After reas your reports, i think your bms have a defect.
OK.
Not directly, there is BMS between.
Seems a bit too late for that + the power path board isn't really the right fit for this as well as this system is indoors. But, thanks for the suggestion though.
Charging still isn't possible? Just asking. Otherwise, what are your ideas?
It has inputs for wall warts as well as solar. Powerpath encompasses UPS but goes further. Most UPSes are actually NOT UPS.
What you are trying to do is very advanced and you have not even identified the correct components. This forum has lot's of posts about this but many are old chips the newer chips like bq series are way better. Good luck.
Of course charging is possible but you need to buy a 3S battery charger. However, that does not solve the UPS problem.
Lets say that ideally you use lipo charger.
Without knowing specs of your BMS we can only guess here.
Also XL4016 (chip) doesn't tell what kind of buck you have. If your's has adjustable CV/CC and you tune it to 12.6V AND <2A, you should be able to charge your battery. Instead if you don't have CC adjustment or it's set at max, it probably goes in tilt because your battery draws more that it can handle.
It does have an adjustable CC/CV.
Buy a commercially available multi charger for RC vehicles that includes lipo. Put two in parallel in the end device if you want hot swappable.
Whenever DC fails? Do you mean AC?
Check these out on Amazon, see if it suits. I have one, works great, auto switches from Ac to DC as soon as I unplug it from mains.
EF ECOFLOW Portable Power Station River 2, 256Wh LiFeP04 Battery/ 1 Hour Fast Charging, 2 Up to 600W AC Outlets, Solar Generator (Solar Panel Optional) for Outdoor Camping/RVs/Home Use
It is because I am using a 12V DC adapter and at the same time, what this setup is suppose to do (aside from charging the battery) is to also power my ESP32 + other components.
The unit I suggested does that, too.
A 12 V lead acid battery would do the job better than li-ion.
I wonder how your xl4016 step-down converter supposed to convert that to 12.6V...
It doesn't and be careful, those bucks can behave weirdly when input voltage is below minimum required for set output.
Does not matter still won't work.
Read your other topic on the same subject for correct solutions.
A couple of houses burnt down here in the UK recently thanks to faulty LiPo charging.
You wouldn't be popular.