HID Ballast and CAN BUS

[MH3.0R]

Calling all the electrical engineers!

The Liberty models from MY04 onwards implemented a Controller Area Network (CAN) BUS for high speed serial communication between the several computers in the vehicle. In other computer domains I have seen spurious noise on power supply systems cause intermittent havoc in computer systems, like random resets and lockups etc.

As I understand the HID Ballast technology, they use a form of high frequency switching to generate the higher voltages required to ignite the Xenon gas in the HID lamps and then drops back to a lower voltage to sustain the arc. The sustaining voltage is still somewhat higher than the 12-13.8 volts available from the basic vehicle electrical system. On that basis, the ballast must also act as a dc-dc converter under normal load conditions. Therefore a constant source of noise generation.

So, we have the potential for an inherently noisy device being inserted into our vehicles which may play have with any one of the intricate computer systems, specifically if the HF noise is carried on the 12 Volt supply.

Am I justified in saying, Buyer Beware!

Higher priced HID Kits that I have observed from Europe, USA, Japan and South Korea, tend to have the high quality filtering embedded in the design and manufacture due to the wide adoption by the automotive industry of the CAN BUS electrical system. They often identify CAN BUS compliance or recommend or supply addtional inline filtering between the Ballast and the bulb.

Now, I am not saying that all cheap manufactured HID Kits or Ballasts will not work for your vehicle. You may be lucky enough to buy a relatively quiet ballast cheaply and you may not experience any problems for the life of your vehicle. Good luck to you, and your bargain basement HID kit.

Spurious noise is a very difficult fault to isolate and if you do experience any strange issues with the electrical system, or if you do hear any additional noise through the stereo systems when the lights are on, please consider the health of some of the most expensive parts of your vehicle may be at risk. The Body Control Unit and the ECU, not to mention all the other computers throughout the car for VDC, EBD, Airbags, etc.

For me the choice will be simple. Identify a high quality ballast which is certified as CAN bus compliant and live comfortably in the knowledge that your vehicle computer systems life is not being shortened. If you are not sure about the compliance, ask for the specs. If they cannot provide you with the specs, I will be walking away with my dollars.

Seeking as much comment from as many sources as possible on this topic. I am by no means an expert or electrical engineer, and willing to eat humble pie in the face of a sound logical and solid electical engieering response. It would be fantastic if we could get Philips to answer this topic!

Kind Regards,

Mark.

[tangcla]

Mark, I was just thinking about this topic again the other day.
Firstly, I don't think the headlight harness on the Liberty has any feedback back into the system like the European cars, which I could see the perils of a cheaper kit.
Also, even if it was, using a relay would solve the problems. You'd only be using your headlight harness as the relay trigger, and you feed all your (dirty? ) power direct from the battery.

[MH3.0R]

Clarence,

Maybe you could have a read of this link to facilitate your understanding of the different HID Kits and ballasts.

http://legacygt.com/forums/showthread.php?t=99296

Kind Regards,

Mark.

[tangcla]

Clarence,

Maybe you could have a read of this link to facilitate your understanding of the different HID Kits and ballasts.

http://legacygt.com/forums/showthread.php?t=99296

Kind Regards,

Mark.

I;ve read it. I don't believe power consumption is a true determinant of reliability. Slimmer ballasts are not liked for that reason, because there is no room for a larger heatsink.

Current over-draw is limited by a fuse in your fusebox so that it does not damage your wiring or any control modules.

I quote from the thread:
No offense but the quality of a ballast does not depend only on the nationality of the parts put into it. I design high volume electronic goods for a living and can assure you that a botched design can contain parts of any nationality. If the kits I tested didn't belong to people using them on their cars, I would have done a destructive tear down and reverse engineering analysis on each.

Of course, your mileage may vary. I, along with a lot of other people, have had no problems with 'cheapo' HID kits. However, there will be one or two freak incidents which will no doubt be circulated on forums, and exaggerate problems - I remember reading a thread where someone was changing the interior dome lights to LED, and (out of coincidence??) the body control module was fried. Put two and two together, and changing LEDs = frying body control module.

[MH3.0R]

Clarence,

Current a basic electronic equation is Power Out + Heat Dissipation = Power In. The heat dissipation is used to determine efficiency. Highr nominal operating temerature contribute to lower component life.

On another front, I agree totally with the thread that you quoted. Poor design is the key as is poor quality control and quality assurance during the manufacyuring process. In some parts of the world, the manufacturing is largely human based and contributes to wider variance in quality of the end product.

And further still, one of my main concerns is in relation to the switching noise and high voltage transients that are evident in some tests of lower priced ballasts when compared to some premium versions.

So, for me, my personal preference is to err on the side of caution and ensure that after market products that I fit to my vehicle will not present new problems. It is my personal preference. I will be looking for CAN bus compliant products for the electrical mods.

Kind Regards,

Mark.

[MH3.0R]

Guys,

On further research I have also found a source that may confirm my opinion at:

http://www.cvel.clemson.edu/Presentatio ... tation.pdf

If you have an electrical engineering background, you may also appreciate this:

http://cnfrs.institut-telecom.fr/pages/ ... s/AEp2.pdf

I found these two docs while simply Googleing for CAN Bus susceptibility. The CAN Bus is sensitive to spurious noise from high voltage switching circuits and these are what ballasts are.

With so many systems in our vehicles dependent on the CAN Bus system, we need to ensure the quality of filtering is suitably high and compatible with our "pride and joy".

So what this means for me, I confirm that I will only be using CAN Bus compliant HID ballasts in my MY05 Liberty, regardless of where they are manufactured. At this point, the price associated with that compliance is somewhat higher than one usually sees on eBay.

Kind Regards,

Mark.

[tangcla]

Which kits are CANBUS compliant?

I'm happy to admit I stand corrected, however I'm still yet to see examples of HID kits frying something

[Arith]

CAN Bus compliant? This is the first I've heard of such issues. I know of several MY04 - MY07 that ran low to moderately price HID conversation kits without an issues for years. Thanks for the info though!

[MH3.0R]

Which kits are CANBUS compliant?

I'm happy to admit I stand corrected, however I'm still yet to see examples of HID kits frying something

Clarence,

I have only heard on one, on the US version of the BB, Legacy GT. I do not recall the details. In any case, I will post a similar thread there to see if I can extract some qualified electrical engineering response.

The main point about spurious electrical noise is not that cheaper kits cause damage, it is that most of the time the impacts go unnoticed or are infrequent and intermittent. Hence the EMC and EMI/RFI compliance requirements. As agreed with you ealier, some cheaper kits operate well and are obviously designed well, just that some are not and most complaints are about these ones.

With so many computer based systems in our vehicles today (including safety critical ones like airbag inflation, central locking opening the car doors after impact, etc), we need to insist on suppliers that the aftermarket products need to be compliant with the current standards.

I would really love to hear from Subaru on this, at least informally.

Kind Regards,

Mark.

[tangcla]

I would really love to hear from Subaru on this, at least informally.

"As this is not under the original manufacturing specifications of the vehicle, we are unable to provide a response."

[CJ1177]

I would really love to hear from Subaru on this, at least informally.

"As it is not standard Fitment, it is there fore non-compliant"

[Ric]

I'm an electrical engineer with over twenty years experience, so I'll bite.
CAN bus uses differential signalling, so is inherently resistant to any external interference.
Car manufacturers pay a lot more attention to making their systems robust than PC manufacturers do.
If anyone in Melbourne suspects their HIDs may be outputting lots of noise, I have test equipment at work which could have a look at it.

[Mano™]

I'm an electrical engineer with over twenty years experience, so I'll bite.
CAN bus uses differential signalling, so is inherently resistant to any external interference.
Car manufacturers pay a lot more attention to making their systems robust than PC manufacturers do.
If anyone in Melbourne suspects their HIDs may be outputting lots of noise, I have test equipment at work which could have a look at it.

Watch out people, the big boss is in force

[MH3.0R]

Ric,

Did you read all of the material in the previously quoted links? Differential signalling is still subjected to differential mode noise susceptibility, yes? And this was quoted as one of the potential sources of interference. I am a little perplexed by your statement, but as I have stated earlier, I am not a qualified electrical engineer.

Be interested to further discuss.

Kind Regards,

Mark.

[Ric]

Ric,

Did you read all of the material in the previously quoted links?

I hadn't before I replied )it wouldn't download last night), but I have now.

Differential signalling is still subjected to differential mode noise susceptibility, yes?

Everything is susceptible to everything else, but the point is "at what level?".
The path your car takes down a road is affected by the cross wind, but does a light cross wind of 5km/h make enough difference to matter...

And this was quoted as one of the potential sources of interference. I am a little perplexed by your statement, but as I have stated earlier, I am not a qualified electrical engineer.

That whole detailed article shows how much detail Bosch have gone into to see how resistant their systems are to external interference.
Also note, they are chiefly worried about Radio frequency signals, from 1MHz to 200 MHz. The power supply inside an HID is likely to be at 200kHz or lower. Your car's ignition is likely to be generating much more noise than the HID, and the CAN network is designed to be immune to it.