Full/Partially Discharged/Fully Discharged Voltage Values for Different Cells

[bonvivantmike]

I thought it might be valuable to have one thread with this information in one place.



For 3.7v Li Ion cells:

4.2v = 100%
4.1v = about 90%
4.0v = about 80%
3.9v = about 60%
3.8v = about 40%
3.7v = about 20%
3.6v = empty
<3.5v = over-discharged


(Black Rose posted this information in another of my threads)



For 1.2v NiMH cells:

1.4v = 100%
1.0v = empty
<0.9v = overdischarged

(Can anyone add any values?)



For 1.5v Alkaline cells:

1.5v - 1.6v = 100%
0.8 - 1.0 v = empty

(Can anyone add any values?)



Feel free to add other cell types.

 

[zipplet]

For Alkaline/Nimh it's impossible to accurately determine state of charge from a simple voltage reading - other than 100% and empty/overdischarged as you already have

That's the reason we buy Ansmann energy-check or ZBT testers.

Good informative idea and thread

 

[Mr Happy]

For 1.2v NiMH cells:

~1.4 V = 100%
~1.2 V = empty
< 1.2 V = damaged

You really can't tell too much from the voltage on NiMH cells except that 1.2 V is empty. A fully charged cell could be anywhere between 1.35 V and 1.45 V depending on the history and type of the cell.

If you find a cell reading less than 1.2 V its state of health is suspect.

 

[VidPro]

Stupid little story time:
Disclaimer, never "Flash Amp" or short curcuit a high energy battery, especially a lithium one.

Voltage vrses Current, to get idea of level of capacity.
There is always questions about how to read capacity VIA reading the voltage, well you can and you can't, here is a story about how we learned some of this the hard way.
Somewhat Long ago in a far off land . . .
Highly dependant on batteries on the job, but using some 20-30 of them Per job, we had many batteries (mostly alakline) that were used for less than 20% of thier total capacity. We couldnt throw them out (cheapskate) and there were too many to use in other devices that were not important.
So we went to RadioShack (now known as the Cell store) and got a simple battery tester. it had an analog meter, little needle in it that moves from green to yellow to red.
we started testing everything , and tossing out batteries that were not in the green.
went back to the job and got BURNED royally, lots of the batteries that tested high green DIED early . The test was simply a voltage meter with colors.
Sooo
When we came back from that job, we used this tester again, and threw out all the batteries did not read Way high in the green. Re-calibrating this minimum Voltage we were going to allow. now they had to be good they all read very high voltages.
Went back to the job and got burned again, few of the batteries that tested high, were dead before the job was over
soo
Knowing that i could have put the batteries under a Load , and tested them better, i tested the batteries by "Flash Amps" using a newly purchaced 10A ampmeter. ONLY ALAKALINES and only the small ones, and only for a short time.
I assaulted each of the used batteries by shorting the ammeter across them, and using only the ones that pumped out major amperage.
Went back to the job again, and every battery that had good output amperage during this harsh amp testing , survived the job just fine.
But
this was still a royal pain in the butt , not having a quick easy simple (anyone can do it) method for sorting out the batteries, requiring the meter. It was harsh on the batteries, and took a lot of power for each test, also it couldn't be used for other various volitile chemistries.
SO
i took apart the (stupid) radioshack meter, and put a simple 10ohm 10W resister across the contact points for the battery. this would read the (red green yellow) voltage thing while the battery had a load on it. It would also completly drain the battery if left in it , probably a good reason why they didnt sell it that way.
Now
my stupid easy meter had a load, i recalibrated where we thought red yellow and green actually were, and this worked great for long and long times. the small load added to the device would read the voltage under a load , instead of the no-load voltage. Job after job the batteries tested with the load voltage , would last long enough to survive the job.
now (of course) we use more rechargable batteries, but i never forgot how Wrong the simple voltage only reading was , for displaying "Capacity" especially and specifically for alkalines and carbon types.

the battery checker lived a long and happy life (almost happily ever after)

voltage this voltage that, but chemicals in the battery (IMO) are more "Power" than voltage and amperage, its all about the WATTS (remember that when looking at specs/graphs). Sure the cell has been tuned and certian chemical reactions have a certian reaction voltage potential, but electricity stuff is more about total Power than just the voltage. if you want to know how usefull the chemicals are in a battery, read the Watts .

We try and put electrical characteristics paremeters on Chemical reactions that output electricity , but really its about the chemicals themselves that were tyring to test.
by putting a light load on a battery test, you can tell a lot more about the battery.

 

[VidPro]

In the same respect, it is also about the battery design.
I will attempt to discuss the Li-Ion voltage referances.
There are many different types of li-ion, stuff that is designed for high discharge, and stuff that is designed for lower discharge rates, with higher capacity for size weight.
the lower rate li-ions have more capacity available at the lower voltages, than do the High-C RC type of batteries, under similar loads.
so
there are high capacity (for weight) batteries that will have much usable capacity at lower voltages.
and
high Discharge rate battereis, that maintain a higher voltage potential throughout its discharge.

so you lean the voltage paremeters (even resting) a bit one way and the other, depending on the type of battery.
Simply:
higher discharge rate design batteries will be exausted in total capacity at higher voltages, or maintain thier voltages better.

 

[zipplet]

Excellent explanation vidpro. Very useful to the newer people around here in my opinion

 

[Bullzeyebill]

VidPro, in your post, what would the lower discharge rate LiIon's be, LiCo? The higher discharge rate LiMn?

Bill

 

[VidPro]

VidPro, in your post, what would the lower discharge rate LiIon's be, LiCo? The higher discharge rate LiMn?

Bill

could be? you mean like the IMR things, i have not tested them.

i just saw the differences between similar chemistry high and low discharge. The high discharge seems to have bigger Plates in the battery (weighs more for capacity, has huge leads)
2 similar li-poly (type li-ion) bagged cells, one for RC specific, and one for "2C" max discharge. the premo RC 10C thing the voltage tanked sooner, it acted depleated at 3.5v wheras a 2C cell still lots of "capacity" between the 3.5 and the 3.0.

so i would ASSume that is also like some of the "safer" chemistry, lower capacity batteries showing very close to the same RUNTIME, because they hold thier voltage up better under load, and more fully chemically convert prior to voltage cutoff points, also handle being discharged harder when depleated. Boost curcuits love to slam the battery harder when its output is lower.

When does a 3000ma 18650 have LESS capacity than a 2400ma 18650? when the 3000 couldnt take the load, due to the design was only about capacity.

 

[mdocod]

CR123s:

100%: ~3.1V +/-0.1V
50%: ~3.1V +/-0.1V
20%: ~3.1V +/-0.1V


hmmmm......

 

[Black Rose]

CR123s:

100%: ~3.1V +/-0.1V
50%: ~3.1V +/-0.1V
20%: ~3.1V +/-0.1V


hmmmm......

At least they maintain their voltage to the bitter end

 

[Bullzeyebill]

VidPro, I don't quite understand that. That seems to be the case with some of the higher capacity NiMh cells, but I have never seen it tested out for LiIon's. The PCB's of some of the higher cap protected LiIon's that are not set up for high discharge rates may have this problem. I would guess that a 2800+ unprotected 18650 would have both good capacity and good runtime at high amp draw. My unprotected 18650 LG's at 2400mAh seem to perform very well in both regards compared to my Pila's, more than the 200mAh difference, particularly with high amp draw loads where I think that the so called over current protection of the Pila comes into play.

Bill

 

[VidPro]

I would guess that a 2800+ unprotected 18650 would have both good capacity and good runtime at high amp draw.

I often guess that unless the actual technology itself changes , like micro-something-or-another or better plating procedure, or thinner but more effective seperators, or different electrolytes, that they will always GIVE-UP something to increase the capacity, without an advancement in the technology. like it will last less time, or it will need different charging, or it wont do as many cycles, or it just cant handle the load.
Depends on whos making the battery i guess, are they taking shortcuts, making the size bigger, reducing the containment , or tossing out vital protection to wedge in more stuff.
i think the "pros" are gaining better technology, instead of sacraficing one for the other.
Only time will tell, like the LG cells have amasing perpetual life, and something like the new sanyo or panasonic high capacity, could have a short life, and i dont think any "accelerated" testing shows what happens in real time. hopefully they did no sacraficing.

still the Battle Bot that whoops is using some extreeme power low-cap ni-cds from the 70s technology 5 minutes of extreeme glory