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Thread: Uneven voltage after running lipos in parallel

  1. #1
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    Default Uneven voltage after running lipos in parallel

    Hi all,

    Recently decided to run my 30" mono on 2 2sp in parallel just to give my some extra run time for the kids. I had previously done it without issue but the last run we had one lipo was down to 30% and the other 4%, I timed the run as usual not sure what could be causing it. The lipos are the same and I balance charge every time. The parallel connector I made from 12awg but the rest of my wiring is 10awg not sure if that might have an effect? Any thoughts? Motor is a 2200kv with a 180a esc and a m440, wires were a little warm but everything else was cool.

    Thanks,
    Ryan
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  2. #2
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    If you are certain that both packs were fully charged, then the low voltage pack or one cell within is probably dying. Time to retire that pack for safety.

    The terms "warm" and "cool" are pretty meaningless. To some folks temps under 110* are "cool" and over 140* are " warm". Others have different ideas. If you don't have a temp gun then you should, it is an important tuning aid and can help prevent permanent damage to you motor, ESC and packs.


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  3. #3
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    Everything is under 110. Packs are less than 2 weeks into use, revo 420 70c 5000mah. What are the chances I got a dud? Maybe I missed it but I'm balancing charging in parallel two packs at a time, I don't think my charger will even start if everything was not connected. Unless I hit single pack instead.... I'll try it again and put a voltage alarm on the pack in question.

    Thanks

  4. #4
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    While charging the two packs the IR's are within .1 and voltage from cell to cell is the same across the 2 cells. After it happened I balanced charged the single pack and it started off at 3.4 and 3.45 but balanced out in the end. Anyone ever had to send back a revo?

  5. #5
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    try charging each pack by itself, not in parallel charge. It is very easy to get a lazy pack when parallel charging.

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    Cool

    IMG_4151.jpg

    A club member's Revo pack from yesterday's racing. High-end charger too.

    I parallel charge all all the time with no problems, been doing it for at least seven years over hundreds of charge cycles on multiple packs from two 2S to two 5S. Wouldn't say it is "easy" to get a "lazy" pack. But then I don't run Revos either....



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  7. #7
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    Wow! That's not good.... I have been paranoid about parallel charging for that reason. I'll do a few cycles as single packs and see what happens, hopefully my pack is still usable. I went with revos and a PL6 to help avoid this type of thing but I guess it doesn't matter.

    Thanks all!

  8. #8
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    BTW the Revo pack in the photo was NOT being parallel charged. It was charged individually, here is the charge setup used.

    IMG_4150.jpg
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    I give up.... :) with technology being what it is I hope someone comes up with a better way rather than rolling dice with your money. If you have packs that you monitor and the IR and voltages are where they should be I figured it would be a good way to prevent this.

    Thanks

  10. #10
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    Is it possible that you have a cold solder joint in your parallel connector?
    Also all your wiring should be 10awg.

    Larry
    Past NAMBA- P Mono -1 Mile Race Record holder
    Past NAMBA- P Sport -1 Mile Race Record holder
    Bump & Grind Racing Props -We Like Em Smooth & Wet

  11. #11
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    Okay thanks, I'll make up a new 10awg connector and go from there!

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    All I can tell you, is that after 35 years of using batteries in all kinds of high power applications, some more demanding then FE, that parallel charging is considered to be the weakest charge method of them all. I'm glad you've had good response, but the electrical community would respectfully disagree with your choice. There are many variables to that method, of which you don't mention at all! This is just but one more example of a veteran racer who feels that they have nothing to learn from anybody else. Myself, even after 35 years, I will continue to listen and soak up good ideas, no matter who presents them. Carry on my good man....

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    That post goes to Fluid's comment...

  14. #14
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    Yet another for the ignore list.....


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  15. #15
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    Quote Originally Posted by Fluid View Post
    BTW the Revo pack in the photo was NOT being parallel charged. It was charged individually, here is the charge setup used.

    IMG_4150.jpg
    Correct me if I'm wrong, but that looks like packs connected to a parallel charging board. What am I missing?

  16. #16
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    For others not ignoring others, the problem with parallel charging is you don't know which pack took the most mah, or if it's even. The only way to know for sure, is to monitor current to each pack in parallel to compare the final mah. Since this is a pain in the a--, it leaves you guessing what happened during charging, which is exactly the OP's problem. Connectors can be an issue, but without knowing the current, then you don't know. If you can do it another way and know for sure, then please share...

  17. #17
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    Quote Originally Posted by Fluid View Post
    Yet another for the ignore list.....


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    You got that down good pal... you should write a book, then no need to interact with others. I suggest you call the book "The Oracle of FE"

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    Quote Originally Posted by fweasel View Post
    Correct me if I'm wrong, but that looks like packs connected to a parallel charging board. What am I missing?
    Yep, and the the other batt on that board is puffed as well, compare to the batts on the other board. What cannot be determined from the picture is what else has happened to that pair of packs, something did if they puffed that way. It may or may not be a revo issue, to make it look that way isn't really quite fair is it?
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
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  19. #19
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    Quote Originally Posted by CraigP View Post
    You got that down good pal... you should write a book, then no need to interact with others. I suggest you call the book "The Oracle of FE"
    Craig
    You have not been around here very long, You may be educated in Electrical, But Jay T. did write the book on model boating many years ago.

    There are many other charger that are made that you may have never heard about, ones designed to do parallel charging.

    Slow down.
    Larry
    Past NAMBA- P Mono -1 Mile Race Record holder
    Past NAMBA- P Sport -1 Mile Race Record holder
    Bump & Grind Racing Props -We Like Em Smooth & Wet

  20. #20
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    I would suggest he reduce his condescending and dismissal tone when answering responses, or don't respond at all. I'm no more interested in his experience, then he is with mine. I'll just try and avoid the guy. His attitude has been going on for a spell now. Having experience doesn't give you the right to disrespect others.

  21. #21
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    Okay, so I balanced charged the individual packs and took it out for a normal 4s 2p run and this is what I got:

    Pack 1 info From charger:
    Mah left:62%
    Total voltage:7.786
    Cell 1: 3.89
    Cell 2: 3.89
    IR during charge: 1 & 1

    Pack 2 info from charger:
    Mah left: 63%
    Total voltage: 7.801
    Cell 1: 3.90
    Cell 2: 3.90
    IR during charge 1 & 1

    With the voltage checker which I don't trust and question it's accuracy
    Pack 1:
    Total: 7.75
    Cell 1:3.87
    Cell 2:3.88

    Pack 2:
    Total:7.77
    Cell 1: 3.87
    Cell 2: 3.90

    Other than cell 2 on the voltage checker which is probably not accurate I don't see much wrong. Hopefully a new 10awg parallel connector will do the trick.

    Thanks all!

    Ryan

  22. #22
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    That's pretty darn good Ryan! It's very hard to make parallel batts current share 100% even. It actually looks like from this run that you have 3 cells very close and one stronger cell, Pack2, #2. Your problem could have very well been resistance differences in the harness. Nice debugging!

  23. #23
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    Quote Originally Posted by R2315 View Post
    Okay, so I balanced charged the individual packs and took it out for a normal 4s 2p run

    Ryan
    4S 2P ???????????????????
    With only 2 - 2S packs and the adapter in the first post.
    is this NOT a 4S-2P setup?

    Larry
    Last edited by TRUCKPULL; 08-21-2017 at 12:14 AM.
    Past NAMBA- P Mono -1 Mile Race Record holder
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    The OP's first post indicated 2s-2p... I took it as a typo...

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    Yes, I ran it as 4s 2p this time because I don't suspect the castle series adapter and wanted to see what the batts did without the parallel adapter. Sorry for the confusion, it was more to try and determine if my homemade adapter was the issue and eliminate the lipos from the equation. I'm up north and don't have the stuff to make a new parallel adapter but I will test that again as soon as I can. I normally run this boat on 4s but like I said experimenting with 2s parallel was for longer run times for the kids. Would a problem with one of my lipos/cells show more in parallel then in series?

  26. #26
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    Quote Originally Posted by R2315 View Post
    Yes, I ran it as 4s 2p this time because I don't suspect the castle series adapter and wanted to see what the batts did without the parallel adapter. Sorry for the confusion, it was more to try and determine if my homemade adapter was the issue and eliminate the lipos from the equation. I'm up north and don't have the stuff to make a new parallel adapter but I will test that again as soon as I can. I normally run this boat on 4s but like I said experimenting with 2s parallel was for longer run times for the kids. Would a problem with one of my lipos/cells show more in parallel then in series?
    Are you using 2 4s lipos to get 4s 2p?

  27. #27
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    2-2s lipos to get 4s @5000 mah or like I was experimenting with 2-2s lipos in parallel to get 10000mah. I guess I used the wrong terminology, sorry.

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