Author Topic: Brymen Crest and Min/Max Function VDC Capability  (Read 8349 times)

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Offline Fungus

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #25 on: September 19, 2022, 12:27:16 pm »
I agree with you that this accuracy level would be practically useless for my measurement

Would make it useless for any measurement.

so I really hope someone can show how I am misunderstanding this.

You're assuming the 100 counts is applied to the numbers shown on screen in crest mode, not to the "specified accuracy" of the meter.

I think a more accurate test would be to simulate a short duration voltage spike on a constant voltage source at varying time intervals.

That's exactly what's shown in the video you posted.

 

Offline joeqsmith

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #26 on: September 19, 2022, 12:43:43 pm »
For any questions regarding the specifications, you could always contact Brymen. 

It seems there is something in the manual for the BM869s where you can place the meter into the 500k mode prior to selecting crest.  This will enable an extra digit but it seems it requires the signal to be stable for a longer period.   I have not checked to see if Brymen has a newer version of the manual and it seems mine was pretty sparse on details.   

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #27 on: September 19, 2022, 12:57:14 pm »
I agree with you that this accuracy level would be practically useless for my measurement

Would make it useless for any measurement.

so I really hope someone can show how I am misunderstanding this.

You're assuming the 100 counts is applied to the numbers shown on screen in crest mode, not to the "specified accuracy" of the meter.

I think a more accurate test would be to simulate a short duration voltage spike on a constant voltage source at varying time intervals.

That's exactly what's shown in the video you posted.

It would make it useless for any measurement above 6 V (Assuming 6000 count mode). Measurements under 6 V would have an accuracy of +/- .105 V like I showed.

The specified accuracy is the normal accuracy for the range you are measuring in. For the BM-839 its (.045%+1D) in the 60.00 V range, resulting in +/- .014V when reading 09.00V.

The 100 counts are applied in addition to the specified accuracy in the range that the meter is measuring in. They would apply to 09.00 V in the 60.00 V range in 6000 count mode resulting in +/-1.00 V.

Total accuracy for 09.00 V in 60.00 V range in 6000 count crest mode is specified accuracy + accuracy due to additional counts = +/- 1.014 volts.

The video I posted shows a test of the crest function with a BM869s using voltage under 5 volts, so we would expect the accuracy to be approximately +/- .1 due to the .001 resolution in 5000 count mode. I have yet to see someone do the same test with a voltage that requires this meter to be in the higher 50.00 volt range with .01 resolution.
« Last Edit: September 19, 2022, 01:50:40 pm by splat2030 »
 

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #28 on: September 19, 2022, 01:29:25 pm »
For any questions regarding the specifications, you could always contact Brymen. 

It seems there is something in the manual for the BM869s where you can place the meter into the 500k mode prior to selecting crest.  This will enable an extra digit but it seems it requires the signal to be stable for a longer period.   I have not checked to see if Brymen has a newer version of the manual and it seems mine was pretty sparse on details.

The manual for the BM869s states that it has a 5000 count resolution in crest mode.
 

Offline armandine2

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #29 on: September 19, 2022, 03:54:27 pm »
Going back to the vehicle battery test - just checked my copy of Dan Sullivan's Fundamental Electrical Troubleshooting pp.168-169

[He has >9.5Volts as a good battery] hedoes not  include anything regarding sample rate and min/max but advises making up some long leads and watching the meter in your lap as you crank test. Which kind of says to me this procedure works with a technician grade DMMs and without min/max.

I'd watch testing of min/max on DMMs measuring short duration signals

my own quick test indicates I'd should probably use my Gossen Metrawatt Metrahit AM Xtra for the measurement (not my Fluke 28II or 287).
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Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #30 on: September 19, 2022, 04:04:17 pm »
I have been looking to purchase a multimeter for automotive/general usage, but I would like something with a very good min/max function that is capable of measuring the instantaneous max. voltage drop at my 12VDC car battery when under the load of cranking the starter. The overall application of the meter is personal use, so unfortunately the higher end meters like the Fluke in the video below are out of the budget. The Brymen BM-829s has caught my interest because the manual states that their crest function is capable of a 1ms (1000X/s) sampling rate, and the normal min/max function is capable of a 50ms (20X/s) sampling rate. This meter has signifiantly better specs than other similar meters I have looked at such as the UNI-T UT161D, which has a min/max function with a sampling rate of only 333-500ms (2-3X/s). Does the Brymen 1ms crest function work with DC voltage, and would it be fast enough to capture the max. voltage drop in this application? Does anyone have any real world experience using either the Bryman crest or min/max in this application that can provide any further input as to its suitability?

I don't think you need a very fast MIN/MAX function to do this test and it actually might be confusing or yield wrong results if it were too fast.  The 13.5ms figure mentioned is from a specification regarding the ability of automotive electronics  to operate properly in a worst-case momentary voltage drop during starting and isn't intended as a battery test--and if it is used as a battery test, you need different numbers than given in your video. 

Your youtuber is giving you a rough rule-of-thumb method that may work on many modern cars with PM starters and modern electronic engine controls.  I don't know where the 9.6 volts comes from, but from experience I can tell you that very early electronic fuel injection cars would sometimes have long crank times because the controllers went offline at ~9.6V and would only come back to life when the engine was spinning fast enough so that the starter load was reduced enough that the battery voltage would come back up.  So a 'crank, no-start' complaint would be caused by a weak battery, something unthinkable on older models.

The Fluke 98 Scopemeter had a built in battery test function that would graph out the battery voltage during the startup cycle.  I just went out and tried my car, a 2010 Honda Accord I-4 that has been sitting for about a week.  The car starts promptly and the battery is known to be good.  The initial OCV was 12.41V, which dropped to 11.9 when the ignition was turned on.  Ambient temp is 64F after an overnight low of ~56F.  I'm sorry the picture isn't better, but the backlight is weak on the 30-year old Scopemeter and although I have the FlukeView software and cable, it hasn't worked since Windows 95.  As you can see, the voltage briefly drops way below 9.6V, but then pops back up to 10V+ right away. 

A Fluke 27 using MIN/MAX gives a MIN of 10.19 volts and a MAX of 14.05 which indicates a good battery and a good charging system according to the test mentioned--both of which are correct results.  That might be a good meter to start with for your usage, or if you are really interested in automotive, start scouring eBay looking for a Fluke 98. 



« Last Edit: September 19, 2022, 04:07:20 pm by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline joeqsmith

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #31 on: September 19, 2022, 04:24:16 pm »
For any questions regarding the specifications, you could always contact Brymen. 

It seems there is something in the manual for the BM869s where you can place the meter into the 500k mode prior to selecting crest.  This will enable an extra digit but it seems it requires the signal to be stable for a longer period.   I have not checked to see if Brymen has a newer version of the manual and it seems mine was pretty sparse on details.

The manual for the BM869s states that it has a 5000 count resolution in crest mode.

Could have been Rec mode or that I am confusing it with a different meter.   Easy enough to download the manual and look.   Sure enough, min/max mentions it.
« Last Edit: September 19, 2022, 04:36:53 pm by joeqsmith »
 

Offline armandine2

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #32 on: September 19, 2022, 04:28:03 pm »
Fluke 98 was re-badged as the Bosch PMS 100

Looking through my copy of Bosch's Engine Test: Fault detection with the oscilloscope they don't mention the crank test - which might indicate that there is some difficulty in the interpretation of trace?
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Offline Fungus

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #33 on: September 19, 2022, 04:33:21 pm »
It would make it useless for any measurement above 6 V (Assuming 6000 count mode).

Which is why I don't think they'd ever make a single meter that works that way, never mind a while range of them.

It would be like making a car whose wheels turn square if you go past 50mph.

Measurements under 6 V would have an accuracy of +/- .105 V like I showed.

Or ... they might have an accuracy of +/- 0.01V, as shown in joe's video.



I just tried it with some 1ms, 2ms, 3ms... pulses and my meter seems to be about 0.1V high on the 50V range, ie. Specified DCV accuracy+100 counts.

I can do more tests but practical testing only tells me about my meter. My meter might be the golden meter in a million that just happens to work well.

The only way to be 100% sure is to write to Brymen and ask them to clarify the statement in the manual.

(Which they probably will - they respond to email).

Please let us know what they say.
« Last Edit: September 19, 2022, 04:45:03 pm by Fungus »
 

Offline joeqsmith

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #34 on: September 19, 2022, 04:36:28 pm »
If my cars go "click",  I know the battery is dead.   No need for anything too fancy.  If it dies often, I would be looking for the current draw.  I seem to get about six years out of them. 

bdunham7's scope shot is nice.  With a better scope, you should be able to see the compression stroke of each cylinder.   We would expect them to be balanced.    Maybe some monkey math applied to determine a weak cylinder.   Certainly we could see if one was totally gone with a hole in it.   :-DD

Offline Fungus

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #35 on: September 19, 2022, 05:01:33 pm »
If my cars go "click",  I know the battery is dead.   No need for anything too fancy.  If it dies often, I would be looking for the current draw.  I seem to get about six years out of them. 

Yep, it's a car FFS.

You don't need to know the exact dip to two decimal places, you just need to know if it dips badly during starting.

7V or 6V? It doesn't matter. You just need to know if it happens or not.

Plus: No matter how accurate a meter's min/max function is it's not going to tell you how long the voltage dipped for or the shape of the dip. That's far more important than knowing the dip voltage to several decimal places.

What's needed is a graph of voltage over time. Only an oscilloscope can do that.

Get the right tool for the job.

bdunham7's scope shot is nice.

Yep. Way more useful than a single number on a multimeter.

« Last Edit: September 19, 2022, 05:07:03 pm by Fungus »
 

Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #36 on: September 19, 2022, 05:19:04 pm »
If my cars go "click",  I know the battery is dead.   No need for anything too fancy.  If it dies often, I would be looking for the current draw.  I seem to get about six years out of them. 

And when that happens in an airport parking lot after 14 hours of security, customs, gate changes and mediocre premium seating in an airplane not of your choice, you may wish you'd been more proactive.

Quote
bdunham7's scope shot is nice.  With a better scope, you should be able to see the compression stroke of each cylinder.   We would expect them to be balanced.    Maybe some monkey math applied to determine a weak cylinder.   Certainly we could see if one was totally gone with a hole in it.   :-DD

Better scope?  It's ancient but in some ways still unmatched, IMO.  The Fluke 98 has that compression function as well, implemented in voltage or current configuration with a nice trace or 'relative compression' bars displayed.  Voltage mode seems to not work very well with modern cars and I don't currently have an appropriate amp clamp.  It's good enough to spot single burned exhaust valves on V8 engines that don't have very obvious running problems.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #37 on: September 19, 2022, 05:34:32 pm »
Fluke 98 was re-badged as the Bosch PMS 100

Looking through my copy of Bosch's Engine Test: Fault detection with the oscilloscope they don't mention the crank test - which might indicate that there is some difficulty in the interpretation of trace?

I've used the feature many, many times and if it gets a good signal  it gives you your choice trace or bars and both are typically quite easy to interpret.  Obviously since you aren't directly measuring compression, there can be things which will interfere with the process.  b/t/w I don't know if the Bosch PMS100 used the same firmware as the Fluke 98, I think the Bosch was an OEM-specified tool for some makes/models and it may have had different specs as a result.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline armandine2

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #38 on: September 19, 2022, 07:14:10 pm »
"easy to interpret" because the car starts or doesn't?"
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Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #39 on: September 19, 2022, 08:02:00 pm »
"easy to interpret" because the car starts or doesn't?"

No, easy to interpret as in "oh look, cylinder number 3 is down 40%, that explains the rough idle".  Provided, of course, that you can do a synced test, otherwise it is "oh look, one of the cylinders is down 40%, I wonder which one?"
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline joeqsmith

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #40 on: September 20, 2022, 12:33:43 am »

If my cars go "click",  I know the battery is dead.   No need for anything too fancy.  If it dies often, I would be looking for the current draw.  I seem to get about six years out of them. 
And when that happens in an airport parking lot after 14 hours of security, customs, gate changes and mediocre premium seating in an airplane not of your choice, you may wish you'd been more proactive.

What ever the circumstances are involving a dead battery, that would be my problem not yours but I appreciate the concern.   I can tell you that I have never had a battery fail that was life changing... :-DD

bdunham7's scope shot is nice.  With a better scope, you should be able to see the compression stroke of each cylinder.   We would expect them to be balanced.    Maybe some monkey math applied to determine a weak cylinder.   Certainly we could see if one was totally gone with a hole in it.   :-DD

Better scope?  It's ancient but in some ways still unmatched, IMO.  The Fluke 98 has that compression function as well, implemented in voltage or current configuration with a nice trace or 'relative compression' bars displayed.  Voltage mode seems to not work very well with modern cars and I don't currently have an appropriate amp clamp.  It's good enough to spot single burned exhaust valves on V8 engines that don't have very obvious running problems.

Referring to the very low res. 

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #41 on: September 20, 2022, 03:05:22 am »
The reason I like the multimeter cold cranking test is because it is not simply a battery load test, but rather a quick and easy whole starting system health check.  Failing this test does not necessarily mean you have a bad battery, it could also indicate that the starter motor is beginning to fail. You would need to separately load test the battery to 1/2 CCA rating to determine if the problem is with the battery, because a starter motor won't typically put a large enough load on the battery to fully test it. The whole point of doing any of this testing is to identify a failing starter or battery so you can replace them before they are completely nonfunctional and result in a breakdown.

I like the suggestion of the Fluke 98 scope or the Fluke 27, but those meters are out of my budget. My vehicles service manual gives a minimum spec of 9.6 volts for a cold cranking test, so I would suggest that a true minimum reading of 7.12 volts is likely indicative of a developing problem with the starting system that has not yet manifested in any drivability issues. The regular min/max function on the Fluke meters needs a duration of 200ms to capture a voltage, so not using the peak function could allow you to show a passing result when in fact you failed the test. If the cold cranking test fails when monitoring voltage but the battery load tests properly, I would recommend retesting with an amp clamp to verify that the max current draw for the starter is in spec.

After all of this research into the Brymen meters I am leaning toward the BM789, but I still would like to confirm the accuracy of min/max and crest. I will try to contact Brymen to see if they can clarify the statement in the manual and give an update.
« Last Edit: September 20, 2022, 04:08:29 am by splat2030 »
 

Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #42 on: September 20, 2022, 04:09:44 am »
I like the suggestion of the Fluke 98 scope or the Fluke 27, but those meters are way out of my budget. My vehicles service manual gives a minimum spec of 9.6 volts for a cold cranking test, so I would suggest that a true minimum reading of 7.12 volts is likely indicative of a developing problem with the starting system (assuming it still cranks the engine over and functions at a basic level). The regular min/max function on the Fluke meters needs a duration of 200ms to capture a voltage, so not using the peak function could allow you to show a passing result when in fact you failed the test. If the battery loaded tested properly, I would recommend retesting with a clamp meter to verify that the max current draw for the starter is in spec.

Fluke 27 can be had reasonably on ebay.  There was a seller a while back with brand new units with case and HV probes for $140.  I realize it is a bit primitive in some ways, but it has its good points like being very durable.

https://www.ebay.com/itm/155101904381

One of the reasons I put the scope shot up is to show that the 9.6 volt specification doesn't include that initial short current surge and resulting large voltage drop.  My battery and starting system are in good condition, that's just what things look like on a scope vs the MIN/MAX feature of a DMM.  The car sits a lot and the battery was a bit discharged, so a I took the opportunity to charge it, top off the water and retest it.  Not much difference and still below 9.6 volts.  That initial surge just what you get when you apply power to a DC motor at standstill when there's no back-EMF yet.


« Last Edit: September 20, 2022, 04:21:52 am by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #43 on: September 20, 2022, 04:30:13 am »
I was looking at the Fluke 27 II which is about $500 new, and the Fluke 98 scope which is about $1000 used. I hadn't really considered used just due to the potential of getting something that was knocked out of tolerance from to the way it was treated by the last owner. That Fluke 27 used for $70 doesn't look too bad, but something like the BM789 new for $175 seems like it would be much more useful due to the additional features. I am hoping I can just buy one multimeter that will meet all of my current and future needs, but I have also been debating back and forth whether I would be better served with both a cheap multimeter and a cheap scope like the Pico 2204a or the Hantek 6074BE rather than just a decent multimeter.

From what I recall my factory service manual recommends using a specific diagnostic tester that has a built in amp clamp for doing the cold cranking test, but also gives that minimum 9.6 volt spec. I'd be interested to see if the results you are showing to 8 volts for that instantaneous drop are typical across multiple different vehicles at different ages, or if your vehicle is an outlier.
« Last Edit: September 20, 2022, 06:25:20 am by splat2030 »
 

Offline bdunham7

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #44 on: September 20, 2022, 04:56:12 am »
I'd be interested to see if the results you are showing to 8 volts for that instantaneous drop are typical across multiple different vehicles at different ages, or if your vehicle is an outlier.

I've tested many vehicles, and while they all have their unique characteristics, mine is not an outlier by any means.  It actually is pretty undemanding of the battery--PM gear reduction starter motor, fairly puny battery cables.   Probably less than 150A cranking current (not the initial surge) cold, less warm.

Edit:  here is an entirely different car, also in known good condition and it only sat overnight
« Last Edit: September 20, 2022, 05:00:04 pm by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #45 on: September 21, 2022, 11:29:39 am »
As an update from my previous post, I have attached the email response I got today from Brymen technical support regarding the accuracy of the crest and min/max modes for the BM789 meter. Unfortunately, they confirmed my calculations that the meter accuracy decreases significantly as you range up in crest mode. I asked them to provide me a calculated accuracy for a crest measurement in each of the 3 lower ranges of 3 volts, 12 volts, and 80 volts. The results are as follows:

The accuracy of a 3 volt measurement is +/- .101 volt, the accuracy of a 12 volt measurement is +/- 1 volt, and the accuracy of an 80 volt measurement is +/- 10 volts. Looks like the crest function is pretty much useless for readings over 6 volts.

They also confirmed that regular min/max/avg mode cannot pick up a signal with a duration less than 300ms regardless of the fact that the meter samples every 100ms in this mode.
« Last Edit: September 21, 2022, 01:27:28 pm by splat2030 »
 
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Offline joeqsmith

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #46 on: September 21, 2022, 11:43:45 am »
Happy to see you going to the source.   Brymen has proven to be very helpful when it comes to having an open dialog. 

Offline splat2030Topic starter

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #47 on: September 21, 2022, 12:03:19 pm »
Kind of a bummer though...I was secretly hoping Mr. Fungus was right on this one!
« Last Edit: September 21, 2022, 12:13:54 pm by splat2030 »
 

Offline Fungus

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #48 on: September 21, 2022, 12:12:54 pm »
Kind of a bummer though...I was secretly hoping Mr. Fungus was right on this one!

Yeah.  :-\

 

Offline NoMoreMagicSmoke

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Re: Brymen Crest and Min/Max Function VDC Capability
« Reply #49 on: September 24, 2022, 04:48:14 am »
I have to ask the dumb question. Why not just buy the correct tool for a battery load test... AKA a carbon pile??? They can be had for cheap from HarborFreight/NorthernTool/Amazon, and will be much more accurate of a battery health test than trying to measure the voltage while cranking the starter.


Something like this... https://www.amazon.com/WINMAX-TOOLS-AUTOMOTIVE-Alternator-Regulator/dp/B082PNSRXN/ref=sr_1_2?crid=YUD2LHFE8TGY&keywords=carbon+pile&qid=1663994835&qu=eyJxc2MiOiIzLjExIiwicXNhIjoiMi41NiIsInFzcCI6IjEuNzkifQ%3D%3D&sprefix=carbon+pile%2Caps%2C89&sr=8-2&ufe=app_do%3Aamzn1.fos.08f69ac3-fd3d-4b88-bca2-8997e41410bb

 


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