I decided after recently having to diagnose a few battery drains I need an amp clamp that can measure low mA readings. With battery cable sizes getting bigger with modern EVs can anyone give me some advice on the T234 and T189? Im not looking to spend the most money possible but want something that will do an accurate job and that wont be needed to be upgraded in 12-24 months. Any help is most appreciated.

I'm sure one of the Nerdz team will chime in. But the best option, in my opinion, is the 189. The 30 amp one. I use it often. For parasitic draw testing.

The first time I was nervous it wasn't accurate, so I tested it by using my old regular set up of breaking the battery connection and putting my DVOM in between to get the draw reading. I then compared it to the 30 amp clamp, set to 1 amp scale. I also created a draw by flipping open the visor vanity light and other small lights to see if it was reading properly. It does.  :)

I forgot to add the larger jaws make it a natural choice for this type of testing.  ;)

Although no current probe is really well suited for parasitic draw testing the TA189 is the best we have seen.  During our tests we found this probe to be accurate to within 10ma so the 5ma spec is a bit hopeful.  Really nice probe though.

http://www.autonerdz.com/ampprobes.html

Don't forget to press the zero button when you turn it on to prevent auto shut down

Logic, good point and press the zero button when not connected to a wire.

Ray 

Thanks for the great replies Nerdz!

So battery is most likely a 9v, is this capable of doing a drain test over night? (15hours).

I was aware the clamps were less accurate than a multimeter but don't like that they have no record function. Everyone that works in a shop knows that the bosses just want quick answers, at least with a recorded pattern you can 'prove' a vehicle is or isn't doing what it's supposed to!

I would not work with a 9v battery. Charge the battery to 12.8v then load test the battery by load testing it.
Minimum battery cranking voltage is 9.8v.

You should at least make sure the battery is good and the battery terminals are tight and clean before checking for battery drains.

I would ck the alternator voltage and amperage output.

I always do a battery negative terminal to the engine block ground voltage drop test

To test for battery drains, I usually leave the hood open, close the hood switch, remove the ignition key and lock the doors.
Move the key some distance away from the vehicle and let the vehicle sit for an hour before checking for the drain. Max battery drain is usually 50 ma

99.9% of the time, you do not have to record the battery drain overnight.

Ray
 

MTech wrote on Jan 20^th, 2017 at 6:11pm:

Thanks for the great replies Nerdz! So battery is most likely a 9v, is this capable of doing a drain test over night? (15hours). I was aware the clamps were less accurate than a multimeter but don't like that they have no record function. Everyone that works in a shop knows that the bosses just want quick answers, at least with a recorded pattern you can 'prove' a vehicle is or isn't doing what it's supposed to!

Current shunt is the most accurate method for measuring current.

If I suspected an intermittent battery drain, I left the hood open in the parking lot all day.

Then every hour or 2, I clamped my amp probe around a battery cable to measure the amp draw.

If you get Tom's TA189, I would connect one lead of a good multi meter in the 400 ma mode to a battery terminal.

Then connect the other lead of the multi meter in series with a test light connected to the other battery terminal.

Let's say the inline ammeter reads 150 ma. Connect the TA189 amp probe any where in that series circuit and the Pico scope should show near 150 ma.

Ray 

MTech wrote on Jan 20^th, 2017 at 6:11pm:

So battery is most likely a 9v, is this capable of doing a drain test over night? (15hours).

;)


rayray wrote on Jan 20^th, 2017 at 7:37pm:

I would not work with a 9v battery.

Ray I took the MTech quote above as discussing the battery that is running the Amp clamp.

To answer his question as I took it, I would say if you are intending to capture this overnight drain watch then you should install a brand new battery which should last this amount of time.

Drift would have to be taken into consideration but large spikes that last periods of time is of course not drift.
Better said anything that rises over time and then falls square is a drain.

Logic wrote on Jan 21^st, 2017 at 5:23am:

Current shunt is the most accurate method for measuring current.

You know when you go to a class and one person asks for a verification on a quote made by the instructor and half the class around him think to themselves they are so glad you asked, well maybe this is one of those times.

Could you go into detail on this above procedure, maybe with examples of scope findings and pictures of equiptment used?

Please and thank you  8-)

This is an example of using the scope to load test the battery cranking and what a battery negative terminal to the engine block voltage drop looks like while cranking.

CH A is the battery voltage and the spec for minimum battery cranking voltage is 9.8v

CH B shows the over 500 amp starter motor amp draw when the flywheel is not turning, to the average 236 amps when the flywheel is turning.

When the engine starts, you can measure the max amperage output of the alternator on most vehicles.

CH C is the cranking negative battery cable terminal to the engine engine block ground voltage drop of 284 mv.

For the ground voltage drop, the scope lead should be connected to the starter case because there may be a layer of corrosion between the starter nose to the transmission.

Ray

---

This one shows a good no load battery voltage of 12.8v on CH A, down to a bad, very low 4.8v cranking.

CH B shows a ground voltage drop of 200 mv

CH C shows the cranking amps and the maximum alternator output amperage of 93 amps on start

Ray

---

rayray wrote on Jan 20^th, 2017 at 7:37pm:

I would not work with a 9v battery. Charge the battery to 12.8v then load test the battery by load testing it. Minimum battery cranking voltage is 9.8v. You should at least make sure the battery is good and the battery terminals are tight and clean before checking for battery drains. I would ck the alternator voltage and amperage output. I always do a battery negative terminal to the engine block ground voltage drop test To test for battery drains, I usually leave the hood open, close the hood switch, remove the ignition key and lock the doors. Move the key some distance away from the vehicle and let the vehicle sit for an hour before checking for the drain. Max battery drain is usually 50 ma 99.9% of the time, you do not have to record the battery drain overnight. Ray

Cheers ray for this info always good to be reminded of the basics.


Yeah I meant the amp clamp sorry for not being more specific. Im new to the scope world but learning more everyday so eventually I may actually be able to say I know what I'm doing!  :)


Mick wrote on Jan 21^st, 2017 at 6:47am:

Logic wrote on Jan 21st, 2017 at 5:23am: Current shunt is the most accurate method for measuring current. You know when you go to a class and one person asks for a verification on a quote made by the instructor and half the class around him think to themselves they are so glad you asked, well maybe this is one of those times. Could you go into detail on this above procedure, maybe with examples of scope findings and pictures of equiptment used? Please and thank you  8-)

+1 on this, Logic it would be most appreciated !

Mick wrote on Jan 21^st, 2017 at 6:36am:

Drift would have to be taken into consideration but large spikes that last periods of time is of course not drift. Better said anything that rises over time and then falls square is a drain.

Again, i have always had very good success with diagnosing intermittent battery drains with periodically going out to the vehicle to ck the battery drain during the day without leaving the equipment on the vehicle for any period of time because of the amp clamp reading drift.

Most of the time, the assumption of an intermittent battery drain causing an intermittent no start usually turned out to be a loose or dirty battery connection, especially the GM side battery terminals that look excellent on the outside but corroded on the inside.

Also defective batteries with a bad cell that would drain the battery voltage or a bad starter connection or bad solenoid terminal corroded or burnt connection or a corroded engine block or transmission ground connection, etc

Ray

Mick wrote on Jan 21^st, 2017 at 6:36am:

MTech wrote on Jan 20th, 2017 at 6:11pm: So battery is most likely a 9v, is this capable of doing a drain test over night? (15hours). ;) rayray wrote on Jan 20th, 2017 at 7:37pm: I would not work with a 9v battery. Ray I took the MTech quote above as discussing the battery that is running the Amp clamp. To answer his question as I took it, I would say if you are intending to capture this overnight drain watch then you should install a brand new battery which should last this amount of time. Drift would have to be taken into consideration but large spikes that last periods of time is of course not drift. Better said anything that rises over time and then falls square is a drain.

Correct Mick that is what he meant......

A 9V battery will last at least 24 hours

One of my staff members is driving a E90 BMW this week end where I suspect the current drain is in the alternator after the car is driven.

We have an EasyLogUSB on it.

https://www.dataq.com/products/lascar/el-usb/

Attached is a file for this car earlier in the week.

Software to view my file can be downloaded at: https://s3.amazonaws.com/lascar_downloads/EasyLogUSB.zip

sorry file type violation

Logic wrote on Jan 22^nd, 2017 at 1:37am:

One of my staff members is driving a E90 BMW this week end where I suspect the current drain is in the alternator after the car is driven.

Hi Logic, so after driving the car for awhile, I take it that when you ck for amperage on the alternator cable with the ignition key off, you get 0 amps?

Ray

Logic wrote on Jan 22^nd, 2017 at 1:37am:

Attached is a file for this car earlier in the week.

Can you put the files alone on the drop site?

These screen shots can be useful at time if all else fails

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Logic wrote on Jan 22^nd, 2017 at 1:37am:

Attached is a file for this car earlier in the week.

Do these look like the files you gave us?

---

Mick wrote on Jan 22^nd, 2017 at 10:06am:

Logic wrote on Jan 22nd, 2017 at 1:37am: Attached is a file for this car earlier in the week. Do these look like the files you gave us?

Yes Mick exactly

Logic wrote on Jan 22^nd, 2017 at 4:38pm:

Mick wrote on Jan 22nd, 2017 at 10:06am: Logic wrote on Jan 22nd, 2017 at 1:37am: Attached is a file for this car earlier in the week. Do these look like the files you gave us? Yes Mick exactly

What is the size of the file you posted for the data and which one on the list would it be?

Mick wrote on Jan 22^nd, 2017 at 5:16pm:

Logic wrote on Jan 22nd, 2017 at 4:38pm: Mick wrote on Jan 22nd, 2017 at 10:06am: Logic wrote on Jan 22nd, 2017 at 1:37am: Attached is a file for this car earlier in the week. Do these look like the files you gave us? Yes Mick exactly What is the size of the file you posted for the data and which one on the list would it be?

TXT and 736kb

.txt attachments now enabled.    ;)

Logic wrote on Jan 23^rd, 2017 at 3:54am:

TXT and 736kb

Logic
None of them files are any where near that size.

Now that Tom has aloud TXT files could you place it here for me.

 

Mick wrote on Jan 23^rd, 2017 at 10:13am:

Logic wrote on Jan 23rd, 2017 at 3:54am: TXT and 736kb Logic None of them files are any where near that size. Now that Tom has aloud TXT files could you place it here for me.

No problemo  attached

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Mick wrote on Jan 21^st, 2017 at 6:47am:

Logic wrote on Jan 21st, 2017 at 5:23am: Current shunt is the most accurate method for measuring current. You know when you go to a class and one person asks for a verification on a quote made by the instructor and half the class around him think to themselves they are so glad you asked, well maybe this is one of those times. Could you go into detail on this above procedure, maybe with examples of scope findings and pictures of equiptment used? Please and thank you  8-)

Try this first

http://www.ni.com/tutorial/7114/en/

You will see that a current shunt is a very accurately known resistor.

if you measure the voltage drop across this resistor then you can use Ohms law to calculate the current.

A multimeter uses a current shunt.

Every time I reach for fluke to use the current shunt in it the fuse is blown, probably from someone in the workshop using my multimeter for a voltage measurement with the leads in the current measurement jacks....blowing the expensive fuse that requires unscrewing the back of the multimeter to replace..

i'm done with it and use stand alone current shunts along with the Pico current clamps..

there are no batteries, oreintation or drif issues with a current shunt

Logic wrote on Jan 23^rd, 2017 at 3:54am:

Mick wrote on Jan 22nd, 2017 at 5:16pm: Logic wrote on Jan 22nd, 2017 at 4:38pm: Mick wrote on Jan 22nd, 2017 at 10:06am: Logic wrote on Jan 22nd, 2017 at 1:37am: Attached is a file for this car earlier in the week. Do these look like the files you gave us? Yes Mick exactly What is the size of the file you posted for the data and which one on the list would it be? TXT and 736kb

OK I opened the file you put up You didnt yet explain what was going on in there but if I was to say the time is over a couple of days and after the first night it was restarted but prior to that the battery voltage got below 12V sitting.

It started and charged then sat overnight again and I see a couple of spikes in the battery voltage.

Where is the device collecting the data from? battery DLC???

Here are a couple of screen shots.

Would you be kind enough to explain what we are seeing here please

---

Mick,

What I have given you is simply a plot of voltage verses time.

We are connected to the positive and negative sides of the battery.

The car has been driven and to the left of Sunday 0:00 when the engine is turned off the gradient of the battery voltage reduction is significant.

The battery then went flat

After the car was restarted and the battery charged the sleep current consumption was normal as seen by the lack of gradient.

What did you theorise from the capture?

Logic wrote on Jan 26^th, 2017 at 11:40am:

Every time I reach for fluke to use the current shunt in it the fuse is blown, probably from someone in the workshop using my multimeter for a voltage measurement with the leads in the current measurement jacks....blowing the expensive fuse that requires unscrewing the back of the multimeter to replace..

Sharing is caring >:(

My fluke got used last week and came back with 4 leads tied to it in knots from hell. I was so puzzled :D

Logic wrote on Jan 26^th, 2017 at 10:47pm:

What I have given you is simply a plot of voltage verses time.

Ok I do see this  ;)


Logic wrote on Jan 26^th, 2017 at 10:47pm:

We are connected to the positive and negative sides of the battery.

Thank you for verifying this


Logic wrote on Jan 26^th, 2017 at 10:47pm:

The car has been driven and to the left of Sunday 0:00 when the engine is turned off the gradient of the battery voltage reduction is significant

How come the battery voltage when not reducing settles back at 14.05V?

Also for 5 hours before the Sunday 0.00 it pull as low as 7.5 Volts yet rebounded to 13.8 Volts ??????

---

Mick wrote on Jan 27^th, 2017 at 11:20am:

How come the battery voltage when not reducing settles back at 14.05V?

That is when the car is being driven.

Mick wrote on Jan 27^th, 2017 at 11:20am:

Also for 5 hours before the Sunday 0.00 it pull as low as 7.5 Volts yet rebounded to 13.8 Volts ??????

Yes the battery went flat then the battery of the car was jump started with jumper leads and a spare barttery which was carried in the boot of the car for that purpose.

From work we have done since it would appear that a control unit will periodically fail to go to sleep.

When it does so it will cause a battery drain when the car is switched off.

When the voltage is zero the control unit will reset.


In the event that the battery goes flat the control unit resets and when the vehicle is next turned off that control unit will go to sleep.

Over time at some point the control unit will fail to sleep again and this fault will remain until the control unit again fails to sleep.

rayray wrote on Jan 20^th, 2017 at 6:04am:

Logic, good point and press the zero button when not connected to a wire. Ray

As well as in the area of where you are measuring.

Hi Ian, do you have any captures where you used the shunt?

Sorry Logic this is really illogical to me, don't want to sound offensive but you may have to explain a bit more detail about this software and it's use, haven't you just proven the obvious? the battery goes flat from a current drain? when it happens is irrelevant but are you using this tool to find which circuit is corrupt is what everyone is interested in.

I brought this tool for measuring long term voltage and current but I've never had to use it for overnight graphing
https://moosh.im/mooshimeter/

JohnN wrote on Jan 27^th, 2017 at 6:17am:

Logic wrote on Jan 26th, 2017 at 11:40am: Every time I reach for fluke to use the current shunt in it the fuse is blown, probably from someone in the workshop using my multimeter for a voltage measurement with the leads in the current measurement jacks....blowing the expensive fuse that requires unscrewing the back of the multimeter to replace.. Sharing is caring >:( My fluke got used last week and came back with 4 leads tied to it in knots from hell. I was so puzzled :D

Every couple of days I put good quality multimeter leads on my Fluke, leads with banana plugs so that I can use both the Pico and other compatable attachments.

Every single frigging time I come back and there are cheap banana leads in the meter with back probe banana pin connectors.

F*&^ing F#@*&ing F(*&^ing H**ll

So yesterday one of my fellows is trying to check the grounds on A E60 V10 M5 with the leads this way and without zeroing the leads...not a F*^^&*ing clue !!!!

So off I go and open up yet another new set of leads...tutor them fo the 150000th time on how to do a proper measurement......

Sometimes it is just impossible

When I try to find out who is doing this they say it was some Asian fellow...called....

autosparky wrote on Jan 27^th, 2017 at 8:33pm:

Sorry Logic this is really illogical to me, don't want to sound offensive but you may have to explain a bit more detail about this software and it's use, haven't you just proven the obvious? the battery goes flat from a current drain? when it happens is irrelevant but are you using this tool to find which circuit is corrupt is what everyone is interested in. I brought this tool for measuring long term voltage and current but I've never had to use it for overnight graphing https://moosh.im/mooshimeter/

autosparky wrote on Jan 27^th, 2017 at 8:33pm:

Sorry Logic this is really illogical to me, don't want to sound offensive but you may have to explain a bit more detail about this software and it's use, haven't you just proven the obvious? the battery goes flat from a current drain? when it happens is irrelevant but are you using this tool to find which circuit is corrupt is what everyone is interested in. I brought this tool for measuring long term voltage and current but I've never had to use it for overnight graphing https://moosh.im/mooshimeter ;

Yes I have proven the obvious the battery does go flat….but ….it does not always go flat.

Through logging the battery over a period of days we now no the pattern of when it starts to go flat…otherwise we are just pissing in the wind.

On one of the logging events we put a switch on the alternator output lead so we also now know that the alternator is not the cause.

Yes we are interested in finding the cause, but you must appreciate why I posted here, another tool that we can all use without flattening endless current clamp batteries.

Perhaps I should put this logging devise on either side of of the logging devise leads…then I can calculate the actual current.

If you read your manual for your Mooshimeter that is how they recommend you use the Mooshimeter to measure current.

The BMW IBS (Intelligent Battery Sensor) works in the same way.

Spence wrote on Jan 27^th, 2017 at 7:24pm:

Hi Ian, do you have any captures where you used the shunt?

I cannot tell you what resistance shunt I used but it gives you the idea

You can use a maths channel to express it in mAmps or amps

So in this instance we have a 711 mV drop across the shunt

Let us say that the resistance across the shunt is 20 Ω

So using OHM's law  V=R x I

then        .711 = 20 x I

therefore   I = 20/.711

                =28.1294 amps

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Logic wrote on Jan 28^th, 2017 at 12:55am:

Let us say that the resistance across the shunt is 20 Ω So using OHM's law  V=R x I then        .711 = 20 x I therefore   I = 20/.711                 =28.1294 amps

The  Calculator did its job but you may want to check your spelling after the numbers :o

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Logic wrote on Jan 28^th, 2017 at 12:55am:

Spence wrote on Jan 27th, 2017 at 7:24pm: Hi Ian, do you have any captures where you used the shunt? I cannot tell you what resistance shunt I used but it gives you the idea You can use a maths channel to express it in mAmps or amps So in this instance we have a 711 mV drop across the shunt Let us say that the resistance across the shunt is 20 Ω So using OHM's law  V=R x I then        .711 = 20 x I therefore   I = 20/.711                 =28.1294 amps

Hey budd I think you got the numbers inverted.   [smiley=smiley-gen101.gif]  Understandable being down under.

I think it's  I = 0.771/20  = 0.03855 amps  =  38.55 ma

Yahhh by golly. Volts equals amps times ohms.

fisher wrote on Jan 28^th, 2017 at 7:15pm:

Yahhh by golly. Volts equals amps times ohms.

Don that is correct but the poster is looking for Amps so Amps equals volts/ohms  8-)

Mick wrote on Jan 28^th, 2017 at 6:35am:

check your spelling after the number

Don't have to post anything at all if it offends you Mick

Logic wrote on Jan 29^th, 2017 at 12:31am:

Mick wrote on Jan 28th, 2017 at 6:35am: check your spelling after the number Don't have to post anything at all if it offends you Mick

So many ways of saying it and of course someone has to be wrong.

I am sorry for being wrong if that makes you feel better and keeps the thread going :D

Mr. Logic divided his ohms by the volts, rather than vice versa.

rayray wrote on Jan 21^st, 2017 at 8:04pm:

amp clamp reading drift

Sorry for a noob question, but what's this? This is the first time i've heard of this.

Logic, did you ever solve this? The info you gave is just a small piece of the picture.

Did you ever load test the battery?
How many amps was the parasitic drain?
Did you check the voltage drop across the fuses to locate the source of the drain?
There are charts online that help give you a rough estimate of how much current is passing through the fuse without having to disturb the circuit.

ralstig wrote on Mar 3^rd, 2017 at 9:15am:

Sorry for a noob question, but what's this? This is the first time i've heard of this.

Drift.

The Amp clamp and not just the one used here are prone to drifting above the zero line.

We always zero the clamp near to the circuit as possible, also snap the jaws open closed a couple of times to get ride of any magnetic build up in the jaws this is known as Degaussing.

After a period of time the zero will rise so the amp clamp will need to be removed from the circuit and the above procedures redone.

Hope this helped ;)