Battery test (In automotive diagnostic )

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Battery test (In automotive diagnostic )

Postby steve-amt » Mon Feb 22, 2016 2:16 pm

Hi

Audi A4 Derv flat battery in morning. How accurate or reliable is the battery test? I jumped the car and ran it for a while to charge battery on the car. Set my Pico 4425 with the battery test Ch A on battery Ch B 2000 amp clamp. It shows battery good but needs charging! Internal resistance was red on first test. Did test again shows all ok in green but req charging. My intuition wants to change the battery.
Is it me am I really thick?
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Re: Battery test (In automotive diagnostic )

Postby FioranoCars » Mon Feb 22, 2016 7:54 pm

The battery test is Ok, not perfect, and better if you use the full 4 channels to cover volt drop to the starter

...but I've had issues with the maths/terminology used for the both the standard 2 channel and extended 4 channel test since they added it, so ignore what they call "Volt Drop", as that reports the total voltage "depression" during cranking, not volt drop on either path to the starter motor!

Doing this test, or ANY battery test for that matter, using a battery that is NOT fully charged will ALWAYS be inconclusive, unless it's charged enough to pass all elements, so in reality it's pointless doing any test unless you have fully charged it FIRST!

There is in my view (IMHO !) no substitute for using a controlled load, carbon pile tester/resistive coil, to load the battery to at least 50% ideally 75% of it's stated capacity (CCA) and remain over 8.6volts for 30 seconds, most batteries that were fully charged but have limited life left/dead cells or other physical issues will fail this within 5 seconds, so is a quick and simple test.

3 Different Standards for CCA testing! All contradict time to test and minimum Voltage to pass!

The Pico Battery test simulates some of this load using the starter motor to apply load (turning over the engine), but not for long enough or at a stable/sustained rate, but has the benefit of testing (using 4 channels) the volt drop on both positive and negative paths, often the cause of mis-diagnosed starter/battery faults. We have long cable paths on many of our cars and see this more often than the starter motor or even alternator failure.

Like all tests, understanding their Pro's and Con's is essential. A Fully charged battery in this case is CRITICAL !!

We have a template we use in the main program, while it does not give us traffic lights (green amber red) to show a customer, it's easier for us to interpret the raw data now we have done over 1000 tests, although the odd car challenges us to say why it has certain attributes at first sight, and we less likely to miss the subtle detail and tell-tells we are able to spot in the raw data. We too can calculate internal resistances, cable resistances etc, it's only Ohms law!

Only have this old sample picture to hand, but hopefully it shows what's possible (and yes there is an issue with 1 channel, so don't take this as being good, just an ideal !!):
Image

Thanks

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Re: Battery test (In automotive diagnostic )

Postby RIMVYDAS » Thu Feb 25, 2016 7:42 am

Hi guys !
It would help a lot to know which 10 th simbol on VIN . But anyway charge battery, and run battery test again . in case its
2005 year or later - possible parasitic current draw . Usually caused by some of controller on CAN comfort bus not going to sleep . VCDS would help a lot .Check for error codes especially something like-Can comfort single wire operation in all controllers .
good luck
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Re: Battery test (In automotive diagnostic )

Postby FioranoCars » Thu Feb 25, 2016 12:41 pm

Hi All
Maybe someone out there can help, even the Pico Team, as the Pico Diagnostic Software for the battery test calculates some of this stuff ...

So the question is, is there a formulae for converting from SAE to EN.

The question relates to the differences in quoted CCA based on the method used, and aside from battery construction issues - both materials and size, which we'll ignore for the moment - The SAE published a table (see below) and a link to a fuller version, but this data seem to be wrong, or at least inconsistent (look at the vale for SAE 400 and then 450 verse the rest). On the fuller version of the file, you'll see that shows IEC and DIN values which are more consistent, giving the impression a straight conversion is possible ...

Image

Larger and broader data - Republished from The USA Society of Automotive Engineers This old document, can't find the original, seems to be everyone's source

The tables in the PDF show that for SAE to IEC a factor 0.65 is pretty consistent and for SAE to DIN 0.55, but the SAE to EN ranges from 0.90 to 0.96

It might not seem important but it's a massive range, and knowing the "right" approximate or exact figure would be very useful. Anyone able to turn a light on this, ideally with a link or reference source, as I'm googled out!

Thanks
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Re: Battery test (In automotive diagnostic )

Postby Steve Smith » Mon Feb 29, 2016 7:56 am

Hello and thank you all for the posts. (Sorry for the late response)

Thank you for the article too Richard as this is something I will keep for reference and the "comments" that follow the article are interesting too.

Having read through, its a wonder how we have ever been able to conclusively diagnose a battery failure!
I too have fallen foul of passing a battery using both the "Drop Test" and the "hand Held" conductance testers only to have the vehicle return with battery failure!

What is clear in this case is that one single battery test does not cover all battery failure conditions and for those "challenging" battery's multiple tests are required, which of course must include the circuit. (A you have demonstrated with your screen shots)

Would it be possible Richard to post your psdata files here as they will provide invaluable test settings for such battery and circuit evaluation?

I will look into the conversion of SAE to EN as soon as I can make contact with the relevant guys on our software team

Take care........Steve
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Re: Battery test (In automotive diagnostic )

Postby FioranoCars » Mon Feb 29, 2016 8:04 am

Thanks, Steve

Yes I'm planning to post the finished psdata file here, but would like to get the best/refined version first, and for that you need to help me, with the bits of data we discussed on PM please! :D :D :!:

I'll try to upload a wide variety of completed tests too, so people can see both good and bad along with those more challenging interpretations, as the test is rarely black and white.

I do think the PicoDiagnostic Battery test can be improved, if only in the presentation and terminology ... but would like to correlate our tests to yours so I can be more precise about the feedback.

Thanks

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Re: Battery test (In automotive diagnostic )

Postby KimAndersen » Tue Mar 01, 2016 8:43 pm

Hi

I found this interesting website from Yuasa which produces batteries to different vehicles and motorcycles.

http://www.yuasa.co.uk/info/technical/understanding-the-specifications/

This website explains some of the standards and specification that are used in determining CCA and there conversion factor.

When I see the above conversion table fram SAE and I compare this information with conversion factor from the Yuasa website are this not the same values I get.

With all these specification and standards - it´s not an easy task to make a battery test seen from the perspective of Picoscope, but as you said Richard there are space to some improvement on this battery test.

Regards
Kim
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Re: Battery test (In automotive diagnostic )

Postby FioranoCars » Tue Mar 01, 2016 8:57 pm

Thanks Kim
Yes, this document is one of the better ones, but is slightly biased to them as a manufacturer, but overall gives as a single document an insight into the technology and issues ... but as you note is contradicting the SAE table (which despite a couple of clear gaff's) is the best and only independent tests I can find.

I would really love to see the original SAE report, if any one can help?

I will post the results of a whole bunch of Battery tests, using standard Pico Verse the Diagnostic test, as we're seeing things we can't correlate, or that are inconsistent ... and we'd love to get things fixed !!

Thanks
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Re: Battery test (In automotive diagnostic )

Postby Steve Smith » Mon Mar 07, 2016 10:01 am

Hello to all and thank you for the continued posts.

I know there will be more to follow as battery testing appears simple on the surface but in fact, the opposite is true.

Even a battery subjected to multiple tests returning a "Pass" may well go on to fail in service (based on the current range of sensibly priced automotive tools)

With regards to SAE and EN conversion used via the Pico Diagnostic battery test, there is no conversion used, the algorithms work from first principles.

Whether a more accurate conversion is out there than the one posted remains to be seen.

I look forward the continued follow up.

Take care......Steve
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