Doesn't make sense.. does my battery broken?33mΩ too much ir??

Get all your technical information about electric bikes here.
Post Reply
mudale222   10 W

10 W
Posts: 81
Joined: Jun 08 2015 5:35am

Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by mudale222 » Jan 05 2020 7:58pm

Didn't used my e bike for couple of months tried them today, seem like my bms cutting on heavy load and shutting off the e bike.
Opened the battery up, no swallow or any change in lipo condition.
The setup is 20S 16Ah with 50A controller. So 3.125C draw at most.
Checked their ir:
Image
Image
Image
Image
Image
Image
Image

what do u guys think? it's enough to make the cell sag so the bms will cutoff power or probable something else?

User avatar
Dui, ni shuo de dui   1 kW

1 kW
Posts: 387
Joined: Jan 29 2016 3:21am

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Dui, ni shuo de dui » Jan 06 2020 12:50am

Let's take a "normal cell:
If my math and method are correct:
-0.003 ohm x 50Amps = 0.15V
So that means this cell, whenever you are pulling 50Amps from it, will sag of 0.15V. If your cell fully charged was about 4.0V, under full 50Amps load the cell voltage will be 4.0 - 0.15 = 3.85V, so it's good.

Now, let's take the cell at 0.033 ohm and do the same:
-0.033 ohm x 50 amps = 1.65V
So that means under 50Amps load the cell that was charged at 4.0V will go down to 4.0V - 1.65V = 2.35V, which should probably trigger your BMS for cell undervoltage protection.

So in summary, yeah, this cell seem to be toast.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

kcuf   100 W

100 W
Posts: 195
Joined: Sep 29 2018 3:21pm

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by kcuf » Jan 06 2020 10:08am

5 bricks #1 cell reading high ir

correct?

suspect more likely imax problem

recommend dc ir test

10s known amp load

use voltage drop to calculate ir

youtube lipo ir testing
In 2013 an ad appears on Russia social networks: Интернет-операторы хотели! Работа в шикарном офисе в Ольгино !!!, зарплата 25960 рублей в месяц

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 06 2020 11:20am

Dui, ni shuo de dui wrote:
Jan 06 2020 12:50am
Let's take a "normal cell:
If my math and method are correct:
-0.003 ohm x 50Amps = 0.15V
So that means this cell, whenever you are pulling 50Amps from it, will sag of 0.15V. If your cell fully charged was about 4.0V, under full 50Amps load the cell voltage will be 4.0 - 0.15 = 3.85V, so it's good.

Now, let's take the cell at 0.033 ohm and do the same:
-0.033 ohm x 50 amps = 1.65V
So that means under 50Amps load the cell that was charged at 4.0V will go down to 4.0V - 1.65V = 2.35V, which should probably trigger your BMS for cell undervoltage protection.

So in summary, yeah, this cell seem to be toast.

Yeah the math is not correct. But yeah cells are toast unless it is a problem congruent to first cell metering.. many JST-Xh are bad and show this kind of thing reliably with many different chargers and parallel boards.

But yeah probally entirely junk multistar. Seen it happen a million times... but usually I stop when a pack goes from 2mOh to ~ 4-5mOh or more.. not 33 or 25mOh... Thats as bad as a bad 18650. Bottlekneck to current.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

AngryBob   100 W

100 W
Posts: 183
Joined: Jul 10 2019 4:37pm

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by AngryBob » Jan 06 2020 12:09pm

It could be the camera angle, but that cell on the far right appears to be massively puffed.

mudale222   10 W

10 W
Posts: 81
Joined: Jun 08 2015 5:35am

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by mudale222 » Jan 06 2020 8:37pm

Thx guys, i'm honor by ur answers.
Bear with me, i got an absolute result.
Dui, ni shuo de dui wrote:
Jan 06 2020 12:50am
Let's take a "normal cell:
If my math and method are correct:
-0.003 ohm x 50Amps = 0.15V
So that means this cell, whenever you are pulling 50Amps from it, will sag of 0.15V. If your cell fully charged was about 4.0V, under full 50Amps load the cell voltage will be 4.0 - 0.15 = 3.85V, so it's good.

Now, let's take the cell at 0.033 ohm and do the same:
-0.033 ohm x 50 amps = 1.65V
So that means under 50Amps load the cell that was charged at 4.0V will go down to 4.0V - 1.65V = 2.35V, which should probably trigger your BMS for cell undervoltage protection.

So in summary, yeah, this cell seem to be toast.
I'm thinking someting isn't right with this math since if u got 4 example 100ohm it will be: 0.100 * 50A = 5V which is more
then 100% of cell voltage so it's doesn't make too much sense.
AngryBob wrote:
Jan 06 2020 12:09pm
It could be the camera angle, but that cell on the far right appears to be massively puffed.
Checked it and seem fine:
Image
Image
Image
Image

So i decide to to second check to all cells by the b6ac.
After that i did manual IR test as offers to me and as seen in youtube.
After that i decided that i'm not pleased with "not completely clear result" :) , so i managed to get me a 25A draw test and
tested them all to see actual voltage drop of each cell and got completely clear result.

My ugly arrangement:
Image

Result (click on pic!):
Image
copy of result 4 the future: https://pasteboard.co/IONd4sC.png
Batt 2+5 are dead. Lipo suck big time! (i only maybe cycle them 50 times, and then rest with 3.8V for a year).
thx

User avatar
Dui, ni shuo de dui   1 kW

1 kW
Posts: 387
Joined: Jan 29 2016 3:21am

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Dui, ni shuo de dui » Jan 06 2020 8:44pm

DogDipstick wrote:
Jan 06 2020 11:20am
Yeah the math is not correct.
It would be more useful to explain why and what should be the correct way.
mudale222 wrote:
Jan 06 2020 8:37pm
I'm thinking someting isn't right with this math since if u got 4 example 100ohm it will be: 0.100 * 50A = 5V which is more
then 100% of cell voltage so it's doesn't make too much sense.
I didn't invent this math actually, it is basic Ohm's law.
If your cell has a 100 ohm internal resistance and you try to pull 50 amps from it, then yes, your voltage will sag to zero.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

User avatar
amberwolf   100 GW

100 GW
Posts: 28925
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by amberwolf » Jan 07 2020 12:23am

it does make sense, becuase it is possible to actually reverse a cell's voltage by overcurrent/overdischarge of it.

so it's voltage goes negative.

if you had 5v of sag on a cell that was at 3.9v to start with, then it would indeed end up as -1.1v, and be even more physically damaged than it started out.

mudale222   10 W

10 W
Posts: 81
Joined: Jun 08 2015 5:35am

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by mudale222 » Jan 07 2020 5:14pm

Yep, did some reading and it's actually possible to reverse polarity at extreme incidents.
In that case - just flip them over... :lol: :lol: :lol:
I'm kinda tempting to try it and see what happen but i got a feeling that it's will go kaboom in my face.. :D

User avatar
amberwolf   100 GW

100 GW
Posts: 28925
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by amberwolf » Jan 07 2020 8:05pm

make sure you have your camera on while you do this, after you have purchased fire and life insurance. :(

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 08 2020 1:07pm

Dui, ni shuo de dui wrote:
Jan 06 2020 8:44pm
DogDipstick wrote:
Jan 06 2020 11:20am
Yeah the math is not correct.
It would be more useful to explain why and what should be the correct way.
mudale222 wrote:
Jan 06 2020 8:37pm
I'm thinking someting isn't right with this math since if u got 4 example 100ohm it will be: 0.100 * 50A = 5V which is more
then 100% of cell voltage so it's doesn't make too much sense.
I didn't invent this math actually, it is basic Ohm's law.
If your cell has a 100 ohm internal resistance and you try to pull 50 amps from it, then yes, your voltage will sag to zero.
There is alot more than just the V=IR of battery's internal resistance. Alot more. You pay attention to one "Law" like it matters when you ignore (10) other "laws"... No you didnt invent the math, you just didnt use it to its complete ability.

So we are picking and choosing our laws now? IDK. Sorry, if you find this "less than" useful. I aint explaining its to complicated. Plus the math is very complicated too.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 08 2020 1:09pm

Also, that puffer on the right is really bad. Lipos are not bad, just "Multistar lipos".... Bad. My homemade lipos are about 7 years old, and still kicking like day 1 ( datalog). 1Moh.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

User avatar
Dui, ni shuo de dui   1 kW

1 kW
Posts: 387
Joined: Jan 29 2016 3:21am

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Dui, ni shuo de dui » Jan 09 2020 1:25am

DogDipstick wrote:
Jan 08 2020 1:07pm

There is alot more than just the V=IR of battery's internal resistance. Alot more.
You pay attention to one "Law" like it matters when you ignore (10) other "laws"... No you didnt invent the math, you just didnt use it to its complete ability.
Okay, maybe.
I'd just appreciate for you to explain, for the sake of learning stuff.
Which (10) other laws have been ignored?
DogDipstick wrote:
Jan 08 2020 1:07pm
So we are picking and choosing our laws now? IDK. Sorry, if you find this "less than" useful. I aint explaining its to complicated. Plus the math is very complicated too.
Not sure why being so sarcastic, I just try to understand. Plus I never said "less than useful".
Sorry if I maybe offended you in some way in my previous post, I'm not a native english speaker so maybe the way I wrote stuff was interpreted differently than what I intended in the first place.

Many people say they know stuff and it's "just too complicated to explain", usually when you dig you find out that they just don't.
Not sayin' it is the case here, but if someone says I'm wrong then I like them to explain why. Especially since this is a technical forum, if anyone says something without having data or tangible arguments to support it then it is normal to doubt it.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

Punx0r   100 GW

100 GW
Posts: 5514
Joined: May 03 2012 8:16am
Location: England

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Punx0r » Jan 09 2020 3:44am

Cell DC IR can be calculated from sag via V = IR just fine! It's not complicated - quite simple :)

Yes, you can reverse a cell in a battery, but this is not really sag. Maximum sag possible on a single cell cannot exceed the cell's open-circuit voltage. So you cannot have 5V of sag on a 4.2V cell. The reality is a 100mohm, 4.2V cell cannot source 50A, so there is no paradox.

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 09 2020 12:52pm

Punx0r wrote:
Jan 09 2020 3:44am
Cell DC IR can be calculated from sag via V = IR just fine! It's not complicated - quite simple :)

Yes, you can reverse a cell in a battery, but this is not really sag. Maximum sag possible on a single cell cannot exceed the cell's open-circuit voltage. So you cannot have 5V of sag on a 4.2V cell. The reality is a 100mohm, 4.2V cell cannot source 50A, so there is no paradox.
Its not accurate. If you are "just fine" with a lack of accuracy, well good for you. I am not. Fact is, V=IR is inacurate here.

Temp? SOC? Alot more go into it. I guess teh IR is the same on a hot day or a cold day, or the cell clearly comes with 2 "IRs", one for hot days and one for cold. Right? (IR varies dramatically with temperature in a way a resistor does not).

"Importantly, IR is a measured number not an intrinsic property, so that different methods of measuring IR give slightly different numbers."

"It just behaves roughly as though it was and that makes it easy to make some predictions about battery performance without having to analyse the electro-chemistry of the internal workings in awful detail. The equations involved and their solution is not the stuff ordinary folks want to be involved in."

"1) Comparing IR values is only valid if they are measured the same way
2) Comparing IR values is only valid if they are measured at the same temperature"

"Overall, precise prediction of cell performance from a simple measurement of IR is probably too much to ask.

However it is very much better than what we currently have and is easy to do and understand for the average punter. It provides good guidance based on a fair history of practical controlled test results. Provided you use the same measuring tool each time and note the test temperature it is a reliable comparative method."

This shit was written years ago,from a scientific standpoing of DIY study by people who have been doing it for years. .... and if you want to find the reference just google the quote. That will tell you much more than I have the heart to on a random online forum. Fact of the matter is one way, on a powerlab, you get one reading, and another, on a Icharger,you get another, and yet again, you do it manually, and get a third different number, ... Which do you trust? Lol. The one that makes the most output? The one that makes the least? The average? Which? Hmmmm.... Do you trust your multimeter or a high end Powerlab? One is obviously wrong.. and you are the scientist, with empirical data.. You have to choose one measurement...


So.. are we talking about "accuracy" or "methodology" here? Is this empirical data or not? Cause if it is not, well hell, you all good with that "voltage" number you got at the end of your figuring.


6(w)*capacity/IR.

Thats all you need to keep track of. IMO. That, and or if your cell is 25+mOh, you got a problem.

Cell DC IR cannot be calculated by V=Ir "sag".... "just fine"... Nope. Not if you want accuracy.

"Sag"... Lol.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

Punx0r   100 GW

100 GW
Posts: 5514
Joined: May 03 2012 8:16am
Location: England

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Punx0r » Jan 09 2020 1:17pm

Congratulations on being technically correct, with no consideration of context.

The scenario is the OP wants a simple test he can perform at home on his battery to discriminate between two very distinct states: 1) "condition = OK" 2) "condition = garbage".

R = V/I works just fine and will likely be more accurate than the IR measuring function on most chargers as it's typically performed with a greater load and in a 4-wire setup.

The measurements will be taken according to common sense i.e. at room temperature and at a SOC representative of actual use (50 - 100%).

From your own quote:
DogDipstick wrote:
Jan 09 2020 12:52pm
"Importantly, IR is a measured number not an intrinsic property...It just behaves roughly as though it was and that makes it easy to make some predictions about battery performance without having to analyse the electro-chemistry of the internal workings in awful detail...is easy to do and understand for the average punter. It provides good guidance based on a fair history of practical controlled test results. Provided you use the same measuring tool each time and note the test temperature it is a reliable comparative method."


Basically, exactly what the OP needs. A good guide. A relative comparison between other cells in the pack. If the absolute measurements are off by 100% it would still have been plenty accurate for his purposes.

Your methods I'm sure are great for lab work compiling cell datasheets for OEMs. I take it the calibration on all your equipment is traceable to national standards?

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 09 2020 2:01pm

"Your methods I'm sure are great for lab work compiling cell datasheets for OEMs. I take it the calibration on all your equipment is traceable to national standards?" Yes, by engineers with very precise battery stacks and certifications.



Its a chemical reaction vs heat thing. No accuracy (manually) is there (0 resolution? is that possible?) (lol doesnt sound very "resolute".... ) when you are testing anywhere from 1250Ah lead acid 2v cells to 2500mAh 18650, and everything between and around, with the generic multimeter. For one thing, that cell has the power to overcome most meters in speed and capability... You could use an oscilliscope if you wanted more accuracy. These specs have been published for years.

Resolution is resolution. The scientist has been f_u_k_i_n_g round with "resolution " for years in an effort to but an"empirical " number on a "finite sequence of numbers" that may or may not be the data that he/she is looking for.

look, I dont know it all. I do know what Ive learned, and when judging IR based on what a "machine" reads ( the charger in the pic above), and asking questions,.... a "manual IR reading" is what is out of context in my opinion.

The excel screenshot above clearly shows the discrepancy. The proof is above, when comparing the manual IR read to the B6ac number sequence. Not a single number is congruent.

Sure, keep on relying on the "multimeter". A ESR meter is a different animal. A ESR meter would not exsist if it was not necessary for yer acuracy and resolution. There is a huge difference between a cold and a hot battery. Yes, 59* degrees average is an acceptable engineering standrd.

Look, Im not an engineer, ( do know a few, at work)... but I dont like it ( in the context of this post) when people tell others that the "R = V/I" eq. is fine for testing a pack that is obviously compromised ( visually, from puffing) and he/she is testing using a machine.... and that pack is a high output Cobalt lipo with some serious SSC available in practical use if something redundant fails or is overlooked.

Its not fine. It is not accurate. In context, relative to this post, esp.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 09 2020 2:03pm

Punx0r wrote:
Jan 09 2020 1:17pm
Congratulations on being technically correct, with no consideration of context.





Thankyou for not considering context, but I would say context is relative here. Thanks for the affirmation.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

Punx0r   100 GW

100 GW
Posts: 5514
Joined: May 03 2012 8:16am
Location: England

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Punx0r » Jan 10 2020 4:29am

DogDipstick wrote:
Jan 09 2020 2:01pm
For one thing, that cell has the power to overcome most meters in speed and capability... You could use an oscilliscope if you wanted more accuracy. These specs have been published for years.
1) You think the OP should be buying a 'scope to troubleshoot his battery?
2) How is response speed of the meter an issue when conducting a basic measurement of DC resistance
3) Please reference these specs - the published standards you recommend for measurement of cell DC IR.
DogDipstick wrote:
Jan 09 2020 2:01pm
Sure, keep on relying on the "multimeter". A ESR meter is a different animal. A ESR meter would not exsist if it was not necessary for yer acuracy and resolution. There is a huge difference between a cold and a hot battery. Yes, 59* degrees average is an acceptable engineering standrd.

[/quote]

Great, that will (still using R = V/I) give you the AC impedance. You could compare it to the datasheet value, but not much use for an electric vehicle, which is a DC load.
DogDipstick wrote:
Jan 09 2020 2:01pm
There is a huge difference between a cold and a hot battery. Yes, 59* degrees average is an acceptable engineering standrd.

[/quote]

There is. That's why you'll see cell IR charts will multiple curves plotted against different temperatures. We hobbyists want to compare against the as-new IR published by the manufacturer. It's a reasonable assumption this will have been measured at room temp., not -20°C or 50°C.

Most national and internation standards specify room temp around 23°C (73°F). 15°C is a little low.


mudale222, feel free to measure your cell's internal resistance using a basic DC load test to get a reasonable idea of their condition. Obviously, any clearly "puffed" cells are not to be trusted, regardless of their capacity or IR measurements.

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 10 2020 11:33am

I am sure my powerlab and the Wayne Giles DCIR meter use 1000Hz. Better than a traditional meter. Doesnt give you results all over the place, like those posted above.

Also, doing it without separate draws is silly, inaccurate, and you get numbers all over the place.

"The two-tier DC load method offers an alternative method by applying two sequential discharge loads of different currents and time duration. The battery first discharges at a low current for 10 seconds, followed by a higher current for 3 seconds (see Figure 4); the Ohm’s law calculates the resistance values. Evaluating the voltage signature under the two load conditions offers additional information about the battery, but the values are strictly restive and do not reveal SoC or capacity estimations. The load test is the preferred method for batteries that power DC loads."

"DC load measurements work well to check large stationary batteries, and the ohmic readings of the device are very accurate and repeatable. High-end test instruments claim resistance readings in the 10 micro-ohm range. Many garages use the carbon pile to measure starter batteries and an experienced mechanic gets a reasonably good assessment of the battery.

The DC load method has limitations in that it blends R1 and R2 of the Randles model into one combined resistor and ignores the capacitor (see Figure 3). “C” is an important component of a battery that represents 1.5 farads per 100Ah capacity. In essence, the DC method sees the battery as a resistor and can only provide ohmic references. In addition, the DC load method gets similar readings from a good battery that is partially charged and a marginal battery that is fully charged. State-of-charge and capacity estimations are not possible."

Yeah lets give the guy the most inaccurate and prone to user error test, to test the integrity of his high power flammable portable lipos with compromised physical structure.... GREAT IDEA.

Not a single administration uses 73 degrees. That I know of. The "US DOT" used 60*. Are we in vehicles? In the US? ( I thought we were... ) Most here use 59* or 60*. All the engineers I have known use 59*. I am in a cooler climate. I dont assume room temp during the winter. Assumptions make for asses, and cheapo junk lipo purchases ( "I assumed it said lipo and meant it was powerful... never actually measured, just assumed")... Hell, my house varies from 55-75 year round. Here is a reference.

NOT a single "73* on THIS list, that I see.

https://en.wikipedia.org/wiki/Standard_ ... d_pressure

"1) You think the OP should be buying a 'scope to troubleshoot his battery? (see below)"

"2) How is response speed of the meter an issue when conducting a basic measurement of DC resistance "( t is the accuracy of the measurement, not the speed we are looking at here, and an oscilliscope is a way to visually graph the data, and then have it for study later.. and accuracy of reading... )

3) Please reference these specs - the published standards you recommend for measurement of cell DC IR. ( Why? So you f-u-c-k-ers can tell me everything I might have wrong and yall can continue to pick apart my knowledge? GTFO here again. I'll tell you this, I have spoken with, and studied "Wayne Giles", whom is awell known hobbyist who has been testing ( consumer lipos) batteries with many others, for years, and designing circuitry for their projects. In direct reference to IR measurement and the IR of large automotive grade lithium polymer cells, and the accuracy or their testing.)

Here:
..............you show me yours (reference) first. Then I'll bring out mine.

I didnot say "should" buy a scope, I said..

QUOTE: "You could use an oscillisco"...

"Could" and " Should" are two different words, with different meanings, in the context and by definition. If you cannot read with comprehension, and decide to retort in error,.... I think you should read more. More comprehension should come to you, with time.

You know, are you guys trying to prove me wrong, or help the OP? Im trying to help the OP get a GOOD, ACCURATE, High RESOLUTION reading. Not prove you guys wrong. Trying to sugest a better DIY way. For the hobbiest, like me, and Wayne, whom have found to much user error in the traditional meth. So much that We dont like to reccomend the methoed you sugestt for accuracy, repeatability, and reliability.

Man, frock off. Keep on picking me apart, I'll leave. No loss to either of us. YOu know I speak in truth.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 23 2020 11:27am

Punx0r wrote:
Jan 09 2020 3:44am
Cell DC IR can be calculated from sag via V = IR just fine! It's not complicated - quite simple :)

Yes, you can reverse a cell in a battery, but this is not really sag. Maximum sag possible on a single cell cannot exceed the cell's open-circuit voltage. So you cannot have 5V of sag on a 4.2V cell. The reality is a 100mohm, 4.2V cell cannot source 50A, so there is no paradox.



No, It cannot ("be calculated from sag via V = IR just fine!"). This has been ascertained by many I have researched. The numbers are all over the place, and unreliable.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

Punx0r   100 GW

100 GW
Posts: 5514
Joined: May 03 2012 8:16am
Location: England

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Punx0r » Jan 24 2020 4:50am

I left this thread alone hoping it would just quietly go away, but since you're bring it back up:
DogDipstick wrote:
Jan 10 2020 11:33am
"The two-tier DC load method offers an alternative method by applying two sequential discharge loads of different currents and time duration. The battery first discharges at a low current for 10 seconds, followed by a higher current for 3 seconds (see Figure 4); the Ohm’s law calculates the resistance values. Evaluating the voltage signature under the two load conditions offers additional information about the battery, but the values are strictly restive and do not reveal SoC or capacity estimations. The load test is the preferred method for batteries that power DC loads."

"DC load measurements work well to check large stationary batteries, and the ohmic readings of the device are very accurate and repeatable. High-end test instruments claim resistance readings in the 10 micro-ohm range. Many garages use the carbon pile to measure starter batteries and an experienced mechanic gets a reasonably good assessment of the battery.

The DC load method has limitations in that it blends R1 and R2 of the Randles model into one combined resistor and ignores the capacitor (see Figure 3). “C” is an important component of a battery that represents 1.5 farads per 100Ah capacity. In essence, the DC method sees the battery as a resistor and can only provide ohmic references. In addition, the DC load method gets similar readings from a good battery that is partially charged and a marginal battery that is fully charged. State-of-charge and capacity estimations are not possible."

Yeah lets give the guy the most inaccurate and prone to user error test, to test the integrity of his high power flammable portable lipos with compromised physical structure.... GREAT IDEA.
I've highlighted in bold the pertitent sections of your quote (which I think is from the Battery Univeristy site). It explains nicely why a simple R = V/I test with a DC load is a good test of DCIR, as requested by the OP. Yes, it does not tell you SoC or cell capacitance or AC performance, but that was not what was needed. Your conclusion of "most inaccurate and prone to user error test" is not supported by the text you quote - you are attempting to read into it a preformed conclusion.

DogDipstick wrote:
Jan 10 2020 11:33am
Not a single administration uses 73 degrees. That I know of. The "US DOT" used 60*. Are we in vehicles? In the US? ( I thought we were... ) Most here use 59* or 60*. All the engineers I have known use 59*. I am in a cooler climate. I dont assume room temp during the winter. Assumptions make for asses, and cheapo junk lipo purchases ( "I assumed it said lipo and meant it was powerful... never actually measured, just assumed")... Hell, my house varies from 55-75 year round. Here is a reference.

NOT a single "73* on THIS list, that I see.

https://en.wikipedia.org/wiki/Standard_ ... d_pressure
Those are standard conditions for establishing chemical reaction rates, not necessarily standard room temperatures for performing laboratory tests. "Are we in vehicles?" No, we're doing battery tests in a room??? You started talking performing battery test for maximum accuracy and I told you that auotmatically means in a temperature controlled (conditioned) lab with measuring equipment traceable to national standards. When testing generally to national and international standards some permit testing in unconditioned labs: I can recall allowable temperature ranges as wides at 18-27°C but most will specifiy 23°C/50%RH or sometimes 20°C/65%RH, usually +/-2°C and 5%RH. Things will vary around the world, but this is my experience and why I asked you which battery testing standards you used, so I could check the conditions it called for.
DogDipstick wrote:
Jan 10 2020 11:33am

"2) How is response speed of the meter an issue when conducting a basic measurement of DC resistance "( t is the accuracy of the measurement, not the speed we are looking at here, and an oscilliscope is a way to visually graph the data, and then have it for study later.. and accuracy of reading... )
You said: "For one thing, that cell has the power to overcome most meters in speed and capability..."

Speed. I.e. rapid voltage transients. There are none in a DC load test, hence my comment. Scopes are great, but you don't need one to visualise a straight-line voltage required to calculate DCIR. A multimeter is perfectly adequate. Implying the OP needs a scope is bad advice.
DogDipstick wrote:
Jan 10 2020 11:33am
3) Please reference these specs - the published standards you recommend for measurement of cell DC IR. ( Why? So you f-u-c-k-ers can tell me everything I might have wrong and yall can continue to pick apart my knowledge? GTFO here again. I'll tell you this, I have spoken with, and studied "Wayne Giles"
As above, I asked so I could check the required conditions. No need to be abusive.

I don't know who Wayne Giles is, but I'm sure he makes perfectly fine battery chargers/analysers. The OP doesn't *need* one to confirm if his cells are alive or dead though. If you ever find yourself saying the *only* way to do something is with commercial product X, then you are likely automatically wrong.
DogDipstick wrote:
Jan 10 2020 11:33am
I didnot say "should" buy a scope, I said..

QUOTE: "You could use an oscillisco"...

"Could" and " Should" are two different words, with different meanings, in the context and by definition. If you cannot read with comprehension, and decide to retort in error,.... I think you should read more. More comprehension should come to you, with time.
Thanks for the clarification. In a similar vein he "could" buy a $1500 fluke meter, a $5K bench PSU and an elephant, but he "should" not. Neither "should" he buy a scope for this task.
DogDipstick wrote:
Jan 10 2020 11:33am
You know, are you guys trying to prove me wrong, or help the OP? Im trying to help the OP get a GOOD, ACCURATE, High RESOLUTION reading. Not prove you guys wrong. Trying to sugest a better DIY way. For the hobbiest, like me, and Wayne, whom have found to much user error in the traditional meth. So much that We dont like to reccomend the methoed you sugestt for accuracy, repeatability, and reliability.
Everyone in this thread except you has attempted to help the OP by suggesting methods by which he can perform basic tests on his battery. Your response was to pour (incorrect) scorn on the methods he used and implied we're all fools. The OP does not need to buy any product from your friend, nor does he need a lab or a scope.
DogDipstick wrote:
Jan 10 2020 11:33am
Man, frock off. Keep on picking me apart, I'll leave. No loss to either of us. YOu know I speak in truth.
Thanks for the further abuse. I note you came back to this thread to stir the pot after I left it to go quiet.

I will say this again:

Basic health check of an ebike battery to see if it can support a DC load: absolutely fine to do V=IR with a ~10s DC load at a sensible/representative of end use SoC and temperature using a multimeter.

User avatar
DogDipstick   1 kW

1 kW
Posts: 420
Joined: Aug 19 2018 12:39pm
Location: Fleetwood Pa

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by DogDipstick » Jan 25 2020 1:28am

I will say this again:

Basic health check of an ebike battery to see if it can support a DC load: absolutely fine to do V=IR with a ~10s DC load at a sensible/representative of end use SoC and temperature using a multimeter.
Yeah right.

I guess that is why everyone rely on that exclusively, for all IR measurement and we have all these reliable ebike batteries that last for years. Lol. Its a hobby to get into, and us as hobbiest have used all the different charges and done it your way, and have found that is not accurate and not a good way for someone who doesn't know much about their battery, to find data on their possession.

For example, here, written out by an old poster, years ago, for its been this way forever... The suggestion you give is not " just fine" for wondering if lipos are healthy. Esp. if you are wondering about the IR readings, ( your empirical data), that you made yourself with a multimeter, against a machine that you have no ideas as to how it measures, or ideas as to its accuracy.
"For example:
If your cell is 15mOhm (0.015Ohm), and you draw 30amps from it, it will drop 0.45v.

If your cell is 1.5mOhm (0.0015Ohm), and you draw 30amps from it, it will drop 0.045v.

The cells resistance changes with SOC to a fairly mild extent (generally +-50%), and greatly with temperature, cold vs hot can be 300% difference or more. "
50%? 300% Sure... little numbers. negligible. lol.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

Punx0r   100 GW

100 GW
Posts: 5514
Joined: May 03 2012 8:16am
Location: England

Re: Doesn't make sense.. does my battery broken?33mΩ too much ir??

Post by Punx0r » Jan 25 2020 5:17am

It's not "my method" - it's Georg Ohm's method.

I've repeatedly stated you must account for SoC and temperature, so your argument above is moot.

Please post details of the method YOU use to determine a more accurate measurement of DC IR. The one that doesn't use Ohm's Law. Because you haven't suggested one yet - just scoffed at other people's posts and asserted that scopes are better than multimeters.

A li-ion cell, as an electrochemical device, is not purely resistive, but can be usefully approximated as one over a certain range of conditions.

Post Reply