Need help - wiring a 3S2P with pcb.- Mtbr.com
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  1. #1
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    Need help - wiring a 3S2P with pcb.

    I am currently looking into building a 3S2P with a pcb wired in. I am still new at this and have just put together a 2S1P using a pre-built 18650 holder with a pcb.

    https://www.batteryspace.com/Battery...ong-20AWG.aspx

    I am now looking to build a 3S2P to power a triple XM-L that will be fed a max of 1.2A. I am looking into the digikey 18650 holders and a pcb from batteryspace:

    https://search.digikey.com/scripts/D...K-18650-PC6-ND
    https://www.batteryspace.com/pcbfor1...3s5alimit.aspx

    The 18650 battery I will be using:
    https://www.batteryspace.com/Li-ion-...62Wh---LG.aspx

    Now is it more reasonable to go with unprotected cells with a pcb wired in or should I just go with protected cells? What is the necessity of having the batteries balanced?

    Here is a sketch of what I think would be the correct wiring for a 3S2P with a pcb wired in (of course the wiring will be a lot cleaner later on):



    Thanks,
    Anthony

  2. #2
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    It would be better to use 2x 3S1P holders from Batteryspace and solder the outputs is parallel for a 3S2P config.
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  3. #3
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    I would forget the holder and just build a proper battery pack using unprotected cells wired to the pcb. Wiring is easy. Make three parallel pairs in series. Pcb connections at both ends and between the pairs. Heat shrink it when done. You will need a proper charger capable of handling 3s Li-Ion pack.
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  4. #4
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    Quote Originally Posted by zemike
    It would be better to use 2x 3S1P holders from Batteryspace and solder the outputs is parallel for a 3S2P config.
    I did look into that but it will be almost $30 for the holders and they also recommend not to solder 2 holders together.

    Quote Originally Posted by Homebrew
    I would forget the holder and just build a proper battery pack using unprotected cells wired to the pcb. Wiring is easy. Make three parallel pairs in series. Pcb connections at both ends and between the pairs. Heat shrink it when done. You will need a proper charger capable of handling 3s Li-Ion pack.
    I'm still not very skilled at using my soldering station, so I'm very hesitant on soldering straight onto the cell ends.

  5. #5
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    Quote Originally Posted by anthonylokrn
    I'm still not very skilled at using my soldering station, so I'm very hesitant on soldering straight onto the cell ends.
    Get cells with solder tabs.
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  6. #6
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    Quote Originally Posted by Homebrew
    Get cells with solder tabs.
    Alright so I am going with what you said on ditching the holders. Does the heat-shrink hold the batteries together tight enough so they don't wiggle around? Last thing I would want is a solder connection coming loose from the batteries shifting.

    I will be using the LG brand 18650 2600mah cells with pre-wired tabs(?)
    http://www.batteryspace.com/Li-ion-1...62Wh---LG.aspx

    Which PCB would be best? (with and without balancing/equilibrium)
    http://www.batteryspace.com/pcbfor11...3s5alimit.aspx
    http://www.batteryspace.com/pcmwithe...t10alimit.aspx

    Is there a do-it-all charger that I can set voltage and current? Hopefully nothing way too expensive..just would be nice to have a charger to use for other battery packs.

    Thanks!
    Anthony

  7. #7
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    the last thing you need is the batterys loose and rubbing together!
    wired in series there is a potential between each casing and will short out if the metal casings get to touch each other
    i used to fix them together with silicon sealer, but its quicker and stronger with hot melt glue
    ...Scun.thorpe, UK

  8. #8
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    Those are the same cells (with tabs) that I've used for the packs that I've built recently. I'm sure you can find a good tutorial on the web for building battery packs. I do use tape and hot glue to hold the pack together and the heat shrink is to isolate the connections from shorts. For a charger, I use the Thunder AC6 for the last year or so and have been pleased.
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  9. #9
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    I use cyanoacrylate (crazy glue) to bond the cells together in the packs I build. It's permanent, but very secure. If I have to dissasemble the packs, it then becomes a simple matter of having to re-heatshrink the cells.

    I'm still trying to find a charger that'll let me charge my Sanyo 30A 3,000mAh cells to a higher voltage (4.35v per cell as per the manufacturer's documentation). Anyobe have any ideas?

  10. #10
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    Quote Originally Posted by Homebrew
    Those are the same cells (with tabs) that I've used for the packs that I've built recently. I'm sure you can find a good tutorial on the web for building battery packs. I do use tape and hot glue to hold the pack together and the heat shrink is to isolate the connections from shorts. For a charger, I use the Thunder AC6 for the last year or so and have been pleased.
    Thanks!

    I was looking into the Thunder AC6 and the Tenergy TB6AC. Do you know what the difference between them? They both look exactly the same.

  11. #11
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    So I'm going to settle on the Thunder AC6 since it seems much more popular.

    Will there be any problems charging/balancing a battery pack with a pcb wired in? I was reviewing a similar/clone on batteryspace and it noted:

    "Charge / Discharge the 7.4V-22.2V Li-Ion/Li-Ion Polymer, 6.4V-19.2V LiFePO4 pack Battery pack without PCB"

    http://www.batteryspace.com/intellig...tterypack.aspx

    Thanks,
    Anthony

  12. #12
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    It's all in the wiring. If you wire your balancing plug correctly, the PCB is totally bypassed by the balancing setup.

  13. #13
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    Quote Originally Posted by BlownCivic
    It's all in the wiring. If you wire your balancing plug correctly, the PCB is totally bypassed by the balancing setup.
    Thanks!

    I just ordered the Thunder AC6. It looks like the balancing ports use JST connectors, does anybody know a good place to order them from, or are they common at most stores (radioshack, frys, etc)?

  14. #14
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    Quote Originally Posted by anthonylokrn
    Thanks!

    I just ordered the Thunder AC6. It looks like the balancing ports use JST connectors, does anybody know a good place to order them from, or are they common at most stores (radioshack, frys, etc)?
    eBay is a good a place as any, see here, not sure about Radioshack and the like, the last one I went in didn't know what a Li-ion cell was.

  15. #15
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    Quote Originally Posted by anthonylokrn
    Thanks!

    I just ordered the Thunder AC6. It looks like the balancing ports use JST connectors, does anybody know a good place to order them from, or are they common at most stores (radioshack, frys, etc)?
    I got mine from here...........
    http://www.all-battery.com/jst-xhv24...3cellpack.aspx
    They use good quality silicone wire. The stuff thats rated at 200 degrees C.
    Leads are on the short side, as can be seen in the pics.
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  16. #16
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    Well finished building my 3S2P 18650 pack..took me roughly 7 hours from start to finish lol. Not the prettiest wiring job, but everything is secure.

    I went without a holder and just used electrical tape and hot glue to bond the batteries together; it's holding up great. PCB was also wired in and just awaiting for my JST connectors to come in to finish the balancing connection. Plastidip will be the final touch.

    I think I would be able to complete another build in less than 3 hours since I am now familiar with the wiring.

    Thanks for the help!
    Anthony

  17. #17
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    So I'm having some problems with my charger or battery packs.

    Using the Thunder AC6, I started charging (no balance yet) the 3S2P 18650 pack on LiPo (3.7V) @ 1.8A 3S (11.1V). The voltage on the LCD of the Thunder AC6 reached 12.6V (maximum for 3S) and it still continued to charge; the charge current did drop though (charger trickling?).

    After waiting a few more minutes, I stopped the charge manually, waited a few minutes, and checked the voltage with a multimeter...13.35V! My PCB overcharge protection is at 13.05V (~4.35V per cell). I proceeded to discharge the pack to a safe voltage and noticed that the voltage on the Thunder AC6 is not matching with my multimeter.

    I double checked using a 2S1P 18650 pack I build using a holder with build-in PCB from batteryspace. Voltage shows 8.85V on my multimeter, but shows 8.05V once I connect it to the Thunder AC6 to discharge.

    I'm not sure what I'm doing wrong, but the batteries are not getting hot at all.

  18. #18
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    Sounds like your meter is inaccurate. You need a known voltage source to check your meter. I built a circuit based on an LM4040-5.0 voltage reference chip to use as a fairly accurate reference. A new unused AA battery will typically measure between 1.6 and 1.65v with no load. The 5v power supply of a desktop PC is pretty close to 5V. Some PCs have a monitor program that'll tell you the voltage to give you an even better reference. Having access to a lab grade meter is even better.....

  19. #19
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    Quote Originally Posted by MtbMacgyver
    Sounds like your meter is inaccurate. You need a known voltage source to check your meter. I built a circuit based on an LM4040-5.0 voltage reference chip to use as a fairly accurate reference. A new unused AA battery will typically measure between 1.6 and 1.65v with no load. The 5v power supply of a desktop PC is pretty close to 5V. Some PCs have a monitor program that'll tell you the voltage to give you an even better reference. Having access to a lab grade meter is even better.....
    Thanks mate! Did a double-take on my meter and it ended up being a low battery (ironic eh?)

  20. #20
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    Hows about a pic or drawing of where you hook your balance leads into the pack? I'm still a bit confused of where you connect them in a pack with a pcb.

  21. #21
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    take a look at this thread ....
    http://forums.mtbr.com/showthread.php?t=671233

    ...http://scriptasylum.com/rc_speed/lipo.html

    what battery pack configuration you got??
    Last edited by HEY HEY ITS HENDO; 01-22-2011 at 01:00 PM.
    ...Scun.thorpe, UK

  22. #22
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    So looking at Anthonylokm's drawing, I would just solder the 4 balance leads directly on the PCB pads where the battery leads are soldered?

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