What's in the little red box on some jump-start leads? (Guess first.)

With the increasing popularity of the mini lithium jump starters for cars, there seem to be some standard components appearing. One of them is this set of plug-in leads with that mysterious little box on one of them. So here's what's inside.
I've not taken a look at a jump starters yet as I don't have a load high enough to test them to their often dubious specifications.
Note that there were two types of package in the unit, one with a rating of 40V and one 45V.
Jerry Korner has done some tests though, so here's a link to one of his test videos.
It appears that there has been a recall on some of these leads due to the exact scenario I described of overcranking and causing the diodes to fail short circuit, followed by rapid failure of the lithium pack.
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