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Thread: Parallel Adapter Question

  1. #1
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    Default Parallel Adapter Question

    Hi all,

    So I'm making a new parallel adapter and I am thinking maybe I got this wrong. I soldered the two wires together like this:

    20170922_155629.jpg

    Do you guys think the draw from each battery would be uneven given one wire will be straight into the bullet and the other attached from the side? or will it pull equal current? that connection is filled solid with solder. let me know

    Thanks!

  2. #2
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    This is going to be battery to two ESC's? Or this is two batteries to one ESC?

  3. #3
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    Two batteries into one esc, finished looks like this:
    20170922_202455.jpg

    Thanks,

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    Quote Originally Posted by R2315 View Post
    Hi all,

    So I'm making a new parallel adapter and I am thinking maybe I got this wrong. I soldered the two wires together like this:

    20170922_155629.jpg

    Do you guys think the draw from each battery would be uneven given one wire will be straight into the bullet and the other attached from the side? or will it pull equal current? that connection is filled solid with solder. let me know

    Thanks!
    Each connection should be a mirror image to the other. Yes, the current will flow slightly different in that type of branch. These are freaking hard cables to build guys!

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    Thanks Craig, if I did it this way do you guys think it would make any difference:
    s-l300.jpg

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    The one side that is soldered to the existing 'could' flow less juice but I think if you wire wrap before solder it should be ok. I always watch my parallel setups anyway. I just try to pay attention to which battery got pulled down more(if any).

    I was taught to braid wires together to join but with 265 strand wire it's hard

  7. #7
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    Okay thanks, I did wire wrap it once so I'm going to leave it for now and keep an eye on things, worst case I'll cut the esc side off and redo it the other way, but ya it's tedious so hopefully this works out.
    Last edited by R2315; 09-22-2017 at 09:58 PM.

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    Quote Originally Posted by R2315 View Post
    Okay thanks, I did wire wrap it once so I'm going to leave it for now and keep an eye on things, worst case I'll cut the esc side of and redo it the other way, but ya it's tedious so hopefully this works out.
    This is one of the things left to do on HPR. I want to sport run 6-7s4p. Parallel connection location and configuration will be crucial.

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    Quote Originally Posted by R2315 View Post
    Thanks Craig, if I did it this way do you guys think it would make any difference:
    s-l300.jpg
    Parallel branch connections should follow strict current sharing rules. The parallel side should be two wire sizes below the main branch. For example, 2 #10's on the right, soldered side by side, both tinned completely before joining. Use flux! Hold that connection in a vise when cooled, re-apply flux the the end, then solder a pre-tinned #8 wire in exactly the middle of the joint of the 2 #10's, in a end-to-end connection. Flux should be used each time the connection is allowed to cool. Need a solder chisel tip of at least 3/16 -1/4" wide, using at least 60-80 watts. Tinning is the key, must be consistent and similar each time. Cold solder joints will always cause issues.

  10. #10
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    Quote Originally Posted by R2315 View Post
    Thanks Craig, if I did it this way do you guys think it would make any difference:
    s-l300.jpg
    Parallel branch connections should follow strict current sharing rules. The parallel side should be two wire sizes below the main branch. For example, 2 #10's on the right, soldered side by side, both tinned completely before joining. Use flux! Hold that connection in a vise when cooled, re-apply flux the the end, then solder a pre-tinned #8 wire in exactly the middle of the joint of the 2 #10's, in a end-to-end connection. Flux should be used each time the connection is allowed to cool. Need a solder chisel tip of at least 3/16 -1/4" wide, using at least 60-80 watts. Tinning is the key, must be consistent and similar each time. Cold solder joints will always cause issues.

  11. #11
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    Quote Originally Posted by R2315 View Post
    Thanks Craig, if I did it this way do you guys think it would make any difference:
    s-l300.jpg
    Parallel branch connections should follow strict current sharing rules. The parallel side should be two wire sizes below the main branch. For example, 2 #10's on the right, soldered side by side, both tinned completely before joining. Use flux! Hold that connection in a vise when cooled, re-apply flux to the end, then solder a pre-tinned #8 wire in exactly the middle of the joint of the 2 #10's, in a end-to-end connection. Flux should be used each time the connection is allowed to cool. Need a solder chisel tip of at least 3/16 -1/4" wide, using at least 60-80 watts. Tinning is the key, must be consistent and similar each time. Cold solder joints will always cause issues. Sorry guys, no fans while you're soldering!

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    Quote Originally Posted by R2315 View Post
    Okay thanks, I did wire wrap it once so I'm going to leave it for now and keep an eye on things, worst case I'll cut the esc side of and redo it the other way, but ya it's tedious so hopefully this works out.
    This is one of the things left to do on HPR. I want to sport run 6-7s4p. Parallel connection location and configuration will be crucial.

    It is a bit to figure out

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    You bet it is Shawn! It's a big job!

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    Now I know where these redundant posts are coming from, the site freezes up!

  15. #15
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    Quote Originally Posted by CraigP View Post
    Parallel branch connections should follow strict current sharing rules. The parallel side should be two wire sizes below the main branch. For example, 2 #10's on the right, soldered side by side, both tinned completely before joining. Use flux! Hold that connection in a vise when cooled, re-apply flux to the end, then solder a pre-tinned #8 wire in exactly the middle of the joint of the 2 #10's, in a end-to-end connection. Flux should be used each time the connection is allowed to cool. Need a solder chisel tip of at least 3/16 -1/4" wide, using at least 60-80 watts. Tinning is the key, must be consistent and similar each time. Cold solder joints will always cause issues. Sorry guys, no fans while you're soldering!
    This actually seems a simple task, at least for the experienced. Silver content solder beneficial as always?

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    Quote Originally Posted by CraigP View Post
    Now I know where these redundant posts are coming from, the site freezes up!
    You to eh? Haha

  17. #17
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    Alright, I gave it another go. Although I don't have #8 on the mains it still should work a little better.

    20170923_194837.jpg20170923_202444.jpg

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    That's nice! The #8 would be for max amp transfer. If your racing, then you want all the amps you can get to reach the ESC with the least loss. I use #10 to #10 branches when I want a squeeze point, to force even current sharing. But the branch outlet wire is much shorter the the two infeed wires.

  19. #19
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    Here's some wire specs that may be helpful:

    #10, high stand count silicone jacketed wire (Castle Creations) has a resistance of 0.0010 ohms/ft at 50 degrees C, or about 122 degrees F. If your wire is any hotter than that then you need to address that. This is also increasing the ampacity by 15%, due to the high strand count, which offsets the skin effect.

    The wire is 0.0000835 ohms/in, which is the unit our boats should be calculated at.

    #8, high stand count silicone jacketed wire (Castle Creations) has a resistance of 0.000597 ohms/ft at 50 degrees C, or about 122 degrees F.

    The wire is 0.0000497 ohms/in, which is the unit our boats should be calculated at.

    As you can see, the #8 is about half the resistance of the #10. So how do you use this? Example using R2315's wire harness:

    The resistance of the parallel branches are 3*.0000835=0.00025ohms. The two are in parallel, so the two wires have a combined resistance of 0.00025/2=.0.000125 ohms. The single wire is 0.00025 ohms and the whole harness is 0.00025+0.000125=0.000375, or 0.375milliohms. You have to two runs, plus and minus, so the
    total is 2*0.375milliohm=0.75milliohm.

    This should run nice and cool. Assuming an overall length of 6".

    Note: edited
    Last edited by CraigP; 09-24-2017 at 12:08 PM.

  20. #20
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    Thanks Craig! very helpful indeed, it's always good to see and have the math to back things up. turns out it's pretty much exactly 6" from bullet to bullet. I'm not doing any racing with this, more to help ensure even battery draw.

    Thanks again!

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