Best ways/sources for 2 cell MagicShine style battery?- Mtbr.com
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  1. #1
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    Best ways/sources for 2 cell MagicShine style battery?

    Last year I snaked a cord down from my easy2led/quazzle headlamp and used a 4 cell. This year I might like to use a little 2 cell - is there any deal extreme or great DIY ways to make one that would be waterproof? I have some cells or could make 2 of them from one geoman pack (I have 3!).
    "It looks flexy"

  2. #2
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    PCB from batteryspace on eBay ($12 or so), Magicshine extension cord from pretty much anywhere (ActionLED I think would be the quickest) and a big tub of plastidip. Wire it all up, dip it several times (Scar uses this stuff) and you're a goodun. I use velcro cinch straps off eBay to strap my battery to my helmet, although I'm thinking about some kind of quick-release attachment using Cateye spacers at the moment.

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  4. #4
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    Quote Originally Posted by Wombat View Post
    Thanks, that's exactly what I'm looking for. DX doesn't seem to have anything. THANK YOU!
    "It looks flexy"

  5. #5
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    What are the approx. run times with the 2 battery packs Vs. 4?

    (yeah, I know, 1/2, duh!)

  6. #6
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    Quote Originally Posted by rideit View Post
    What are the approx. run times with the 2 battery packs Vs. 4?

    (yeah, I know, 1/2, duh!)
    GOOD question as it could be different.
    "It looks flexy"

  7. #7
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    Depending on the amount of current your light pulls on high, the 4 cell may give you more than twice the run time as the two cell.

    The 4 cell pack should have less voltage sag on high than the 2 cell. Please correct me if I'm wrong.

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    Quote Originally Posted by ThinkBike View Post
    Depending on the amount of current your light pulls on high, the 4 cell may give you more than twice the run time as the two cell.

    The 4 cell pack should have less voltage sag on high than the 2 cell. Please correct me if I'm wrong.
    I'm sure this will be the case, but the difference will be slight. Most Quazzle boards use a boost type driver. The downside to that type of driver is that as the battery voltage drops, the current drain increases. Discounting driver efficiency because I don't know that number, the draw from the pack will be ~1.6A when the cells are near the end of useful charge. That is not too much for a decent quality cell.

  9. #9
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    I think the key point is the "decent quality cell". MS type lights typically draw around 1.8A or so on high, which is less than 1A per cell in a 4 cell pack and well within the abilities of even low quality cells. If the light engine is one of the 1.5A modules the current draw will reach ~2.3A at full discharge (9.6Vx1.5A/6.2V=2.3A, I think that's right), which at >1C could easily be above what the BAK cells can provide. Given that the Chinese lights tend to be built down to minimum spec possible to cut costs, that wouldn't be an unreasonable assumption. The Panasonic batteries used in the Geoman pack would be more than capable of sustaining that current though.

    Only way to tell is to buy and try!

  10. #10
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    I think my current one is 1.1A and looking to upgrade soon to the 1.4A model. The one linked above will probably work fine and it's relatively inexpensive.
    "It looks flexy"

  11. #11
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    I own 3 identical new style Geomangear 6.0 Ah battery packs. They're not working for me.

    All 3 packs cut power to the light when there is approximately 50% of pack capacity left when running light at 75% to 100% brightness.

    Light is 16.5 watts.

    If light is run at approximately 50% power and lower, then I get full calculated run time.
    Last edited by ThinkBike; 10-10-2012 at 03:37 PM.

  12. #12
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    Quote Originally Posted by ThinkBike View Post
    I own 3 identical new style Geomangear 6.0 Ah battery packs. They're not working for me.

    All 3 packs cut power to the light when there is approximately 50% of pack capacity left when running light at 75% to 100% brightness.

    Light is 16.5 watts.

    If light is run at approximately 50% power and lower, then I get full calculated run time.
    I had that issue with the Xera and the Geomangear packs. They are a sliggtly lower voltage and the Xera lights start flashing or like you said, can turn them to medium and be OK.
    "It looks flexy"

  13. #13
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    the voltage of all li-ion cells is the same. Either the cell voltage is being pulled down too far by more current than the cells can handle to the point where the battery PCB trips (unlikely, as Panasonics are really good cells), the PCB voltage trip setting is too high or the PCB overcurrent protection is set too low (as current increases with discharge on boost lights). Lowering the drive current reduces voltage sag, which would help with the first 2, and obviously helps with the latter.

    gticlay - the problem with various lightheads and the Geomangear packs is that the voltage discharge curves differ between cells (so one cell might be 50% discharged at 3.6V, another at 3.4V, even with the same capacity) - a lot of the MS and other heads have voltage warnings that didn't match the new batteries, so they warn of low capacity artificially early. Could also be what THinkbike is experiencing too, but I know that the early voltage warning problem was pretty common when those packs first came out.

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    Gticlay,

    I'm sorry to hear you're having or had the same problem with the Geomangear packs. Unfortunately the problem I'm having is more than just a flashing low power light. You can ignore the indicator light, you can't ignore no light at all.

    Mattthemuppet, I hear what you're saying. The 4 cells used in the pack are Panasonic NCR18650A with excellent high current drain capabilities. It's too bad that the PCB is shutting the pack down way to early.

    Once the pack has shut down, even if it's still half full, it can't be used until it's reset. You reset the pack by plugging it into the charger.

    So, you can be on the trail with a half full pack, no light and no way to reset the pack.
    Last edited by ThinkBike; 10-10-2012 at 06:25 PM.

  15. #15
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    Quote Originally Posted by mattthemuppet View Post
    the voltage of all li-ion cells is the same. Either the cell voltage is being pulled down too far by more current than the cells can handle to the point where the battery PCB trips (unlikely, as Panasonics are really good cells), the PCB voltage trip setting is too high or the PCB overcurrent protection is set too low (as current increases with discharge on boost lights). Lowering the drive current reduces voltage sag, which would help with the first 2, and obviously helps with the latter.

    gticlay - the problem with various lightheads and the Geomangear packs is that the voltage discharge curves differ between cells (so one cell might be 50% discharged at 3.6V, another at 3.4V, even with the same capacity) - a lot of the MS and other heads have voltage warnings that didn't match the new batteries, so they warn of low capacity artificially early. Could also be what THinkbike is experiencing too, but I know that the early voltage warning problem was pretty common when those packs first came out.
    It's what geoman told me. I guess he was incorrect?
    "It looks flexy"

  16. #16
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    Quote Originally Posted by gticlay View Post
    It's what geoman told me. I guess he was incorrect?
    I really couldn't tell you to be honest, this is all armchair conjecture based on my own limited experiences with li-ions. I'm pretty sure Geomangear was being straight up when he was talking about MS lights with his batteries, as most of the people experiencing that problem didn't have a reduced runtime but warning lights coming on too early.

    However, each PCB is specified according to the use it's expected to receive, especially the overcurrent protection. You don't want it so high as to melt the wires before it trips, but it can't be too low or it'll trip inappropriately. Most MS single emitter lights (and the Xera too, which is odd in your case) draw <2A as they have buck drivers - voltage is stepped down so current draw from battery is lower than current used by LED. So a trip level of 2.5 or 3A would be perfect - current should never get close to that level unless there's a short. But if that same battery is used in a high powered boost light, 2.5A would be right on the limit at high currents and low battery voltage, especially as Panasonic voltages tend to dip lower and stay that way for longer (in my experience at least) than other brands. So, if all that guessing is right, then there's nothing really wrong with the PCB, it's just very conservatively set and being used outside the parameters it's designed for.

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    After reading your last post Mattthemuppet, I think you're right. I'm using the packs in a manner for which they weren't designed.

    I think I'll have to look in the mirror to find the person responsible for the problem.

  18. #18
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    Quote Originally Posted by ThinkBike View Post
    Gticlay,

    I'm sorry to hear you're having or had the same problem with the Geomangear packs. Unfortunately the problem I'm having is more than just a flashing low power light. You can ignore the indicator light, you can't ignore no light at all.

    Mattthemuppet, I hear what you're saying. The 4 cells used in the pack are Panasonic NCR18650A with excellent high current drain capabilities. It's too bad that the PCB is shutting the pack down way to early.

    Once the pack has shut down, even if it's still half full, it can't be used until it's reset. You reset the pack by plugging it into the charger.

    So, you can be on the trail with a half full pack, no light and no way to reset the pack.
    I think you were mis understanding - the light would actually go into "dead battery" mode. I think it was flashing but could have been just super low light. That was last year so now I don't really remember.
    "It looks flexy"

  19. #19
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    Quote Originally Posted by ThinkBike View Post
    After reading your last post Mattthemuppet, I think you're right. I'm using the packs in a manner for which they weren't designed.

    I think I'll have to look in the mirror to find the person responsible for the problem.
    I wouldn't be so harsh on yourself ThinkBike, it's not something you could know in advance without detailed specifications from the manufacturer, which I'm pretty sure Geomangear never specified. If they were my batteries, I'd look into replacing the PCB with an aftermarket one that has a higher overcurrent limit - most of the multicell PCBs I've seen typically have a 5 or 7A limit. If you can find one that balance charges the 2 banks of parallel cells then you could even consider it an upgrade

  20. #20
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    be careful putting a higher current PCB onto a pack that already has one. Putting a higher current one on a pack that has cells that cant source that current cant cause immediate pack failure.

  21. #21
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    Quote Originally Posted by BallisticBatteries View Post
    be careful putting a higher current PCB onto a pack that already has one. Putting a higher current one on a pack that has cells that cant source that current cant cause immediate pack failure.
    You sell something like that? Don't you sell rc batteries? I think you used to sponsor a few of my friends in the bad old nicad rc days.
    "It looks flexy"

  22. #22
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    Quote Originally Posted by BallisticBatteries View Post
    be careful putting a higher current PCB onto a pack that already has one. Putting a higher current one on a pack that has cells that cant source that current cant cause immediate pack failure.
    true, although the packs they're referring to (Geomangear replacement packs) use NCR18650(A?) cells which are more than capable of supplying the current. I've seen them tested up to ~1.5C.

  23. #23
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    Quote Originally Posted by ThinkBike View Post
    I own 3 identical new style Geomangear 6.0 Ah battery packs. They're not working for me.

    All 3 packs cut power to the light when there is approximately 50% of pack capacity left when running light at 75% to 100% brightness.

    Light is 16.5 watts.

    If light is run at approximately 50% power and lower, then I get full calculated run time.
    I've seen this problem before on other pack / light head combinations. I don't have any experience with Geomangear packs but it's likely the same problem.

    The problem is usually caused by the way the LED driver draws current from the battery. Most modern drivers are based on switching regulator technology. That means the driver pulses power into a storage component (typically an inductor), to get the desired output. The drivers typically have capacitors on the input side to smooth out most of the fluctuation in the power draw from the source. But at higher power levels, the input capacitors don't smooth it out completely. This means the power is drawn from the battery in large pulses. This often fools the over-current protection on the PCBs. If you look at the current draw from battery using an oscilloscope, you can see what's happening.

    You can usually prevent the problem by opening up the battery back and adding an additional filter capacitor to where the leads attach to the protection PCB. Something like a 47uf tantalum capacitor will usually do the trick. It would also likely work if you attach the additional filter capacitor to the input of the driver instead of the battery.

    Just as an aside, this is exactly why mainstream manufacturer have warning statements like "do not use any parts of my light system with another brand of light". It's difficult, and hence much more expensive, to engineer a components that's guaranteed to work with any other components.

  24. #24
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    I use a Baja Designs battery with my home-brew XPG 7-up and it never seems to have run time issues.
    "It looks flexy"

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