Battery testing

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#1
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Hi freaks,

 

So I have been wondering where to post this question exactly, but i ended up posting it here as its more a "General Electronics" thing.

 

Suppose that I want to know the state-of-health, quality, etc.. for two different types of batteries:

 

- Alkaline battery

- Li-ion battery

 

My question is, what kind of different tests I should apply to these batteries...are there any standard procedures of testing that I need to know ? is there is a Battery Managment System BMS that does all these thing. Am speaking about some sort of rapid testing to test around 1000+ battery in day or so.

 

any help would be appreciated, or more like "Getting started thing"...

 

Regards,

Moe

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This had been discussed widely - google is your friend!

 

https://batteryuniversity.com/

 

Yes there are many techniques, and some special chips to implement (some of) those techniques

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awneil wrote:

 

 

Yes there are many techniques, and some special chips to implement (some of) those techniques

 

Would be happy to hear it ?

 

But my point is, its more from an industrial point of view, In companies where you have battery powered devices, how do you test them to make sure there are fine.

 

Am not speaking here about understanding the SoH, SoC..etc

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It's almost impossible to know a battery's "state of health" simply from a single instantaneous reading. I suppose if the battery chemistry has a very well defined discharge profile then by reading the terminal voltage very accurately you might be able to gauge where on the curve you were. But this is why mobile phones and similar have constant monitoring systems so they know how much energy has been put into the battery and the rate at which it was consumed so they know where in the "life" the thing is.

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clawson wrote:

It's almost impossible to know a battery's "state of health" ...

 

^^^That.

 

If you look at most batteries voltage/time graphs they show a fairly swift drop in voltage from their 'full' voltage, followed by a long steady plateau, followed by a fairly swift further drop in voltage as they reach their end of useful capacity.

 

If you measure the voltage whilst on that plateau you have no way of knowing how far along it you are, and that probably covers a range of 90% of usable capacity.

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Okay, in these kind of situation, is there is any digital devices lets say that you can set the threshold capactity...e.g.:

 

An alkaline battery of size AA, 2 in series, 3.3V...you put it in device, it checks what it needs to check and then gives a notification (e.g. Green LED) that it pass the exam, otherwise Red Led..., from an industrial point of view, have any one got to deal with these kind of devices, any suggestion ?

 

Regards,

Moe

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As already noted, simply measuring terminal voltage - especially open-circuit - bears very little relation to remaining capacity at all.

 

Again, there's plenty of published work on this

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Last Edited: Mon. Mar 30, 2020 - 12:55 PM
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Short NO

Unless you have good data for that specific AA batt. and you need to have the temperature.

If you have that my guess is that you with a relative high current in a short time. Then look at the voltages drop and recovery should be able to give you a good idea.

Last Edited: Mon. Mar 30, 2020 - 12:55 PM
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Back in my RC days, I had (still have) a device that you placed a fully charged battery into and it would discharge it and measure how long that took, you could then compare that what was expectd and to others of the same type to determine it's remaining capacity.  This would work for any rechargable, but it takes time, and would not work for primary batteries.

 

Jim

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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sounds like a fuse tester ... !!

 

laugh laugh laugh laugh laugh laugh laugh 

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awneil wrote:
sounds like a fuse tester ... !!

I should have added, discharged at a known constant rate.....  blush

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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I mean your test shows how much energy was stored - by the end of that test, there is nothing left!

 

I think the OP is asking for a way to know how much energy is currently left ... ?

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Well the OP's question was battery condition, they specifically stated they were looking for SOH, not SOC!

Perhaps I misunderstood the question!???

 

Jim

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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Ah - you may be right.

 

But that test may not be representative of how the battery performs in "Real Life" ...

 

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I currently have my trusty old Triton charger sat on the desk in front of me. Like many NiCd/NiMh/LiPo chargers for RC before it, it has the ability to discharge packs both to gauge their capacity and also refresh them (in NiCd/NiMh in particular it can help to clear "memory")

 

 

I find that the results you get from a charger/discharger like this are a pretty strong indicator of how battery packs will behave under load in a plane.

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I remember my first cellphone when you put in the charger it would start by discharge for some time (10 min or so)

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Moe123

 

For little alkaline cells, you can simply apply a known load and measure the delta volt drop.   It will give a decent estimate.  What do you want to know?  50% or 100% ready, or do you need to know whether it is 98.5% vs 96.3% charged?  Go/NO go test is pretty easy. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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There is a BIG problem with all batteries to estimate charge state.

 

It depends hugely on LOAD! I'm not just talking about discharge rate. Internal battery resistance means that the terminal voltage will be lower, at a given battery charge state, when the load current is higher. This gives an apparent state estimate that is lower than it really is.

 

Further, this internal electrical resistance is, in part, electro-chemical. This means that the apparent battery state does not return, instantly, when the load is removed. It can take minutes, or longer. 

 

The short take-away from this is that your goal of measuring thousands of batteries per day is somewhat of a fantasy. 

 

Here is a snap-shot of what I am currently doing. I make a battery powered device. It SHOULD last a long time with a pair of C cells. When it is screwed up (software), the life can be 5-10 days. When it operates correctly, it can be 45 to 90 days. Now, with just one battery (they are in parallel), I get half life, so 45 day life turns into 23 days with a single cell. I can tell, pretty well, what the life will be at the 50% discharge point. That is 12 days. BUT, I can usually tell if it is going to be good or not in 2-3 days; by that time, I can see if it is AFU or if it is (relatively) good, but not how bad or how good. That is how I have been doing it. Though, I should be clear, my interest is in how the instrument behaves, not how good any particular battery is. I should also add that this device has highly irregular battery energy consumption patterns, which come from WHEN a microSD memory card is written (device  sleep current is microAmps, write current is 100+ mA).  

 

What I am now doing is starting with a software build with known good battery life, and another software build with known poor battery life. I have a test fixture using super-capacitors that will run the instrument. By measuring the super-cap  discharge rate over some time interval, I can determine the average current for the known good unit and the known bad unit. Then, in the future, I can compare new software builds against the known cases, and do this in a few minutes.  

 

Not sure this will help but maybe it will?

 

Cheers

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Mon. Mar 30, 2020 - 07:45 PM
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Moe123 wrote:

Am speaking about some sort of rapid testing to test around 1000+ battery in day or so.

 

Are these new cells, particularly the Alkaline ones?

 

If so you could simply sample 1 in every 50 and do a full discharge test. Statistically the others will be the same.

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Moe123 wrote:

Am speaking about some sort of rapid testing to test around 1000+ battery in day or so.

 

That's a big pile of AA's!!!!

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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Here is a good little circuit that provide a general check for alkalines. Li-ion is probably more complex/difficult, since it has the "sudden rolloff".  Sudden rolloff is much harder to test, since you might be only 2 inches away from the cliff going straight to the bottom.

 

https://www.edn.com/circuit-provides-constant-current-load-for-testing-batteries/

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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I think I have one of these laying around somewhere, I can send the OP.

You know it gotta be good, it came from RadioShack

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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I think I have one of these laying around somewhere, I can send the OP.

I bought my wife a digital version...she didn't like it since it lacked the red/yel/green scale.  "is 0.88V good? "

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Measuring battery impedance works well for lead-acid. Not sure how well it works for other chemistries.
A method I used was to have a 1kHz square wave switch a known load across the battery. Then measure the AC component. A simple job for a micro.

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In one battery charger project I made it so the system periodically took the battery off charge and placed a load on it and measured the voltage while on that load. Then, if needed swapped it back to charge.
The voltage and load that I used was determined from a practical test on a tested good cell in various states of charge.
Doing a practical test to get data would seem to be the way to go.
It worked well.
Quite cheap to make one for each cell, or maybe a number of units can be connected to multiple cells.

In one military application there where around 600 batteries in one room they all had a built in tester if the battery condition got to low it would set off a piezo buzzer, we used to chase around the racks looking for which battery had gone down LOL.
Maybe use a LED.

Last Edited: Mon. Mar 30, 2020 - 11:58 PM
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clawson wrote:

I currently have my trusty old Triton charger sat on the desk in front of me. Like many NiCd/NiMh/LiPo chargers for RC before it, it has the ability to discharge packs both to gauge their capacity and also refresh them (in NiCd/NiMh in particular it can help to clear "memory")

 

 

I find that the results you get from a charger/discharger like this are a pretty strong indicator of how battery packs will behave under load in a plane.

 

Is that for the planes Clawson???

Have not been out in a year.

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I would like to go back and ask Moe a question which I do not think has been directly asked:

 

What do you mean by "state-of-health, quality, etc."? I ask because the question might refer to a variety of things that have been alluded to, but not really stated. For example?

 

A. Does this refer to the current present state of charge of the battery?

 

B. Does this refer to the ability of a battery to hold charge?

 

C. Does this refer to the ability of a battery to deliver charge (e.g. energy)?

 

D. Does this refer to the fraction of remaining useful battery life?

 

Each of these means something different (though are often related in a variety of sometimes obtuse ways). Each of these is measured differently (and not always consistent across battery chemistries). Each takes different amounts of time to determine. 

 

A little clarity here would help all of us, and probably, also the OP.

 

Jim

 

edited, hopefully with your agreement Jim, in the interests of avoiding any ambiguity because of language difference. Ross.

 

<add> Good catch - jim </add>

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

Last Edited: Thu. Apr 16, 2020 - 03:31 PM
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Also, do you want to actually precisely measure these things or indirectly predict them?  Measuring may be more accurate, but much much slower (such as actually discharging the battery, using coulomb counting, monitoring temperature rise,etc).  Predicting & inferring some things may be the only practical way, if you are trying to hurry through 100's of batteries.  Sort of like burning rubber down your street vs getting on a dyno.  You need to specify the max allowable uncertainties. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ki0bk wrote:
That's a big pile of AA's!!!!

When I see a pile of batteries like this I alwasy fear that tiny chance that some of those batterie will create a perfect short circuit where they are is series. surprise

 

 

And why not test a mechanical properties of the batteries? laugh

https://www.youtube.com/watch?v=ZywsCbWEun8

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vlkon wrote:
And why not test a mechanical properties of the batteries? laugh

https://www.youtube.com/watch?v=ZywsCbWEun8

https://www.youtube.com/watch?v=W41beDEZaMY

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This just popped up on my FB:

 

Analog Devices wrote:

 

The circuit shown in Figure 1 is an electrochemical impedance spectroscopy (EIS) measurement system for characterizing lithium ion (Li-Ion) and other types of batteries. EIS is a safe perturbation technique used to examine processes occurring inside electrochemical systems. The system measures the impedance of a battery cell over a range of frequencies. The data can determine the state of health (SOH) and state of charge (SOC) of a battery.

 

 

https://www.analog.com/en/design-center/reference-designs/circuits-from-the-lab/CN0510.html

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Will have to read, now. Big question in my mind is how to correlate such measurements with the actual state of the battery.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Wow!...that is pretty impressive piece of gear.  They really went to town in the measurement dept:

 

Next, the voltage across the battery is measured. The voltage drop across each component is very small in the range of microvolts (μV) ....

Using the discrete Fourier transform (DFT) hardware accelerator, a DFT is performed on the ADC data where the real and imaginary numbers are calculated and stored in the data FIFO for both the RCAL voltage measurement and the battery voltage. 

 

Someone spent a lot of lab time (years) developing this battery of knowledge and this test hardware....of course battery tech forms entire industries, with many researchers and $$$ at stake, especially nowadays.

 

It's a bit amusing, that in the end they still say open the comm port & get the terminal going to see the results.  Simplicity never goes outta style.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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I have to admit to a sneaking curiousity which I have not yet investigated in more than the most trivial of details: battery charging for electric vehicles. The concepts don't seen difficult but the numbers scare me... maybe a capacity of 50 or more kWh, terminal voltages at somewhere around 120v, currents peaking at maybe two or three hundred amps.

 

When charging stationary, I *presume* some sort of cell monitoring at multiple points on the stack - a series connection of lots of 3v(ish) cells - but I have no idea whether it just shoves volts in at the top and lets the battery pack get on with it, or whether there are smarts in the external charger.

 

As for regenerative braking... hmmm. MPTT chargers for each cell pack?

 

I dunno, and my google-fu does not lead me to obvious places to find out. People seem to want to keep schtumm about it.

 

Neil

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Neil,

 

This is when we need Carl, "MicroCarl", to jump in with some firsthand engineering knowledge.

 

 

Ross McKenzie ValuSoft Melbourne Australia

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barnacle wrote:
I *presume* some sort of cell monitoring at multiple points on the stack

I think so.  ISTR Linear Tech (now Analog Devices) had chips to do that sort of thing?

 

People seem to want to keep schtumm about it.

I guess at this stage this is the kind of stuff that can give a car maker a competitive advantage in the market ... ?

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barnacle wrote:

maybe a capacity of 50 or more kWh, terminal voltages at somewhere around 120v, currents peaking at maybe two or three hundred amps.

 

Model S has a 100 kWh battery, with a pack voltage of 400V, and a few different charging options, but the supercharger has the highest power at 150-200 kW at 480V DC, so over 400A.

 

barnacle wrote:
As for regenerative braking... hmmm
More than 60 kW worth, apparently.

"Experience is what enables you to recognise a mistake the second time you make it."

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avrcandies wrote:
imaginary numbers

I have lots of those in my codes as well ... it'shard to imagine the results. laugh

 

ka7ehk wrote:

Will have to read, now. Big question in my mind is how to correlate such measurements with the actual state of the battery.

 

Jim

You probably have to first make a lot of measurements on known batteries so you can then compare the unknown one. It is odd that there is not combined with a temperature measurement since that should significantly influence properties of the battery.