u/Agitated_Comfort8279

Can someone help me understand the difference between a battery energy storage system and an uninterrupted Power System?
Both use batteries and do the work of providing electricity in case power from the grids go off and act as a back-up...
then what exactly is the difference??

I am new to the biking world and looking for affordable helmets.

I have shortlisted SMK, LS2 and MT helmets
Please suggest which ones are good apart from these also.