100% discharge rate capacity

Batteries, Chargers, and Battery Management Systems.
goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

100% discharge rate capacity

Post by goatman » Feb 04 2020 11:26pm

im looking at batteries, why aren't people testing the life cycle of batteries at the cells 100% discharge rate capacity. isn't that when a cell is operating exactly the way its designed to?

User avatar
e-beach   1 GW

1 GW
Posts: 3302
Joined: Jan 10 2012 9:48pm
Location: Any Los Angeles area beach I am at. Or Santa Monica or possibly the south bay beaches.

Re: 100% discharge rate capacity

Post by e-beach » Feb 04 2020 11:50pm

You do mean only going to the manufactures recommenced cutoff voltage, right?

Manufactures do test to the lowest voltage. And full cycles. Check out the data sheets. With a catch, or course. The manufacture tend to market their products at the lowest possible c rate discharge thinking that their cells will look better. And, for some proposes they do work better. For hard riding e-bike riders maybe not so much. So what is the e-bike answer? Not fully charging or discharging. It makes it look like the cells last longer, but in reality they are just not going through full cycles, consequently they last longer.

:D :bolt:
Favorite Quotes:
"This is L.A., sugar. There is no 'over the top." Chris Erskine
"At a certain point the entropy wins." Maria Helena Braga

Current Build: ProFlex 757 Expert full suspension. Yescomusa 36v 800w Rear DD, upgraded 10AWG solid core through axle phase wires. 15ah Headway, 1000+ cycles, 80% DOD 30A Tronsung controller.

Past: Trek 4500 Yescomusa 36v 800w front DD.
Liahona, Yescomusa 36v 800w generic front DD.
1992 Trek 800, Yescomusa 800w 36v front DD.

john61ct   100 GW

100 GW
Posts: 5046
Joined: Dec 18 2018 2:06pm

Re: 100% discharge rate capacity

Post by john61ct » Feb 04 2020 11:58pm

These are tests designed to mimic Real World usage,

in real life, as opposed to matching the mfg extreme "do not approach" min/max specs,

we don't want to stress the cells so much.

The actual stored capacity (range) above 4.1V and below say 3.2V (both at rest) is hardly worth

shortening their lifespan by 90% of the cycles they are capable of when treated more gently.


goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 1:21am

a thread onwhy high c rates live less than low C rate, cant remember exact title, but e-s member jonescg stated

viewtopic.php?f=14&t=104529#p1527180

so if a cell is designed to work a certain way, why not operate them that way and test them that way and not the way theyre labelled.

example:

40t 35amp 4000mah, standard discharge capacity 0.2c@800mah is >4000mah
when 40t is discharged at 10amps it achieves 100% discharge rate capacity/3900mah
@35 amps its about 91.5% capacity
after 250 cycles at 35amps its at 2400mah or 60% of original capacity

they did the same thing to the 25r 10amp is 100% but lifecycle it at 20amps

why not life cycle test at 10amps/100% capacity, it wouldn't be operating under stress, why not test a 50e at 91.5%

50e 9.8amp 5000mah, standard discharge capacity 0.2c@980mah is >4900mah
50e discharged at 0.2c is 100% discharge rate capacity 4900mah
@4.9amps its about 97% capacity
after 500 cycles @4.9amps its at 3802mah or 80% of capacity
BUT they call it a 9.8amp cell so why not perform the cycle test at 9.8amps like they did the 40t 9.8amps is 95%capacity it would probably be 3200mah or how about test the 50e at 91.5% capacity to compare with the 40t at 91.5% capacity.

im not being a 40t cheerleader

if a cell is being life cycle tested shouldn't it be tested at 100% discharge capacity
isn't that the maximum efficiency of the active charge storage matrix,

whats the result of a 50e if it was life cycled at 0.98amps 100% discharge rate capacity

whats the result of a 40t if it was life cycled at 10amps 100%

whats the result of a 25r if it was lifecycled at 10amps 100%

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 1:32am

heres another chart, I don't know how to bring it over

viewtopic.php?f=14&t=102682&start=50#p1504066

Ianhill   10 MW

10 MW
Posts: 2038
Joined: Sep 25 2015 5:55pm

Re: 100% discharge rate capacity

Post by Ianhill » Feb 05 2020 6:36am

What are the noticeable effects of a degraded battery ? Capacity loss, increased IR off top off my head and both of these make that c rating drop with cycle life but this is never mentioned on the data sheet just a max rating from new not the average plot of the complete data set giving more of an idea of the range of the cell from new and degrade over time so it's easy to see where on the range your cells in hand would be.

Plus these cycle life test's are not repeatable in real world usage, an ebike battery or portable drill etc experience differing temperature extremes throughout the test aging them in a more extreme way than a controlled pack or indoor environment harsh cold is the worst on c rates and trying to pull amps at this point is not a good idea.

The life of a cell is a complex one and the discharge rate at the beginning creating x amount of heat will not be the same for the end of life and because they all have varying life styles owners permitting that can dramatically shorten their life to a 1/4 of its lifetime or worse so it safe to say that there's room for improvement on the way some handle cells discharge max when down the line that cell will become useless if spec'ed at its limit from day one.

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 1:43pm

if im looking at pack design after I choose my volts I look at amps and ah if use 25 to 35 amps but spend most of my time around 25/30 amps, if a pick a cell that is 10amp 100% capacity I need 3p and the cell will be discharging around 97% to 100% capacity/efficiently but if I want around 20ah

30q is 3ah, 6p 18ah
40t is 4ah, 6p 24ah

if I run those packs at 6p/95% ill be degrading them a lot quicker than if I separated the packs into two separate 3p/100% packs and have them separated with a battery selector switch, run on pack A til its done and then switch to pack B. the temperatures ive been seeing for 100% is about 23 c to 60 c. if I keep the batteries between 23 and 40 it should be ok. two separate 3p packs wont get as hot in the middle as 1 6p pack

50e at 5amps or 1c runs at 97%, I would need 6p to run at 30amps and 97%, nice easy build no switching of packs but the information is bad

a person hears everyone is running around 2c through the batteries, 2c/10amp on a 50e would be 95% and after 500cycles it wouldn't be at 3800mah/80% it would be way lower

a 50e should be a 5amp cell not 10amp or give the 10amp cycle life
the more p you add to a 50e the better cycle life it has, if I need 6p of 50e to get my 30amps/97% after 500 cycles ill have 22.8ah instead of 30ah and if I go 10p the lifecycle will be more efficient 98.5%? more ah

a 40t at 3p is 100% but no info on life cycle at 6p but its probably around 95% if I went 10p probably 92% if I want a 30amp average

if I look at different makers theres no real info only the standard discharge test of 0.2c/?mah

atleast Samsung gives an idea of a cells discharge rate capacity at different amps

with a 40t once you get the amps you want that should be size of the pack but if you need more ah and start adding more p the worse the packs life cycle

LuboN   100 mW

100 mW
Posts: 38
Joined: Mar 08 2015 2:33pm
Location: Slovakia

Re: 100% discharge rate capacity

Post by LuboN » Feb 05 2020 3:04pm

I am sorry to inform You that You got it totally wrong. Please read some battery life related threads to get the basics right first.

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 3:59pm

LuboN wrote:
Feb 05 2020 3:04pm
I am sorry to inform You that You got it totally wrong. Please read some battery life related threads to get the basics right first.
by docware » Oct 15 2019 2:52am

The rate at which a battery or cell can be charged or discharged is limited by the rate at which the active chemicals in the cells can be transformed.
Forcing high currents through the battery results in incomplete transformation of the active chemicals reducing the battery’s effective charge capacity and it also causes unwanted, irreversible chemical reactions to occur because the chemical transformations cannot keep up with the current demands.
The unwanted chemical transformations consume some of the active chemicals causing the battery to lose capacity and thus age prematurely.

From the above we can expect that with each charge/discharge cycle the accumulated irreversible capacity loss will increase. Although this may be imperceptible, ultimately the capacity reduction will result in the cell being unable to store the energy required by the specification. In other words it reaches the end of its useful life and since the capacity loss is brought on by high current operation, we can expect that he cycle life of the cell will be shorter, the higher the current it carries.

A.jpgA.jpg (78.73 KiB) Viewed 692 timesThe capacity reduction at high discharge rates occurs because the transformation of the active chemicals cannot keep pace with the current drawn. The result is incomplete chemical reactions and an associated reduction in capacity. This may be accompanied by changes in the morphology of the electrode crystals such as cracking or crystal growth which adversely affect the internal impedance of the cell.

Ageing Accelerators
The previous paragraph indicated some of the basic ageing factors inherent in the battery chemistry. From this we can see that certain external environmental and usage factors, such as those following, can be considered as ageing accelerators.

High and very low temperatures
High energy throughput rate (Charge and discharge rates)
Mechanical stress or vibration which can give rise to open or short circuits or seal failures.

Operating Environment
In addition to the ageing accelerators noted above there are some less obvious environmental factors which can influence battery life.

A temperature gradient across the battery can increase the rate of battery ageing. From Arrhenius we know that, with a 10°C difference in temperature across the battery, some cells will age at twice the rate of others giving rise to unbalanced stresses on the cells resulting in premature failure. High pressure or cyclic pressure changes can cause mechanical failures of the cells.
High humidity can give rise to corrosion causing increased contact resistance at the battery terminals.

doesn't that chart state what im asking, if you run a battery at its most efficient rate of discharge it will last longer

wouldn't that mean discharging at as close to its 100% discharge rate capacity?

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 4:01pm


john61ct   100 GW

100 GW
Posts: 5046
Joined: Dec 18 2018 2:06pm

Re: 100% discharge rate capacity

Post by john61ct » Feb 05 2020 4:51pm

The cells are **not** "designed for" operating at their most stressful possible ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the cell at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods will affect cell longevity reliability.

john61ct   100 GW

100 GW
Posts: 5046
Joined: Dec 18 2018 2:06pm

Re: 100% discharge rate capacity

Post by john61ct » Feb 05 2020 4:54pm

If you want someone to check your math, more likely to happen if you just post a very short sequence, written clearly

or even better one question at a time.

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 5:32pm

hey john

stresses can be many things,
a cell operating at 100% shouldn't be too stressed if that's where it retains its capacity
a cell operating at 90% seems to get a little stressed out and starts to lose capacity

am I wrong by thinking if a cell is operating at its 100% discharge rate capacity that its operating the way its designed

the further away from 100% the cell operates at, the faster it degrades

john61ct   100 GW

100 GW
Posts: 5046
Joined: Dec 18 2018 2:06pm

Re: 100% discharge rate capacity

Post by john61ct » Feb 05 2020 6:59pm


goatman wrote:stresses can be many things
That is the only true statement in that post.

> a cell operating at 100% shouldn't be too stressed

Every cell datasheet showing lifetime cycles vs average DoD% I've ever seen, no matter the chemistry, proves that is false

> if that's where it retains its capacity

No idea what that is supposed to mean

> a cell operating at 90% seems to get a little stressed out and starts to lose capacity

Absolutely false, running at say 60% capacity might give triple or 5x the lifetime cycles compared to even 80%, much less 90%.

100% is just stupid, might lose thousands of cycles compared to that 60%.

> am I wrong by thinking if a cell is operating at its 100% discharge rate capacity that its operating the way its designed

yes absolutely wrong. In fact I'm very curious where you could ever have picked up such a silly idea.

> the further away from 100% the cell operates at, the faster it degrades

The opposite is objectively true and easily verified by the data sheets from the manufacturer.

I'm not saying those are accurate in absolute terms, nor valid used to compare between manufacturers

but they all certainly are super clear on that universal causal relationship (a strongly inverse one) between lifetime cycles and average DoD%

And all the above is objectively clear, even before asking, are you talking about trying to maximise capacity usage at the top of SoC?

or getting closer to 0% at the bottom?

Because **either** are clearly harmful, at the bottom is just a quicker murder thus more obvious. Doing **both** is a worst case scenario.

The ideal with all the LI chemistries, is avoiding both ends, centering a low % capacity cycling around the nominal mid-point.

Hope that helps clear things up for you.


Ohbse   10 kW

10 kW
Posts: 880
Joined: Dec 26 2013 5:15pm
Location: Auckland, New Zealand

Re: 100% discharge rate capacity

Post by Ohbse » Feb 05 2020 7:07pm

Splitting packs and switching between them is a design fail. End result will be higher degradation due to stress, lower performance due to sag and only half your battery mass contributing. Heat will be higher.

The rated discharge rate for any cell is the maximum that cell can output before it becomes too hot, too saggy, too short a lifespan. Running a cell below this maximum rating is obviously the best way to maximise lifespan.

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 7:20pm

100% is just stupid, might lose thousands of cycles compared to that 60%.

I think I see the confusion I created

take a 40T at a 10 amp discharge rate it has 100% discharge capacity

im not saying discharge the battery of all its 100% capacity

im saying discharge the cell at 10 amps

if you want to start at 4.1v and end at 3.5v, good, but do it at 10amps

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 7:37pm

I don't know how to get the pdf here

if you get the data sheet of Samsung 50e
section 7.9
discharge rate capabilities

_________________________discharge condition

current___________ 10amp 20amp 30amp 40amp

relative capacity____100%__ 95%__ 93%__ 90%


7.10
cycle life with rated charge and max continuous discharge

capacity after 250 cycles

charge is 6 amps
discharge is 35 amps

capacity 2400 mah and 60% of standard capacity at 25c


my question is why didn't they test this cell at 10 amp discharge, if the battery is working at 10amps how is that stressfull

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 8:32pm

52v luna wolf pack battery 14s4p

2 battery options lg mj1 and 30q

recommend if requesting 50amp bms use 30q

4p of 30q is max 12.5 amps/cell for 50 amps

a 30q has a 100% discharge rate at 10 amps

does luna know something

theres a lot of mixed reviews of the 30q




docware wrote: ↑
Nov 19 2019 10:27am
Some people on the Pedelec forum mentioned soldering as a root cause of the issue. Fortunately you read German :D ... wasn't sure if he was being a litte facetious (single cell), so brought up the subject of vaping (i'm not a smoker or drinker). You may have also noticed that when googling VTC6 (or HG2) vs 30Q some of the google comparisons are about vaping. Makes one wonder if as many of these 3000mAh 15-20A cells are sold to vapers as ebikers? Seems to be a tossup as to which cell is better whether for vaping or a DIY pack build ... but maybe these 3000mAh 15A-20A cells aren't the best cells for a 8P14S DIY ebiking build ?

"I use the Sony VTC6, as well as the Samsung 30Q. The VTC6 are slightly better cells. Their internal resistance is lower, and they have a bit less voltage sag. They also have about 4% more energy. But, overall, they’re very similar to the 30Q, and you’d probably not notice any difference.

For the ones you mentioned I would choose 30Q. I have had personal experience w/ VTC6 and LGHG2 degrading at a higher rate than 30Q."

Deciding which 3000mAh 15-20A cell to use for a sizeable DIY triangular bike pack usually comes down to cost (8P14S 112 cells). Currently at IMR in quanties of 100-199 ... VTC6 $4.85, HG2 $3.25, 30Q $3.85.

One might ask why Luna doesn't offer the VTC6 as an option in their 52V Wolf pack instead of 30Q or MJ1? Does it basically come down to the bottom line of cost savings even though VTC6 has a 20A rating to 30Qs 15A rating (so big deal).

Reminds me of the good ol' days when it was all about V8 horsepower between Chevy and Ford. Now it's about mAh capacity, amp rating and NCA vs NCM originating from Japan, South Korea and China. No longer America :(

Ohbse   10 kW

10 kW
Posts: 880
Joined: Dec 26 2013 5:15pm
Location: Auckland, New Zealand

Re: 100% discharge rate capacity

Post by Ohbse » Feb 05 2020 8:38pm

goatman wrote:
Feb 05 2020 7:20pm
I think I see the confusion I created

take a 40T at a 10 amp discharge rate it has 100% discharge capacity

im not saying discharge the battery of all its 100% capacity

im saying discharge the cell at 10 amps

if you want to start at 4.1v and end at 3.5v, good, but do it at 10amps
Running a cell to 100% of energy content will increase its rate of degradation.
Running a cell at 100% of its current/power output will increase its rate of degradation.

In your hypothetical use case, discharging from 4.1v and ending at 3.5v at 1amp will result in much longer service life, less heat, less stress, better performance.

Cell manufacturers test at the most the cell can do. It's obvious that running it at a lower output, it will live longer. It's 'worst case scenario'.

Ohbse   10 kW

10 kW
Posts: 880
Joined: Dec 26 2013 5:15pm
Location: Auckland, New Zealand

Re: 100% discharge rate capacity

Post by Ohbse » Feb 05 2020 8:41pm

goatman wrote:
Feb 05 2020 8:32pm
52v luna wolf pack battery 14s4p

2 battery options lg mj1 and 30q

recommend if requesting 50amp bms use 30q

4p of 30q is max 12.5 amps/cell for 50 amps

a 30q has a 100% discharge rate at 10 amps

does luna know something

theres a lot of mixed reviews of the 30q
1. Luna definitely doesn't know much about building battery packs that last. They have time and time again sold packs destined for a very short, very stressed lifespan.
2. The 30q is rated at 15a as per Samsung, as quoted in your own post.
3. Cell testing is complex with lots of competing factors. Energy vs Power vs Lifespan, all at different temperatures and of course price. Obviously Luna doesn't make packs from VTC6 as they're substantially more expensive and for a while there, very difficult to obtain in quantities.

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 9:01pm

the 30q has a 100% discharge rate at 10 amps and 5amps 97% and 15 amps 97%

if you run it at 15amps 97% it loses 60% of its capacity after 250 cycles

if you run a 30q at 5amps97% will it lose 60% of its capacity

I guess I need to find someone that has life cycled a 30q,40t or 25r 250 times at 10 amps to see what its capacity will be

I might be able to find a 30q at 3 amps wich should be disastrous

john61ct   100 GW

100 GW
Posts: 5046
Joined: Dec 18 2018 2:06pm

Re: 100% discharge rate capacity

Post by john61ct » Feb 05 2020 9:05pm

goatman wrote:I think I see the confusion I created

take a 40T at a 10 amp discharge rate it has 100% discharge capacity

im not saying discharge the battery of all its 100% capacity

im saying discharge the cell at 10 amps

if you want to start at 4.1v and end at 3.5v, good, but do it at 10amps
OK, I understand what you mean better now, but again, I'm afraid no the opposite is also true in this case too!

The lower the actual C-rate, the more energy capacity you get per cycle.

And the longer the cell will last, until you get below 0.4C or so,

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 9:19pm

I really should try to clarify what I mean by 100% discharge rate capacity

is when a cell can deliver 100% of its capacity

30q- 0.2c/0.6a and 10amps

40t- 0.2c/0.8a and 10amps

50e- 0.2c/0.98a

goatman   100 kW

100 kW
Posts: 1392
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: 100% discharge rate capacity

Post by goatman » Feb 05 2020 9:53pm

goatman wrote:
Feb 05 2020 9:01pm
the 30q has a 100% discharge rate at 10 amps and 5amps 97% and 15 amps 97%

if you run it at 15amps 97% it loses 60% of its capacity after 250 cycles

if you run a 30q at 5amps97% will it lose 60% of its capacity

I guess I need to find someone that has life cycled a 30q,40t or 25r 250 times at 10 amps to see what its capacity will be

I might be able to find a 30q at 3 amps wich should be disastrous
30q

by Pajda » Nov 21 2019 4:19pm

Here is another of my unwanted remarks 8)

I need to say something about this test https://www.e-cigarette-forum.com/threa ... g2.807131/ revealed by Mooch in 6/2017. I'm not afraid to say that if it wasn't published,the world will be a better place. This is unfortunatelly the example of information which makes more bad than good. There is not a problem in the results themselves. I made tests with similar settings and can confirm that the test results are correct with the Samsung 30Q as a clear winner. The problem is that this particular result leads to generalization that "Samsung 30Q must be then good in other settings as well". I am quite confident that Mooch is another victim of this seductive idea and so he just do not expect that there should be any problem with 30Q cycle life under another, particularly lower test settings. But he cannot be more wrong.

This level of capacity loss at 5C discharge rate should be clasiffied as excellent result. But the major problem is, that Samsung 30Q shows almost identical capacity loss under 3C and even under 1C continuous discharge rate. So at 3C continuous discharge rate its cycle life at 100% DoD is outperfored after just 100 cycles by M29, 29E6, E7 and even Panasonic PF performs significantly better than the Samung 30Q. At 1C discharge rate 100% DoD, the cycle life of 30Q is nothing but total disaster in comparison by almost all cells on the market. The same problem is with its DCIR rise, which is enormous with exponential course. Only narrow 70% or less SoC window helps 30Q to get at least usable results.

Ohbse   10 kW

10 kW
Posts: 880
Joined: Dec 26 2013 5:15pm
Location: Auckland, New Zealand

Re: 100% discharge rate capacity

Post by Ohbse » Feb 05 2020 10:48pm

Each time you clarify, it makes it significantly more confusing...

A 30q that is cycled at 1a output will last for longer than one that's cycled at 3amps which will last longer than one cycled at 10a etc. Both time spent discharging AND number of cycles over its life.

Put another way, a 30q that completes 250 cycles @ 10a discharge will lose MORE of its original capacity than one that is cycled 250 times @ 3a discharge.

Higher discharge power = shorter lifespan.

Deeper discharge = shorter lifespan.

I have cycle tested 30q vs hg2 and several others at all sorts of power levels. After extensive testing I bought 5000 30q's. I have one pack that has done ~30,000 km with less than 10% of its original capacity loss when tested. It does sag more under load, but not unacceptably and is now being retired from daily use anyway.

Post Reply