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  1. #1
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    LVC Harness - LVC made "easy"

    I've gotten a couple of PM's on the LVC harness idea I had in this thread http://monster.traxxas.com/showthread.php?t=425846

    I wanted to start a new thread to clarify what it is, why you might want it, and how it fits on. It really simplified LVC's for me.

    Disclaimer: I'm definitely very new to the RC scene, and far, far from really knowing what I'm doing, but the harness idea seemed obvious to me. For advanced LVC or Lipo advice, read the FAQ, or ask someone who knows more then me! Neil really helped me figure out Lipo's, can't thank him enough!

    First, what I see as the advantages:
    • You don't have to cut the leads on your EVX2.
    • It's quick to remove if you want / need to (different batteries, even a different LVC for bigger Lipos, etc)
    • If you goof your soldering, you can try again and not worry about ruining anything.


    So, that being said, here's the harness.



    Fairly straightforward for a 2cell Lipo. I used the Novak Smart Stop. Just make a Traxxas "extension" with a male connector on one end, the female on the other, and on one of the ends (doesn't matter which) add the LVC positive and negative leads in to the solder joint. They easily fit inside the connector for me, so no need for shrink wrap.

    And here it is on the car.




    In this image:

    1 is the harness
    2 is the BEC side connection - find this by plugging in both batteries, turn the car on, and unplug one battery. If the car immediately goes off, you unplugged the BEC side. If the car stays on, the cable still connected is the BEC side. You'll also notice when you go to charge your batteries the one on that side has a lower voltage left after running.
    3 is the cable from the lvc to the receiver box
    4 is the cable from the EVX2 to the LVC (unplugged out of the receiver box and replaced by '3')

    A side note, you could have a 4 cell LVC by doing basically the same thing, but using two extensions, with one lead of the LVC to each extension. The 2 cell version on the BEC side seemed safer to me, though.

    As for how it works? Perfect! I've run it easily two dozen times or more, and had no problems at all!

    I hope this clarifies LVCs for some, it's worth it to go lipo's! Don't let the unknown of an LVC get in your way.

    - Tony

  2. #2
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    Better yet get a 4s lipo LVC, run your batteries in series on 1 plug jump the other plug and snag a BEC to power your Rx. Never have any worries or issues.

    PS make sure you disable the stock BEC (pull the center wire out of the Rx plug)
    Neu 1515 2.5d & 1.5d, 2x MMM -sIck IaM

  3. #3
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    You need the bec wire to run it as he has installed a LVC not a UBEC. The way he has it all hooked up the 2s battery(on the bec side)will reach the lower voltage first, and the other 2s battery will be slightly higher in voltage.No Problems.
    Last edited by 1truckerdan; 08-26-2008 at 08:23 PM.

  4. #4
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    Quote Originally Posted by 1truckerdan
    You need the bec wire to run,he has installed a LVC not a UBEC. The way he has it all hooked up the 2s battery(on the bec side)will reach the lower voltage first, and the other 2s battery will be slightly higher in voltage.No Problems.
    There is a problem w/ that theory.. you are taking for granted the two lipo's run the same mAH until they hit LVC. Best test your lipo's to find out because 99.9% of packs run different mAH and have different IR ratings. The pack will get drained faster on the BEC side of the stock ESC, but if that lipo happens to have 400mAH more guess what happens to the other lipo. YES lipo's can very by that much from the same maker same size in the same batch, EVEN the best lipo's are different so I"m sure it only gets worse with lower quality lipo's.
    Neu 1515 2.5d & 1.5d, 2x MMM -sIck IaM

  5. #5
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    Quote Originally Posted by 1fasterevo
    There is a problem w/ that theory.. you are taking for granted the two lipo's run the same mAH until they hit LVC. Best test your lipo's to find out because 99.9% of packs run different mAH and have different IR ratings. The pack will get drained faster on the BEC side of the stock ESC, but if that lipo happens to have 400mAH more guess what happens to the other lipo. YES lipo's can very by that much from the same maker same size in the same batch, EVEN the best lipo's are different so I"m sure it only gets worse with lower quality lipo's.
    I'd wondered about that, so I used my hyperion duo to cycle my lipos, to make sure one pack didn't drain quicker then the other or hold less mah. My packs were very close to each other, and I just verify them after each run to make sure I'm keeping the pack that's lower on the BEC side.

    - Tony

  6. #6
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    I agree that ALL packs DO differ in mah(even same brands,same mah,same cell count)If you charge both 2s packs seperatly,watch to see which pack takes more mah, then you should keep the pack with less mah(charged)on the bec side, then you should have no problems.Or you could do like I did, I made an adaptor so I can balance charge 2 2s packs in series on one charger.

  7. #7
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    Quote Originally Posted by 1fasterevo
    There is a problem w/ that theory.. you are taking for granted the two lipo's run the same mAH until they hit LVC. Best test your lipo's to find out because 99.9% of packs run different mAH and have different IR ratings. The pack will get drained faster on the BEC side of the stock ESC, but if that lipo happens to have 400mAH more guess what happens to the other lipo. YES lipo's can very by that much from the same maker same size in the same batch, EVEN the best lipo's are different so I"m sure it only gets worse with lower quality lipo's.
    Kraegar, thanks for linking me to this post. Great stuff.

    Considering the post above though, and the fact that to run a 2S LVC you have to be more concerned about balancing before you run, which pack to use, and the capacity of the batteries, etc, would there be any problems if I wired a 4S LVC to the ESC connectors permanently and then use the receiver extension to disconnect/connect the LVC/ESC depending on what type of battery I want to run?

    If I want to run NiMH then I just remove the LVC from the receiver "pigtail" or extension and just hook up the ESC to it as in the stock configuration. The LVC will still be hanging in the car because it is soldered to the battery leads, but it won't be connected anywhere else and it won't manage power to the receiver.

    Leaving the LVC soldered on to the ESC without connecting to the receiver won't create a problem, or should it?

    Thank you!
    Last edited by djbis; 09-12-2008 at 12:45 PM.
    Faster Higher Longer Harder
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  8. #8
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    I don't know if that'd be ok or not. You could make two of the harnesses, one for each side of the LVC (red cable to one, black to the other).

    I don't find it too hard to watch my batteries. I just labeled one A, the other B, and A always goes on the LVC/BEC side.

  9. #9
    RC Turnbuckle Jr.
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    I vote "sticky"
    also rated 5 stars...thank you for this
    be nice.

  10. #10
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    Quote Originally Posted by HoovHartid
    I vote "sticky"
    also rated 5 stars...thank you for this
    So is that an Obama Vote? or McCain?

  11. #11
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    I am looking for a beginner's take on upgrading the E-Revo to LiPo power. Any suggestions on a previous thread that covered the fundamentals?

    I am mostly confused with all the "C" and "S" abbreviations.

    The E-Revo its supposed to make LiPo and Brushless upgrades a snap (as per the manual), but by looking at most upgrades on this board I don't see any "snappy" upgrades. Everything is very involved and requires extra parts and or messy wiring.

    OH, and yes, I am reading over the E-Revo FAQ as we speak.
    Faster Higher Longer Harder
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  12. #12
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    Easiest way is sell the stock esc and get a MM w/ BEC and fan on 4s and slap a bit of tape over the USB port and she is pretty well water resistant.. I wouldn't go diving, but you can thrash through just about anything from my experience. Castle coats those boards making them pretty flexable.
    Neu 1515 2.5d & 1.5d, 2x MMM -sIck IaM

  13. #13
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    Quote Originally Posted by 1fasterevo
    Easiest way is sell the stock esc and get a MM w/ BEC and fan on 4s and slap a bit of tape over the USB port and she is pretty well water resistant.. I wouldn't go diving, but you can thrash through just about anything from my experience. Castle coats those boards making them pretty flexable.
    That's good to hear!
    Everybody seems to like the MM for monster truck applications, eventhough is not advertised for that really (that's what the MMM is for I guess?)

    But yeah, I defenitely want to use my E-REVO in winter. Dealing with the tuning of a nitro engine in harsh temps/environments really takes the fun out of it. This is where Electric should really bring the fun element back for me.
    Faster Higher Longer Harder
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