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Can a smart EE improve Modern Ferrari reliability for all Ferraris?

Discussion in 'Technical Q&A' started by fatbillybob, Apr 30, 2020.

  1. fatbillybob

    fatbillybob F1 World Champ
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    While researching racecar kill switches a came across the concept of TVS (transient voltage suppression) diodes used in modern cars and modern alternators. I come from old school zener diodes. I read the article below and it talks about placing TVS diodes in the CAN line. We know that you should never jump a ferrari battery. We know Ferrairs blow up aribags and can get all kinds of MIL's from voltage issues especially powering up presumably causing voltage spikes. There are many things that cause voltage spikes and perhaps Ferrai electrical systems lack robustness because they lack TVS. Why can't we have the robustness of a normal car? My Ram 2500 diesel could get stuck by lightening and be totally OK with it.

    Could a smart FChat Electrical engineer come up with a prescription to increase the robustness of modern CAN line Ferraris with simple TVS diodes?


    https://www.designnews.com/content/automotive-circuit-protection-using-high-reliability-tvs-diodes/17152594333139
     
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  3. OffsetImage

    OffsetImage Rookie

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    I have been working on Ferraris at the dealer level for over 3 years (probably jump started 100+ cars of all years and models) and have never had an issue jump starting a battery unless someone has jumped the car wrong/ reversed the cables. What kind of problems are you trying to avoid by installing these?
     
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  4. DoubleD33

    DoubleD33 Formula 3
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    There is a thread in the 458 section on electrical. I asked somewhat the same question.... is there one thing that is missing from the computers?

    the gist is Lithium batteries are more fitting to this style electrical system....also the coding of how they talk may not be the best...

    But I am in agreement... what makes the Dodge/Ford/GM computer system work with out a lithium battery.
     
  5. RedNeck

    RedNeck F1 Veteran
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    Let us know what dealer you work for so we can avoid them.
     
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  6. fatbillybob

    fatbillybob F1 World Champ
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    It is possible that newer Ferraris have TVS built into them since Ferrari does not actually make its own electronics. At the Dealer for last 3 years could also mean you working on new Ferraris. I have not worked on anything newer than a 430. These boards are full of senarios of dead batteries and Ferraris jumped resulting in things like airbag lights and other MIL's resulting in things like needing to replace airbag modules. The conventional wisdom has been to not jumpstart Ferraris. Early CAN BUS cars perhaps pre-2010 I suspect lack TVS that was already being seen in daily driver Fords and chevys for the masses. The big manufacturers could take away your transmission dipstick but they could not prevent a battery failure so there had to be consumer access.

    It would be great to find out that for a simple TVS diode pack we could enhance the robustness of our systems without negative side-effects. The history of Ferrari over 40 years of fixing them is there are many flaws.
     
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  8. epb0

    epb0 Rookie

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    Do you have technical explanations, or just repeat urban legend ?
     
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  9. RedNeck

    RedNeck F1 Veteran
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    Both.
     
  10. epb0

    epb0 Rookie

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    You can jump car's battery to external battery or another car with wire, there is any danger.
    The car don't know if voltage come from own battery or from external battery ;-)
    The voltage is same (arround 12,5V with external battery, or 14,4V max with another car who running) than own battery.
    All components of car resist minus 16V.

    May be you should turn off/on cut battery for have a clean restart for some ECU, but root cause is previous under voltage, not right voltage recovery.
     
  11. RedNeck

    RedNeck F1 Veteran
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    Thanks although I've been in electronics for years, and know a 360 owner first hand that has suffered the after effects of a jump start on their car. It's also well known throughout this community and other Ferrari communities. You have 12 posts here. Maybe spend a bit more time on the forums before getting on the soap box.
     
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  13. fatbillybob

    fatbillybob F1 World Champ
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    I have no idea what is trying to be said here but if the bottom line is 12volts is 12volts and the car does not care where it is coming from that's not the point and irrelevant. The problems are believed to be voltage spikes. We know this is a past issue because we used to have alternator failures from spike disconnections before TVS diodes. And someone must be clued into this because as cars get more computer intensive they have greater clean power needs and these TVS diodes are in new systems.
     
  14. epb0

    epb0 Rookie

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    The number of post has no importance, this is not the subject.
    I'm curious to read a technical explanation.
     
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  15. epb0

    epb0 Rookie

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    #12 epb0, May 2, 2020
    Last edited: May 2, 2020
    Of course you should never disconnect a battery when the engine is running, that's not the point.
    But connecting a battery to another battery is never a problem.

    After everyone does as he pleases ! I'm like our friend OffsetImage, I started a lot of cars as well, and continue to do so. And as I work in engineering with a manufacturer, even prototypes are affected ;-)
     
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  16. RedNeck

    RedNeck F1 Veteran
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    It does somewhat. If you spent a little more time on the forums you would know that the search function is worth its weight in gold. The subject has been covered many, many times.
     
  17. mxstav@comcast.net

    Nov 24, 2005
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    I play a smart EE at work (I have been fooling my bosses for years!). I have been designing electronics for automobiles from the mid '80's as a supplier to Ford, Ford Benetton/Cosworth, GM, Mercury Marine, Allison Transmission to name some. You raise a number of questions, some interrelated, some not. This may be long winded, but it is a broad topic that I will try to condense.

    Automobiles face many electrical transients from various transient sources. These include:
    1) ESD (electrostatic discharge) from "charged" humans touching wiring, as well as "charged" machines getting plugged into a harness (think of the OBD2 plug or a USB port).
    2) Load dump, which is caused by battery being disconnected from a running vehicle while the battery is being charged.
    3) Inductive transients, caused by solenoids being switched on and off.
    4) Ignition transients, caused by the high voltage spark ignition system coupling to a wiring harness.
    5) Bulk current injection, high frequency noise inductively coupled into the wiring harness.
    6) AC battery line noise, AC noise injected on top of the battery voltage simulating a defective alternator
    7) Radiated susceptibility, RF noise directed at the wiring harness and unit under test simulating a transmitter (or similar RF source) radiating energy nearby. (It could be a local broadcasting transmitter, a police radio, a cellphone...)
    8) Double Battery Jump, simulates jumping a dead battery with a 27V source

    Anything being powered by the vehicle battery is susceptible to these transients. Hence, automakers require extensive testing of electronic devices to prevent failures from these transients. Several standards exist that specify to what level devices need to be tested. These include ISO7637, ISO16750, GMW3097, GMW3172 among others. The GMW standards originate from General Motors and are widely adopted in the industry. Many automakers (Ford, Honda, Toyota, Volvo, etc) also have their own, proprietary standards that they want any suppliers to meet. These tests require months to complete, and is there is a failure, the failure mode must be determined, a corrective action implemented and the testing restarted. As the guy trying to get his design to pass, I can say it's a huge pain in the ass! However (sigh), it is necessary.

    To address your specific question about CAN and TVS's, typically they are included in all CAN bus circuits. This is because the CAN transceiver (also known as the PHY or physical layer) will typically blow up from ESD without one. TVS's differ from zener diodes in their speed and their load capacitance. In general, a device meant to handle a lot of power has a lot of capacitance. This kills high speed signals like a CAN bus. Old-school CAN (90's - early 2000's) rate was only 125k bits per second. This increased to 1M bits per second in the 2010's. Now, CAN-FD (flexible data rate) is used at up to 5M bit per second. The higher the speed, the less capacitance they can tolerate. The TVS designed for a 125k bps bus may degrade a 5M bps bus. A zener diode will typically have too much capacitance to be used on a CAN bus or any high speed signaling bus. Also, CAN is a 5V bus (sometimes 3.3V). It is not directly powered by the vehicle battery (aka "12V"). Typically, a battery filtering/transient protection circuit is used ahead of the regulator that drops battery voltage to the 5V or 3.3V used by the CAN and CPU. Thus, power line transients are not likely to effect the CAN bus where a TVS (on the CAN lines) would protect it. A TVS on the CAN lines is there to protect against ESD.

    Usually, passenger car electronics is designed to withstand 36V on the battery line without damage. The electronics may not function at 36V, but it will not be damaged. The vehicle manufacturer will specify the upper end of battery voltage for vehicle operation. I think most vehicles will still operate at Vbatt = 27V and will shut off somewhere between 27 - 36V. Some will require even higher upper limits for operation.

    That being said, I have no idea where the notion that it is dangerous to jump start a Ferrari comes from. I am not a big fan of Bosch and Marelli electronics. I do not think they are as robust as domestic electronics (personal bias). However, I am certain they conform to the same general design guidelines as all automotive electronics. Never disconnect the battery from a running vehicle. This is what causes a load dump. Even doing that, however, should not damage the OEM vehicle electronics. It is all designed to withstand a load dump. (Caveat being that some vehicles have central load dump protection. In this case it is possible that the electronics in such a vehicle may not be protected from a load dump. However, the central load dump protection should still suppress the transient.)

    In the last 10 years or so, the Automotive Electronics Council (AEC) started to specify how automotive semiconductors should be tested for use in vehicles. This greatly raised the bar for the quality level in automotive electronics. Today, all leading automotive electronic manufacturers require the use of AEC-Q parts. Here is a link that describes what it is about:

    https://media.monolithicpower.com/mps_cms_document/w/e/Webinar_-_Fundamentals_of_AEC-Q100-6Nov2018.pdf

    Here is a good instruction video on automotive electrical transients:
    https://training.ti.com/iso7637-test-pulses
     
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  18. fatbillybob

    fatbillybob F1 World Champ
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    Thanks for the through explanation! I understand what you are saying and see no reason for issues with jumping dead Ferraris. However, I have worked on anything pre-2010 for about 40 years. There must be a dozen cases right on fchat of "jumped my Ferrari now I have an airbag light!" There is a relationship of jumped Ferraris with increased numbers of MIL's and other electrical malfunctions that are not exactly as easy as using an obd2 code reader and reseting the MIL. I'll jump my BMW, ram truck or anything else but I never jump any Ferrari...I'll leave it at that.

    Do you think that modern Alternators can survive load dumps from battery isolation switches we use in racecars converted from streetcars? In the old days we needed to protect the alternator by simultaneous severing at the field wire. Now alternators don't have that wire to attack. They must be on the inside. But if they can survive the very occasional load dump I won't worry about it. It is OK if life is shortened. Everything on a race car is temporary.
     
  19. JCR

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    Those two manufacturers stuck with the terrible Bosch "torpedo" fuse long after the rest of the world had gone to blade fuses.
     
  20. tazandjan

    tazandjan Three Time F1 World Champ
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    FBB is correct. Too many documented cases of jumping 80s through 2009s Ferraris and causing problems for there not to be something missing in there or an extra path for excess current.
     
  21. fatbillybob

    fatbillybob F1 World Champ
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    PM'ed to ask how's the dry fly action in Tn. but I can't.
     
  22. tazandjan

    tazandjan Three Time F1 World Champ
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    FBB- Have not made it yet. Right now the spring creeks in southern Kentucky look like they may be more fun than Tennessee tailwaters that are trying to drown you half the time.
     
  23. fatbillybob

    fatbillybob F1 World Champ
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    Well post some pics in the future. Love to see good looking water. I want to fish really badly. California season shut down at least 1 more month. Montana has a 14day outsider self-quarantine in place...they are not getting my business in 2020. Driving seems like better option than flying at this time so maybe try Lee's Ferry because it is driveable.
     
  24. hessank

    hessank Formula 3
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    Not sure where I c&p this from but its in my notes and FBB is correct, lots of documented cases.

    Image Unavailable, Please Login
     
  25. mxstav@comcast.net

    Nov 24, 2005
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    I am not sure what you mean about "an survive load dumps". It is not the alternator that fails - it is the alternator that is the source of the voltage pulse. The issue with a load dump is the field winding is no longer being controlled. Under high RPM, high charging currents, the field winding contains a lot of energy E = 1/2 L* I^2. The energy is proportional to the square of the current. When the load (battery) is suddenly removed, the energy, stored in an electric field, needs to go somewhere. The energy is converted into a high voltage (V = L di/dt). The voltage proportional to the rate of change of current and inductance of the field winding. This is what fries the electronics.

    If you are concerned about the cutoff switch causing a load dump, you could put a load dump suppressor on the back of the alternator. This will kill the load dump at the source. If you are interested in one, let me know the dimensions where it needs to mount and I can see if I can put one together for you.
     
  26. mxstav@comcast.net

    Nov 24, 2005
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    In the nearly 40 years of being in the automotive electronics industry, I have never seen a field return for a load dump failure. I have seen plenty of failures in DV/PV testing, but nothing from the field. I believe the jump start issue is perhaps a low battery voltage issue that was not addressed by the module designer.
    Once the battery drops below a certain voltage, the electronics can no longer function. For most vehicles this is around 5V of battery. At this point the CPU's in the various electronics modules should be held in reset. This is the state where the CPU is prevented from operating. If the CPU is allowed to operate at a voltage level that is below its recommended minimum operating voltage, all bets are off. The (correct) operation of the CPU is not guaranteed - it could perform random operations like starting to write bogus data to flash. When proper operating voltage is restored, the unit may fail its power-up diagnostic and default to a "safe" state. The "safe" state is determined by the manufacturer and could be just sitting there indicating an error.

    Battery drop outs is one of the tests conducted during ISO and GMW testing. The battery voltage is deliberately cut-out for various pulse times to ensure that nothing bad happens to the unit under test. There is also another test where the battery voltage is slowly ramped down and then up to ensure correct operation during low voltage conditions.
     
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