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  1. #1
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    Review & dissection of magicshine battery mj-828

    Executive summary – for the regulars

    Nice new battery case, might even be water resistant.

    Same old battery inside

    Note this is the deal extreme case, NOT the replacement battery from geoman or various other sellers.

    Background

    I bought a magicshine bike light mj-808 with an updated battery back that appears to be better designed & possibly even rainproof. I am one of those people that pulls new stuff apart to see how it works & this was no exception

    The battery pack is known as mj-828. It is not listed separately on DX but there are a few listed on ebay.

    The same battery pack is used in the similar light with a different housing & clip xml light but the extra $20 did not seem worth it to me.

    As I understand it, there are four issues with the magicshine batteries:

    • Getting wet
    • Overcharging
    • Excessive discharging
    • Defective cells
    Makes them sound like gremlins – don’t get them wet, don’t feed them after midnight.

    What really got my attention was this Material Safety Data Sheet “At contact of electrolyte with water traces of hydrofluoric acid may be formed”.

    Despite the focus on flames, personally I am far more concerned about any possibility of coming into contact with hydrofluoric acid, so a waterproof battery pack was high on my list of priorities.

    The before shots

    The promotional shots are as good as any.





    Getting it apart

    Getting it apart was easy. The end caps are held on by two external allen head bolts. Undo these, trying not to lose the nuts or washers, and both end caps simply slide out.



    Initial impressions reinforced the build quality you have come to know and love from these lights – in my case there was a piece of foam caught under the o-ring which would have done a nice job of wicking water straight past the seal and nothing to indicate any grease on the o-ring. It seems that o-ring grease is as uncommon as thermal paste in these Chinese factories.

    The housing is simply a tube of aluminium



    One side is flat while the other 3 have a curve, so the caps only fit on one way.



    The battery pack itself

    Call me optimistic, but I was hoping that having put the battery pack in a better case that they might have paid some attention to the battery itself. I was surprised to see a centre tap wire & dared to hope that it might possibly be used for balancing.



    Alas it appears this was there on the old packs and is only used for over/under voltage shutdown and doesn't perform any balancing see this thread on mtbr at post 87

    To my untrained eye the PCB appears to be the same





    On the plus side there is nothing to indicate that the battery is any worse than the original – yes I am an optimist.

    The volt meter

    One of the pieces of marketing on this pack is that it has a backlit lcd display showing volts & a little fuel gauge with 5 steps. To my way of thinking this “feature” is completely useless

    • When I mounted the battery on my bike, there was no easy way to see the lcd
    • The led on the back of the light changes from Green to Blue to Orange to Red as the voltage drops.
    • It displays voltage of the pack, which doesn’t tell you if the pack is out of balance
    In case you care, here is a pic of the volt meter circuit board



    I voted with my soldering iron & removed it. Oops there goes my “warranty” but it means there is one less thing to go wrong & there is now a convenient spot to put a switch to turn the battery off rather than having to unplug it from the lighthead.

    It probably sums up the build of the pack that when I removed the volt meter I discovered they fitted strain relief to the cable to stop you pulling it out of the end cap. Unfortunately the strain relief they chose was a steel circlip – two nice points of thin conductive material – just what you don’t want putting pressure on you power lead, so I removed that too and replaced it with a small plastic zip tie.

    Putting it back together

    It’s just a reverse of the disassembly steps right? After spending a couple of fruitless hours trying to re-insert the end caps & o-rings, contemplating replacing the o-rings with silastic & general frustration, I had a closer look at the end caps.



    Each one has four screws –if you look carefully you will see them hidden under round pieces of plastic. The end caps are actually two parts that squeeze the o-ring, so once you take the cap out, it won’t just slide back in.

    Instead you have to loosen the four screws till they are just holding the pieces together, lubricate & re-insert the o-ring, insert the end cap & tighten the four screws. When done this way it was a work of minutes.

    The observant will see that these screws introduce eight potential leak points & a piece of glorified sticky tape is unlikely to last the distance. The bodger in me wanted to fill the heads with silastic, but I know if I ever want to reassemble it again, silastic in Phillips head screws is a PITA. For now I have kept the plastic dots, but will need to find a better solution

    Conclusion

    The new housing addresses one problem – waterproofing, but the other three remain. Overcharging & discharging can be addressed with care and a better charger. Time and monitoring the voltages of the individual cells will reveal defective cells.

    Welcome to the Chinese lottery – you pays your money and you take your chances
    Last edited by find_bruce; 05-31-2011 at 02:58 PM. Reason: Correct error identified by Catman

  2. #2
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    Thanks for the review/dissection.
    baker

  3. #3
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    Nice review Thanks
    I always type in bold cuz I'm blind as a bat
    For the Rich there is therapy!!!! for the rest of us we have Mountain Biking


  4. #4
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    well, on the plus side it looks like a nice robust case and it shouldn't be too hard to replace the cells as and when they die

  5. #5
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    Nice review Bruce.

    Don't let that MSDS document scare you. All of that stuff is basically "worst case scenario". The cell would have to be very badly damaged for that stuff to happen.
    Interesting that the MSDS is for a German made battery.

    The link you posted for the MS XM-L light is wrong. The MJ 808E is using a coated battery. Likely the same actual battery though.

    The link for the MJ 828 battery list the water-resistance grade at " IP67 ", for what that's worth.

  6. #6
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    Quote Originally Posted by mattthemuppet View Post
    well, on the plus side it looks like a nice robust case and it shouldn't be too hard to replace the cells as and when they die
    Yep, that's exactly what I was thinking. Nice neat holder to put some quality cells in. Of course the next problem will be deciding on a good PCB to use. People seem to recommend Battery Space, but I am not paying $78 shipping for a $5 part.

    Quote Originally Posted by Cat-man-do View Post
    Don't let that MSDS document scare you. All of that stuff is basically "worst case scenario". The cell would have to be very badly damaged for that stuff to happen.
    Interesting that the MSDS is for a German made battery.

    The link you posted for the MS XM-L light is wrong. The MJ 808E is using a coated battery. Likely the same actual battery though.

    The link for the MJ 828 battery list the water-resistance grade at " IP67 ", for what that's worth.
    Thanks Cat, the link was right it was my description that was wrong I will edit the post to correct.

    IP67 certainly sounds impressive, but as I recall from flooding dive lights, its no guarantee against faulty assembly, poor o-rings or lack of lubrication.

  7. #7
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    Thanks for the detailed look.

    Some of those soldering joints are pretty bad; in fact the one on the lower right here looks cold (as do some of the surface mount joints):

  8. #8
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    Nice review. It does seem if you could put in a decent battery and use a decent charger, the packaging seems ok, if waterproofing is managed outside of the case. . Just toss the cheap cells after they fail or burn-up.

    BTW, All the comments about tape remind me of way back while in college I wanted to pick up a cheap FM Tuner. Radio Shack sold one for $100. Like you just had to look inside, and found black electrical tape holding things together. Guess what went back- rather quickly.

  9. #9
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    Nice review..

  10. #10
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    How do you access the screws under the cap to loosen them? I can't get past the little plastic circles.I noticed the battery pack in mine is slightly different - it's a single solid black part, possibly containing the 4 batteries in your review.

  11. #11
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    Quote Originally Posted by Skirmish666 View Post
    How do you access the screws under the cap to loosen them? I can't get past the little plastic circles.I noticed the battery pack in mine is slightly different - it's a single solid black part, possibly containing the 4 batteries in your review.
    On mine the little plastic circles were just stuck on & I could slip a small flat jewellers screwdriver past the edge to get it out without damage.

    Yes the batteries were contained in black plastic shrink wrap - I cut it off & replaced it. Better if you can get the proper shrink wrap, but I just used 1" wide electrical tape & wrapped the batteries.
    Last edited by find_bruce; 02-28-2012 at 08:36 PM.

  12. #12
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    Balancing

    Just to add to this excellent review... here's a of shot of what you're looking for in a PCB with built-in balancing for each bank of cells. This is an 11.1V (nominal) pack and you'll see a tap for each cell at 3.7V, 7.4V, and B+ (11.1V).

    This allows the use of an inexpensive non-balancing charger. Then after the charger is disconnected, the voltage between each of the three cell is balanced, so that they're all three exactly equal. This prevents the scenario of one cell dropping in voltage over time, while the other two take up the slack by being overcharged. JFWIW
    Attached Thumbnails Attached Thumbnails Review & dissection of magicshine battery mj-828-new_2900mah_2.jpg  


  13. #13
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    nice review, thanks !

    couple of comments:
    think , the round one, is better, easier sealed.
    the balance pcb is a good idea.
    still , like the extra leads, so I could measure, and use my fancy RC charger.
    did build/mod a pack, with a 3pin connector.
    but then you have to use a adapter cable, and that's just ugly.
    workaround, to add 1pin connector, separate.
    that way , you still have to use a adapter cable, at charging / balancing,
    but don't need an adapter, to use it on the bike.
    did come up with a waterproofing solution, but not too many like to use a waterbottle,
    everybody is so much in being fast, as to remove the water-bottle cage, for the extra aero advantage,...
    just some ideas, thoughts
    cheers, Rob

  14. #14
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    pethelman, can you link to the supplier of that balance pcb? I've been having weak google-fu lately.

    Thanks!
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