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Cell discharge mapping [Serious]

Does anyone have the discharge mapping for lithium-ion cells?

I have a great map for LiFePO4 that works very well. Wondering if anyone had this for lithium-ion.

Best lithium-ion chart so far (IMHO)

Best lithium-iron chart so far (IMHO)

(none)

LiFePO4

charge: 3.65 V
100% 3.6 V
90% 3.315 V
80% 3.301 V
70% 3.287 V
60% 3.273 V
50% 3.259 V
40% 3.246 V
30% 3.232 V
20% 3.218 V
10% 3.204 V
0% 3.19 V

in a 12S configuration, this becomes

charge: 43.8 V
100% 43.2 V
90% 39.78 V
80% 39.612 V
70% 39.444 V
60% 39.276 V
50% 39.108 V
40% 38.952 V
30% 38.784 V
20% 38.616 V
10% 38.448 V
0% 38.28 V

3 Likes

How would this mapping take into account different cutoffs?

This is just the physical cell’s characteristics and will vary from cell to cell anyway. This information can be had from the discharge graphs, but it’s much less friendly to use in that form.

nicer than ion with ion’s huge spread from full to empty. dont know why everyone uses ion instead of lipo for this reason.

1 Like

Courtesy of @eBoosted found on the old forum seems pretty close in my experience

If anything it’s a little on the aggressive side as you can discharge to 2.5 but almost no one does that as its a minimal capacity gain.

Properly telling battery percentage when its not a constant current flow is always a bit of a shitshow especially in the 3.6v range to have really accurate capacity measurements you need a coloumbmeter and monitoring software/hardware to essentially track current in vs current out.

2 Likes

This is what I use…

PERCENTAGE VOLTS per CELL Volts 10S Pack Volts 12S Pack
100% 4.2 42.00 50.40
90% 4.1 41.00 49.20
80% 4.0 40.00 48.00
70% 3.9 39.00 46.80
60% 3.8 38.00 45.60
50% 3.7 37.00 44.40
40% 3.6 36.00 43.20
30% 3.5 35.00 42.00
20% 3.4 34.00 40.80
10% 3.3 33.00 39.60
0% 3.2 32.00 38.40
5 Likes

That’s linear though

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I didn’t say it was right, just what I used :slight_smile:.

6 Likes

your discharge graph doubles discharge from 100 to 90%:

image

is that on purpose?

this is just a linear discharge graph but can modify the cutoff voltage:

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Yes, it’s on purpose. It falls from 44V to 40V in a matter of seconds but then stays there for a long time.

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true, it goes fall off a cliff from full charge.

I found this

components_tenergydischarge

and from that I produced this

components_tenergydischarge

and extrapolated this

Li-ion voltage Cell 10S 12S
charge 4.20 42.00 50.40
100% 4.00 40.00 48.00
90% 3.80 38.00 45.60
80% 3.72 37.15 44.58
70% 3.66 36.60 43.92
60% 3.61 36.10 43.32
50% 3.58 35.75 42.90
40% 3.54 35.35 42.42
30% 3.51 35.10 42.12
20% 3.43 34.30 41.16
10% 3.30 33.00 39.60
0% 3.00 30.00 36.00

Of course you do need a coulombmeter to get an accurate reading, but this is for estimating based only on voltage.

7 Likes

Well with ackmaniacs app you can get the total WH (if you measure from start to end). Or with hobby charger measure how much capacity you put back into the battery. Total WH usable would vary greatly based on cutoff voltage and slightly from end of charge voltage used. For example cut off from 3.2v down to 2.9v i saw a big increase in range.

Been meaning to track my WH consumption myself so i can get an accurate battery % estimate and estimated range.

1 Like

by BIG increase… what increase are you experiencing, in terms of Kms, or better %increase in range???

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Well me and @thisguyhere did a 45 mile ride, I would have hit 3.2v 10 miles short of that ride… Also I can hit hills when I’m at 3.5v per cell without hitting cutoff (which is scary)… So maybe 10-20% extra. My battery is 12s7p

2 Likes

This could be redone with a different cutoff – I scaled the bottom so that 100% fell on 3.0V

2 Likes

You have to this for each individual cell, there isn’t a global discharge curve

Go here, find your cell and to the mapping on the 0.2C discharging, works like a charm, if you want to go a step further you can do a polynomial regression and find the equation that relates open circuit voltage to state of charge

https://lygte-info.dk/review/batteries2012/Common18650IndividualTest%20UK.html

This is for NCR18650GA

2 Likes

Do have this information for a 30Q cell with 2C discharge? In increments of 10%?

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You can get from here, but I can do it latter

https://lygte-info.dk/review/batteries2012/Samsung%20INR18650-30Q%203000mAh%20(Pink)%20UK.html

3 Likes