there for reference, more so a "what-if" scenario. If in some alternate reality where a Li-Ion cell were to bottom out at 4.0V.

17

Updated Post #1 with a somewhat visual representation, and a link to the doc. The graphs all look the same because there's no variability in the calculations.