Lithiums - mAh/100th V - Discharge Tests

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Lithiums - mAh/100th V - Discharge Tests

Post by DrkAngel » Oct 30 2011 10:44am

Prologue:
I believe this method of graphing to be a much preferable representation of battery capacity.

Graph program is a free download from http://www.padowan.dk/graph/.

Li-ion - Lithium Cobalt - LiCo
2600 mAh (laptop recycled cells (Gateway) - unbranded dark red - "China" )
Discharged using iMax B6
Tested at .2C discharge rate, to reduce skewing due to "voltage sag"
Voltage monitored at cell with digital meter

Charged to 4.25V
..V... mAh
4.23V .. 4
4.22V .. 5
4.22V .. 6
4.20V .. 9
4.19V .. 18
4.18V .. 37
4.17V .. 38
4.16V .. 38
4.15V .. 38
4.14V .. 38
4.13V .. 38
4.12V .. 38
4.11V .. 40
4.10V .. 40
4.09V .. 42
4.08V .. 43
4.07V .. 44
4.06V .. 44
4.05V .. 44
4.04V .. 42
4.03V .. 43
4.02V .. 42
4.01V .. 43
4.00V .. 44
3.99V .. 44
3.98V .. 43
3.97V .. 45
3.96V .. 46
3.95V .. 45
3.94V .. 45
3.93V .. 47
3.92V .. 48
3.91V .. 47
3.90V .. 45
3.89V .. 43
3.88V .. 42
3.87V .. 44
3.86V .. 45
3.85V .. 57
3.84V .. 57
3.83V .. 78
3.82V .. 82
3.81V .. 86
3.80V .. 88
3.79V .. 89
3.78V .. 86
3.77V .. 94
3.76V .. 98
3.75V .. 103
3.74V .. 102
3.73V .. 105
3.72V .. 120
3.71V .. 125
3.70V .. 100
3.69V .. 100
3.68V .. 100
3.67V .. 78
3.66V .. 74
3.65V .. 72
3.64V .. 74
3.63V .. 72
3.62V .. 71
3.61V .. 70
3.60V .. 45
3.59V .. 43
3.58V .. 43
3.57V .. 24
3.56V .. 20
3.55V .. 20
3.54V .. 20
3.53V .. 17
3.52V .. 14
3.51V .. 12
3.50V .. 10

Output is reasonably steady from about 4.18V till 4.1V.
Slowly increases from 4.1V till 3.85V
Then increases sharply from 3.85V till it peaks around 3.7V.
Below 3.7V output decreases rapidly till it reaches minimum usable at 3.6V.

Based on these figures:
For Li-ion (LiCo),
Charge-discharge voltages should be,
Maximum 4.18V
Minimum 3.6V

3.85V to 3.65V is the muscle bulge of the discharge curve.
To take full advantage of this "bulge" I would recommend "bottom balancing", at 3.65V.

Charging above is 4.2V is worthless, and unnecessarily damaging.
Same for discharging below 3.6V.
Smooth LiCo s.JPG
Smooth LiCo s.JPG (10.87 KiB) Viewed 6694 times
Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!
Attachments
Smooth LiCo.jpg
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Last edited by DrkAngel on Nov 16 2011 10:31pm, edited 5 times in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Oct 30 2011 11:03am

Li-Po - Lithium Polymer - LiPo
2160 mAh (laptop recycled cells - unbranded "Made in China")
Discharged using iMax B6
Tested at .2C discharge rate, to reduce skewing due to "voltage sag"
Voltage monitored at cell with digital meter
Charged to 4.20V (charging to 4.25V produced no additional "usable" mAh)

..V... mAh
4.23V ..
4.22V ..
4.21V ..
4.20V ..
4.19V ..
4.18V ..
4.17V .. 1
4.16V .. 1
4.15V .. 2
4.14V .. 4
4.13V .. 4
4.12V .. 7
4.11V .. 10
4.10V .. 14
4.09V .. 17
4.08V .. 21
4.07V .. 31
4.06V .. 39
4.05V .. 40
4.04V .. 59
4.03V .. 68
4.02V .. 82
4.01V .. 45
4.00V .. 75
3.99V .. 70
3.98V .. 60
3.97V .. 90
3.96V .. 70
3.95V .. 70
3.94V .. 75
3.93V .. 75
3.92V .. 70
3.91V .. 66
3.90V .. 68
3.89V .. 66
3.88V .. 70
3.87V .. 80
3.86V .. 100
3.85V .. 110
3.84V .. 120
3.83V .. 130
3.82V .. 75
3.81V .. 80
3.80V .. 75
3.79V .. 75
3.78V .. 75
3.77V .. 65
3.76V .. 55
3.75V .. 55
3.74V .. 45
3.73V .. 45
3.72V .. 45
3.71V .. 36
3.70V .. 39
3.69V .. 35
3.68V .. 34
3.67V .. 29
3.66V .. 28
3.65V .. 27
3.64V .. 26
3.63V .. 25
3.62V .. 29
3.61V .. 26
3.60V .. 27
3.59V .. 24
3.58V .. 24
3.57V .. 27
3.56V .. 24
3.55V .. 21
3.54V .. 20
3.53V .. 20
3.52V .. 16
3.51V .. 17
3.50V .. 14

Output is reasonably good from about 4.05V till 3.75V.
Very noticeable, is a muscular bulge near 3.85V.
Decreasing till it reaches minimum usable near 3.7V.

Based on these figures:
For my recycled LiPo,
Charge-discharge voltages should be,
Maximum 4.10V
Minimum 3.7V

I would recommend "bottom balancing", at 3.75V.

Charging above 4.1V looks worthless, and unnecessarily damaging.
Same for discharging below 3.7V.
Smooth LiPo s.JPG
Smooth LiPo s.JPG (10.06 KiB) Viewed 6694 times
Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!
Attachments
Smooth LiPo.jpg
Larger
Smooth LiPo.jpg (38.88 KiB) Viewed 784 times
Last edited by DrkAngel on Oct 30 2011 12:08pm, edited 1 time in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Oct 30 2011 11:38am

The Lithium Cobalt seems to have a very constant capacity, till it peaks strongly, near the lower range of its voltage, but drops drastically to an empty state.
Smooth LiCo s.JPG
Smooth LiCo s.JPG (10.87 KiB) Viewed 6685 times
The Lithium Polymer has a much more gradual taper from full capacity, and towards empty.
Smooth LiPo s.JPG
Smooth LiPo s.JPG (10.06 KiB) Viewed 6685 times
Which raises the possibility that a compromise, between the two might be recommended?
LiPo LiCo s.JPG
LiPo LiCo s.JPG (13.85 KiB) Viewed 6681 times
LiPoCo s.JPG
LiPoCo s.JPG (16.74 KiB) Viewed 6685 times
Introducing the LiPoCo "Hybrid" pack
Smooth LiPoCo s.JPG
Smooth LiPoCo s.JPG (10.67 KiB) Viewed 6685 times
Of course, balance charging might be tricky?
But the steadier, overall, curve might make it worthwhile.
Best asset is the buffering of the LiCo's sharp drop from max capacity to empty!
Last edited by DrkAngel on Oct 31 2011 12:05pm, edited 1 time in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by SamTexas » Oct 30 2011 12:05pm

:roll:
Last edited by SamTexas on Oct 31 2011 12:12pm, edited 1 time in total.

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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Oct 31 2011 10:52am

Please note:
The LiCo is a 2600mAh cell,
compared to the LiPo cell which is 2160mAh.

So, for a direct comparison, the LiPo line might-should be moved up, about 25%?

Image
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Re: Lithium - mAh/100th V - Discharge Test

Post by 999zip999 » Oct 31 2011 12:27pm

that looks interesting.

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Re: Lithium - mAh/100th V - Discharge Test

Post by neptronix » Oct 31 2011 12:44pm

I recommend you get a RC charger that can produce standard discharge graphs. This data is in a non-standard format and the voltage over time discharge graph is what big corps and hobbyists both use.

Image

So basically this data might be useful to you, but needs to be in a different format in order to actually compare with the other 99.9% of battery graphs on the web, on manufacturer spec sheets, etc.


Bottom balancing has been discussed on this forum, and is not recommended for any chemistry.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Oct 31 2011 1:18pm

neptronix wrote:So basically this data might be useful to you, but needs to be in a different format in order to actually compare with the other 99.9% of battery graphs on the web, on manufacturer spec sheets, etc.
Exactly my point! ........ Useful!
I think my type graph might be more useful ... to everyone!
In fact, I specifically decided to create this type of graph, because the "standard" type was so useless!
neptronix wrote:Bottom balancing has been discussed on this forum, and is not recommended for any chemistry.
"Bottom balancing" implies balancing at the manufactures "fully discharged" voltage, variously listed from 2.7 - 3.0V.

I recommend balancing at near the minimum "my recommended usable voltage" 3.6 - 3.7V!

If you want to get the most from your batteries ... balancing at the minimum "usable" voltage will up the battery capacity, as well as protect from over discharging a single cell or bank, which is how the most damage is done.
This is especially well demonstrated in the LiCo graph, where the maximum mAh capacity per 100th V is near the minimum usable Voltage.

Of course, I also recommended lowering the peak charge voltage.
This will provide a safety buffer, allowing weaker banks to charge higher, and still remain in the safe voltage range.
Peak charge capacity is minimal and the loss of capacity is likewise minimal!
Last edited by DrkAngel on Nov 02 2011 9:23am, edited 2 times in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 01 2011 11:03am

I learned a lot from my graphs.

LiCo:
mAh capacity is much better at the lower voltages
3.7V to 3.8V holds almost as many mAh as 3.9V to 4.2V
I will have to make sure and take better advantage of this muscular bottom end.
Has a very wide usable range 3.6V to 4.2V

LiPo:
The LiPo has a much narrower, but beefier range.
3.8 to 4.05 holds about 80% of usable capacity

My LiPo might be prime candidates for a "heavy", or "fast", charge.
A high amp, charge at 4.2V might attain the 4.05V, towards 90% charge, quickly, without having to apply any type of damaging "overvoltage"(above 4.2V)

While this type graph might seem like a lot of work, I certainly learned enough to make it well worth my effort.
Last edited by DrkAngel on Nov 02 2011 10:00am, edited 2 times in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by neptronix » Nov 01 2011 12:37pm

I don't consider it useful, it's quite odd.. and probably laborious to produce ( versus just hitting a button on an RC charger )

All spec sheets for cells are going to have the standard type graph, so good luck getting everyone on board.
The standard type graph can also much easier show voltage sag at varying levels of C, which is very important to know when speccing out a cell..

As for why bottom balancing is not ideal, i don't even want to expend the energy to argue that. The information is on the forums, which it seems you do not read and learn from..
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 01 2011 10:00pm

DrkAngel wrote:
neptronix wrote:So basically this data might be useful to you, but needs to be in a different format in order to actually compare with the other 99.9% of battery graphs on the web, on manufacturer spec sheets, etc.
Exactly my point! ........ Useful!
I think my type graph might be more useful ... to everyone!
In fact, I specifically decided to create this type of graph, because the "standard" type was so useless!
I would think everyone would consider this type of graph to be more useful than the "standard" type.
If you would like to map the functional capacity of your type battery, (watts per 100th volt), I would recommend the following standards:

List the Brand, mAh capacity, formulation - LiPo, LiCo, LiMn, NiMh, SLA etc.
Use a regulated discharge (digitally metered) I used an iMax B6 - about $25
Discharge at a low rate to reduce "voltage sag"(.2C = 5 hours)
Digitally meter voltage at the cell - much more accurate, than through the discharge device
Top and bottom voltages are the most volatile - need the closest monitoring.

A faster discharge, .5C?, should work OK, might even demonstrate a better "actual use" capacity-output? (2 hour test)

I will add link to free graphing program ... have to find it again ...
Last edited by DrkAngel on Nov 02 2011 9:00am, edited 1 time in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by neptronix » Nov 01 2011 10:26pm

Better start petitioning A123, Panasonic, Toshiba, LG, Samsung, flightpower, hobbyking, etc etc etc ;)

I'll give them the heads up that some guy on the internet found a better way to do it using a piece of freeware and a 30 dollar lipo charger, and you can follow through from there.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 02 2011 3:45am

neptronix wrote:Better start petitioning A123, Panasonic, Toshiba, LG, Samsung, flightpower, hobbyking, etc etc etc ;)

I'll give them the heads up that some guy on the internet found a better way to do it using a piece of freeware and a 30 dollar lipo charger, and you can follow through from there.
Trusting companies to rate their own products might be worse than ... foolish!

The dishonest will always try to make themselves look better.
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Re: Lithium - mAh/100th V - Discharge Test

Post by dogman dan » Nov 02 2011 6:14am

I don't know about more or less useful, but I certainly found it interesting. The same data is pretty much there in the standard format of graph, but sometimes just looking at something graphed a different way makes your brain click on it different. Then you see something you never saw in the other form, even if it was there right in front of your face.

I see now why my lipo ride seems to always end at 3.8-3.85v. I'm spending a lot more time riding at that voltage than I thought. I don't see any point though, in a hybrid pack. Just carry a big enough pack, of whatever you are packing.

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Re: Lithium - mAh/100th V - Discharge Test

Post by miuan » Nov 02 2011 6:55am

I've always imagined that a derivation of the standard discharge plots could be more informative, especially at very low discharge rates, so we are able to tell SOC from resting voltage. I like it.

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Re: Lithium - mAh/100th V - Discharge Test

Post by parabellum » Nov 02 2011 9:01pm

Very interesting approach! Only correction(simplification) can be made is, changing mAh scale to Wh scale which will kind of better reflect useful battery charge state and show in first look difference between high and low side.
Bottom balancing or somewhere in the middle balancing makes no sense (you loose precious WATS) and is complicated, so neptronix is right and equipment he is speaking of is just charger doing log file (not specs of manufacturer).
I may repeat, but your graph is very interesting and detail giving from SOC point of view of different variations of chemistry's. I just realized that Li and Li is not always same.
Very interested in RC type LiPo graphs.

Nice work!

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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 03 2011 11:12pm

parabellum wrote:Very interesting approach! Only correction(simplification) can be made is, changing mAh scale to Wh scale which will kind of better reflect useful battery charge state and show in first look difference between high and low side. ...
Nice work!
Usable, on the LiPo looks to be 3.75 - 4.05V.
Or .3V of an average 3.9V = about 7%. so you can have a Wh graph by keeping 3.9V the same and tilting the graph up 3.5% at the 4.05V point, which also drops the 3.75V point down a similar 3.5%.
But that seems to be an extremely minor variance from the mAh graph ...

Voltage up 3.5% at 4.05V and down 3.5% at 3.75V, scaled in between, might have lines overlapped and indistinguishable from each other.
Last edited by DrkAngel on Nov 17 2011 9:48am, edited 2 times in total.
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Re: Lithium - mAh/100th V - Discharge Test

Post by parabellum » Nov 04 2011 12:14am

Thanks for the info!
That makes RC LiPo even more attractive. :D

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Re: Lithium - mAh/100th V - Discharge Test

Post by liveforphysics » Nov 04 2011 12:42am

DrkAngel wrote:Please note:
The LiCo is a 2600mAh cell,
compared to the LiPo cell which is 2160mAh.

So, for a direct comparison, the LiPo line might-should be moved up, about 25%?

Image

Both of these are the same chemistry, it's LiCoO2 vs LiCoO2 that you're looking at. If you die-cut one into sheets and heat-seal it in a little pouch, or roll up the layers in a jelly roll and stuff it in a can, the comparison you make between them is strictly the blends of other agents those individual mfg's used rather than any fundamental difference between an 18650 container being used vs a foil pouch container.

LiPo can be the most pathetically saggy cell you've ever seen in your life, try cycling a cell phone battery. Some of them took out everything that lower resistance or provides electrochemical buffering in favor of more energy storage in the cathode, and reducing costs. Other LiPo cells like a Nano-Tech are almost exclusively things to improve conductivity and provide voltage high buffering.
Both are LiCoO2 LiPo, but they don't look remotely similar. Likewise, you could take any Nano-Tech formula or whatever you wanted and roll it up and stuff it in an 18650 can, and the discharge curves would be identical to a nano-tech cell of the same capacity.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 04 2011 6:08am

parabellum wrote:Thanks for the info!
That makes RC LiPo even more attractive. :D
RC Lipo Test, is done with WinForce 5700mAh cells.
These are "budget" (cheapo) LiPo.
Previous trials show these cells to be "Hyper-optimistically" rated at 15C, 20C surge.
Strangely, other WinForce cells, I've used, seem to honestly output, as rated. ???

Anyway, test results will be posted this weekend.
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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 05 2011 10:24am

liveforphysics wrote:
DrkAngel wrote:Please note:
The LiCo is a 2600mAh cell,
compared to the LiPo cell which is 2160mAh.

So, for a direct comparison, the LiPo line might-should be moved up, about 25%?

Image
Both of these are the same chemistry, it's LiCoO2 vs LiCoO2 that you're looking at.
Correct.
Both these cells are Lithium Cobalt.
What I would classify as the "standard" "Li-ion", chemistry.
Technically, the "Polymer" moniker is merely the indication that the electrolyte has been polymerized-gelled, as opposed to the original, liquid, electrolyte.
Polymer can be correctly applied to almost everything, (Lithium), currently produced, including, some 18650's and, "choke", LiFePO4.
Personally, I prefer to reserve the Li-ion label to Lithium Cobalt formulations and ...
LiPo for Lithium Cobalt Flat cells.
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DrkAngel   100 GW

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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 05 2011 6:27pm

WinForce 5700mAh Li-Po - Lithium Polymer - LiPo
5700mAh (New, "Made in China")
Discharged using iMax B6
Tested at .2C discharge rate, to reduce skewing due to "voltage sag"
Voltage monitored at cell with digital meter
Charged to 4.26V

Adjusted numbers to high to low format ... 8)

4.23 .. 0
4.22 .. 0
4.21 .. 0
4.20 .. 10
4.19 .. 17
4.18 .. 24
4.17 .. 28
4.16 .. 30
4.15 .. 31
4.14 .. 33
4.13 .. 36
4.12 .. 36
4.10 .. 37
4.09 .. 35
4.08 .. 38
4.07 .. 36
4.06 .. 35
4.05 .. 36
4.04 .. 37
4.03 .. 38
4.02 .. 39
4.01 .. 37
4.00 .. 36
3.99 .. 36
3.98 .. 35
3.97 .. 35
3.96 .. 35
3.95 .. 36
3.94 .. 37
3.93 .. 35
3.92 .. 36
3.91 .. 35
3.90 .. 35
3.89 .. 37
3.88 .. 36
3.87 .. 42
3.86 .. 50
3.85 .. 54
3.84 .. 49
3.83 .. 48
3.82 .. 47
3.81 .. 47
3.80 .. 46
3.79 .. 46
3.78 .. 47
3.77 .. 51
3.76 .. 59
3.75 .. 62
3.74 .. 63
3.73 .. 65
3.72 .. 66
3.71 .. 68
3.70 .. 72
3.69 .. 75
3.68 .. 76
3.67 .. 90
3.66 .. 94
3.65 .. 95
3.64 .. 108
3.63 .. 114
3.62 .. 120
3.61 .. 122
3.60 .. 125
3.59 .. 110
3.58 .. 105
3.57 .. 100
3.56 .. 100
3.55 .. 95
3.54 .. 85
3.53 .. 70
3.52 .. 70
3.51 .. 60
3.50 .. 55
3.49 .. 56
3.48 .. 55
3.47 .. 53
3.46 .. 52
3.45 .. 49
3.44 .. 46
3.43 .. 38
3.42 .. 35
3.41 .. 32
3.40 .. 30
3.39 .. 28
3.38 .. 23
3.37 .. 22
3.36 .. 17
3.35 .. 16

"Usable" looks to be from about 4.1V down to 3.5V.
I was shocked that the beefiest part of the mAh capacity was between 3.5 - 3.7V.
It explains why I was so disappointed by these cells, I never discharged them so far as their best capacity point.
Recharging at 3.7V, I was only using about 1/2 actual capacity!

Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!
WinForce 5700mAh s.JPG
WinForce 5700mAh s.JPG (11.99 KiB) Viewed 5596 times
Attachments
WinForce 5700mAh.jpg
Larger graph
WinForce 5700mAh.jpg (48.19 KiB) Viewed 778 times
Last edited by DrkAngel on Nov 09 2011 10:29pm, edited 2 times in total.
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DrkAngel   100 GW

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RC LiPo vs 18650 Li-ion vs Recycled Lipo

Post by DrkAngel » Nov 07 2011 9:02am

Latest mAh per 100th Volt test was with the rather common WinForce 5700mAh cell.

Yellow is the laptop recycled Lipo, that I use. - 4320mAh
Pink, is the laptop recycled 18650 cells that I use. - 5200mAh
Green, is the new, RC type, LiPo, that I was considering using. - 5700mah
Image
The graph shows shocking differances!
For an accurate comparison - equalized capacity:
18650 Li-ion, (Pink), should be stretched to about 10% greater capacity.
Recycled LiPo, (Yellow), should be stretched to about 32% greater capacity.

Graph program is a free download from http://www.padowan.dk/graph/.
Last edited by DrkAngel on Nov 14 2011 4:36pm, edited 1 time in total.
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miuan   10 kW

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Re: Lithium - mAh/100th V - Discharge Test

Post by miuan » Nov 08 2011 10:17am

DrkAngel: do you have any Turnigy 20C 5Ah cell for testing?

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DrkAngel   100 GW

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Re: Lithium - mAh/100th V - Discharge Test

Post by DrkAngel » Nov 08 2011 8:08pm

miuan wrote:DrkAngel: do you have any Turnigy 20C 5Ah cell for testing?
Bottom of my barrel, just have, still to test:
Unbranded LiFePO4 5000mAh
Sony Brand LiPo 4320mAh.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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