Megohmmeter - Loss of Isolation Diagnostics
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- čas přidán 12. 06. 2024
- Watch as I create high voltage short circuits to the vehicle chassis and cause "Loss of Isolation" trouble codes to set. Learn how the vehicle detects these short circuits and how you can diagnose their source with a Megohmmeter. A 2017 Chevrolet Bolt EV is the test vehicle.
TIMELINE:
0:00 Introduction
0:25 Safety Warning
0:40 High Voltage (HV) Insulation/Isolation example
2:50 On-Car high voltage power distribution
4:55 Live HV measurements (Car Powered Off)
6:15 Live HV measurements (Car Powered On)
7:36 MUST-SEE: Shorting the 381V battery positive cable to vehicle chassis
9:57 Which Diagnostic Trouble Codes (DTC)s were set
11:18 MUST-SEE: Shorting the 381V battery negative cable to vehicle chassis
13:25 What can happen in an automobile accident
13:50 MUST-SEE: How loss of isolation can occur through conductive liquids
14:41 How the car performs active isolation testing and passive isolation testing
16:10 Normal passive scan tool data values for loss of isolation detection
18:30 See the results of an 11 Mega-ohm connection to vehicle chassis
20:50 See the results of a 4.65 Mega-ohm connection to vehicle chassis
22:20 See the results of a 1.16 Mega-ohm connection to vehicle chassis
23:00 See the results of a 551 kilo-ohm connection to vehicle chassis
23:35 See the results of a 222 kilo-ohm connection to vehicle chassis
23:40 MUST-SEE: The 318-265 kilo-ohm threshold to trigger a loss of isolation DTC
24:50 MUST-SEE: GM On-Star notification of battery problem
25:15 See the results of a 110 thousand ohm connection to vehicle chassis
25:51 MUST-SEE: See the results of a 0 (zero) ohm connection to vehicle chassis
26:54 See my voltage drop measurement table
27:35 MUST-SEE: See the results of a conductive liquid connection to vehicle chassis
30:00 How to determine the location of a loss of isolation problem
32:08 Clearing Secured High Voltage DTCs with a GM GDS2 scan tool
33:00 Hybrid/EV battery pack active isolation test
34:35 Hybrid/EV battery pack heater passive isolation test
37:28 The Megohmmeter and the factory specifications for isolation resistance
40:30 Example of using the Fluke 1587 Insulation Tester (Megohmmeter)
44:05 Video summary
ABOUT US:
Weber State University (WSU) - Department of Automotive Technology - Ardell Brown Technology Wing - Transmission Lab. This episode covers what happens with the high voltage system that loses isolation (High Voltage Leak) with the vehicle chassis of an electric vehicle (EV), plug-in electric vehicle (PHEV), or hybrid electric vehicle (HEV). A 2017 Chevrolet Bolt EV is used as an example vehicle in this video.
WSU is a leader in Hybrid and Electric Vehicle education. This topic is taught as part of our 4-year bachelor's degree program. For information on joining the Weber Automotive program, visit: www.weber.edu/automotive
This video was created and edited by Professor John D. Kelly at WSU. For a full biography, see www.weber.edu/automotive/J_Kel...
ADDITIONAL TRAINING FOR YOU
Join us for hybrid and electric vehicle training with two online courses and in a 5-day on-campus boot camp with Professor John D. Kelly. See www.weber.edu/evtraining
DONATE TO OUR DEPARTMENT
Please consider a donation to the Department of Automotive Technology at Weber State University here: advancement.weber.edu/Automotive
![62kWh isolation problem [part 1]](http://i.ytimg.com/vi/Ug9YdxXqkJ4/mqdefault.jpg)
This guy makes it easy to understand. I went to a 4 night class leaving with more questions and confusion
Great video John. The P0AA6 is Ford's loss of isolation DTC, and it's a code lots of techs struggle with. As your video shows, it's a super simple concept and easy to diagnose if you understand what the code is monitoring for.
Unplugging connectors one at a time is a great test, but on the Focus BEV, the ACCM, DC/DC, and PTC heater all have interlock circuits monitoring the connectors. We have dummy connectors that plug in to close the interlock, then we check the PID values for leakage on positive, negative, or internal battery.
Another point worth mentioning about how safe these vehicles are to work on; Ford no longer uses the fiberglass "Shepard's hook" as a technician removal tool. And, the upcoming Mach-e will not require insulated tools or gloves. Respect the potential of the systems, follow the procedure, and understand the theory and you'll be safe.
What a fascinating demo, I didn't realize the high voltage system is isolated on the ground side, too. Traditional safety for high voltage is to offer a low impedance grounding path from chassis back to the transformer, so a human hand that touches chassis will be reliably bypassed in favour of the lower resistance route. Dogs lost their lives by tinkling on the ground beside the wrong power pole without that.
Thank you very much. It was fun to experiment with. Thanks for your feedback!
Thank You Professor ! Your depth of knowledge and attention to details is rarely found these days in academia. I can assure you that I will never be working on an electric vehicle of any kind not even a golf cart but your devotion to details and conveyance of knowledge is first class ! Thank you for your hard work and sharing it with us.
Thank you very much!
Thank you Professor for this straight to the point explanation. It helps me a lot in explaining how to troubleshoot a HV vehicle Isolation Faults to my students. More power and God bless you always.
Best explanation of isolation in an EV for the battery I've seen! This is great!!
I Don't even have to watch your videos for class anymore but you are such a great professor I always learn something new from you or your videos! Thanks for sharing your knowledge!!!
Thanks, that is awesome!
My neighbors keep asking me if power-washing my Bolt or getting it through an automated car wash is safe. I know now what to tell them. I also have a link to this channel to give them. Thank you Professor Kelley! :)
I'm surprised more people don't freak out about that
When I bought my 2017 VW e-Golf the closer stressed that there was high voltage under the hood, and that I could be killed. He insisted that I should not open the hood and only let their techs open the hood. I kept my mouth shut, knowing that he had no idea what he was talking about. Thank you for another useful video.
These videos you have assembled remind me of the engineering level material that our Prof's at SAIT pushed us to absorb back in my Collage days. Little did i know how important the teachings that were imparted upon me 'would be' later in my career. I fall back on the fundamental lessons nearly daily, and they help me push the boundries of my career. You are a scolar and a gentalman!!! I especially enjoyed your series on the early toyota E-CVT transmissions as it pertains to my 2007 Nissan Altima Hybrid daily driver. Thank you Mr. John Kelly for your excellent videos ;)
Such an underrated channel. I’ve learned so much from here. Keep it up!
Thank you
Instablaster.
Excellent video professor. This is a great lesson in the inherent safety of unreferenced or "Floating" DC Power Supplies. Prospective EV buyers should understand that this type of supply is very safe because neither terminal is referenced to ground or common (the vehicles chassis in this instance). Electric Vehicles are very safe.
Glad it was helpful!
Thank you so much! I recently found your channel, and you are amazing. As a tinkerer, I’m thankful of you to not do things I should not do and be careful with the things I own! All your videos are very very thorough, and I never end up with questions! Again, thank you, and have a happy holiday season!
Thank you
Thankyou Professor Kelly for the information. I've only had training on the Prius High Voltage system, including removing the HV Battery assembly, the HV Inverter assembly, removing the safety covers on both, and the jumper straps on the individual batteries for testing. Very, Very Interesting! Oh yes, also checking the High Voltage Capacitors in the HV Inverter, for High or Low Voltage with the High Voltage Battery Assembly cables disconnected.
Again, very interesting! The training paid off when I had to remove the inverter to replace coolant hoses under the inverter. The vehicle had been in an accident. With help from an iATN member named Carolyn, I was able to keep the transmission in neutral even after powering down, by removing a relay in the underhood power center on the driver's side near the firewall or bulkhead. When we brought the car to the body shop, I told the techs there to block the front wheels or the car might run away from you! HA! It ran great after body and mechanical/electrical repairs. I apologize for the long comment. Mike C.
Awesome, thanks for your feedback
John thank you - I am testing Monday and this is very helpful.
Good to hear!
I once had a co-worker ask me, with a straight face, if I could drive my Chevy Volt in the rain, or did that put me at risk of being electrocuted. And this was somebody in a *technical* position! The level of ignorance toward EV safety can be absolutely astounding. Another outstanding video, Professor! Great job! Thanks for doing what you do!
Thank you. That is a common question. Education is essential.
I always answer questions along these lines with comparisons to trains. Incredible how technically backward the general public is.
That person may be in a technical position but if they have that sort of misconception I would be very skeptical that they are qualified to do their job.
See this one tomorrow with anothers few ones, saturday is my Jhon Kelly marathon day. thanks for sharing, Professor !
Thank you
WOW, by far one of the intressting Videos of the Year for HV-Car Tests !! THANK YOU !!!
Thank you
Thank you for another extremely informative video. My 2019 Bolt EV is running great, but it is always nice to understand more about how it works..
Thank you
Great job Professor! I’m learning much from your Hybrid training courses!
Professor Kelly, thank you for all the videos and sharing of your knowledge, it is very much appreciated.
Man, this is a GREAT channel!! Thank you, Professor J. Kelly
Thank you very much
You do a wonderful job of explaining everything
Excellent video, thanks so much!
Thank you very much!
Mr. Kelly, as always, a fine and thorough video. Impedance and resistance, however, have separate meanings with respect to AC and DC circuits. Keep up the fine work. Happy holidays!
Thank you and thanks for your feedback. Happy holidays to you!
Another excellent video! You explain everything in great, easy to follow, detail to aid understanding of how modern cars actually work...
Thank you Kelvin
First rate instruction. Your “school” is very fortunate to have you in its faculty. Thx 👍
Thank you very much
Thankyou for another great video. If I was young again I would seriously become the best at working on this new generation of electric vehicles. It would be a great living to have with little competition from other mechanics that can't afford the computer tools needed to diagnose problems. Before retiring, I worked on mainframes, micro computers, networks, microfiche printers and a vast amount of printing machines for the last 40 years. Machine repair has always been my passion.
Thank you very much
Computer tools aren't a new thing for mechanics though. Mechanics have been diagnosing and repairing computer related issues since the 1980's. The difference in computer tech is very small when comparing internal combustion vehicles to electric. It isn't uncommon to have 30+ computers networked over CAN data bus circuits in modern gas-powered vehicles. The big difference is literally learning the high voltage systems, this video is a fantastic example of this.
Wonderful video, Clear and 100% scientifically correct.
Bravo, great video. A tip from my teaching experience: when using autoranging multimeters you can disable the autoranging and set a specific range for the display, which eliminates what happened at like 6:12 where the meter showed a few millivolts. We experienced folks know that means zero, but a novice student is sometimes distracted by having a non-zero display.
Thank You Professor Kelly for you excellent videos. Have a safe, blessed holiday season.
Thank you very much
DEAR MR. PROFESSOR,
THANK YOU, THIS VALUABLE INFORMATION, IN THIS CASE STUDY.
Thanks a lot professor ur vids are very knowledgeable and interesting, appreciate the effort u put to these vids.
Superb! You are one of the reasons I have decided to buy a Bolt EUV.
Привет из Беларуси! Очень нравятся ваши качественные и интересные уроки! Спасибо за просвещение!
Greetings from Belarus! I really like your high-quality and interesting lessons! Thanks for enlightening
Thank you
Your videos are gold.
Please keep it up guys.
Thank you very much.
Excellent stuff professor really helpful information.....always pleased when i see one of your videos pop up....nothing anywhere near as good here in the uk....infact BMW will not provide battery isolation information readily
Thank you very much!
Very helpful vídeo. Full of information, details and tips. Congratulations.
Thank You ! First class training !
I am not a technician, but I am a very curious person. Your videos are a joy to watch because you are clear and not too fast. I must add that in the Netherlands we had an accident with a Tesla hitting a tree where the car could not be approached by the fire department because sparks kept flying around. So, it can go very wrong. In fact, the fire department had to call up somebody from the Tesla service center on the other side of my small country to assist making the car safe. That took hours. The driver, by the way, was killed at impact, not because of electrocution or the long duration before help could be given.
Wow, that is terrible! Thanks for your feedback.
in case the pack gets damaged, as can be the case in high speed accidents, individual cells can short circuit, spark and release a LOT of heat. But that still would not result in electrocution risk for the firemen, as they are still not part of a full closed HV circuit.
They heat from Li-ion cells should be treated with respect and care and is dangerous for that reason.
Of course it can go wrong if the battery pack is physically damaged. Just the same as it can go wrong if a fuel line or tank ruptures near a hot engine or exhaust. Driving any vehicle is inherently unsafe, but I don't think it is reasonable to say that an electric vehicle is less safe than a gas/petrol or diesel vehicle. Much is done to make the lithium battery packs in cars as safe as possible, which is why there are not many problems seen with them. Most of the problems we see with lithium batteries in general are as a result of companies and/or nations with no safety standards building and selling garbage. That isn't going to be the case on any mainstream EV.
Amazing information as usual. Welcome back!
The best professor I have listen to. Very knowledgeable an explains well. I worked for a dealership an services Leafs an he taught me more than the one week training they sent me to.
Thanks so much. Enjoyed all the videos.
Wow, thanks!
Thank you for posting these incredibly awesome videos. I have learned so much from you.
Thanks for watching!
Very good Professor
MERCI Monsieur le Professeur ...Très bien expliquer et votre anglais est très facile à comprendre...Thankyou SIR..
Thanks for watching
Excellent teaching skills, thank you
Very informative video, Good job professor 👏👏
mr Kelly, you are the best!
That's the exact Mega meter I use at my job on navy ships and oh yes they *WILL* shock you. I can attest to that myself. We have to meg each and every cable we install *BEFORE* we hook up any equipment. This meter is extremely useful in testing the integrity of HV cables installed in electric vehicles. In addition to testing the resistance to ground, we can also test the resistance between conductors - on multi lead cables.
Dang I love this stuff.
Welcome back professor ❤️
Thank you
Kuch samajh aya
Thank you, Prof. Kelly!
Outstanding knowledge about electric cars. Thank you.
Thank you
Professor Kelly, your videos encourage me to keep going even when injury & disease has me stuck unable to do anything other than watch these videos. Thank you so much for being an encouraging example & for the cool EV content. I drive a 2016 Nissan LEAF 30kWh & our other car a 2005 Prius II // I love electric motors & batteries & energy storage capacitors & high power switching electronics contractors & SSR's & microcontrollers & compute & digital systems. Your videos are cool & they show why EV's are super interesting. Also really like your collection of Fluke meters, they are really well made. I keep a DIY modded Sperry DM-350A (added external hard on/off switch for the meter battery) so I can leave control dial turned to DC 0-20vdc mode since that's the range I measure most of the time :)) Thanks for sharing this useful information :) God Bless
Battery Systems with multiple battery cells usually contain
BMS or battery management system to balance & minitor all the cells
CC or charge controller that can independently charge each cell & cells in series
Fuses or breakers to open the circuit, usually on positive side of battery, to safety if shortening occurs
Thermistors or temperature sensors to keep track of cell or pack thermal state during charge & discharge & storage
Pack properly designed should prevent overcharging, over discharging, damage from shorting & against thermal runaway or fire & or cell expansion disconnection & other safety aspects to minimize chance of venting with flame, fire or explosion
Great Quality Video Sir, very Informative and Educational.
Learning something New everyday. - Every-DAY.
.Thank You!!!
Saludos Master. Sigo aprendiendo gracias
Excellent explaining sir !
I love this stuff.
A note on why its called a Meg-ohm meter, its because a company called Megger makes HV test equipment for the Electrical Power Sector, including a tool commonly called a "megger" which tests for isolation, using a high voltage, ultra low current test current. So there would be some trademark malarkey involving a Mega-ohm meter sounding like a branded Megger Ohm meter.
Megger make mega-ohm meters....
They also make devices that use kilovolts to measure mega-ohms....
Rather like Druck making pressure calibrators in Germany (look up the translation).
Thanks for your feedback!
Thank you for these videos. They are a great resource.
Very informative, thanks!
Thank you for another great video
Thank you
Thank you Professor
Thank you
Trank you for this very good lesson.
Looking forward to seeing your new videos
Contenido técnico excelente
My all questions are answered. Thank you very much ☺️☺️
Thank you very much
It's the best channel on the world we want to see even tesla repair on you nice Chanel thank you very much
Happy New Year for you and family Professor.
Regards from Comox Valley BC
❄⚡🔥👍snow+spark=fire. Thank you for valuable insight information Professor.
Thank you
Great info John, really enjoy.🍁🍁🍁🇨🇦🇨🇦🇨🇦
Thanks Professor and welcome back happy New Year in 2020 regards
Thank you again , you are a great man !
Great video. Your videos are wonderfully helpful to those of us outside of the formal education setting. I have seen a fair number of CZcams videos with people mishandling high voltage batteries and doing very dangerous things. Your careful instruction has almost certainly prevented injuries or even deaths in the hobbyist community.
Thank you very much!
Thanks Professor. Very informative.
Thank you
Thank you sir looking forward to your next video.
Hi Professor John! Thank you for that.
Thank you
Awesome workshop! :D I don't know how many hours of boring courses I have taken, and most of them have been summarized here. It would have been nice two more things. One, difference between CAT III 1000V vs CAT IV 600V. And second, with the Meger, to mention that the button in the lead is doing two things: when you press, it energizes and takes the measurement, but in case that you are measuring something with capacitance, that capacitance will get charged, so if you remove the lead after the measurement, you will most probably get a 500 V or 1000 V shock... (if the capacitance is big, you might have some kJ of energy there... not enough to kill... but it's not a nice experience) So the way to go is, once you have finish the measurement, keep the lead connected and then release the button. That will force an "active discharge" through the Meger (you will see the voltage going down in the display). Then you will know that the capacitance is discharged and it is "safe" to touch the component. Enjoy! :D
Thanks David. CAT III 1000 V vs CAT IV 600 V is in relation with the maxim transient voltage that the lead and the meter can receive. The value is taken from power systems in AC (CEI 31010-1), how much is the meter close to the substation, but in EV (DC) is different, despite of the standard is saying for EVs you have to use CAT III.
Thank you very much Sir.
great video learned so much, thank you for your time
Thank you
Perfect. Really appreciate the normal speed too.
Hope all is well post fender bender.
Thank you very much
Thank you so much for your technical lessons sir
Thank you
Thank you Professor, thank you very much!
Thank you
Great example on the flashlight! So risk of electric shock is almost 0 because of the DC high voltage battery. On the other hand, during charging, there are many other factors that can make an AC electric shock to happen!
True. That is why the protective earth to chassis ground connection must be made first before any charge station current is allowed. Improper wiring could certainly cause some problems. Thanks for your feedback.
Sir you are important person for automobile section
Thank you
Fascinating.
You are outstandingly genius love you
Very good video. Thank you for doing this.
Glad you enjoyed it! Thanks for watching
Very deep knowledge.
Amazing stuff. Many thanks for that.
Thank you
Great to see again.
Very important information 👍 Thank you.
Thank you
Great information Thank you Professor
Thank you
Excellent as always. I have hunted to find if battery was isolated from chassis to no avail
thank you, great video
Thanks a lot for yours job.
Thank you so much
Thank you
Sr. Thanks for share this and Merry Christmas.
Thank you, Merry Christmas to you
Thank you, Sir🙏
Thank you sir
Professor Kelly, can you recommend a thorough book on theory and operation of hybrid vehicles? Perhaps the textbook(s) you use at WSU. You're the best hybrid vehicle instructor in America, possibly the world. Thanks for sharing your immense storehouse of knowledge of hybrid and electric vehicles!