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Luna rack mount Slim Pack fuse danger

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  • Luna rack mount Slim Pack fuse danger

    This is what I wrote on my trouble ticket to Luna:

    "This is more of an FYI as I am dealing with the problem myself. The battery pack quit delivering power while I was out on the ride; I had only used about 1/3 of the expected charge. It was very much like a fuse had blown.

    When I got back to my shop I separated the the battery from its mount so I could get to the fuse. I pulled the fuse (30A) but it was OK. Put it back in and checked the pins and HAD voltage (hadn't checked for voltage before as it was obvious there was none so I thought) Now that's really weird so I pulled the fuse again and checked for voltage at the fuse socket---zero! But there was still power at the output pins???

    Time to pull the battery pack apart because something ain't right. Well guess what; the fuse holder wasn't wired into the circuit; never had been---WTF! All this time I'd been running this battery with effectively no fuse at all. Yeah the fuse that will protect me in case of a short that could start a fire.

    FWIW the real no power problem was a wire un-soldered itself in the part of the rack the battery pack plugs into. I suspect increased resistance of a loose female connector caused the heat that melted the solder.

    I notice you no longer sell this model; is the by-passed fuse holder a common problem? This is a serious safety defect IMHO. I will post some photos on the forum.

    Regards,"


    Fuse holder/bulkhead/fuse:

    Click image for larger version  Name:	WP_20170909_056.jpg Views:	4 Size:	1.04 MB ID:	44966

    Never any provision to wire into circuit:
    Click image for larger version  Name:	WP_20170909_054.jpg Views:	3 Size:	1.00 MB ID:	44967

    The reason for the pack failure:
    Click image for larger version  Name:	WP_20170909_060.jpg Views:	2 Size:	1.02 MB ID:	44968

    BTW the model # was 52-SLIM-11.5ah-PF.
    Attached Files
    Last edited by pliebenberg; 1 week ago.

  • #2
    That model was discontinued because it did not meet our quality standards.
    The fuses should never have been there in the first place since the BMS itself acts as a fuse and shuts down the pack if necessary.

    It was one of those things where the assembler in China added it as a nonfunctional "feature" with the intent of getting us to pay more to have it wired in when restocking.


    (Please note knowledgebase section of the form is meant for documentation, this post will be moved out of KB)

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    • #3
      Shouldn't purchasers of this product been notified? At the very least then make this a "sticky"?

      Why should we trust the BMS?

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      • #4
        Practically no models come with a physical fuse, besides a couple of the least popular ones.
        Most ebike battery packs that use lithium ion rely on the battery management system to manage the battery.

        It's up to you if you want to trust the bms and I'm not trying to convince you one way or the other. If you wanted to you could easily wire up an inline fuse on the discharge wiring with a crimper, or even solder the fuse already half installed on the pack. It does add a bit of extra complexity (i.e. you are adding a potential point of failure) but other than keeping that in mind if you ever need to do troubleshooting, either way is fine.

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