"Noob" battery/charger help.- Mtbr.com
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  1. #1
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    "Noob" battery/charger help.

    Couple months ago, i knew absolutely nothing about batteries except you put em' in and the light goes on, lol. After much research i now have just a basic knowledge of the different types of batteries and chargers but have a couple random questions to get me over he first "hump".

    Would like a charger that will charge my flashlight batteries (cr123a or 18650) and my "MS" battery packs (or replacement packs). So, dumb questions are;

    1. Looking at a multi-balance charger (like IMAX or Tenergy) but still a little shaky on how they work. As far as i'm understanding, the battery pack must be pre-wired a certain way (3rd wire?) to take advantage of the "balance" mode? So for example a stock MS battery pack wouldn't benefit? Is it better to just charge them (MS vs. flashlight) with specific chargers?

    2. How does it charge say one cr123a or 18650 (or does it)? I mean physically, i don't see how it attaches to the battery. Do you need some kind of holder with leads on it for "clips"?

    3. And as far as i understand, it's the "pcb" protector on the MS batteries that are the problem. Can't the faulty pcb's just be replaced or are they in the battery itself?
    Last edited by DiscoDust; 12-16-2010 at 06:00 AM.

  2. #2
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    1. You need to make a balancing out for MS-battery. If you just charge it with original charger, it may degrade due to unbalancing between cells.
    2. I use DIY holder for 18650s. My charger has 2 wires with crocodiles - I plug them to the holder.
    3. PCB is not the only problem. Cells in MS pack often have DIFFERENT capacity, so you need to balance them.

  3. #3
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    here are some simple, cheap 18650 battery holders.............
    http://search.digikey.com/scripts/Dk...393250&k=18650

    and here is a cr123a holder from the same place........
    http://search.digikey.com/scripts/Dk...93250&k=cr123a

    I can't speak for the cr123a holder, but the 18650 holders have tabs sticking out of the backside of them that you could in theory clip alligator clips on for charging purposes.
    But I would just solder some kind of connector to them.

    As far as balance charging goes, it may not benefit you NOW without modding those MS packs, but if you see yourself in the future building packs, it will really come in handy.

    It is good in the sense that you can adjust the exact output on the charger though. Thats why I got one.

    This is the one I got....
    http://www.xheli.com/thac6bachwac.html

    It comes with several different connectors, and is a pretty slick little setup.
    Look, whatever happens, don't fight the mountain.

  4. #4
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    Quote Originally Posted by DiscoDust

    3. And as far as i understand, it's the "pcb" protector on the MS batteries that are the problem. Can't the faulty pcb's just be replaced or are they in the battery itself?
    The biggest problem with the magicshine packs is the cells themselves. They contain soft shorts which is why they are self-discharging much too quickly and at different rates and throwing the packs badly out of balance. Soft shorts can also lead to more serious problems, which may be related to the recall, but I don't have anyway to know if that's what is driving the recall. It is what is causing the packs to become unusable from a runtime perspective.

    The PCB also has issues in that the per cell low voltage safety cutoff voltage is much too low. It's right below 2v and should be at least 2.5-2.7 volts.

    If you want more details, you can look back at other posts I've made on this topic.
    Last edited by MtbMacgyver; 12-16-2010 at 01:53 PM.

  5. #5
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    Quote Originally Posted by savagemann
    It is good in the sense that you can adjust the exact output on the charger though. Thats why I got one.

    This is the one I got....
    http://www.xheli.com/thac6bachwac.html
    I bought and just received this one:

    http://www.all-battery.com/tenergyb-...rger90252.aspx

    It appears to be the same one as you show above, but the AC adapter is external. Can you please explain what you mean above by "you can adjust the exact output on the charger"?

    I'm trying to charge some Samsung 30A 3,000mah batteries, and the Samsung spec'd voltage cut off is 4.35v. Without the ability to raise the cutoff voltage of the charger (4.2v), I'm not able to achieve 100% charge on these cells. I see that under the back vinyl cover plate, there are some adjustment pots with some indication of direction of turn for raising or lowering the voltage. I'm wondering if I could maybe get 100% charge into these batteries if I could adjust the cutoff voltage up. There's no indication on this in the instructions.

    Oh, and don't feel too badly for me. I had a coupon for 13% off, and shipping was free so I probably paid about the same as you (for a lesser charger - external AC adapter).

  6. #6
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    Thank you so much for all the info. Think i got the basics. That Thunder charger looks pretty pimp with the software and all. Think that would definitely be one i could "grow into" and take care of all my battery charging needs.

    Just curious, i see the posts recommending some aftermarket battery packs to replace the MS ones. Are any of the pre-made packs "balancable" or do you HAVE TO build them yourself? How exactly do you know if they can be balanced...what's the key word or what do you look for? Three (or more) wires? Or is just the way they are wired together? You would think they would all be "balancable", does it cost more money or something?

  7. #7
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    Quote Originally Posted by DiscoDust
    Thank you so much for all the info. Think i got the basics. That Thunder charger looks pretty pimp with the software and all. Think that would definitely be one i could "grow into" and take care of all my battery charging needs.

    Just curious, i see the posts recommending some aftermarket battery packs to replace the MS ones. Are any of the pre-made packs "balancable" or do you HAVE TO build them yourself? How exactly do you know if they can be balanced...what's the key word or what do you look for? Three (or more) wires? Or is just the way they are wired together? You would think they would all be "balancable", does it cost more money or something?
    I've never seen a pre-built li-ion pack using 18650 cells that comes with a balance connector installed. I assume this is because having a balance connector bypasses the built in protection circuitry and the folks that sell pre-built packs are unwilling to expose themselves to the liability of providing a path around the protection circuity. So you'll probably have to add it yourself if you want one.

    These connectors are common on lipo packs that do not include protection circuitry. They allow some of the protection logic to be provided by the charger in addition to balance function.

  8. #8
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    Quote Originally Posted by DiscoDust
    Just curious, i see the posts recommending some aftermarket battery packs to replace the MS ones.
    Yes. Not cheapo, but it's MS-compatible (and I can use this accus for future builds if I decide to):
    http://forums.mtbr.com/showpost.php?...5&postcount=20

  9. #9
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    @BlownCivic: I have the same Thunder AC6 charger. You can tune most of the parameters like charge current etc. I haven't had the need to go outside the standard cutoff but that may be tuneable as well. Google up the manual to see details

    @DiscoDust: If you read some of the info MtbMacgyver, you'll see that balance charger won't fix the issues with the MS battery being unbalanced. It's the poor quality of the cells causing the problems. A pack built with good brand name quality cells from the same lot will have a lot less variation making the balance unnecessary for all practical purposes. I haven't seen any of the major bike light companies using balance charging so don't worry about it. The AC6 is still a good charger even if you don't use the balance feature.
    Long Live Long Rides

  10. #10
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    Again, thank you guys so much. It all makes prettty good sense and i now understand the problem with the MS packs.

    Just one thing i'm still not clear on:

    You cannot have a protected battery pack AND have it be a "balancable" at the same time?

    So "RC car style" battery packs simply rely on the charger for a cut off instead of a PCB in the pack itself? Why do they risk the liability but not with battery packs for lights? Could have sworn i saw a post with someone using an RC battery pack for a light?

  11. #11
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    Quote Originally Posted by DiscoDust
    Could have sworn i saw a post with someone using an RC battery pack for a light?
    Post #8
    I use LiPolys with buzzer as low-voltage indicator.

  12. #12
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    Ha, thanks "klynk". Your setup looks great. So it's protected with the "buzzer" and it can be balance charged? And forgive my "noobness", but are you talking like a doorbell buzzer (audible) or is that an electronics term for a PCB type thing? I've got a lot to learn, lol.

    I did see another post somewhere where the battery pack looked just like an RC battery pack, not as intricate as yours in the can. They were even talking about how it strapped to the frame better being flat.
    Last edited by DiscoDust; 12-17-2010 at 03:37 AM.

  13. #13
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    Yes, buzzer is audible.
    Ordinary LiPolys are softshell, so they can be easily damaged.

  14. #14
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    Quote Originally Posted by DiscoDust

    So "RC car style" battery packs simply rely on the charger for a cut off instead of a PCB in the pack itself?
    That's correct, RC packs typically do not have any built in protection electronics. They rely completely on the motor controller to provide a voltage cutoff during discharge, and the charger to provide voltage cutoff during charge. It's an incomplete safety solution on discharge because it only monitors the overall pack voltage instead of per cell voltage. On charge, a good charger using the balance connector, will monitor the voltage of each cell. But in both cases this setup doesn't include the redundancy of a separate protection PCB that's common for lithium battery pack in consumer electronics.


    Quote Originally Posted by DiscoDust
    Why do they risk the liability but not with battery packs for lights?
    You have to keep in mind that in RC applications, the currents are so high and weight is so critical that it's technically impractical to have built in protection PCBs. The weight and size of a protection PCB is proportional to the current it can handle. So a protection PCB for an airplane pack that runs 40 amps would be huge. So there is some level of tradeoff between safety and practical functionality. We really don't have that same constraint in the bike light world so I wouldn't expect to see the same approach to battery safety.

    There is also a view that the RC market is more technical and hobby oriented than a more mainstream consumer product. But, lipo safety is a huge ongoing debate within the RC world. There is even a crowd that refuses to use the technology. I don't know how the battery makers handle this from a pure legal point of view. Could be why a large percentage of them are based overseas.

    Quote Originally Posted by DiscoDust
    Could have sworn i saw a post with someone using an RC battery pack for a light?
    Technically it'll work. It's just a matter of how much effort you want to put into providing your own protection or how much risk you want to take by running without protection. Keep in mind that nearly every RC motor controller provides good customizable voltage cutoff. Most of the low cost bike light heads do not. If you use something like a taskled driver, you can at least get a good overall pack cutoff, but not per cell voltage monitoring. It's also important to understand that if one cell in an RC pack does drop voltage when being discharged at 30-40amps, it becomes immediately apparent in reduced motor performance. With a bike light, it can go completely unnoticed due to the nature of the regulated LED drivers.

    In the end, why wouldn't you provide full protection for a bike light pack. Just to save a couple of dollars? A 3 or 4 cell protection pcb in the current range for bike lights costs less than 10 dollars.

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