Battery test issue in Pico 6.11.12

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Battery test issue in Pico 6.11.12

Postby victor2k » Thu Sep 29, 2016 12:55 pm

Hello,
Why the Battery test from Pico 6.11.12 report 12.1v if the measured voltage at the start of test is 12,7v(this was a displayed value on the upper bar when I pressed start)?The calculated capacity is 1231 CCA?Wow...
I used for test Pico 4425,TA167,and the old equivalent of TA125(a black one cable).
I will upload later the registered file.
Thank you
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Re: Battery test

Postby victor2k » Thu Sep 29, 2016 7:24 pm

The same battery was tested with same setup and the result was 994 CCA capacity,only based on 12,6 v detected at the start of test?23-24% diference based only on the state of charge?
My friend's car is a Chrysler 300C what show at the morning start many CAN faults, engine and transmission work in limp-mode,steering sensor need recalibration at the first start in every day(after 6-8 hours of rest )so I need to know the health of battery before to change ECUs :|
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Re: Battery test issue in Pico 6.11.12

Postby victor2k » Tue Nov 01, 2016 2:55 pm

Hello,
The same battery was tested by dealer and the result was 873 CCA ...in 30.09.2016 at 17*C.
I think it was used a Midtronics tester.
145% and 117% was the results using Pico Diagnostics compared to 102%.
I think you must recheck the math behind of Battery test.The test must check the initial voltage for a surface charge .
Thank you
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Re: Battery test issue in Pico 6.11.12

Postby Steve Smith » Wed Nov 02, 2016 3:05 pm

Hello Victor and thank you for the post and files.

In all three tests it would appear the capacity of the battery is greater than the specified 850 CCA when using the “EN” specification

Can you confirm which specification/standard is quoted on the battery?

You can amend your results by opening your files, changing the units to DIN and then clicking on Analyse.

This brings your capacity figures to a more realistic value than the initial test of over 1000 CCA with an initial voltage of 12.1 V

I am not sure if we have a measurement error in your first test (140629) as you have pointed out 12.1 V in the parameter list and above 12.5 V in the graph view. (Could possibly be a bug too!)

Have you been able to confirm the reason for the CAN faults during morning starts?

It does sound like a voltage threshold issue. (Do any of the nodes report battery voltage errors?)

I agree, we must confirm the battery to be fine before looking at ECU’s.
Can we measure battery voltage under the conditions specified by the customer? This may help to confirm Battery supply voltage or voltage distribution error as a reason for CAN codes (If related to voltage)

I have some notes below Victor that may help with the characteristics of the PD battery test:

I think its best here to start at the beginning with regards to battery testing.

One thing we must agree on is that testing batteries conclusively is near impossible without following the specific criteria laid down by the various industry standards. To follow such criteria will often leave the battery unserviceable!

We must not confuse the industry standard method of battery testing (SAE EN DIN) with the Pico Diagnostic (PD) battery test even though the results stated are in the same units of CCA

The CCA rating of any battery is a complex figure arrived at by design, therefore, any battery test result (Measured CCA / Percentage of Specified CCA) obtained during a PD battery test can only ever be an instantaneous, calculated estimate based on the measured resistance of the battery.

With the Pico Diagnostic battery test with have the advantage of safely drawing current from the battery where others don’t. (The cranking performance test)

Drawing current during the cranking phase allows for an “instantaneous CCA estimate” in the field and could never match the conditions specified by the industry standards with regards to time, load and volt drop given we are cranking for minimal time (Av. 1 second) with no control over the load from various OCV’s (Open Circuit Voltage) to varying volt drop levels.

The fundamental value assisting with the estimation of instantaneous CCA is battery resistance and is calculated as:

OCV =12.20 V, Lowest recorded Voltage = 7.23 V, Voltage drop = 12.20 – 7.23 = 4.97 Volt Drop

Battery resistance is calculated from peak starter inrush current using Ohms law:

Maximum inrush current = 560 A. Battery resistance 4.97/560 = 0.008875 Ohms

Estimated instantaneous CCA is then calculated for each industry standard based on instantaneous measurement

The battery test results then display the Battery Capacity CCA value (447 CCA EN) using the figures derived from the calculations above where the specified battery CCA value was 468 EN. (Entered by user) 447 CCA is therefore 95% of the specified 468 CCA EN.

Displayed as Capacity is 95% of 468 EN.

I hope this helps Victor, take care…….Steve
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Re: Battery test issue in Pico 6.11.12

Postby victor2k » Wed Nov 02, 2016 6:59 pm

Hello,
Thank you for your answer.
My question was why the same battery tested with the same hardware give different results(and diferrence is a big one).
I am sure about the initial value of voltage because I measured 12,7 v with Fluke 233.
I can't be sure about the standard of battery(is a Duracell AGM imported from USA ).
The common sense tell me to choose SAE standard.
Also (I think) isn't used a german standard on the american market...but why I selected EN?I don't know.It's my mistake :?
TCM was the source of CAN faults...after the replacement all is normal,no abnormal discharge of the battery.
Thank you
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Re: Battery test issue in Pico 6.11.12

Postby Steve Smith » Thu Nov 03, 2016 10:27 am

Hello Victor and thank you for the feedback on the CAN faults and the clarification of the initial battery voltage from test 140629 (12.7 V using your meter and not 12 .1 V)
Always good to get feedback

With regards to “My question was why the same battery tested with the same hardware give different results (and difference is a big one)”.

This surrounds the “Initial Voltage” erroneous assessment made by the Pico Diagnostics (PD) battery test in test 140629. (Erroneous possibly due to connection as test 140623 is correct)
An initial assessment is made on the estimated battery SOC using the Open Circuit voltage (OCV)

In test 140629 OCV = 12.1 V which equates to approx. 30% SOC. Such a low OCV will change the resistance value calculated as described in my post above (OCV – Lowest Voltage)

The differing resistance value calculations between test 140629 and 140623, combined with the estimated SOC levels will have an effect on our final test results.

The algorithm Pico use to calculate the final test results factor in a number of variables such as OCV (high/low) non liner loading, temperature, battery design, battery specification, battery resistance (that initially falls with increased current flow) load time, recovery time and rate, to arrive at our estimated instantaneous CCA value.

A point to add here about battery testing (given the time of year we are approaching)

There is no fool proof method for testing 100% of all battery faults (this includes the impedance test) but we can be on our guard when testing batteries for all vehicles.

Perhaps the fundamental check for technicians when testing battery’s is to not rely solely upon the CCA rating stated on the battery. Whilst this is generally correct for the battery it is not necessarily correct for the vehicle. This could most certainly manifest itself as a “Battery Pass” based on an example CCA rating of 350 when fitted to a vehicle requiring a CCA rating of 850.

During cranking, the delivered current will most certainly result in an instantaneous estimated CCA rating of “Capacity is 100% of 350 SAE”, the giveaway however will be the recorded “Lowest Voltage”

Given we are testing for an Instantaneous Estimated CCA value in these scenarios we should repeat the battery test perhaps twice more whilst monitoring the Lowest Voltage and final capacity rating as we are likely to see a pattern such as:

Test 1. 100% of 350 SAE, Test 2 85% of 350 SAE, followed by Test 3 indicating a rapid decline, e.g. 30% of 350 SAE accompanied with a hideous Lowest Voltage value.
In such a scenario battery capacity is clearly insufficient (Too low)

Remember a battery of this failure type is obviously not sufficient for this vehicle requiring a CCA rating of 850 but may prove serviceable for vehicles requiring ratings of 350 CCA and below.

I hope this information reveals an insight into the Pico battery test and highlights some of the pitfalls with battery testing.

Take care……..Steve
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Re: Battery test issue in Pico 6.11.12

Postby FioranoCars » Mon Nov 07, 2016 7:45 pm

Hi All
I've been talking to Steve for over a year about this test/feature of the PicoDiagnostic, and a few anomalies therein (well for several years about those, especially report formatting/printing).

Anyway back to the battery test ... the first things to note are the massive differences between SAE (American) and DIN (German/European - oh, and Europe have their own standard too) the later (DIN) is much stricter/harsher test conditions, but for those curious, Yuasa have a basic run down here of the different standards:
http://www.yuasa.co.uk/info/technical/understanding-the-specifications/

Practically, there are a few things to consider, or at least be aware of ...
1. always try to conduct any battery test with a fully charged battery. Testing in not fully charged will mean benchmarking the numbers becomes impossible (there is no reliable SOC correction factor), so it's fine to test a battery to see if it's got a dead cell or other defect beyond recharging, but sadly even then, a fully topped up (electrolytes) and fully charged battery is the best place to be starting from. There are lots of state of charge tables with temperature correction applied, just google them, as that figure moves with temperature and battery technology (gel verse wet cell are different!)

2. Most modern batteries have EN or SAE ratings over 400amps, even with starter motor inrush currents (pico seconds of load, not 30seconds or 150 seconds are per the standards) that is hard to replicate, even a big carbon pile load tester struggles to get above 400amps, so again hard to actually load the battery to a proper level. This current load (both the time and actual test load) is not strictly a linear relationship, mostly calculations are using linear "guestimates", different battery manufacture processes affect different batteries in different ways (so not all "lead acid" wet batteries follow the same path). Using the wrong starting CCA or using the wrong standard (EN or SAE) will cause serious issues.

3. The temperature, well ok, there is a reasonably well accepted correction factor, so the -17.8c test voltage of 8.5v becomes at 21.1c a minimum of 9.6v - quite a difference, and not a linear relationship ... GM did some studies, and that is now taken as the ground work for CCA adjustment/correction ... by most people, though I'm sure others will have different ideas, so for instance, a 600CCA battery at 55f (12.8c) would be considered for test purposes to now be a 920CCA (ok, 919.5 CCA) battery ... this GM correction factor was based on the SAE standard from memory ...
What does that mean? ... that when loaded to to 920Amps for 30seconds the battery should remain above 7.2v Still this needs to be accurately compensated, battery temp, not the current sun or snow outside, 5c is a big difference.

4. Surface charge,as mentioned already by Victor and Steve, will critically impact the initial battery voltage, which is a cornerstone of the calculation for the test, get this wrong and all the rest of the test/result is a product of a mistake. Rubbish in ... and all that.

5. To test fully to any of these standards, as Steve said, is almost destructive in nature, so is totally impractical for a garage to use!

So while the small hand held digital testers can make a guess as to the state of the battery and it's potential CCA rating, they are only a guess (well complex maths with lots of assumptions on how the battery will behave under different conditions that the test is being conducted at!), and not backed by any real load being applied ... which in a significant number of "checking suspect batteries" becomes relevant and indeed visibility of false positives or other misleading data become a major issue.

So using a good old fashioned load tester (carbon or resistance coil type) where you actually load the battery with hard and heavy amps, will give a better indication of the real world potential of the unit, mainly because you are loading for an extended period of time (ideally 10-30seconds), rather than a split second of cranking (most cars fire in under 1second) or even less time at the peak in rush current (the number used by PicoDiagnostics) which is mere pico seconds.

No doubt that the crank test is better than a hand held testers, and Pico's test has enormous value, but to compare results with different testers without exactly matched conditions (inc charge level) will be very hard to make sense of, and probably still no sense with everything perfectly aligned!

I'm not sure what correlation has been done by Pico between using the current peak in rush, to using instead cranking (or even extended cranking with spark or fuel disabled) and using that extended data (peaks and troughs of current), to see how the results relate? After all the peak amps is probably pretty imprecise due to the response of the amp clamp, verse the voltage measurement of the scope, so possible further scope for error, whereas the cranking is smoother and less likely to incur a clamp response error? I'd like to think the downside of lower amps loaded, but longer period of measure would be an advantage?

So, Steve this is a nudge to consider all those points raised (over the last 4 years I think!) about this test, so that the word "Volt drop" is not used ambiguously (especially during extended volt drop tests) etc etc :roll: :roll: :roll:

I hope that some of the background helps others, as it took a while to get some of the data, and many emails with Steve filling in little gaps and generally helping guide me through the subject matter patiently, certainly not as simple as I first though all those years ago! Thanks Steve, and look forward to bug fixes (I also recall a EN/SAE error/label thing?) and improved reporting soon ...

I'll get my coat!

Richard
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Re: Battery test issue in Pico 6.11.12

Postby STC » Tue Nov 08, 2016 12:42 am

Post by Steve Smith » Wed Nov 02, 2016 3:05 pm

One thing we must agree on is that testing batteries conclusively is near impossible without following the specific criteria laid down by the various industry standards. To follow such criteria will often leave the battery unserviceable


I wonder if the underlying objective here is to test Batteries or to Sell more of them ?

I refer to a recent thread here topic14581.html

A couple of points I made in that thread and still stand by:

Can you use the CCA Rating of a battery that you are testing for any diagnostic value ?

If you are doing that test for research purposes I have to drop out. If it is as part of a diagnostic process then Starter Current + B Voltage and crank it for 10, 15 seconds and calculate the RPM along that time. Do that again for belt and braces.

If it is spinning the engine fast enough to satisfy Injection criterea - Box Ticked -Move on!


and then

SAE J537 CCA test
Fully charge battery according to SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 7.2V (1.2V/cell) for 30 seconds.

DIN CCA test
Fully charge battery according to SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 9V for 30s and 6V for 150s



IEC CCA test
Fully charge battery according to SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 8.4V for 60 seconds.

Ohms law. A fully charged battery say 12.8volts with a load of 500amps can be achieved by introducing a resistance of 25.6 Mohms at -18c. No walk in the park achieving that. Labaratory Conditions.
In the absence of that huge resistor and a laboratory capable of achieving and maintaining those temperatures you may as well lay a rusty crowbar across the Positive and Negative terminals on a winters day, take voltage measurements over time and know for sure that you still have not achieved any where near the right test conditions for CCA Assignment or Measurement.

Watts Law. That 25.6 Mohm resistor will need to be rated at 330MWatts.



Massive difference in what it was designed and tested to do and what it is doing RIGHT NOW. Is it contributing to the non start/slow start issue in front of you or not ??

Not wishing to discourage you in your pursuit of excellence, just pointing out the possible/ probable challenges.
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Re: Battery test issue in Pico 6.11.12

Postby FioranoCars » Tue Nov 08, 2016 1:11 am

STC wrote:
Not wishing to discourage you in your pursuit of excellence, just pointing out the possible/ probable challenges.

Absolutely right, with battery testing there is no excellence, but ... being as close as is practical or possible is not a bad goal, however my quest is more realistic than it was, but I still have some ideas to test out (like mentioned about cranking, or other current drain over longer periods but more reasonable and sustainable levels) ... never one to sit on imperfection :wink:

Also far better to understand volt drop and parasitic drain along with alternator A/C ripple or even Alternator raw output and Starter motor consumption, far more root causes lie in those regions than bad batteries! And I'll bet hard cash more of those 3 items (Bat/Alt/Starter) are replaced completely inappropriately (without proper testing) than any other item on a car.

We digress, so see you tomorrow? Bacon butties at 11's ? ... and Mr Dillion at 12:30 or something like that?

Richard
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Re: Battery test issue in Pico 6.11.12

Postby STC » Tue Nov 08, 2016 1:18 am

Richard
And I'll bet hard cash more of those 3 items (Bat/Alt/Starter) are replaced completely inappropriately (without proper testing) than any other item on a car.


Indeed Yes. BUT NOT on My Watch :D (or yours)

Lambda Probes, MAF, Wheel Speed sensors, Crank & Cam Sensors, Diesel HP Pumps, Land Rover Freelander DDE 4 - LP Pressure Sensors and Pumps (recently) are well up there in my humble experience.

See you at 11am
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