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Thread: Cheap ballasts output in DC instead of AC?

  1. #1
    Senior Member HID MASTER StupidPig's Avatar
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    Cheap ballasts output in DC instead of AC?

    OK, we all know that the bulb life will be shorten if you powering the HID bulb with the ballasts outputting DC instead AC. Yesterday, XenonDepot representative in 8th Civic forum, posted an information about their ballasts are outputting in AC, but other vendor's cheap ballasts (Apexcone/DDM and Xentec are mentioned) are outputting in DC. I'm not sure how true his statement is, since I'm not having the technical capability to verify this by myself, so that I could like to see what you guys think about this.

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    It should be easy to verify, if it's dc wouldn't only 1 of the electrodes in the salt mixture bubble wear faster, instead of both wearing equal when using ac? Has anyone run one of these suspect ballast for a long time? If so maybe post a closeup of the bulb.

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    Quote Originally Posted by Crv Jimmy
    It should be easy to verify, if it's dc wouldn't only 1 of the electrodes in the salt mixture bubble wear faster, instead of both wearing equal when using ac? Has anyone run one of these suspect ballast for a long time? If so maybe post a closeup of the bulb.
    Yes, that would be true. 1 electrode would wear more quickly if DC. AC would wear equal at both. A True DC bulb (they do exist but rare) would have a slightly thicker electrode on 1 side.

    If true that some are DC, this would save quite a bit of manufacturing cost in the components inside. Improve profit margin at the expense of bulb life being less than 1/2 compared to bulbs being fed AC as they were designed for. It might take a couple to a few hundred hours of bulb use to evidence this DC vs AC to the bulb issue.
    D1S is where its at, Radically better EMI and RFI performance. Only the new Japanese cars still use D2 bulbs, the others have all changed to D1S.

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    Senior Member HID MASTER StupidPig's Avatar
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    Anyone running those cheap ballasts (e.g. DDM) for long time and able to take a picture of the bulb to verify this? I been switching to new retro too often, and I doubt my bulb will shown significant difference between the two electrodes even the ballasts are in really in DC like Xenondepot said.

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    Senior Member HID Recruit av6g6's Avatar
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    This could be true, but I am running ddm ballasts and have been running the same bulbs since december. I can look at them and see. If it turns out to not be true I will surely never ever buy from xenondepot. I hate when companies make direct accusations with nothing to back it up just to push their products. Integrity is still important.

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    There seem to be some DC ballast around for cheap aftermarket ones, some are now stating"high efficiency DC ballast" as if good sales talk...whatever..

    I saw it on rakuten(jap online market..),so there must be some parts supply line going to some other cheap brand I guess...



    It won't be issue if entire HID lamp system package made for proper DC drive type. In fact, DC drive will produce less noise and compact circuit size are +aspect of DC ballasts.

    But I can't imagine those cheap ballast maker consider proper design of specific DC bulb. Setting up line for DC bulb production for those DC ballast is totally off direction when it comes to AFTERMARKET use.

    Those probably just want to cut production cost at inverter, control circuit.
    If DC ballast is prefered, OEM maker all shift to DC ballast and DC bulbs.


    It is only theory talking here since I don't have DC ballast in my hand and long term bulb life test though.

    Long story short, HID bulb(AC) is not made for DC drive
    simply,,not proper. Period.


    I can imagine conversation like,,
    How can we cut more production cost,,
    How about omitting inverter( proper high quality fullbridge, control IC, programing can be costly),
    It will light up AC bulb, less noise, yay, let's omit noise control circuit,
    it will not show immediate issue on bulb probably, if it does, we can sell more bulbs, who will notice difference..etc..



    Not sure which brand is using DC drive, but I personally think that is unresponsible for vehicle's safety fucntion part=light

    Even if they make DC bulb for their DC ballast, all OEM optic system designed based on AC drive ark charactor(color positioning, ark curve..etc..)
    It won't work with proper conversion anyway( in very micro level talking)

    And if DC is preffered, all OEM will shift to DC system.



    Anyway, so many aftermarket parts flood around online market,,it is very important to have interest in "why they are cheap"

    Like my other past study shows,,cheap aftermarket product(bulb) didn't have proper gas pressure, contents ballace, no consideration on safty(UV)..etc.. same standard on ballast I guess.

  7. #7
    Quote Originally Posted by upashi
    Even if they make DC bulb for their DC ballast, all OEM optic system designed based on AC drive ark charactor(color positioning, ark curve..etc..)
    It won't work with proper conversion anyway( in very micro level talking)
    This is too true. Besides, change the way you power it, you change the arc characteristics. Over time, the arc will lengthen one way but not the other, and you rlight distribution will start getting sloppy.

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    Quote Originally Posted by bshanahan14rulz
    Quote Originally Posted by upashi
    Even if they make DC bulb for their DC ballast, all OEM optic system designed based on AC drive ark charactor(color positioning, ark curve..etc..)
    It won't work with proper conversion anyway( in very micro level talking)
    This is too true. Besides, change the way you power it, you change the arc characteristics. Over time, the arc will lengthen one way but not the other, and you rlight distribution will start getting sloppy.
    Yes all these comments have been correct in this thread about DC. Only the earliest automotive OEM HID systems (~ 1996 ) were DC to the bulb. It is not preffered for DC output except for High speed cameras with thousands of frames per second. High speed camera work much preferes or requires DC output because most AC output ballasts are feeding about 400 Hz to the bulb.
    D1S is where its at, Radically better EMI and RFI performance. Only the new Japanese cars still use D2 bulbs, the others have all changed to D1S.

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    Senior Member HID Recruit av6g6's Avatar
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    Well I actually e-mailed ddm about the issue and I got an e-mail response pretty quickly. If what he says is correct and he didn't make a mistake, then he's saying that ddm ballasts are D/C and that he's never heard of a non-DC (AC) ballast used in the manner I am using it. I guess on a car.

    Not quite sure who you got your info from, but I've never heard of any Non-DC HID ballasts used in the manner we supply them for.
    -Girard (SD)

    Ticket Details
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    Ticket ID: CAQ-694040
    Department: Tech Support
    Priority: High
    Status: Closed

  10. #10
    Senior Member HID MASTER StupidPig's Avatar
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    He may be confusing about the input and output.... For sure, the input to the ballasts is 12V DC for car use. Well, I don't think DDM customer service guy know a lot of HID stuff though.

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