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  1. #1
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    DX Charger Modification & Battery Pack Builds

    I have two older LED lights I'm going to upgrade and I needed to build the battery packs and modify a charger to fill 'em up.

    One pack is a 1S2P and the other is a 1S4P. I bought one of the DX chargers and a couple of 2.1mm jacks.

    DX Charger Modification & Battery Pack Builds-p1020740.jpg

    It appeared to have just enough room near the top of the charger.

    DX Charger Modification & Battery Pack Builds-p1020739.jpg

    DX Charger Modification & Battery Pack Builds-p1020741.jpg

    Step drilled a couple of 1/2" holes.

    DX Charger Modification & Battery Pack Builds-p1020742.jpg

    Ohmed-out and soldered up the leads.

    DX Charger Modification & Battery Pack Builds-p1020743.jpg

    Installed the jacks.

    DX Charger Modification & Battery Pack Builds-p1020744.jpg

    Finished soldering the jumpers.

    DX Charger Modification & Battery Pack Builds-p1020745.jpg

    Put it back together.

    DX Charger Modification & Battery Pack Builds-p1020746.jpg

    Hmmmm.... It isn't working...

    DX Charger Modification & Battery Pack Builds-power-supply-power-supply-not-impressed-mozilla-firefox-11192012-94210-pm.jpg

    Why not?
    Last edited by marpilli; 11-19-2012 at 08:03 PM.
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  2. #2
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    Well, I took it back apart and realized (in my excitement) I soldered to the wrong connections on the jack.

    DX Charger Modification & Battery Pack Builds-copy-p1020743.jpg

    Fixed that and started putting everything back together again.

    Then the dreaded happened. As I was pushing the board back into place (not as gently as I should have) the negative tabs on the charger pushed up and ripped free from the traces.

    I'll be darned if I'm gonna order another one of these and wait four weeks for it.

    I followed the trace back to the lead from the transformer an soldered in a jumper.

    DX Charger Modification & Battery Pack Builds-p1020748.jpg

    This time I put it back together more carefully and everything was working as I had expected.
    Last edited by marpilli; 11-19-2012 at 08:07 PM.
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  3. #3
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    Since I scavenged laptop batteries for my project (I wanted to keep the initial cost down if possible) I purchased battery holders that had a protection PCB added to them. One 1S2P and one 1S4P. They looked similar to this (except mine had a foam cover on top):

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    I removed the factory leads and soldered on a heavier lead with a 2.1mm plug on the end.

    DX Charger Modification & Battery Pack Builds-p1020749.jpg

    I covered the exposed area with liquid electrical tape. It's really a great multi-use product if you have some around.

    DX Charger Modification & Battery Pack Builds-p1020751.jpg

    Rather than zip ties, I used wax lace to secure the lead. I have a ton of it from a previous job (where I dressed cabling) and I can pull it much more securely than zip ties.

    I left the batteries exposed until I'm confident the cells are good. After I use them for awhile, I'll lace in the batteries and probably wrap the pack.

    Finished packs:

    DX Charger Modification & Battery Pack Builds-p1020752.jpg

    DX Charger Modification & Battery Pack Builds-p1020753.jpg

    I built a couple of 2.1mm jack/plug extensions.

    DX Charger Modification & Battery Pack Builds-p1020754.jpg

    Next, I ran the packs down a bit on my XML test rig (I setup for the first light upgrade) so they would take a charge. I previously charged each battery individually on the DX charger before modifying it.

    Plugged in the charger...

    DX Charger Modification & Battery Pack Builds-p1020757.jpg

    Plugged in the battery packs... Charging!

    DX Charger Modification & Battery Pack Builds-p1020758.jpg

    Put them in a safe place while they're charging.

    DX Charger Modification & Battery Pack Builds-p1020759.jpg
    Last edited by marpilli; 11-19-2012 at 08:25 PM.
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  4. #4
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    Thank you to all of the previous contributors who gave me the ideas for this.
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  5. #5
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    Good job, but it's really better if you simply by an extra charger and charge each cell separately. Even if you run them for a while and they seem fine, charging each cell is much better long term.
    "It looks flexy"

  6. #6
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    Great job! How long does it take to fully charge the packs?
    "By Your Command"

  7. #7
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    Thank you, both.

    gticlay, with the packs being nothing more than a holder for single cells it'll be easy for me to charge them individually if I decide to go that route. And, my charger modifications still allow the charger to accept single cells. Best of both worlds.

    pucked up, I'm not sure. I pre-charged all of the cells a few days ago and I didn't run them down very much before trying to charge them in a pack configuration. I believe the charger has an output of 500mAh or 650mAh. Either way, I'm looking at a "slow chugger" that will take awhile to charge.

    Once I have a light ready, I'll run them down a bit more, charge them back up, and report back with the durations.
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  8. #8
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    very neat job! I just drilled a hole in the side for a MS cable and called it a day, yours is much neater I'm guessing that the battery -ve for both channels is a common trace then? If you rip up a trace in future, you can often fix it by scraping away some of the green covering on the trace a bit further up and bridge the gap with a blob of solder or a short piece of wire. A bit of liquid tape and no one will know the difference!

    Good to see a lipo sack in use, although those batteries will be charged at such a low rate that I doubt you'll have any problems.

    Gticlay - charging multiple cells in parallel is no different to charging a single cell, it's just slower. There are no deleterious effects on cell health or risk of unequally charged cells. If there's one lower capacity cell in there, it'll just trip the PCB when it's discharged and stop the charging when it's charged. Completely different kettle of fish with multiple batteries in series though.

  9. #9
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    matt, thank you.

    Yes, both of the neg terminals were on a common trace. I considered trying to scratch-and-solder; but, decided I'd had enough frustration so I took the easy route.

    I once had a NiMH battery start smoking in an unattended charger. I remember one of my kids asking "Daddy, what's that smell?" It was melting the housing of the charger when I figured out what was happening. After seeing a couple of photos of popped Li-ion batteries I decided it wasn't worth the risk of not bagging them while charging.
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  10. #10
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    Quote Originally Posted by mattthemuppet View Post
    Gticlay - charging multiple cells in parallel is no different to charging a single cell, it's just slower. There are no deleterious effects on cell health or risk of unequally charged cells. If there's one lower capacity cell in there, it'll just trip the PCB when it's discharged and stop the charging when it's charged. Completely different kettle of fish with multiple batteries in series though.
    It's actually an even better situation than you're describing. When you have multiple cells in parallel, the voltage of all the cells has to be exactly equal because the wires that connect them together force that to be the case. So a weak cell won't actually trip the protection PCB on charge or discharge. What happens is the weak cell will stop contributing any current sooner than the other cells on discharge and essentially just float at the voltage of the other parallel cells. The same thing happens on charge. A weak cell will become fully charged before the other cells and will stop absorbing charge current and just float at the voltage of the other cells. The protection PCB will only trip if the voltage of the set of parallel cells goes out of range. Meaning all the cells are becoming over charged or discharged.

    Net, it's a pretty safe and stable configuration to have li-ion cells in parallel. The main thing you have to watch out for is the current will only split evenly between the cells if they have similar characteristics. Hence, if you want to guarantee that you won't exceed the maximum charge or discharge current for a single cell, you have to stay below the single cell current limits for the whole pack. That's not such a big deal for a 2p pack, but it's more of an issue as the cell count goes up. Keep in mind that the absolute current limits for a descent quality cell is typically 1C on charge and 2C or 3C on discharge. So for a pack made with 2.6AH cells, that means you shouldn't charge at more the 2.6 amps or discharge at more the 5.2 to 7.8amps depending on your cell specs.

    The other thing you have to watch, is don't assemble parallel cells with some cells fully charged and some discharged. They need to be at approximately the same state of charge when you put them in parallel. Otherwise, the charged cells will "charge" the discharged cells at a high current because the only thing limited the current is the very low resistance of the wires connecting them together. This will typically exceed the current limits on the cells and can be dangerous.

  11. #11
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    Quote Originally Posted by MtbMacgyver View Post
    It's actually an even better situation than you're describing. When you have multiple cells in parallel, the voltage of all the cells has to be exactly equal because the wires that connect them together force that to be the case. So a weak cell won't actually trip the protection PCB on charge or discharge. What happens is the weak cell will stop contributing any current sooner than the other cells on discharge and essentially just float at the voltage of the other parallel cells. The same thing happens on charge. A weak cell will become fully charged before the other cells and will stop absorbing charge current and just float at the voltage of the other cells. The protection PCB will only trip if the voltage of the set of parallel cells goes out of range. Meaning all the cells are becoming over charged or discharged.

    Net, it's a pretty safe and stable configuration to have li-ion cells in parallel. The main thing you have to watch out for is the current will only split evenly between the cells if they have similar characteristics. Hence, if you want to guarantee that you won't exceed the maximum charge or discharge current for a single cell, you have to stay below the single cell current limits for the whole pack. That's not such a big deal for a 2p pack, but it's more of an issue as the cell count goes up. Keep in mind that the absolute current limits for a descent quality cell is typically 1C on charge and 2C or 3C on discharge. So for a pack made with 2.6AH cells, that means you shouldn't charge at more the 2.6 amps or discharge at more the 5.2 to 7.8amps depending on your cell specs.

    The other thing you have to watch, is don't assemble parallel cells with some cells fully charged and some discharged. They need to be at approximately the same state of charge when you put them in parallel. Otherwise, the charged cells will "charge" the discharged cells at a high current because the only thing limited the current is the very low resistance of the wires connecting them together. This will typically exceed the current limits on the cells and can be dangerous.

    Isn't that what was happening with the MS batteries - they were 2 packs of 2 and one or 2 cells would not co-operate with the rest. Dead battery.
    "It looks flexy"

  12. #12
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    MtbMacgyver, awesome information. Thank you!

    gticlay, I thought I read the MS battery packs were 2S2P. The charger wasn't a balance type charger and when one cell went bad the pack became useless. Note, I have no personal experience with this. Just regurgitating what I remember reading.
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  13. #13
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    Quote Originally Posted by MtbMacgyver View Post
    It's actually an even better situation than you're describing...
    thanks again MtbMacgyver, my patchy knowledge has become a little less patchy

    Quote Originally Posted by gticlay View Post
    Isn't that what was happening with the MS batteries - they were 2 packs of 2 and one or 2 cells would not co-operate with the rest. Dead battery.
    I think what often happens with MS packs is that one or both of the cells in one parallel pair will soft short and self-discharge, which results in that pair overdischarging and the good pair overcharging, as the lighthead and charger only sense the voltage of the pack as a whole. As an aside, about half of the laptop battery packs I've salvaged have one bad parallel pair and the other pairs are fine - the pack PCB presumably measures the voltage of each pair and bricks the pack when they go too far out of balance.

  14. #14
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    Quote Originally Posted by gticlay View Post
    Isn't that what was happening with the MS batteries - they were 2 packs of 2 and one or 2 cells would not co-operate with the rest. Dead battery.
    The problem with the magicshine batteries, at least the 3-4 bad packs that I disassembled and analyzed, wasn't related to the arrangement of the cells. It was that the cells were poor quality and were developing internal shorts. This is typically caused by contamination with metal particles during the manufacturing of the cells.

    This was causing one pair of cells to self discharge and get out balance relative to the other series connected pair of cells. Which in turn was causing the protection PCB to shutdown the pack early on discharge when the weak pair was at the lower voltage limit, and it was shutting down the charge early when the good pair of cells was at the upper voltage limit. The protection PCB was actually doing its job correctly.

    If you have defective cells, you're going to run into problems no matter how they are arranged. In the Magicshine battery case, the pack getting out of balance was a symptom of the problem, not a cause. The cause was the defective cells with internal shorts.

    This is conjecture on my part, but I suspect the few catastrophic failures we heard of with Magicshine packs were cases where people had defective cells and malfunctioning protection PCBs. In that case the pack would get badly out of balance and with a broken protection PCB the cells would go way outside the acceptable voltage range during charge and discharge. With the number of magicshine packs solds, you're going to have a few protection PCBs that fail .... especially considering the quality. Hence the few catastrophic failures was the intersection of packs with defective cell and defective protection PCBs and used enough to induce a failure.

  15. #15
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    I have been modding DX chargers with external charging wires for several years.

    It's a great way to go for charging soldered battery packs

    It's way easier to just bring wires out through the case and put plugs on the end.
    I use 15 amp Anderson Powerpole connectors on my lights, battery packs and chargers

    Here's a shot of the modded chargers I sell that charge the battery packs I make.



  16. #16
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    Quote Originally Posted by El34 View Post
    I have been modding DX chargers with external charging wires for several years.

    It's a great way to go for charging soldered battery packs

    It's way easier to just bring wires out through the case and put plugs on the end.
    I use 15 amp Anderson Powerpole connectors on my lights, battery packs and chargers

    Here's a shot of the modded chargers I sell that charge the battery packs I make.
    That looks great. Yeah, I think I over-thought the charger (by adding the jacks). But, I don't regret it.

    I've used the Andersen Powerpole connectors way back when I worked for a telco and would wire up high current -48v systems. They have a high-quality product and I didn't realize they made them for smaller gauge wire. I'll keep that in mind for the future, thank you.
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