I have had some issues with the design of the Ellie-II, and I am not exactly sure what caused this instance, Chopper.
I have expressed my findings previously in PM's to FiveMega, but I am now concerned about this as a safety issue that your instance raises. I am making this post with absolutely no intention to impugn or demean Fivemega's reputation/quality. FiveMega remains my favorite modder.
My major issues were the inside ridge that blocks using a KIU/Mag D switch (above switch hole), and the top battery holder plate makes contact with narrow body (below switch hole).
FM told me that this Ellie was designed primarily to
work with the AW Soft-Starting multi-level switch, which uses the ridge, and isolates the battery holder top.
However, AW's switch is only rated to work with 150W which is easy to exceed with overdriving 90-100W bulbs--so many would need to use KIU setup with 4s or higher Li-Ion setups.
In addition,
FM's sales thread says the Ellie-II will "accomodate
this type
(AW) switch
or stock M*g "D" switch." (which is a part of the KIU assembly that you used, Choppers). To use the KIU/stock switch you have to Dremel grind out the inside ridge (just above the switch hole).
With this design, the FM Ellie-2 battery holder top contact plate (& Modamag's quad-wide 18650 as well) is too wide. If you slide an empty quad-18650 battery holder inside of an empty Ellie-II, you will see that
the cap makes metal on metal contact with the narrow neck of the body, below the switch area. This will result in a dead short of the positive battery pack against the negative grounded body. I do not regard the HA inside coating as an adequate insulator for this high voltge pack.
Looking at your pictures, Chopper, I cannot rule out the possibility that you may have had a dead short created from this scenario. I do not believe a switch overheating would give such a damage pattern on the top of battery holder as you show. Obviously if the inside plastic of the switch is all melted, it may be from that. Look inside of the body to see if it appears the HA coating shows arc electrical damage to verify the cause. If there was an arc/dead-short, it may also have heated and melted the bottom of the Mag switch.
The safest resolution which would be to get a thin Delrin or Nylon washer that would insulate the top battery contact plate from the inside narrow body area. After brought to his attention, I feel FM should have sent a cheap, thin insulator washer out to everyone purchasing the Ellie, or redesigned the cap with the same kind of
insulating plastic layer he provided in his 3x17670 M-6 Battery holder here. The voltage and current output of 4x18650 Li-Ion (especially Emoli/Sony-V) is no joke. Then there are the 8s & 12s holders with body extensions that could be downright dangerous.
Now in FM's defense, should the buyer/user have an awareness of these kind of issues before purchasing? Yes. Do they all? No. This is the first FM product (of which I have bought many--and praise his quality routinely) that I have had this safety concern, and people should be aware of it and careful.
The other non-safety item in the Ellie-II sales thread which is not correct is where he says the Ellie-2 "Can accept all FM3 heads, 3.5" and even M*g "D" head." In fact,
none of the 6 x FM3H-2 heads I have will fit the threads of the Ellie-II. All other FM3 & 3.5" heads will fit the Ellie-2. Interestingly, my FM3H-2 heads fit the original Elephant threads. There is no easy way to resolve this, so I have accepted it, but sales thread should be corrected.