Yet Another Parasitic Draw Case

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ronw38
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Re: Yet Another Parasitic Draw Case

Post by ronw38 »

I feel your pain, some times we get to close to the woods to see the trees, that battery has to die, keen to hear the end result. Face to face word for word a lot of forum queries are easily fixed, we do not have that as a group, the advantage of the forum is to be able to sort the wheat from the chaff as far as your procedures go and comment on your experiences or expertise. I guess what I am saying is fixing problems by correspondence is not easy, but we love it Cheers Ron W

Steve Smith
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Re: Yet Another Parasitic Draw Case

Post by Steve Smith »

Hello and thank you for the post on what is a truly challenging subject.

When you have carried out all the possible testing at your disposal and have not come to a conclusion what more can you do?

I have seen these exact symptoms with 12 V batteries failing without warning or pattern

I have been able to prove categorically that the vehicle is not discharging the battery using the Volt Drop method here here and yet the battery fails almost overnight when placed back into service!

I like both Livius (off car) and Rons (on car) suggestions as these lead us to internal battery failure.

The prolonged logging of battery open circuit voltage (OCV) off car is most certainly a hands-free test and I can’t think of anything better than PicoLog 6 version 6.1.16 which can be downloaded for free here and will connect to your existing PicoScope

I truly admire the efforts you have gone to in order to prove what is and what is not at fault and the purchase of your logging meter is a typical example.

However, with that said, PicoLog can provide you with exactly the same data using your existing PicoScope hardware.

Below is a very brief introduction to PicoLog 6 that will get you going
PicoLog UI
PicoLog UI
For a far better introduction could you take a look here where our Test & Measurement colleagues provide a far superior overview of this awesome software

Below is an example of a PicoLog file capturing a 42 V battery OCV at 1 sample per second over 15 minutes. (obviously you would set your logging for as long as you like)
PicoLog Graph view
PicoLog Graph view
The data above can be exported to Excel to present a graph in the style of your logging meter
Excel Export
Excel Export
I guess the downside to all the above is that logging will consume your Scope/PC and this may not be practical for days/weeks of data capture.

A practical alternative however might be Raspberry Pi (cost effective mini PC) and this article/video is definitely worth digesting https://www.picotech.com/library/data-loggers/raspberry-pi-extends-data-logger-capability

Throw into the mix remote access, (e.g. VNC) you could then be informed when the values you have configured for logging have been compromised or log into your device remotely and view the logging progress live. (The same applies to PicoScope or any other application for that matter)

Returning now to the most recent case I have reviewed, here we have a 3-month-old 12 V conventional battery that fails without warning to the point where the vehicle will not crank accompanied with flickering instrumentation.

One such event occurred when the vehicle was parked to collect children from school (no longer than 10 minutes) where upon return it failed to crank and required “boosting”

The battery was replaced and the faulty unit evaluated for testing.
The Pico Diagnostics battery test returned “Battery is good but needs recharging”
A battery conductance test returned SOC 100 % SOH 44 %
A high capacity discharge test (drop test) returned an instant fail!

Regarding battery testing with any form of battery tester please read the following forum posts here and here

To give the battery the benefit of the doubt, a CTEK recharge was carried out incorporating the RECOND mode whilst monitoring the battery voltage and current using PicoScope
CTEK Charge Program
CTEK Charge Program
Note below how each mode of the charging process was captured and how it resembled the CTEK steps above
Charge Cycle
Charge Cycle
What I found interesting was the charger did not detect sulphation at Step/Mode 1 and so pulsed current was not detected.

Once charging was complete the battery was tested again (off car)
Conductance test returned SOC 100% SOH 0 %
A high capacity discharge test (drop test) returned an instant fail with cell number 1 boiling whilst under test ( no evidence of boiling during the first test)
Drop Test
Drop Test
Such a fault indicates a short within the battery under load but not all batteries are as clean cut as this one and your battery is one such example

To conclude:
For batteries where all tests pass and the vehicle still suffers with inexplicable battery failure (assuming no discharge via the vehicle) then a bench logging test is the way to go to capture minuscule internal discharge (off car)

I hope some of this helps, take care……Steve

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hexibot43
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Re: Yet Another Parasitic Draw Case

Post by hexibot43 »

1st I want to report with confidence that I returned the vehicle to the customer today. The vehicle sat at our shop for the course of a week with a new battery in it. No sign of a loss in battery charge over that time.

I have the old battery still on my bench. Charged last Friday to 12.43 Volts and a state of 80% charge. Tested to be at 680CCA. This morning I tested it again to 12.33 Volts and a state of charge of 70%. So I lost 10% of the charge over 2 days with nothing connected to it. So if I follow that thinking I will be at 50% state of charge in 10 days. It was worse connected to a vehicle, but that doesn't sound good to me at all.

Now I'm thinking to myself - what would be considered a normal drop off in battery voltage in that period of time with nothing even connected to the battery?

I want to thank everyone that has helped me here. I truly appreciate being able to talk with like minded people. I'm the only one at our shop that uses a DVOM. Or has a DSO, etc,.. I'm kinda on my own. At times I feel like throwing it all away, and telling them Good Luck. But I'm to damn stubborn to do that.

I was taught to not disturb things when looking at electric problems. And so I really want to be looking at this battery in the car. Along with that, I really have it in my mind to look at Amps. Yes the Voltage really can tell me a lot. But I want an Amps reading. I can't seem to help myself. I am thinking if I know that I might get a better idea of what is the problem. And is it rhythmic. Does it have duration and period? I guess i could possible see that with voltage, but I'm so use to looking at Parasitic draw in the form of Amps I can't help myself.

I had installed Picolog on my laptop. I was excited to try logging a problem like this. I set it up. And attached one of my Current Clamp probes. The amount of drift I was getting from the Current Clamp was more than the drain I was looking to log. I became frustrated, and scrapped the idea. I find myself rethinking my testing. If I had simply looked at voltage, as the PicoScope is designed to do, My data would not suffer from the Amp Probe being thrust into the equation. I could have valid data that would start me on the path. It would again no be in the form of Amps, but valid. And if I did see a fall of in voltage I could take it farther then. But why complicate it until then?

I will recharge this battery again and do an extended log with the picoscope and picolog. See what I can see.

Thank you all again.

Marcello aka hexibot43

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Re: Yet Another Parasitic Draw Case

Post by Steve Smith »

Hello Marcello, thank you for the reply and keep your head up, it gets very lonely at times but your thirst for knowledge will keep you company forever.

I think you have the proof you need with your free-standing battery losing 10% over 2 days (remember to allow for minor errors)

I understand the need to interpret this discharge in amps as this makes sense. However, using the current clamp for prolonged logging introduces drift; and to allow for current measurement, additional load would be required for the battery. (This would no doubt accelerate the discharge rate)

If we think this through OCV is a perfect indicator of SOC
Internal battery resistance can provide a good indication of battery SOH

How you choose to measure the internal resistance is another discussion altogether and this link is a must read https://batteryuniversity.com/learn/article/how_to_measure_internal_resistance

The method you choose is dependent upon the “duty” expected of the battery and so for automotive applications, the DC load method seems more applicable (The variables however are huge)

I like the idea of comparing apples with apples and if it is possible, could we have your suspect battery measured against a new identical battery and plot the discharge over 1 week?

I know this may not be possible and of course costly/time consuming but it will present a bench mark for future tests

The figures I have from various manufacturers suggest that a conventional lead acid battery for ICE vehicles (with no abnormal parasitic drain) the battery capacity should remain above 30% after 60 days.
Based on these figures fully charged free standing battery (off car) should be longer

30% = 12.0 V to 12.1 V and places the battery in the “Sulphation Danger Zone”
10% = 11.8 V to 11.9 V and this is the zone for “Permanent damage by sulphation”
Interesting fact here, from 100 % SOC (>12.6 V) to 10 % SOC (11.8 V to 11.9 V) is only 0.8 V!

These figures we must take with a pinch of salt as they are presented by battery manufacturers but they are most certainly eye openers

Ironically in the real world, I have found batteries that have been cycled from 100% SOC to low a SOC (due to a parasitic fault) perform exceptional well once the fault has been rectified and battery fully recharged

The following article on parasitic drain here includes a “Battery Reserve Calculator” which serves as an indication of expected SOC for a given parasitic drain. If we note these figures for “on car” tests, it provides an indication of how well a battery should perform “off car” (when fully charged)

See below:

By using the parasitic current values obtained during the sleep mode of the vehicle, you can calculate an indication of the approximate time a customer can expect to leave their vehicle standing before the health of the battery is affected. To do this, use the following formula:
1. Fully charged battery at 21 degrees centigrade
2. Amp hour rating (stated on the battery) /100 x 70 = 70% of Amp hour value
3. Calculated 70% of Amp/hour rating/parasitic value obtained during sleep mode = Hours before battery recharge is required
4. Calculated hours before battery recharge is required /24 = days before battery recharge is required

Example (77 Ah battery):
(77/100) x 70 = 53.9% of stated Ah rating of the vehicle battery
53.9%/0.040 A = 1347.5 hours
1347.5 hours/24 = 56 days before the battery will require recharging

I hope this helps, take care…….Steve

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Re: Yet Another Parasitic Draw Case

Post by Steve Smith »

Following on from the Parasitic Drain calculator above (Hours/Days before recharging is required)

Thanks to Glen and his father at Ashbrook Garage they have created the attached spreadsheet to assist with calculation process.

Enter your battery Ah rating and the measured parasitic value (in amps) and the spreadsheet will calculate the hours/days before recharging is required
Image 1
Image 1
Battery loss.xlsx
Calculator
(11.08 KiB) Downloaded 200 times
I hope this helps, take care.....Steve

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hexibot43
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Re: Yet Another Parasitic Draw Case

Post by hexibot43 »

Having a little trouble getting Picolog up and running on the Raspberry PI. Got it running on my Imac today. Yesterday it would not sample more than 1 sample. That kind of defeated the whole reason for setting this up. I only changed the sample rate from 1 per second to 500ms, and suddenly it started working.
Excerpt from online Manual for Picolog
PicoLog is a data acquisition tool that collects, records, displays and analyzes
measurement data. It has the following capabilities:
Supports any Pico converter up to the PicoScope 3000 Series
I am running a Picoscope 4423. I'm hoping that online manual is wrong about this? It seems to be working on the IMAC. Could this cause issues? I don't want to start a three week capture only to hear my scope won't work correctly. And I don't want to keep going on the RaspberryPi if this a mistake.

I can see many reasons for the logging with picolog. Picoscope 6 and 7 are great. But there are many times when looking at data after the course of days or weeks is what I really need.
Last edited by hexibot43 on Sat Jul 18, 2020 5:19 pm, edited 1 time in total.

Steve Smith
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Re: Yet Another Parasitic Draw Case

Post by Steve Smith »

Hello and thank you for the feedback

Most certainly your 4000 series scope is fine with PicoLog

In the post above (Image PicoLog UI) you can see have used the 4425

My experience with PicoLog Raspberry Pi is limited but following the links provided by our Test and Measurement colleagues has seen my Raspberry Pi logging with Windows seamlessly (Sorry I have not used the device with IMAC)

I really believe in the Raspberry Pi option as it has the huge advantage of not consuming your workshop PC with essential but mundane logging tasks.I am using a Pi at present to log the internal battery voltage of our 3 output NVH interface (TA259) when accessories are connected. It is so convenient to know its logging away indefinitely (hands free) where I can check in at anytime to review. (This logging may take 3 to 4 months to complete)

I hope this helps but if you hit a wall then please feedback when you can and I will liaise with the team here or you can go direct to support@picotech.com

Take care......Steve

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hexibot43
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Re: Yet Another Parasitic Draw Case

Post by hexibot43 »

Thanks Steve.

Just needed to hear it. Down to missing one cable which I bought today. So will be starting up with the RPie tomorrow. It is working well on my IMAC for the moment. But as you say, I don't really want to run it on that. I would like to have it very mobile. My IMAC is not moving anywhere soon.

Thanks again,

MAB

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hexibot43
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Re: Yet Another Parasitic Draw Case

Post by hexibot43 »

Sorry I am still having issues on the raspberry pi install.

I Wanted to say thanks to whoever's updated the website for picolog to include my picoscope 4423. Feels great to be included.

I thought I had picolog installed it on the latest raspian os. I am use to software installing to the current folder. I'm guessing it installs elsewhere. I will start again on Monday. All the hardware ready. Very close.....just watched video for set up again and they stated need at least buster raspian. Not sure if I have that? Hopefully something stupid I missed.

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hexibot43
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Post by hexibot43 »

Covid 19 has not kept me slow at work. So haven't been able to spend as much time as I'd like But Almost!

I found where the software was installed. Not in the directory I was currently in. I had to watch the video a couple more times on doing the install. Installed to Directory : Application or other folder.

And very easily run from the GUI. Unfortunately, I wasn't yet able to get the Pico key installed, that allows the system to work. So far when I run the wget on the command line it just sits and hangs there. Doesn't seem to be able to complete.

Now that I have the software installed. Hopefully in the AM I will be able to get the key thing figured out.

The software install had worked. I just hadn't watched the video quite well enough. Yes, I watched while working on a car. Along with many other interruptions. Probably the same reason I screwed up the key installation.

Charging my problematic battery for tomorrow. Plan on starting another logging of it finally on a Raspberry Pi and Picolog. Fingers crossed.

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