Battery test (In automotive diagnostic )

Can someone clarify for me, what means: Charging at 80% or Charging at 30%.
What the percentage means and what is applied to?

It seems that there is a massive gap in interpretation of battery condition testing!

We cannot test batteries - Period. It has been noted many times in the past that subjecting that accumulator to the right test to award it a bla bla rating would destroy it - Period !!!


Ignition on, 20 minutes, and it still cranks swiftly = ??


Start disabled Crank it for 10 seconds, once, twice, thrice - Make a judgement ?

Battery testers are for the fast fit monkeys in my bubble !

Can it can turn the starter motor fast enough for long enough ?

Many thanks for answering. However, it is not what I am after. I know the battery is fine, starter motor runs fine. I just wanted to know from the designer perspective, what that 80% means. How it is calculated and what is applied to.

what that 80% means. How it is calculated and what is applied to

That is my point - it is a fruitless task - No One Knows other than the Marketing / Pricing Office

I think this is best answered by Steve Smith or someone else at Pico ...

In my historic research, which included lots of guidance from the Pico boys, into the figures and calculations, I did not focus on this particular aspect, but I can say from the data I have that in basic terms it uses some or all of these:
- Initial battery voltage
- voltages during cranking
- amps & voltage post cranking at idle/no load
- amps & Voltage during alternator load element

The simple thing is that more amps being output show the battery is less charged, this combined with assumptions about the battery voltage levels, can be interpreted together (with many assumptions, especially due to smart charging system strategies) that the battery is at a level of charge

So charging at 60% means, as I understand it, that the battery is at 60% of it's potential, and is being charged, so 80% would mean the battery is closer to fully charged ... these indicators can be used to assess if the test was appropriate (too low a charge in the battery means the tests could be meaningless).

But as I said, it's best that someone from Pico offers their version of what they mean as they do not disclose the logic/calculations used to "create" these numbers.

Some of the other numbers have serious flaws, and have had for 4 or more years, so PLEASE Pico boys and girls take a look at them and fix them!

On the subject of battery testing, there are tests using the scope during cranking that will tell you heaps about the car, battery, cables, and engine, so it's not irrelevant, just needs to be in context, which without knowing the logic applied is hard ... so best create your own tests.

I hope that answers to a small degree what the % mean?

Richard

I think this is best answered by Steve Smith or someone else at Pico ...

Without doubt Yes !!! If answerable!

In the interim you may or may not chose to suffer me. On the frontline -Ear firmly to the ground - proven track record ......

My qualm with battery testing/testers is always the same - It is it aimed at battery sales.


My thoughts to your post:

- Initial battery voltage
A Variable - The software does not confirm beyond doubt if the engine was run/ battery charged I minute or 1 hundred years ago - Flawed

- voltages during cranking
Another Variable, Each car, Petrol, Diesel, Low compression .... Infinite Variables -Flawed

- amps & voltage post cranking at idle/no load
Simple or Smart Charge, Alternator Condition & Age, Belt Tension, Starter Wear .... I could go on ! - Again not Definitive

- amps & Voltage during alternator load element.
Simple or Smart Charge, Alternator Condition & Age, Belt Tension .... I could go on ! - Flawed and not definitive - We seem to have a pattern going on here !!!

I still insist that the way forward is to prove or deny that it (the battery) can perform the duties it is employed to accomplish with ease and maintain a reserve.

Crank it fast enough for long enough and have a shed load in reserve and be able to do so for months.

liviu2004 wrote:Many thanks for answering. However, it is not what I am after. I know the battery is fine, starter motor runs fine. I just wanted to know from the designer perspective, what that 80% means. How it is calculated and what is applied to.

liviu2004 wrote:Many thanks for answering. However, it is not what I am after. I know the battery is fine, starter motor runs fine. I just wanted to know from the designer perspective, what that 80% means. How it is calculated and what is applied to.

In layman terms;

Not knowing the type of equipment you are using I'll generalize;

On my equipment I have a "Display Mode", which can be switched between Volts - Battery % - ALT % or Time.

The display mode when set on volts will show the terminal voltage while charging at a set rate, i.e. trickle, fast, rapid.

This voltage reading does not tell you how long the battery will take to charge, i.e. a charging battery reads 11.5 V.

What it does do is provide an indication of the voltage, percentage of charge, or time.

Most batteries are sealed for life and we have no way other than a sight glass to tell us the condition of or charge of the battery, its not very good.

A typical understanding of the charge rate % can show;

Percentage of charge Specific Gravity Percentage of charge reguired

0 % 1.120 100%
25 % 1.155 75 %
75 % 1.225 25 %
100 % 1.265 0 %

So you know the percentage of charge of your battery, i.e. 80%, and I'll assume you know your amp hour rating for the battery you are charging/testing, so you can calculate the approximate time needed to bring your battery, i.e. 80% charged to 100% charged.

Just a note - your battery may not show on the label a amp hour A/H reading but show a reserve capacity number, let's say 60, divide this by 2 and add 16.

Amp hour rating = Reserve capacity + 16
2

To calculate the time needed for charging the battery;

Look at your percentage charge, i.e. 80% in this example;

You need another 20% charge, so 0.20. Now multiply the A/H rating by the charge needed, i.e. 0.20, and divide by the charger setting you desire, i.e. trickle, fast etc. These specifications should be in your manual for the charger, so lets say 4 A

Amp Hour Rating x % of charge required x 1.25 = Hours of charge
Charger setting

80 x 0.20 x 1.25 = 5 hours to charge battery to 100 %
4

Increasing the amps charge rate from 4 A to 15, 20 etc will reduce the time required to charge the battery.

Now while batteries are not the easiest items on a vehicle to test, with 100 % accuracy, and depending upon your investment on equipment, the customer is not going to want to sit in reception for a couple of hours while you carryout long term tests on their battery, so a digital conductance test will show the state of charge, the state of health, so a battery fully charged and more than able to perform a cold cranking test CCA is not a guarantee that because the battery shows 100 % charged, is able to crank the engine, is going to remain reliable for the longer term, hence if you can show the customer a printout saying SOC 100%, but SOH 70%, at least you can provide some evidence that the battery is not perfect and let the customer make an informed decision whether to buy new or not.

But hopefully I have answered your question.

Dear Technician. A great explanation. Thats what I do.

I do believe I observed a post here from some one else. But again it has disappeared in a poof of smoke. He like Hoodeni. Hehehehehe! I thought he mentioned about you doing a CCA test. What flavour DiN. did you use. Got a freezer LOL!!

But I can't see where you mentioned you performed this test. And personally I also concur battery's are not the easiest thing to test. Fuses and light bulbs are easier.

I have a computerized state of the art battery/charging system tester, over £1000 to buy, it can do all sorts like flash reprogramming etc, I'm not saying its perfect, but the standards STC was referring to are built into the tester, I simply read the details off the battery and enter them into the charging station,select the menu, depress go and leave it to charge and test etc. I did not say previous I had completed any CCA tests, I just went the extra mile to explain what the 80% meant for the member asking the question.

I concur. I don't believe anybody, including the self proclaimed, on this forum has completed a true CCA test. It's not practical. You can perform all sorts of tests all day long on an old battery and all it will prove is it was good for the test. That is it period. Your test equipment can only give you guidance and nothing more.

I too have used electronic battery testers as guidance for customers not as a sales pitch. The very fact you gave the guidance gives one credibility. "Hey the battery test shows it is at only at 80% of it's capacity it won't be a problem in the next few months but Blah blah blah". That extra mile is appreciated.

Thank you for the posts and so sorry for the late feedback as trying to catch up with the relevant people is difficult whilst travelling.

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

One thing we all 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. This 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 (Approx. 1 second) with no control over the load from various open circuit voltages (OCV’s) to varying volt drop levels.

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

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 measurements taking into consideration battery recovery rate post cranking.

The battery test results then display the instantaneous 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.

Moving onto some additional questions.

What is the meaning of the Charging Circuit Status, E.g. Charging at 110 % ?

Charging at 110% is based upon battery voltage deviation from a known constant.
The “constant” used is the nominal voltage of a 100% charged Lead Acid battery being 14.4 V with an OCV of 12.6 V

The nominal voltage of a 100% charged Lead Acid battery is then compared to the charging voltage recorded during the charging of the battery.


E.g. Battery charging at 14.6 V

Nominal voltage (100% SOC) = 12.6 V
Nominal total deviation = 100% charged (14.4 V) – 100% SOC (12.6 V) = 1.8 V deviation

Battery voltage deviation for (battery charging at 14.6 V) 14.6 V - 12.6 V = 2.0 V
Nominal battery voltage deviation (ratio) 2.0 V / 1.8 V = 1.11
Charging status % is therefore Nominal voltage deviation (ratio) x 100 = 111%"

CCA calculation does not appear to change when selecting SAE, EN or DIN, Why?

Having spoken to the software engineers, this is possible post capture but perhaps not very intuitive.

With your test results on screen, (saved using the SAE standard for example) Select EN and then click analyse. The Instantaneous estimated CCA results will then change to suit the relevant standard selected. The same can be said for changing from Lead Acid to AGM batteries. Altering the temperature value post capture will change the results in real-time without having to select analyse

Do we consider stating CCA% with Capacity misleading and not possible based on our test procedure?

The results obtained are an instantaneous estimate of the relevant industry standard selected by the user, and like any battery tester, will provide and “estimate” only. The results obtained are most certainly accurate based on the formula mentioned above.

Different battery failure types will impact the results differently so resulting in some faulty batteries passing the relatively short PD test?

I cannot disagree with this statement but the same can be said for the “Impedance” type measurement/testers too. There is no fool proof method for testing 100% of all battery faults 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.

Testing on anything less than a fully charged battery produces non-linear loading and so inconsistent battery test results?

Once again you cannot disagree with this statement/question. For the PD battery test to function, the vehicle must a least crank / start and therefore the battery is required to be in a reasonable state of charge. The industry standard tests require conditioning of the battery to impossible levels that no battery test can claim to simulate. (There are pro and cons of all tests)

Often one of the test results from a variety of battery testers will be “Battery requires recharge” in which case inconclusive results may have been obtained. (Alarm bells have to be ringing with such test results if OCV value is normal)

With regards to non-linear loading, the algorithm Pico use to calculate the final result factors 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.

The details of the Pico algorithm are proprietary and the results obtained are based on the variables above as accurately as possible, but I do concede the results are not without question.

I hope this information is of some help and brings about some clarity to the results

The image below will help summarize the results:



Take care………..Steve