I liked the 'BUDDY'S' pun :2thumbs: :clap: It's certainly better'n BUDDETTE!

. And it could've been either or a combination if both that caused the failure - but if you've resolved it, lessons have been learned, & things are now working.... then I reckon it's probably time to chalk this all up to experience & move on.

hyea:
BTW, here's a post from another Spyder Forum about Lithium Batteries (it's not my post, but it
is by someone I respect & who I believe knows what they're on about,
especially when it comes to Spyders & their electricals!)
A lithium battery has an unloaded terminal voltage of 14.4V. An AGM lead acid battery has a unloaded terminal voltage of 12.8V. Your regulator will be set up to charge an AGM battery to 13.8V (the float voltage) which is short of the lithium battery's fully charged voltage.
Also, a lithium battery will suck as much current as it can get when charging from a constant voltage charger (your regulator). Things will get hot. It should be charged with a dedicated lithium battery charger, which provides constant current until the lithium battery is fully charged.
So, some electronic intervention will be needed.
You can fit a lithium battery straight in. It will probably work, but not ideally and probably with some problems.
Now I wouldn't expect you'd see 'problems' per-se any time soon after fitting up a good quality well charged lithium battery; and maybe some of the circuitry embedded in most lithium battery cases will help mitigate any issues developing over time, but in my experience and as per the quoted post, with a lithium battery installed in your Spyder you should be at least
aware of the potential for 'less than ideal' operation over time and at least try to give your lithium battery a proper charge every now and then - but then we are told that they do last longer if you keep them/operate them within the right temperature range (23°C - 26° C or there-abouts... 25° C is frequently espoused as 'ideal'

) and largely between 20 & 80% of full charge.
There's a
lot of info out there about them if you want to go searching (both here & elsewhere, some of it quite technical &/or academic! :shocked: ) and it might pay you to do some reading/research the best charger/maintainers to use with your lithium battery. :thumbup:
Over to you! :cheers: