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 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.
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.
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.
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.
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.
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 grateful for this content because I want to be able to help people with hybrid vehicles in the aftermarket world. I can rewind and review content to really learn how to fix hybrids. Thanks for the info. Understanding the pids really makes life easier for troubleshooting
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.
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.
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 ;)
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!
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.
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.
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.
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
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.
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!!!
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.
I find it interesting that they go through great lengths to isolate the battery from the chassis but they don't really do much when the isolation is lost. In the power distribution world this is referred to as a "ground fault" and hence the name Ground Fault Circuit Interrupter for the type of breaker that protects against this. I would expect the car to return to a safe state in the event of lost isolation by opening the contactor on the battery. In high power DC systems this is done to prevent fires. A single fault is not a problem but if you get a 2nd fault you may be passing current through items that shouldn't be conducting that much current (signal wires, chassis connections, etc). For this reason, most high power DC systems will trip off in the event of a single "ground" fault or loss of isolation. Anyway, great videos!! I always enjoy watching the stuff you do on electric automobiles.
@@WeberAuto Yes, the first loss of isolation is not a big deal. The 2nd point of lost isolation can cause a shock or a fire. That is why most industrial machines that use ground isolation trip off on the first loss of isolation. You don't want main battery level power flowing through some small wire somewhere or part of the frame.
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.
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).
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.
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
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
Awesome video, I enjoyed watching your channel. Just a side note, in hybrid and electrical vehicles, the air conditioning oil is non conductive. At least it shouldn't be if the proper oil is in the system.
I sure hope I never have to do this but your info is there should the need arise. Another great dive today up Tempanogas canyon. So much to learn about these machines in both operation and monitoring. Yet to see what my electric usage will be but I am charging only from 10pm to 8am. When cold I start car 30min before use with cabin heat on & on charger.
Great video. Your videos are wonderfully helpful to those of us outside of the formal education setting. I have seen a fair number of RUclips 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 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!
At 12:30 a "megger" is also used to accurately measure extremely high resistance, for example, between two points in the earth (which would have extraordinary, but measurable, amounts of resistance). Very informative video, and sad to report that too many other colleges are not taking electric vehicle maintenance seriously enough to create adequate curriculum.
Great video, helped to explain what may be going with the Toyota Rav 4 hybrid 2019-2021 ...MGR cable connector corrosion Toyota did change the connector design in 2022.....To address this problem..... Would you recommend any type of moister / corrosion inhibitor applied to the connector proactively
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!
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!
As far as I know whenever the airbag is triggered the pyro fuse(s) in the battery will blow also. On Teslas whenever you open a high voltage enclosure a microswitch will open the first responder loop.
Thank you professor.so far i thought that, negative supply is connected to ground in Ev just like ICE car.but i learned from you that, dual powersupply sytem is used inEV. That is +ve and -ve to common ground.Usually i saw this type powersupply in HiFi audio amp.Moreover i request you in future please add circuit diagram to explain the power supply trouble shooting.I HOPE you will use some circuit diagram to explain the electrical ciruit. Once again i thank you for your kind information.God bless you for your best health.
From my experience working on electric buses, moisture can still get in - or develop rather - in a hermetically sealed compartment, due to heat buildup...*IF* the compartment or device within is not cooled. I reported this moisture buildup to the engineers who insisted that water was getting into the battery compartment. The vehicle was never washed and there was no rain. The engineers decided to replace the gasket on the roof mounted battery compartment AND clamp down the edges of said compartment using angle iron all around the edge of the battery compartment top cover. This did not solve the issue. I recommended that the compartment either be vented or some type of cooling system be put inside / through the compartment. Eventually they came up with a cooling system. - not sure if it was liquid or air because I quit before the system was introduced on the buses I was working on. This moisture buildup reaped havoc on the connectors linking the batteries to the module that sat directly on top of each connector - they turned green on the inside, which resulted in a drop in cell voltage. These connectors attached to ribbon cables had to be replaced. If for whatever reason moisture seeps into the battery compartment and problems should develop, the connectors need to be inspected. If green on the inside, replace them. This can also cause one or more cells within a battery to malfunction and the battery may have to be replaced - depending on what type perirhinal device / equipment is attached directly to the battery or located within the battery compartment..
Recently learned about a Bolt that got issues with snow getting stuck OVER the battery pack. Apparently the snow got packed in there while getting through many inches of snow. Isn’t there anything blocking snow from getting in there ? Or is it wide open ? How dangerous can that be as it’s putting pressure on the battery pack ? I know the dealer had to remove the whole pack to remove the snow (too cold in there for it to melt by itself) and they had to replace some components.
The battery is sealed, there is no danger. GM does recommend a monthly undercarriage wash if you can find a carwash that does that. That will help keep that area clean.
Profossor John Kelly, I enjoyed watching your videos. I learned a lot from them. Thank you very much. How can I join your course online. I am Sami Haddad from Jordan.
@@WeberAuto I am honored and humbled that you responded John Kelly. I have taught electronics and electricity for 45 yrs (87 yrs old and retired now). I have met and studied under a myriad of instructors across the country. And I have NEVER been as impressed as you have done. You are truly one of THE greatest instructors I have EVER heard. Awesome! I would give any thing to take a lesson in one of your classes. That will not happen of course, but what a thrill of my life that would be. Keep up the great work dear Sir
Fantastic job as usual professor. Question, are the resistance values just so high on the monitoring circuit that the battery is considered isolated from the chassis? Seems like since there is a connection to the chassis on both negative and positive side of the battery but just through very high resistors that it be correct to say the system is not isolated.
Love your videos, thank you. I have a 2017 Bolt and would like to purchase an inverter to use in the event of a power at my home. What is largest size inverter can I use. Don’t plan to go crazy, just frig, light or two and maybe my internet and WiFi devices. Thank you.
fridge? Most fridges are going to need more than can be just be hooked off from the 12V side. For up to ~150W you can just pluginto the cigarette lighter.
I had this isolation code pop up on my 2017 Bolt a couple weeks ago. I jumped in the car to go to work when it was 11 degrees out and the service light was on. Everything operated normally. When I left work the light was off and hasn't came back on since. I pulled codes and it was displayed as a history code.
P1AF0 Drive Motor Control Module Hybrid/EV Battery Voltage System Isolation Lost. The DTC will never set while the vehicle is plugged in to charge or while being driven. This isolation fault may be caused by any component in the high voltage system, it does not know which one.
Did you know your power chair also has a isolated ground or some call it a floating ground. Whenever you turn on your chair it checks for shorts between chassis and power supply hot and ground. After five to ten years of use, the carbon dust in the brushed motors may form a high resistance short causing your chair to give a motor fault. I have fixed my chair and customer chairs by removing brushes and blowing compressed air through the commutator. This give a quick fix if you can reach the brushes to do the work.
![62kWh isolation problem [part 1]](http://i.ytimg.com/vi/Ug9YdxXqkJ4/mqdefault.jpg)
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.
This guy makes it easy to understand. I went to a 4 night class leaving with more questions and confusion
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 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.
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!
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
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.
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.
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
I'm grateful for this content because I want to be able to help people with hybrid vehicles in the aftermarket world. I can rewind and review content to really learn how to fix hybrids. Thanks for the info. Understanding the pids really makes life easier for troubleshooting
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.
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 ;)
Best explanation of isolation in an EV for the battery I've seen! This is great!!
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.
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.
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
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.
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!
MERCI Monsieur le Professeur ...Très bien expliquer et votre anglais est très facile à comprendre...Thankyou SIR..
Thanks for watching
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 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
First rate instruction. Your “school” is very fortunate to have you in its faculty. Thx 👍
Thank you very much
I find it interesting that they go through great lengths to isolate the battery from the chassis but they don't really do much when the isolation is lost. In the power distribution world this is referred to as a "ground fault" and hence the name Ground Fault Circuit Interrupter for the type of breaker that protects against this. I would expect the car to return to a safe state in the event of lost isolation by opening the contactor on the battery. In high power DC systems this is done to prevent fires. A single fault is not a problem but if you get a 2nd fault you may be passing current through items that shouldn't be conducting that much current (signal wires, chassis connections, etc). For this reason, most high power DC systems will trip off in the event of a single "ground" fault or loss of isolation.
Anyway, great videos!! I always enjoy watching the stuff you do on electric automobiles.
Thank you and thanks for your feedback. As you may have seen in the video, a single direct short to chassis only causes 222 micro amps of current.
@@WeberAuto Yes, the first loss of isolation is not a big deal. The 2nd point of lost isolation can cause a shock or a fire. That is why most industrial machines that use ground isolation trip off on the first loss of isolation. You don't want main battery level power flowing through some small wire somewhere or part of the frame.
DEAR MR. PROFESSOR,
THANK YOU, THIS VALUABLE INFORMATION, IN THIS CASE STUDY.
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.
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!
Sir you are important person for automobile section
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.
Another excellent video! You explain everything in great, easy to follow, detail to aid understanding of how modern cars actually work...
Thank you Kelvin
See this one tomorrow with anothers few ones, saturday is my Jhon Kelly marathon day. thanks for sharing, Professor !
Thank you
John thank you - I am testing Monday and this is very helpful.
Good to hear!
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!
You do a wonderful job of explaining everything
Superb! You are one of the reasons I have decided to buy a Bolt EUV.
Such an underrated channel. I’ve learned so much from here. Keep it up!
Thank you
Instablaster.
Professor Kelly, thank you for all the videos and sharing of your knowledge, it is very much appreciated.
WOW, by far one of the intressting Videos of the Year for HV-Car Tests !! THANK YOU !!!
Thank you
Very good Professor
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 job Professor! I’m learning much from your Hybrid training courses!
Excellent as always. I have hunted to find if battery was isolated from chassis to no avail
Perfect. Really appreciate the normal speed too.
Hope all is well post fender bender.
Thank you very much
Outstanding knowledge about electric cars. Thank you.
Thank you
Awesome video, I enjoyed watching your channel. Just a side note, in hybrid and electrical vehicles, the air conditioning oil is non conductive. At least it shouldn't be if the proper oil is in the system.
Wonderful video, Clear and 100% scientifically correct.
I sure hope I never have to do this but your info is there should the need arise. Another great dive today up Tempanogas canyon. So much to learn about these machines in both operation and monitoring. Yet to see what my electric usage will be but I am charging only from 10pm to 8am. When cold I start car 30min before use with cabin heat on & on charger.
Have fun! Thanks for watching
Great video. Your videos are wonderfully helpful to those of us outside of the formal education setting. I have seen a fair number of RUclips 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!
Excellent video, thanks so much!
Thank you very much!
mr Kelly, you are the best!
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
It's the best channel on the world we want to see even tesla repair on you nice Chanel thank you very much
At 12:30 a "megger" is also used to accurately measure extremely high resistance, for example, between two points in the earth (which would have extraordinary, but measurable, amounts of resistance). Very informative video, and sad to report that too many other colleges are not taking electric vehicle maintenance seriously enough to create adequate curriculum.
Great video, helped to explain what may be going with the Toyota Rav 4 hybrid 2019-2021 ...MGR cable connector corrosion
Toyota did change the connector design in 2022.....To address this problem.....
Would you recommend any type of moister / corrosion inhibitor applied to the connector proactively
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!
Thanks a lot professor ur vids are very knowledgeable and interesting, appreciate the effort u put to these vids.
Thank you Professor
Thank you
Thank you for posting these incredibly awesome videos. I have learned so much from you.
Thanks for watching!
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!
Man, this is a GREAT channel!! Thank you, Professor J. Kelly
Thank you very much
Excellent teaching skills, thank you
Welcome back professor ❤️
Thank you
Kuch samajh aya
Thank you for another great video
Thank you
My all questions are answered. Thank you very much ☺️☺️
Thank you very much
❄⚡🔥👍snow+spark=fire. Thank you for valuable insight information Professor.
Thank you
As far as I know whenever the airbag is triggered the pyro fuse(s) in the battery will blow also. On Teslas whenever you open a high voltage enclosure a microswitch will open the first responder loop.
Thanks for watching
Thank You ! First class training !
Thank you professor.so far i thought that, negative supply is connected to ground in Ev just like ICE car.but i learned from you that, dual powersupply sytem is used inEV. That is +ve and -ve to common ground.Usually i saw this type powersupply in HiFi audio amp.Moreover i request you in future please add circuit diagram to explain the power supply trouble shooting.I HOPE you will use some circuit diagram to explain the electrical ciruit. Once again i thank you for your kind information.God bless you for your best health.
Thank you very much
Thank You Professor Kelly for you excellent videos. Have a safe, blessed holiday season.
Thank you very much
Your videos are gold.
Please keep it up guys.
Thank you very much.
From my experience working on electric buses, moisture can still get in - or develop rather - in a hermetically sealed compartment, due to heat buildup...*IF* the compartment or device within is not cooled. I reported this moisture buildup to the engineers who insisted that water was getting into the battery compartment. The vehicle was never washed and there was no rain. The engineers decided to replace the gasket on the roof mounted battery compartment AND clamp down the edges of said compartment using angle iron all around the edge of the battery compartment top cover. This did not solve the issue.
I recommended that the compartment either be vented or some type of cooling system be put inside / through the compartment. Eventually they came up with a cooling system. - not sure if it was liquid or air because I quit before the system was introduced on the buses I was working on. This moisture buildup reaped havoc on the connectors linking the batteries to the module that sat directly on top of each connector - they turned green on the inside, which resulted in a drop in cell voltage. These connectors attached to ribbon cables had to be replaced.
If for whatever reason moisture seeps into the battery compartment and problems should develop, the connectors need to be inspected. If green on the inside, replace them. This can also cause one or more cells within a battery to malfunction and the battery may have to be replaced - depending on what type perirhinal device / equipment is attached directly to the battery or located within the battery compartment..
Saludos Master. Sigo aprendiendo gracias
Very informative video, Good job professor 👏👏
Thank you for these videos. They are a great resource.
Thank you, Prof. Kelly!
Professor you made American great again.
Thank you so much for your technical lessons sir
Thank you
Very helpful vídeo. Full of information, details and tips. Congratulations.
Looking forward to seeing your new videos
gracias por tu ayuda John te amo
Thank you again , you are a great man !
grazie professore
Thank you
Thank you Professor, thank you very much!
Thank you
Thanks for this superb video I’m pretty sure GM has no such training video.
Thank you! Their service information on the topic is pretty thorough, but was difficult to understand without some experimentation.
Trank you for this very good lesson.
Great Quality Video Sir, very Informative and Educational.
Learning something New everyday. - Every-DAY.
.Thank You!!!
Hi Professor John! Thank you for that.
Thank you
Very good video. Thank you for doing this.
Glad you enjoyed it! Thanks for watching
Recently learned about a Bolt that got issues with snow getting stuck OVER the battery pack. Apparently the snow got packed in there while getting through many inches of snow.
Isn’t there anything blocking snow from getting in there ? Or is it wide open ? How dangerous can that be as it’s putting pressure on the battery pack ? I know the dealer had to remove the whole pack to remove the snow (too cold in there for it to melt by itself) and they had to replace some components.
The battery is sealed, there is no danger. GM does recommend a monthly undercarriage wash if you can find a carwash that does that. That will help keep that area clean.
WeberAuto Thanks ! I’m still surprised some snow got up there, but it’s good to know that GM recommend to keep it clean !
great video learned so much, thank you for your time
Thank you
Meg in isolation tests comes from the German firm Megger, famous producer of Megger isolation meters.
Profossor John Kelly, I enjoyed watching your videos. I learned a lot from them. Thank you very much.
How can I join your course online.
I am Sami Haddad from Jordan.
You are outstandingly genius love you
Absolutely top notch!!!
Thanks for watching
Very important information 👍 Thank you.
Thank you
Absolutely great. NONE finer!
Thank you
@@WeberAuto I am honored and humbled that you responded John Kelly.
I have taught electronics and electricity for 45 yrs (87 yrs old and retired now). I have met and studied under a myriad of instructors across the country. And I have NEVER been as impressed as you have done.
You are truly one of THE greatest instructors I have EVER heard. Awesome! I would give any thing to take a lesson in one of your classes. That will not happen of course, but what a thrill of my life that would be. Keep up the great work dear Sir
Fantastic job as usual professor. Question, are the resistance values just so high on the monitoring circuit that the battery is considered isolated from the chassis? Seems like since there is a connection to the chassis on both negative and positive side of the battery but just through very high resistors that it be correct to say the system is not isolated.
Love your videos, thank you. I have a 2017 Bolt and would like to purchase an inverter to use in the event of a power at my home. What is largest size inverter can I use. Don’t plan to go crazy, just frig, light or two and maybe my internet and WiFi devices. Thank you.
fridge? Most fridges are going to need more than can be just be hooked off from the 12V side. For up to ~150W you can just pluginto the cigarette lighter.
Great information.
But when would a first responder be in danger
Almost never from electrical shock.
I had this isolation code pop up on my 2017 Bolt a couple weeks ago. I jumped in the car to go to work when it was 11 degrees out and the service light was on. Everything operated normally. When I left work the light was off and hasn't came back on since. I pulled codes and it was displayed as a history code.
Very interesting. Do you recall which DTC was set?
@@WeberAuto P1AFO I think?
@@WeberAuto Some additional information. The car was outside overnight not plugged in and I preconditioned it for 15 minutes.
P1AF0 Drive Motor Control Module Hybrid/EV Battery Voltage System Isolation Lost. The DTC will never set while the vehicle is plugged in to charge or while being driven. This isolation fault may be caused by any component in the high voltage system, it does not know which one.
When parked outside and preconditioning, was the outside temperature cold or hot? Thanks. This could help narrow the fault.
Did you know your power chair also has a isolated ground or some call it a floating ground. Whenever you turn on your chair it checks for shorts between chassis and power supply hot and ground. After five to ten years of use, the carbon dust in the brushed motors may form a high resistance short causing your chair to give a motor fault. I have fixed my chair and customer chairs by removing brushes and blowing compressed air through the commutator. This give a quick fix if you can reach the brushes to do the work.
I did not know that. Thanks for sharing.