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  1. #1
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    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light

    Bought a CREE XM-LT6 LED Bicycle Light on eBay from Hong Kong about a month back, used it about 6 times, i estimate i charged it 3 times, then on the 4th charge the Battery pack exploded, violently.

    It was being charged at the other end of my house in a spare room where i keep my biking gear. They had been on charge for about 2 hours when i heard 4 loud bangs, but to begin with I thought they were coming from outside. I then went through to the spare room to check and found that the Battery's had exploded all over the room causing dents in the wall, smashing the bar adaptor they were plugged into and causing burns all over the carpet. From the look of the carpet burns i was luck not to have had a serious house fire.

    As you will see from the pictures below there is very little left of the battery's or casing....

    I know these Cree lights are often sold under various names, and are fairly popular due to there decent brightness and low price, a friend has exactly the same pack but his is called the SSC P7 or something...


    Just thought i would give anyone else who has this pack or similar a heads-up..
    Attached Thumbnails Attached Thumbnails Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-cree_xm-lt6_led_rechargeable_bicycle_light_and_headlight.jpg  

    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-photo-1-.jpg  

    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-photo-2-.jpg  

    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-photo-4-.jpg  


  2. #2
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    A lot of people are buying cheap clone light sets off of ebay. It's a well known fact that a lot of these batteries being sold are built with cells that were rejected by the more elite brand companies. Usually this means you just get a crap battery that has less capacity. Some of the rejected cells could have the dreaded "internal soft shorts". These are internal short-circuits within the cell material. If they are bad enough the battery can go into "thermal runaway". When this happens none of the protection devices built into the battery or external circuit protection can stop the cell from exploding. It only takes one cell to go bad. When that happens a chain reaction can occur as each cell gets exposed to the heat of the other bad cell.

    For the record an otherwise good cell could develop a "soft short" as well if the battery sustained a big enough impact. It could also happen if the charger malfunctioned and tried to charge the battery beyond it's designed limit.

    As it stands you probably don't know what really caused this to happen as it could have been any of the possibilities I mentioned. You should report the incidence to the Consumer Product Safety Commission. We need to get these "bad batteries" out of the market place. I'm not dissing Li-ion technology per say, I'm dissing people who are selling products that they know are using materials that have been previously known to be "UNSAFE".

    A poor product is one thing but the marketing of a dangerous product is something that needs to be stopped. A word of warning to anyone who bought an ebay bike light with battery....charge the battery in a safe place and preferably in a fire-proof container. Monitor the battery while being charged and make sure it is not over-heating. Never leave the battery unattended while charging. Remove from the charger when the battery is charged.

  3. #3
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    Caution;  Merge;  Workers Ahead!

    Holy Razor's Edge Batman what a close shave!
    I'm glad that no one got hurt & and damage was minimal.
    Thank God the pack wasn't strapped to your CF frame.

    Thanks for reporting this.
    It looks like most of the generic packs out there with the blue heat shrink jackets over the 18650. Hard to say what exactly caused the catastrophic malfunction. To be safe I'd discard the charger too.

    Like Cat-man-do recommends, I'm going to get a LiPo Fireproof bag for extra precaution.
    12 LiPo Guard Fireproof Bag - $5.95 : EP Buddy, We Power Your RC Hobbies!

    Be safe everyone.
    Last edited by spartacus001; 02-04-2013 at 05:53 AM.

  4. #4
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    Wow. Just jumping into this clone market have 3 Chinese batteries....that is scary stuff.
    Thanks for the link Sparacus.

    And these batteries.....can they explode like that while not on the charger? Say..I have the thing at the recommended middle capacity charge and am storing it? ( I don't use lights at all in the summer...just spring ,winter and fall.

    Also...what about charging these batteries outside in the cold? Any forseeable problem? Running an outlet strip outside for a few hours to charge means I don't have to worry about it.
    Last edited by the mayor; 02-04-2013 at 07:11 AM.

  5. #5
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    First i'd like to say i'm glad you and the other members of your household are ok, and that you all still have a house to sleep in tonight. I do have to say though that my only surprise is that we havent hered about another incident like this sooner with those cheep ebay systems. As the others mentioned, charge in a protective battery bag and dont leave unattended.

  6. #6
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    potentially scary stuff. Cat man's advice is sound. Luck of the draw with these batteries, with respect to safety. Glad no more damage was done to you, your home, or family. It is also pretty standard that the batteries included with these lights are just garbage, and don't live up to their specs at all.

    Having a background in r/c hobby, I decided to convert some of my LiPo's for use with the MTB lights. I feel they are safer as you know what you are buying, generally. In the process of disassembling the eBay battery packs and seeing the hodge-podge solder jobs, and other indications of very low quality and potentially dangerous materials, I am very wary of using any of those batteries any more. I remove and re-use the PCB, then store/throw away the ebay batteries safely.

    And, when charging the LiPo's I also use the LiPo bag and place the batteries on non-flammable surfaces, and away from flammable/explosive materials.

  7. #7
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    I had been charging them in the garage but I considered the potential damage to cars, people and risk of fire.

    I live up here in Canada so I didn't want to deal with the additional complication of sudden condensation when I transfer the batteries from the cold to a warm environment.

    Until my LiPo fire bags arrive I'll be charging my batteries a metal tool box in the basement.
    Last edited by spartacus001; 02-04-2013 at 12:56 PM.

  8. #8
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    Good thought on condensation.

    FYI.....I had a laptop battery explode about 10 years ago. HP took care of it very quickly.

    And yeah ...I guess it could POSSIBLY happen more with these cheap batteries.
    But there has to be a butt load of these out there.....and I'd think that every forum would be full of horror stories...even fake and over exaggerated....if there were problems. When the whole Geoman/ MS thing happened...I only saw 1 picture of a closet that had damage ( I may have missed more??)

  9. #9
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    Quote Originally Posted by the mayor View Post
    .....And yeah ...I guess it could POSSIBLY happen more with these cheap batteries.
    But there has to be a butt load of these out there.....and I'd think that every forum would be full of horror stories...even fake and over exaggerated....if there were problems. When the whole Geoman/ MS thing happened...I only saw 1 picture of a closet that had damage ( I may have missed more??)
    Considering the number of these batteries out there floating around it really is a wonder it doesn't happen more often.

    If you have a way to monitor the charging safely that would be the best thing you can do. I have thermal monitoring but the stuff I have doesn't include an alarm. Having a thermal alarm would warn you if the battery was going into thermal runaway.

    Keep in mind the catastrophic failure rate of Li-ion batteries is very low. That is because the better places that make batteries put the cells through serious quality control before using them to build battery packs. The problem is the discarded cells are picked up and used by people who have the idea that they can still be used in the construction of cheap power sources. They do this thinking that the "cheap consumer goods" market is off of every ones radar. Unfortunately this fact is what helps give Li-ion technology a "black eye"

  10. #10
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    I've been wondering when this would happen/get reported.

    Cheap batteries, and cheap chargers are a disaster waiting to happen.

    Glad you were home, no one was in the room, and nothing major happened.

  11. #11
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    Holy cow! After the Geoman battery recall, I bought some used metal ammo cans and store and charge my batteries in them. Never used a Lipo pouch, but they are supposed to work well. In one of my ammo cans I have 4 batteries in it though so if one goes up the others will likely be lost too, so I think I will pick up some Lipo bags to separate the batts from each other while they are all in one ammo can. That way if one goes up hopefully the others will not. Thanks for posting this chick0 as it reminds us to be safe when charging and storing our batteries.

  12. #12
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    sorry to see this happen and glad that you're ok!

    In case someone sees this post and it happens to them VENT THE ROOM AND LEAVE THE HOUSE FOR SEVERAL HOURS. Exploding li-ion batteries can release hydrogen fluoride gas which is incredibly nasty stuff and can cause permanent lung damage.

  13. #13
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    Quote Originally Posted by mattthemuppet View Post
    sorry to see this happen and glad that you're ok!

    In case someone sees this post and it happens to them VENT THE ROOM AND LEAVE THE HOUSE FOR SEVERAL HOURS. Exploding li-ion batteries can release hydrogen fluoride gas which is incredibly nasty stuff and can cause permanent lung damage.
    I can back Matthemuppet up on this, the spare room and in fact the whole house smelt horrendously bad for more then 2 days after, even with the rooms being continuously ventilated..

  14. #14
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    Quote Originally Posted by mattthemuppet View Post
    sorry to see this happen and glad that you're ok!

    In case someone sees this post and it happens to them VENT THE ROOM AND LEAVE THE HOUSE FOR SEVERAL HOURS. Exploding li-ion batteries can release hydrogen fluoride gas which is incredibly nasty stuff and can cause permanent lung damage.
    Glad you mentioned this Matt. Not the kind of thing one thinks about when something like this happens. Time for me to search out a thermal monitor with alarm. Maybe something like this...

  15. #15
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    How much does the temp of these things go up before they blow?

    And I asked about chargers before....but is there a charger available that shows details like current charge, etc...and may give details on possible problems? I have a Sears charger that claims to have a diagnostic mode that will not charge the battery if it thinks there is something wrong.

  16. #16
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    With the pack disassembled I've been charging the individual cells with a smart charger. I use a multimeter to record the history of all my cells.
    The guys over on CPF really like ver 4 of this smart charger.

    Here is an excellent review of the Nitecore Intellicharger from CPF:
    Sysmax/Nitecore/Jetbeam i4 Intellicharger Review (V2): current/voltage comparisons

  17. #17
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    Thanks for the info. But this won't change my current charging habits just like it didn't with the MagicShines several years ago.

    Lithium Ion batteries will always have the potential for this kind of problem. Do you think Boeing is using "discarded cells" on the new 787? Same battery type, same issues. Just use common sense and even then you could have an issue.

    Such is life.
    How can anyone who's been riding as long as I have, be so slow???

  18. #18
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    Cat pretty much hit the nail on the head. The Li-Ion batteries were most likely of lower quality. The internal soft short are a know issue where the cells have latent failures. If this was the root cause here you most likely will not know.

    Would try to replace the pack with a Lithium Polymer pack. The initial cost for a Li-po is a little higher but the total lifecycle cost is significantly lower.

  19. #19
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    Quote Originally Posted by Rock View Post
    Thanks for the info. But this won't change my current charging habits just like it didn't with the MagicShines several years ago.

    Lithium Ion batteries will always have the potential for this kind of problem. Do you think Boeing is using "discarded cells" on the new 787? Same battery type, same issues. Just use common sense and even then you could have an issue.

    Such is life.
    Yeah....I'm have to agree with you here.
    Time to take off the tin foil hat...and just use common sense.
    Like I said earlier....I had a new laptop battery blow years back.
    And I was going to buy a MS light when the whole battery FUBAR happened....so I held off. But looking back...I only saw 1 battery that caused the whole commotion.
    And with the butt load of clone batteries out there...this is the first I've seen that blew.

  20. #20
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    Quote Originally Posted by Rock View Post
    Thanks for the info. But this won't change my current charging habits just like it didn't with the MagicShines several years ago.

    Lithium Ion batteries will always have the potential for this kind of problem. Do you think Boeing is using "discarded cells" on the new 787? Same battery type, same issues. Just use common sense and even then you could have an issue.

    Such is life.
    Not Li-On in all cases, but it's my understand that many planes are designed so a run-away condition will melt through the bottom of a wing, and thus jettison the entire battery, before a disaster ... Ni-Cad's of the past = Almost always incorporated a melt the bottom out, into the aricraft design.

    The manufacturers of aircraft understand the problem, very well ... Once you reach the point, it's gonna blow.

  21. #21
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    Quote Originally Posted by the mayor View Post
    How much does the temp of these things go up before they blow?

    And I asked about chargers before....but is there a charger available that shows details like current charge, etc...and may give details on possible problems? I have a Sears charger that claims to have a diagnostic mode that will not charge the battery if it thinks there is something wrong.
    As far as how hot they get before they blow...I read about that somewhere but at the moment escapes me but I believe it is quite high.

    Li-ion batteries really don't get that hot when charging. If I was using a thermometer to monitor the battery during a charge I would start to worry if I began to see it go over 100F. If I see that happen I would immediately take the battery outside and then dispose of the battery properly.

    Sorry Mayor, I can't help with the fancy charger issue. Would be sweet though if a charger came with a built in thermal monitor. So we don't confuse people here, other battery chemistry can get quite warm when it charges but Li-ion is not one of them.

  22. #22
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    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light

    It has been mentioned, I think in this thread and likely many others in the lights forum about using r/c hobby chargers. They aren't too expensive and offer all kinds of settings and info while charging. I use one for my r/c batts I've converted to bike light use, but have yet to hook one of these LI-ion batteries up to it. Not sure how it would work through the pcb circuit, probably fine, just wanted to research more before doing so. I have something like this... https://www.hobbyking.com/hobbyking/...ischarger.html

  23. #23
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    Crap. I bought a pair of these lights, and two of my friends each bought two sets.

    One of my friends owns a battery store. I'm gonna disassemble my stepson's packs and test his batteries and replace them if necessary with better quality cells.
    I like turtles

  24. #24
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    Glad the OP didn't have a fire.

    Had the same light. Too tempting when it claims 1200LM for $33.

    Died after one use. Sent it back. Amazon reviews were positive...

    Amazon.com: CREE XML XM-L T6 LED Bike Bicycle Light HeadLight HeadLamp 1200LM Red: Sports & Outdoors

  25. #25
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    Xtar has just released their newest VP1 smart charger featuring a digital display of the charging status.

    VP1

    Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-vp1.jpg

    Quote Originally Posted by the mayor View Post
    How much does the temp of these things go up before they blow?

    And I asked about chargers before....but is there a charger available that shows details like current charge, etc...and may give details on possible problems? I have a Sears charger that claims to have a diagnostic mode that will not charge the battery if it thinks there is something wrong.
    Attached Thumbnails Attached Thumbnails Exploding Battery pack - CREE XM-LT6 LED Bicycle Light-53705055125506821952893.jpg  


  26. #26
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    That's a nice charger if you run individual batteries....but most of use run premade packs....and that doesn't look like it will work.( or am I missing something?)

  27. #27
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    Yes. Only used for charging/monitoring individual cells.

  28. #28
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    One thing I want to add to this, Never charge a Li-ion pack when the pack is below 30F. Doing so can cause shorts to develop in the pack. When you come in after that winter ride bring the pack inside and give it some time to warm up before plugging it in.
    Jim Harger
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    After the first battery issue a couple of years ago, I had enough and built a dynamo front wheel to power my commuter lights. Now, I get plenty of (not blinding) light from 2 XMLs and a red XP-E, and all I ever have to do is turn em on and clean the lenses. (Oh, and ride my bike, which I enjoy even more, now that doing so also lights my way.) No batteries, chargers (in fire-proof bags?), range anxiety or noticeable drag from the hub. May I offer you some Koolaid?

  30. #30
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    Quote Originally Posted by jack in the matrix View Post
    May I offer you some Koolaid?
    No thanks!

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    Oops

    Just realized I left my cheap battery on the charger all last night and today. In my garage tho.

    Hope the house is not burned down when I get home.

    Geez, completely forgot.

  32. #32
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    Scary!

  33. #33
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    This makes all my light screw ups look minor.
    Thanks!

  34. #34
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    Quote Originally Posted by mb323323 View Post
    Just realized I left my cheap battery on the charger all last night and today. In my garage tho.

    Hope the house is not burned down when I get home.

    Geez, completely forgot.
    A simple solution for this is to plug the chargers (if you have more than one) into a power strip and then plug that into a timer. You can have the timer shut off the power after 6 hours or something.

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    As sidenote, I've read of some occasional cases in german mountainbike forums, that bikelights imported from China/Hong Kong and the like, shipped via the common postal channel, were stopped and rejected to import at the german customs authority border. Expressely for "unsafety of the charger, not complying with the german (EC) standards".
    So at least it seems to be a known issue even in some customs agencies.

    Regards

  36. #36
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    Quote Originally Posted by CHnuschti View Post
    As sidenote, I've read of some occasional cases in german mountainbike forums, that bikelights imported from China/Hong Kong and the like, shipped via the common postal channel, were stopped and rejected to import at the german customs authority border. Expressely for "unsafety of the charger, not complying with the german (EC) standards".
    So at least it seems to be a known issue even in some customs agencies.

    Regards
    That almost sounds "Facist". I have the feeling there is likely quite a black market in Germany. At least where I live if I want to buy "cheap junk electronics", I'm free to do so as long as it doesn't hurt anyone else.

    Interestingly, no one stopped the Germans from exporting the first VWs into the United States back in the day. Need I say those first VW Beetles were pieces of crap ( yeah, I owned one ). Still, that didn't stop people from buying them because they were dirt cheap.

  37. #37
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    Well these heap packs have pretty bad recycled cells inside which are not in the same condition with varying capacity. The PCB does not prevent them from overcharge and does not see the balance lead when charging through the PCB with the charger that came with the light. I have tested this, as I got an unbalanced pack with the light. Two cells were topped to the 4.3V!!!! but the other two just sit at 8.4V - 4.3V = 4.1V. That was here probably the cause of the explosion - the unbalanced state. So it does not need to explode if you charge it with a balance charger skipping the PCB. The cells are likely unbalanced in most cheap lights, so be careful using them! Electrical knowledge is required when handling these lights - at least I think.

    Quote Originally Posted by Action LED Lights View Post
    One thing I want to add to this, Never charge a Li-ion pack when the pack is below 30F. Doing so can cause shorts to develop in the pack. When you come in after that winter ride bring the pack inside and give it some time to warm up before plugging it in.

  38. #38
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    Things like this is why I've never used original chargers supplied with lamps like this. I always balance charge my batteries using RC charger.
    I'm pretty sure MK96 is right, one group of batteries had less capacity than the other and it got severely overcharged. Btw, 4.3V isn't a problem even for a bad quality 18650, so imbalance must have been even greater, and then even high quality cell would go thermal.


    Quote Originally Posted by Action LED Lights View Post
    Never charge a Li-ion pack when the pack is below 30F. Doing so can cause shorts to develop in the pack.
    Not only it can cause shorts to develop, it also ruins battery capacity. After a few cold charges battery can have it's capacity considerably reduced.

  39. #39
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    Quote Originally Posted by bobale View Post
    Things like this is why I've never used original chargers supplied with lamps like this. I always balance charge my batteries using RC charger.
    A properly design battery pack (like all the ones we sell) have a balancing circuit built into the PCB with a lead to the center connection. However, these PCB's, and all hobby chargers, treat parallel pairs as a single cell. Balancing is only for cells in series and does nothing for mismatched pairs.
    Jim Harger
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  40. #40
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    That's why I've added balance connector to every multi-cell pack I have, so I can really balance them and monitor votages at cell level.

  41. #41
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    I'm sorry Jim, but with all due respect I strongly doubt that the PCB in your battery packs balance charge. Balance charge PCBs are characterised by large thick wires used to burn of dV between series wired cells and I have never, ever, seen this type of PCB used in bike battery packs whether from Chinese manufacturers or high end US and German lights. I've even looked into using them myself to avoid having to add balance taps to my batteries, but they're seriously expensive and bloody huge (e.g.http://www.batteryspace.com/pcmwithe...02s20-265.aspx)

    The lead to the center connection is for voltage monitoring individual parallel banks, nothing more, presumably with a trip voltage built into the PCB that, should, in theory, prevent such massive cell imbalance that results in fire/ explosion from overcharging.

    Parallel cells can never get out of balance as the voltage of individual cells in the parallel banks will "float" until termination voltage is reached. Similarly, on discharge, a cell with lower capacity that it's brothers in a parallel bank will simply stop contributing current once it's fully discharged.

    The BIG problem is series cells getting out of balance, as a result of differences either in capacity of the series cells or through different rates of self discharge. The PCBs in commercially available battery packs do nothing to prevent this imbalance as it is purely a function of the quality and matching of the cells at assembly. Balance charging with a balance tap will paper over the cracks of an unbalanced pack, but it won't treat the symptom of the problem, which is poor cell choice.

    Now, I'm not casting any aspersions with regard to the packs you sell as I have no experience of them and I'm sure that they're what you say they are. They do not, however, have balance PCBs.

  42. #42
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    Quote Originally Posted by mattthemuppet View Post
    .....The BIG problem is series cells getting out of balance, as a result of differences either in capacity of the series cells or through different rates of self discharge. The PCBs in commercially available battery packs do nothing to prevent this imbalance as it is purely a function of the quality and matching of the cells at assembly. Balance charging with a balance tap will paper over the cracks of an unbalanced pack, but it won't treat the symptom of the problem, which is poor cell choice....
    You can also use a " 4-cell holder" to get around this problem but then you have to remove the cells and charge each cell separately. I was doing this with one of my other lamps but soon found the ( cells in/ cells out ) routine quite tedious. So much easier to just plug the battery into a single charger.

    Sure would be nice if standard 4-cell 7.4 volt Li-ion bike batteries came with pre-setup balance leads ( like some of the Li-Po ). Now if they did you would need a much more expensive charger but that almost goes without saying.

  43. #43
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    Quote Originally Posted by Cat-man-do View Post

    Sure would be nice if standard 4-cell 7.4 volt Li-ion bike batteries came with pre-setup balance leads ( like some of the Li-Po ). Now if they did you would need a much more expensive charger but that almost goes without saying.
    It's not just the more expensive charger (although you can get 2S/3S mini balance chargers for not much), it's the issue of waterproofing an extra cable and plug. That's my biggest peeve and I think it would add a lot to the cost of the light, without really providing much benefit. For high quality batteries, balance charging isn't going to make a huge difference (general use and age will have far more significant effects); for cheap batteries, it's not going to affect the underlying problem of cheap cells, but at a cost that I doubt any of them would pick up.

  44. #44
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    Quote Originally Posted by spartacus001 View Post
    Xtar has just released their newest VP1 smart charger featuring a digital display of the charging status.

    VP1

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    Would it be tough to attach a lead to these to charge sealed battery packs? I've done this in the past with simple chargers.

    Any other suggestions for inexpensive but safe chargers?

    I use a good quality hobby charger but when I make light sets for friends I've been getting them cheapo chargers. Be nice to find something in the middle for them.

  45. #45
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    I think hobby charger is the best solution ;-) Perhaps some from hobby-king.

  46. #46
    Action LED Lights
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    Keep in mind, a hobby charger balances batteries in series but will do nothing for mis-matched cells in parallel.
    I agree with Cat that the best DIY solution would be individual protected cells in a battery holder. (I'm working on a source.)
    Jim Harger
    Action LED Lights
    www.action-led-lights.com

  47. #47
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    Quote Originally Posted by Action LED Lights View Post
    Keep in mind, a hobby charger balances batteries in series but will do nothing for mis-matched cells in parallel.
    I agree with Cat that the best DIY solution would be individual protected cells in a battery holder. (I'm working on a source.)
    A nice 8.4V battery case like this would be great.

  48. #48
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    WOW, scary being I just got mine in the mail today

    Ok so I ordered one of these lights came in today. Didnt realize the companies were selling possibly already soft shorted cells.....

    But luckily for me I preplanned (cause the wall chargers for and Li based batteries are asking for problems) to take the cord off the charger and plug into my smart charger.



    One of the few things I have left from my RC days. Kept it cause it charges ANY rechargeable battery I have, even for my cordless drill and so on. Now even happier I still have it cause I can safely charge these. I do have to say for hte money you cant go wrong on these lights, especially if your like me and a DIY type person with alot of knowledge on building battery packs and LED light systems. $27 for a light I can mod the hell outta with new pack for less than another $50 and will be comparable to high end $200+ lights
    Great lights:

    www.ituolights.com

    Life on 2 wheels is the only life for me. Especially once it gets dark.

  49. #49
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    Quote Originally Posted by tigris99 View Post
    $27 for a light I can mod the hell outta with new pack for less than another $50 and will be comparable to high end $200+ lights
    Should plan on at least looking at the driver and assembly care too. The cheapo lights typically some components that are under-spec'd on the driver. Poor soldering is common. If it has a buck style driver, check that the inductor is glued to the board. Poor heat path/no thermal transfer compound. Fun stuff for a DIY type person though.

  50. #50
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    ya that was what I was referring to as mod the hell outta lol. New driver, LED, and cells for the pack. So $27 for a housing, pouch, switch (which I like cause its lit) and long as wires with connectors already. As well as battery monitor possibly. Dont know much about drivers yet learning that atm so thnx for the pointers about that, things to check!!!
    Great lights:

    www.ituolights.com

    Life on 2 wheels is the only life for me. Especially once it gets dark.

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