PCB replacement for 18650 2S2P pack- Mtbr.com
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  1. #1
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    PCB replacement for 18650 2S2P pack

    Any suggestions for specs and sources on a replacement PCB for an 18650 2S2P (7.4v) pack?

    I was reading http://www.batteryspace.com/pcbfor74...mit2round.aspx and noted that this is not acceptable to a 15 W halogen. Would this work for, say a Magicshine 808 type light?

    Thanks
    Rich

  2. #2
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    The surge current from a cold halogen is probably the reason why they advise against using it with a 15W halogen. It could exceed the 5A rating of this PCB during the warm-up of the filament. I'll bet it would be OK with a 15W halogen if you add a soft-start circuit.

    The Magicshine uses a less power - about 10W - and unlike halogen (or any incandescent), you don't have to worry about a high startup current.

  3. #3
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    Sounds like a winner then.

    Thanks
    Rich

  4. #4
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    Looks like this is it.

    http://cgi.ebay.com/Protection-Circu...item335f518d08

    Now, the wiring diagram is not complete. Guessing that the battery will need to be hooked to both B +/- with a common line to the balance?

  5. #5
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    Quote Originally Posted by rmbassett21
    http://cgi.ebay.com/Protection-Circu...item335f518d08

    Now, the wiring diagram is not complete. Guessing that the battery will need to be hooked to both B +/- with a common line to the balance?
    Example wiring diagram shown for this similar product (scroll down).

  6. #6
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    Hope not too off topic.

    Such a noob question but in the same line of thinking, can you add a balancer circuit to an ex'g setup?

    I have seen recent posts where they had issues with a battery and my current battery is 3p2s i think so lots to go wrong....
    "mountain biking and flyfishing, what more do you want?" - Yeah, I said it

  7. #7
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    Quote Originally Posted by random walk
    Example wiring diagram shown for this similar product (scroll down).
    What volt/current do you charge these at?

  8. #8
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    Quote Originally Posted by jbflyfshr
    Such a noob question but in the same line of thinking, can you add a balancer circuit to an ex'g setup?
    Yes. You can either replace the existing PCB with a combination protection/balancing PCB (these are much more expensive than a protect-only circuit). Or you can install a balance plug, and charge with a balancing charger.

  9. #9
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    Quote Originally Posted by flyxaos
    What volt/current do you charge these at?
    Lithium ion batteries require a somewhat complex Constant Current/Constant Volage (CC/CV) charge method in order to be safe. From the user perspective, charging should be as simple as plugging it into the charger, and letting the intelligent charger take care of the complexities.

    http://batteryuniversity.com/learn/a..._ion_batteries

  10. #10
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    Wiring???

    I have a MagicShine battery and understand that the PCM allows the pack to drop down to 2.0V before cutting off. From what I have read, this is too low and I should have something more on the order of 3.5 V. I am thinking of replacing the PCM with

    http://cgi.ebay.com/Protection-Circu...item335f518d08

    I have also thought about replacing it with this board:

    http://www.batteryspace.com/pcbfor74...a-1alimit.aspx

    Would the following be the correct wiring and would it work with the above board.

    http://mysite.verizon.net/resxqr4f/Document1.bmp

    This looks like there is a connect at the +/- terminal for all four cells?????

    Finally, what is the difference between the COM and BM pads? None?

    Thanks
    Rich

  11. #11
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    Quote Originally Posted by rmbassett21
    I have a MagicShine battery and understand that the PCM allows the pack to drop down to 2.0V before cutting off. From what I have read, this is too low and I should have something more on the order of 3.5 V. I am thinking of replacing the PCM with

    http://cgi.ebay.com/Protection-Circu...item335f518d08

    I have also thought about replacing it with this board:

    http://www.batteryspace.com/pcbfor74...a-1alimit.aspx

    Would the following be the correct wiring and would it work with the above board.

    http://mysite.verizon.net/resxqr4f/Document1.bmp

    This looks like there is a connect at the +/- terminal for all four cells?????

    Finally, what is the difference between the COM and BM pads? None?

    Thanks
    Rich
    That first one may be the exact board that's already in the magicshine pack. If my memory is right, it looks like the exact same PCB layout.

  12. #12
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    Yup, my MS PCB looks exactly like this. The real question is: which version of the Seiko protection IC does it use? Some versions cut off at higher voltages and will properly protect the battery: http://datasheet.sii-ic.com/en/batte...on/S8232_E.pdf

    Finally, what is the difference between the COM and BM pads? None?
    COM and B- are not the same. COM connects in the middle of the cells. B- connects to the most negative terminal of the entire battery.

  13. #13
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    Mine too. From the photos that I have seen for packs that were cracked open, this looks like the one. Any comments on the cross wiring at the junction between the cells and the COM/BM. I thought that this is the balance piece.

    Thanks
    Rich

  14. #14
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    The BM pad on the first board and COM pad on the second board are the same thing. That terminal is needed so the board can measure the voltage of each individual cell bank. It doesn't provide balancing in the case of these particular boards.

  15. #15
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    Would the T1 and T2 connections on this board possibly be intended for balance charge connections?



    http://cgi.ebay.com/Protection-Circu...item335f518d08

  16. #16
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    Quote Originally Posted by BlownCivic
    Would the T1 and T2 connections on this board possibly be intended for balance charge connections?



    http://cgi.ebay.com/Protection-Circu...item335f518d08
    Probably not, but since there are no real specs you can only guess. I would guess they are a provision for a temperature sensor thermistor. Very likely aren't connected up on this particular board since that function isn't mentioned.

    Since it appears to be the same board as in the magicshine pack, I would guess it has the same incorrect low voltage settings. Yes, they could have populated a different IC on the board, but that wouldn't be all that common since the same exact PCB typically mean it comes from the same manufacturer. If I bought one I'd check the part number on the chip or actually test out the voltage thresholds before I built it into a pack.

  17. #17
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    So, would the http://mysite.verizon.net/resxqr4f/Document1.bmp
    be the correct wiring or would you jump over the center conductor between the two parallel legs

    or http://mysite.verizon.net/resxqr4f/Document2.bmp?
    Last edited by rmbassett21; 11-30-2010 at 03:19 PM.

  18. #18
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    Hmmm... doesn't seem to make a difference????

  19. #19
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    Quote Originally Posted by rmbassett21
    Hmmm... doesn't seem to make a difference????
    It makes a big difference. The first one is correct. The second one isn't a valid 2s2p configuration and is dangerous because the voltage of the parallel cells aren't locked together.

  20. #20
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    I updated the link. As both the mid point connections go to the COM/BM I can link them with a cross or just both to the COM/BM. Just a little more wire.

    You are correct, the first time it left half of the pack unprotected.

  21. #21
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    Quote Originally Posted by rmbassett21
    I updated the link. As both the mid point connections go to the COM/BM I can link them with a cross or just both to the COM/BM. Just a little more wire.

    You are correct, the first time it left half of the pack unprotected.
    You can connect all the batteries together close to the cells and then run a single wire to the COM/BM terminal on the protection PCB.

  22. #22
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    Question about packaging: how are the PCBs typically packaged physically in relation to the cells in a pack? I don't think I've seen a picture of a pcak deconstructed to show this.

    The reason I ask is, I found a nice waterproof case that I can fit in up to 6 18650s, but they would have to be in a sort of "staggered" arrangement due to the dimensions of the case.

    Top view attached.

    So there is hopefully enough room on top of the cells for "2-round" PCBs (like this one). This would all be carefully wired and shrink-tubed together.

    Also, am I mistaken that each series pair in a 7.4V pack requires its own PCB?

    Thanks for the help.

    P.S. This waterproofing may be overkill for mountain biking, but I plan to also use this pack to power lights when I go kayak fishing at night. You can catch some really big ones in San Diego when the grunion are running!
    Attached Images Attached Images  

  23. #23
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    My memory of EE is that each set of cells in parallel should be on either side and should be OK with the one board as you will have a voltage source on one side and separate voltage source on the other, etc, etc, etc...

    You will need to be careful of the charge voltage as a 2s3p will have different resistance than a 2s2p.

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