I used one to rejuvenate a boats leisure battery that was “dead” after 24 hours on a ctek it was showing as chargeable and after 36 hours was charged it was initially showing under 6v and ready for scrapping.... ctek charger was £60 leisure battery was £120 so in that instance paid for itself twice over!
That sod the one I got in Lidl for £14 has been great too, ctek have the adapters and stuff to make life easier especially on cars with hard to reach batteries and the towing electric adapter is genius
https://www.disco3.co.uk/shop/tow-el...e-etc-p45.html